CA2041322C - Rapid-setting flowable backfill composition and method of using - Google Patents
Rapid-setting flowable backfill composition and method of using Download PDFInfo
- Publication number
- CA2041322C CA2041322C CA 2041322 CA2041322A CA2041322C CA 2041322 C CA2041322 C CA 2041322C CA 2041322 CA2041322 CA 2041322 CA 2041322 A CA2041322 A CA 2041322A CA 2041322 C CA2041322 C CA 2041322C
- Authority
- CA
- Canada
- Prior art keywords
- class
- composition
- fly ash
- accordance
- rapid
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
- E01C11/00—Details of pavings
- E01C11/005—Methods or materials for repairing pavings
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
- C04B28/021—Ash cements, e.g. fly ash cements ; Cements based on incineration residues, e.g. alkali-activated slags from waste incineration ; Kiln dust cements
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
- C04B2111/00663—Uses not provided for elsewhere in C04B2111/00 as filling material for cavities or the like
- C04B2111/00706—Uses not provided for elsewhere in C04B2111/00 as filling material for cavities or the like around pipelines or the like
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
- C04B2111/0075—Uses not provided for elsewhere in C04B2111/00 for road construction
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S106/00—Compositions: coating or plastic
- Y10S106/01—Fly ash
Abstract
The subject invention relates to a rapid-setting self-hardening backfill composition and method of installation. The composition comprising a minor amount of Class C fly ash as a primary constituent and other filler materials such as Class F fly ash in major amount. When such materials are combined with water in controlled amount, they produce a backfilling material which is flowable and self-leveling for easy installation in utility trenches and similar excavations in street and roadway surfaces to support relatively heavy compressive loads within relatively short periods of time without settling. The self-hardening initially flowable mixtures attain considerable strength for withstanding traffic loads without undue settling in time periods of about 4 hours. The rapid-setting of the composition provides a rapidly attainable strength of the order of about 20 psi within about 4 hours to permit overlaying a wearing course of paving material and reopening of excavated areas of streets and roadways without undue traffic delays and congestion. The backfilling composition ranges in amount from about 2 to 10 parts by weight filler material to about 1 part by weight Class C fly ash with sufficient water to react with both Class C fly ash and filler material. The composition utilizes by-products of coal-fired power stations to form a most economical backfilling material and method of utilization to provide both early strength and precisely controlled permanent strength to permit ready reexcavation.
Description
~Q~4~,~~~
RAPID-SETTING FLOWABLE BACRFILL COMPOSITION
AND METHOD OF USING
BACKGROUND OF THE INVENTION
Technical Field The present invention relates generally to utilization of fly ashes and other by-products of coal combustion in the generation of electrical power by coal-fired power stations. The invention relates, more particularly, to a rapid-setting self-hardening flowable backfilling composition which contains coal combustion by-products and method of utilizing same which permits backfilling of excavated utility trenches, the composition having an early strength gain to withstand normal roadway traffic loads without undue settling.
Background Information The backfilling of utility trenches in roadway surfaces, for example, trenches for gas, water, sewer and electrical conduits, has often created problems in the past wherein the roadway surfaces must be closed 'to traffic for considerable periods of time to allow the backfilling material to gain sufficient strength to withstand placement of a paving course overlay and subsequent exposure to normal roadway traffic. loads. After the ordinary maintenance, repair, or installation of conduits under roadway surfaces, lengthy periods of time and special materials have been required for such backfilling of excavations prior to laying down a paving course and resuming normal traffic over such filled excavations. This is particularly true where the pavement or other wearing course must be placed over a backfilled conduit area to withstand heavy loads. Where a conduit line is installed using the open trench method of construction and where relatively poor soil conditions exist, the normal method of construction to obtain the desired compaction of the backfilled material has been to remove the original soil and replace it with sand, gravel, or the intermixed original material, to obtain the specified backfill condition to withstand traffic loads. In some cases, it has been necessary to backfill in relatively thin layers and then mechanically compact each such layer which has resulted in a very expensive method of construction and maintenance which is unduly time consuming.
Additional problems have been encountered where the soil bedding for the conduit has been so undesirable that it must be removed and replaced with adequate bedding material for the conduit. It is important to have proper bedding under conduits so that the resulting compressive forces are equalized throughout the length of the conduit especially under roadway surfaces where rigid pipe is utilized as the conduit material. If the bedding or backfill does not uniformly support.the conduit throughout its length, the conduit may be sheared, ruptured or otherwise fail, due to uneven compressive loading.
Where utility trenches are backfilled, the use of concrete is not an adequate solution to provide proper support for the conduit or the overlying roadway surfaces. If the backfill material is concrete, it is extremely difficult and expensive to subsequently excavate through the concrete to either repair or replace the conduit, or install lateral connections to the conduit, as desired or required.
In the prior art, controlled density fill materials have been utilized which include a Portland cement as one of their constituents; however, such cement-containing compositions normally attain much greater strength than required and present severe problems upon reexcavation for subsequent maintenance, repair or modification of the conduits. Some such backfilling materials for conduit trenches have obtained compressive strengths in the range of 200 to 800 psi which make reexcavation extremely difficult and costly to perform. Existing flowable backfilling materials which have been designated as controlled-density fill materials do not have the normal structural strength of concrete and require more expensive constituents than the present invention to obtain desired compressive strengths which are less than conventional concrete.
The present invention utilizes primarily fly ashes which are by-products from coal-fired power stations which are relatively inexpensive and readily available.
Some particular fly ashes exhibit cementitious properties which are valuable for the preparation of rapid-setting self hardening backfill materials which are capable of meeting city street and state highway road specifications for backfill materials beneath roadways. Class C
fly ash containing significant amounts of calcium oxide is particularly valuable for use in the subject invention to obtain high early strength which is readily controllable within desired limits and permit its ready use in roadway excavations which may be reexcavated as required without difficulty.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, there is provided a rapid-setting self hardening flowable backfill composition consisting essentially of a combined mixture of filler material in major amount, Class C fly ash in minor amount, the filler ranging in amount from about 2 to 10 parts by weight to about 1 part by weight Class C fly ash, and sufficient water to react with the Class C fly ash and the filler material to form a self leveling non-settling flowable material for backfilling introduction into excavated areas of roadways having sufficient early strength to withstand placement of a paving course overlay and subsequent exposure to normal roadway tragic loads within about four (4) hours.
According to another aspect of the present invention, there is provided a method of backfilling excavated trenches in roadways comprising the steps of intimately combining and intermixing a rapid-setting self hardening flowable backfill composition the composition consisting essentially of filler material in major amount, Class C fly ash in minor amount, the filler material ranging in amount from about 2 to 10 parts by weight to 1 part by weight Class C fly ash, and sufficient water to react with the Class C fly ash and the filler material to form a flowable non-settling backfilling material having su~cient early strength to withstand placement of a paving course overlay and subsequent exposure to normal roadway traffic loads, and introducing the flowable backfilling material in self leveling relation into excavated areas of roadways, the backfilling material having an initial unconfined compressive strength of about 20 psi within about four (4) hours.
In one specific embodiment of the invention the filler material in major amount is comprised of Class F fly ash.
Thus, it can be seen that it is an object of this invention to provide a rapid-setting self hardening backfill material which utilizes a minor amount of Class C fly ash as a primary constituent and which is capable of interaction with other filler materials in major amount.
When such materials are combined with water in controlled amount, they produce a backfilling material which is flowable and self leveling for easy installation into utility trenches within roadways as well as other areas to support relatively heavy compressive loads within relatively short periods of time without settling. The utilization of Class C fly ash containing calcium oxide in conjunction with other fly ashes, such as Class F
fly ash, or other filler materials, to react with controlled amounts of water, provide self hardening initially-flowable mixtures which attain considerable strength for withstanding traffic loads without undue settling in time periods of about four (4) hours. Such early hardening to obtain a rapidly attainable compressive strength of the order of about 20 psi within about four (4) hours permits re-opening of excavated areas of streets and roadways without undue traffic delays and congestion.
Another object of this invention is to provide a backfilling material which utilizes readily-available raw materials which attain high early-strength gain for short-term reforming or reconstruction of roadway sub-surfaces after excavation of selected areas wherein the roadway surfaces may be reopened at an early date and are capable of withstanding normal traffic loads without undue settling after placement of a paving course overlay. The backfilling material may be overlaid with a wearing course of paving material within about four (4) hours to obtain high early-strength gain which strength progressively increases over relatively short periods of time to a maximum compressive strength which permits reexcavation of the backfilled areas without undue ditliculty and at lesser expense. Thus, the backfilling material which utilizes various classes and types of coal combustion by-products is capable of curing to a high early strength without the addition of chemical additives or cementitious materials, and further cures to a maximum strength substantially less than concrete to facilitate easy reexcavation.
As indicated above, in a specific form of the invention, the filler material in major amount may be comprised of Class F fly ash having different properties and characteristics than the Class C fly ash, the Class F and Class C fly ashes both being considered essentially pozzolanic materials except Class C fly ash also possesses cementitious properties. The backfilling composition is extremely economical in its use of normally discarded by-products of coal combustion which axe intermixed with water in controlled amount at the excavation site at the time and place of the backfilling operation. The components may have varying fineness and the Class C fly ash must be kept in a dry state until intimate intermixing with water as the only required reactive liquid component. It is not essential that the Class F fly ash be kept in a dry state.
Following the removal of the original soil from utility trenches, for example, and suitable repair or maintenance of underground conduits, the subject backfilling material is used to backfill the excavations to substantially fill the same, the composition being combinedly mixed "in situ" for immediate flowable self leveling installation to permit over-layment of a paving material within a short time period. The backfilling material is capable of obtaining an initial unconfined compressive strength of the order of about 20 psi within about four (4) hours so that a wearing course can be placed to reopen the roadway to traffic, the backfilling material also being able to withstand other types of compressive loading such as where structures are built thereover including buildings, bridge abutments, embankments, ~o~~.~~2 or other structures which create substantial compressive loads. The subject fly ash containing backfill material does not experience the uneven settling after passage of heavy loads thereover which is common with conventional soil backfill material.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The invention involves the utilization of readily available and economical raw materials namely, fly ashes which are basically pozzolanic materials which are generated in large quantities by coal-burning power stations. A preferred material is Class C fly ash containing a significant quantity of calcium oxide having pozzolanic and cementitious properties which reacts with water to form calcium hydroxide and other hydration products which subsequently harden into a relatively strong structural material having controlled strength.
According to ASTM Designation No. C618-89, Class C
fly ash is defined as fly ash normally produced from lignite or sub-bituminous coal which meets the applicable requirements for this class being a finely divided residue that results from the combustion of ground or powdered coal. This class of fly ash in addition to having pozzolanic properties also has cementitious properties. Some Class C fly ashes may contain lime contents higher than 10 percent by weight. Class F fly ash is defined as fly ash normally produced from burning anthracite or bituminous coal which meets the applicable requirements for this class which also has some pozzolanic properties. For purposes of this invention, a minor amount of Class C fly ash along with a major amount of filler material and water is preferred for obtaining the desired early-strength gain of the reacted material with controlled minimum and maximum strength gain for a roadway backfilling material.
RAPID-SETTING FLOWABLE BACRFILL COMPOSITION
AND METHOD OF USING
BACKGROUND OF THE INVENTION
Technical Field The present invention relates generally to utilization of fly ashes and other by-products of coal combustion in the generation of electrical power by coal-fired power stations. The invention relates, more particularly, to a rapid-setting self-hardening flowable backfilling composition which contains coal combustion by-products and method of utilizing same which permits backfilling of excavated utility trenches, the composition having an early strength gain to withstand normal roadway traffic loads without undue settling.
Background Information The backfilling of utility trenches in roadway surfaces, for example, trenches for gas, water, sewer and electrical conduits, has often created problems in the past wherein the roadway surfaces must be closed 'to traffic for considerable periods of time to allow the backfilling material to gain sufficient strength to withstand placement of a paving course overlay and subsequent exposure to normal roadway traffic. loads. After the ordinary maintenance, repair, or installation of conduits under roadway surfaces, lengthy periods of time and special materials have been required for such backfilling of excavations prior to laying down a paving course and resuming normal traffic over such filled excavations. This is particularly true where the pavement or other wearing course must be placed over a backfilled conduit area to withstand heavy loads. Where a conduit line is installed using the open trench method of construction and where relatively poor soil conditions exist, the normal method of construction to obtain the desired compaction of the backfilled material has been to remove the original soil and replace it with sand, gravel, or the intermixed original material, to obtain the specified backfill condition to withstand traffic loads. In some cases, it has been necessary to backfill in relatively thin layers and then mechanically compact each such layer which has resulted in a very expensive method of construction and maintenance which is unduly time consuming.
Additional problems have been encountered where the soil bedding for the conduit has been so undesirable that it must be removed and replaced with adequate bedding material for the conduit. It is important to have proper bedding under conduits so that the resulting compressive forces are equalized throughout the length of the conduit especially under roadway surfaces where rigid pipe is utilized as the conduit material. If the bedding or backfill does not uniformly support.the conduit throughout its length, the conduit may be sheared, ruptured or otherwise fail, due to uneven compressive loading.
Where utility trenches are backfilled, the use of concrete is not an adequate solution to provide proper support for the conduit or the overlying roadway surfaces. If the backfill material is concrete, it is extremely difficult and expensive to subsequently excavate through the concrete to either repair or replace the conduit, or install lateral connections to the conduit, as desired or required.
In the prior art, controlled density fill materials have been utilized which include a Portland cement as one of their constituents; however, such cement-containing compositions normally attain much greater strength than required and present severe problems upon reexcavation for subsequent maintenance, repair or modification of the conduits. Some such backfilling materials for conduit trenches have obtained compressive strengths in the range of 200 to 800 psi which make reexcavation extremely difficult and costly to perform. Existing flowable backfilling materials which have been designated as controlled-density fill materials do not have the normal structural strength of concrete and require more expensive constituents than the present invention to obtain desired compressive strengths which are less than conventional concrete.
The present invention utilizes primarily fly ashes which are by-products from coal-fired power stations which are relatively inexpensive and readily available.
Some particular fly ashes exhibit cementitious properties which are valuable for the preparation of rapid-setting self hardening backfill materials which are capable of meeting city street and state highway road specifications for backfill materials beneath roadways. Class C
fly ash containing significant amounts of calcium oxide is particularly valuable for use in the subject invention to obtain high early strength which is readily controllable within desired limits and permit its ready use in roadway excavations which may be reexcavated as required without difficulty.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, there is provided a rapid-setting self hardening flowable backfill composition consisting essentially of a combined mixture of filler material in major amount, Class C fly ash in minor amount, the filler ranging in amount from about 2 to 10 parts by weight to about 1 part by weight Class C fly ash, and sufficient water to react with the Class C fly ash and the filler material to form a self leveling non-settling flowable material for backfilling introduction into excavated areas of roadways having sufficient early strength to withstand placement of a paving course overlay and subsequent exposure to normal roadway tragic loads within about four (4) hours.
According to another aspect of the present invention, there is provided a method of backfilling excavated trenches in roadways comprising the steps of intimately combining and intermixing a rapid-setting self hardening flowable backfill composition the composition consisting essentially of filler material in major amount, Class C fly ash in minor amount, the filler material ranging in amount from about 2 to 10 parts by weight to 1 part by weight Class C fly ash, and sufficient water to react with the Class C fly ash and the filler material to form a flowable non-settling backfilling material having su~cient early strength to withstand placement of a paving course overlay and subsequent exposure to normal roadway traffic loads, and introducing the flowable backfilling material in self leveling relation into excavated areas of roadways, the backfilling material having an initial unconfined compressive strength of about 20 psi within about four (4) hours.
In one specific embodiment of the invention the filler material in major amount is comprised of Class F fly ash.
Thus, it can be seen that it is an object of this invention to provide a rapid-setting self hardening backfill material which utilizes a minor amount of Class C fly ash as a primary constituent and which is capable of interaction with other filler materials in major amount.
When such materials are combined with water in controlled amount, they produce a backfilling material which is flowable and self leveling for easy installation into utility trenches within roadways as well as other areas to support relatively heavy compressive loads within relatively short periods of time without settling. The utilization of Class C fly ash containing calcium oxide in conjunction with other fly ashes, such as Class F
fly ash, or other filler materials, to react with controlled amounts of water, provide self hardening initially-flowable mixtures which attain considerable strength for withstanding traffic loads without undue settling in time periods of about four (4) hours. Such early hardening to obtain a rapidly attainable compressive strength of the order of about 20 psi within about four (4) hours permits re-opening of excavated areas of streets and roadways without undue traffic delays and congestion.
Another object of this invention is to provide a backfilling material which utilizes readily-available raw materials which attain high early-strength gain for short-term reforming or reconstruction of roadway sub-surfaces after excavation of selected areas wherein the roadway surfaces may be reopened at an early date and are capable of withstanding normal traffic loads without undue settling after placement of a paving course overlay. The backfilling material may be overlaid with a wearing course of paving material within about four (4) hours to obtain high early-strength gain which strength progressively increases over relatively short periods of time to a maximum compressive strength which permits reexcavation of the backfilled areas without undue ditliculty and at lesser expense. Thus, the backfilling material which utilizes various classes and types of coal combustion by-products is capable of curing to a high early strength without the addition of chemical additives or cementitious materials, and further cures to a maximum strength substantially less than concrete to facilitate easy reexcavation.
As indicated above, in a specific form of the invention, the filler material in major amount may be comprised of Class F fly ash having different properties and characteristics than the Class C fly ash, the Class F and Class C fly ashes both being considered essentially pozzolanic materials except Class C fly ash also possesses cementitious properties. The backfilling composition is extremely economical in its use of normally discarded by-products of coal combustion which axe intermixed with water in controlled amount at the excavation site at the time and place of the backfilling operation. The components may have varying fineness and the Class C fly ash must be kept in a dry state until intimate intermixing with water as the only required reactive liquid component. It is not essential that the Class F fly ash be kept in a dry state.
Following the removal of the original soil from utility trenches, for example, and suitable repair or maintenance of underground conduits, the subject backfilling material is used to backfill the excavations to substantially fill the same, the composition being combinedly mixed "in situ" for immediate flowable self leveling installation to permit over-layment of a paving material within a short time period. The backfilling material is capable of obtaining an initial unconfined compressive strength of the order of about 20 psi within about four (4) hours so that a wearing course can be placed to reopen the roadway to traffic, the backfilling material also being able to withstand other types of compressive loading such as where structures are built thereover including buildings, bridge abutments, embankments, ~o~~.~~2 or other structures which create substantial compressive loads. The subject fly ash containing backfill material does not experience the uneven settling after passage of heavy loads thereover which is common with conventional soil backfill material.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The invention involves the utilization of readily available and economical raw materials namely, fly ashes which are basically pozzolanic materials which are generated in large quantities by coal-burning power stations. A preferred material is Class C fly ash containing a significant quantity of calcium oxide having pozzolanic and cementitious properties which reacts with water to form calcium hydroxide and other hydration products which subsequently harden into a relatively strong structural material having controlled strength.
According to ASTM Designation No. C618-89, Class C
fly ash is defined as fly ash normally produced from lignite or sub-bituminous coal which meets the applicable requirements for this class being a finely divided residue that results from the combustion of ground or powdered coal. This class of fly ash in addition to having pozzolanic properties also has cementitious properties. Some Class C fly ashes may contain lime contents higher than 10 percent by weight. Class F fly ash is defined as fly ash normally produced from burning anthracite or bituminous coal which meets the applicable requirements for this class which also has some pozzolanic properties. For purposes of this invention, a minor amount of Class C fly ash along with a major amount of filler material and water is preferred for obtaining the desired early-strength gain of the reacted material with controlled minimum and maximum strength gain for a roadway backfilling material.
~~~~.e~a~.~a~
The self-hardening flowable backfill material of this invention comprises an intimately-combined filler material in major amount which may consist of Class F fly ash, coal combustion bottom ash and coal combustion boiler slag, the latter two materials being much coarser than the indicated Class F fly ash. The fineness of the filler material may vary through wide limits and does not necessarily require a .fineness comparable to most fly ashes. The composition utilizes a minor amount of Class C fly ash which has the higher~lime content as indicated for this class designation.
The filler material ranges in amount from about 2 to 10 parts by weight to about 1 part by weight Class C fly ash, a preferable ratio being about 3 parts filler material to 1 part Class C fly ash. A preferred filler material is Class F fly ash having less pronounced cementitious properties than the Class C fly ash.
A typical Class F fly ash from the Picway, Ohio power plant of Columbus Southern Power Co. has the following representational analysis and physical properties:
The self-hardening flowable backfill material of this invention comprises an intimately-combined filler material in major amount which may consist of Class F fly ash, coal combustion bottom ash and coal combustion boiler slag, the latter two materials being much coarser than the indicated Class F fly ash. The fineness of the filler material may vary through wide limits and does not necessarily require a .fineness comparable to most fly ashes. The composition utilizes a minor amount of Class C fly ash which has the higher~lime content as indicated for this class designation.
The filler material ranges in amount from about 2 to 10 parts by weight to about 1 part by weight Class C fly ash, a preferable ratio being about 3 parts filler material to 1 part Class C fly ash. A preferred filler material is Class F fly ash having less pronounced cementitious properties than the Class C fly ash.
A typical Class F fly ash from the Picway, Ohio power plant of Columbus Southern Power Co. has the following representational analysis and physical properties:
TABLEI
Chemical Analysis ASTM C-618CLASS F % BY WEIGFIT
Silica 42.3 Aluminum Oxide 25.2 Iron Oxide 20.8 Combined 1,2 & 3 Min 70a 882 Titanium Dioxide 1.6 Calcium Oxide 0.7 Sodium Oxide 0.3 Potassium Oxide 1.5 Sulfur Trioxide Max 50 1.1 Phosphorus Pentoxi.de 0.2 Other Constituents 4.7 Total % 99'9 ph @ 26C, 1% slurry Available Alkalies, o Max 1.50 0.46 Sp. Cond. , @ 21C
Llmho of 1% Slurry 255 Physical Tests Moisture Content, ~ Max 30 0.1 Net Ignition Loss,.% Max 60 5.32 Retained on No. 325, (wet-sieved) Max 340 22.29 Specific Gravity 2.30 Autoclave Expansion Max 0.80 0.18 Water Requirement, o Control Max 105% 105 Strength Activity Index with Cement at 28 days Control Min 750 75 with Lime at 7 days, psi Min 800 psi 913 a~~'~~,~i~s~
A typical Class C fly ash from the Rockport, Indiana power plant of Indiana Michigan Power Co. has the following representational analysisand properties:
physical TABLE
IT
Chemical Analysis ASTM-C Class C o by Weight Silica 37.6 Aluminum Oxide 18.0 Iron Oxide 5'9 Combined 1,2, & 3 Min 500 61.5 Titanium Dioxide 1.5 Calcium Oxide 25.2 Magnesium Oxide 5.3 Sodium Oxide 1.9 Potassium Oxide 0.4 Sulfur Trioxide Max 50 1.9 Phosphorus PentoXide 1.3 Other Constituents 0.2 Total % 99.2 ph @ 26~C, 1% Slurry 11.6 Available Alkalies, % Max 1.50 1.26 sp. Cond, @ 21~ 1218 Umho of 1o Slurry Physical Tests Moisture Content, % Max 30 0.04 Net Ignition Loss, % Max 6a 0.30 Retained on No. 325, o (wet-sieved) Max 340 19.05 Specific Gravity 2.68 Autoclave Expansion Max 0.80 0.007 Water Requirement, Control Max 105% 93 Strength Activity Index with cement at 28 days, Control Min 750 99 with lime at 7 days, NA NA
psi The Class C fly ash must be maintained in a dry condition and the filler materials are normally maintained in an essentially dry condition prior to their being intermixed with a prescribed reactive amount of water, preferably at the ~~~.a~~~
backfilling site for installation within the excavated area or areas. A preferred ratio of total solids to water is about 2.3 to 1 parts by weight, although the water content may be varied slightly from such precise ratio depending upon the given characteristics of the particular Class C fly ash used and the preferred characteristics of the backfill material end product. A preferred combined mixture comprises about 52% by weight Class F fly ash, about 17o by weight Class C fly ash, and about 31% by weight water.
The following components are employed in the preferred backfill composition in the indicated amounts:
PREFERRED LOWER RANGE
500 1b. class 330 1b. class 600 1b. class C ash C ash C ash 1550 1b. class 1620 lbs. class 1470 1b. class F ash F ash F ash 870 lbs. water 870 lbs. water 850 lbs. water The amount of water is critical and must be sufficient for flowability and essentially self-leveling;
excess water will retard adequate early strength gain. The composition is formulated in the range of 1 part Class C fly ash to 10 parts Class F fly ash (about 200 lbs. Class C to about 2000 lbs. Class F) and from 1 part Class C to 2 parts Class F (about 700 lbs. Class C to about 1400 lbs. Class F).
The material is not a paving material but is a fill material to be overlain with a wearing course of paving material at a relatively short time period (e. g. 4 hours or less).
After the coal combustion by-products are intimately intermixed with water, such as by a rotary mixer, the backfilling composition is placed within the excavated areas in a flowable self-leveling condition. The excavations are substantially filled to near roadway level following which a roadway wearing course of paving material such as asphalt or concrete is installed thereover to provide a durable wear-resistant roadway surface.
~~4~.~~:
The paving course can be placed over the backfill within a period of from about 2 to 4 hours depending upon the rate of strength gain. Where the overlay is comprised of asphalti.c material, the roadway can be opened to traffic almost immediately. Where the overlay is concrete, a longer period is required depending upon its thickness and specific hardening properties. High early-strength concretes are available and known in the art to form such paving course.
The backfill material is capable of obtaining an unconfined compressive strength of about 20 psi within about 4 hours following which time period the pavement course overlay may be placed and the roadway surfaces may be opened to traffic without enforcing reduced traffic loads. The roadway surface may be impacted by such rolling traffic thereover without undue settlement or the formation of wavy surfaces or potholes. The backfilling material is capable of curing to approximately 25 to 40 percent of its 28-day unconfined compressive strength within about 4 hours to be fully, capable of withstanding traffic loads which may vary from 2-20 tons of loading pressure without adverse effects on the backfilling material. The composition is capable of curing to approximately 60 to 75 percent of its 28-day strength gain within about 7 days, this progressive increase in compressive strength further strengthens the backfilling material during its permanent underlying of the roadway surfaces which are then in continuous traffic supporting use.
The composition is capable of curing to a maximum strength of about 150 psi over its lifetime to permit ready reexcavation of the material at a subsequent date as may be desired or required. It is not uncommon for the previously excavated and backfilled areas to again require reexcavation to facilitate further maintenance or repair work on the underlying conduits.
As stated, mixtures containing purely cementitious materials or those which contain Portland cements are undesirable in view of reexcavation difficulties which can and do occur with such materials.
A preferred backfill material comprising the intimately combined mixture of Class C and Class F fly ash's and water has the following representational physical properties:
~ASZE zzz Unit Weight (Fresh Weight)------------------- 105 lbs.ft3 Resistance to Penetration (Avr. At 4-Hours)-- 400 psi Coefficient Of Permeability------------------ 2.6 x 10-5cm/sec Unconfined Compressive Strength 4-Hours 30 psi (2.16 TSF)*
28 days 75 psi (5.4 TSF) 91 days <150 psi (10.8 TSF) Atterberg Limits----------------------------- Non-Plastic pH (At 1-Month)___-_________________________- g.52 Resistivity (At 1-Month)---------------------- 1160 ohm-cm Redox Potential (At 1-Month)------°---------_ + 150 mv.
Thermal Resistivity (At 24-Hours)------------ 100°C-cm/W
Color (Can Be Modified Within Limits)-------- Gray *TSF is defined as tons per square foot.
The backfill:ing material provides a superior material for use as a backfill in utilizing readily available and most economical constituents and avoids the difficulties of layered compacting which is frequently required with other common types of backfilling materials. The subject backfilling material is intimately mixed at the site of the excavation, or closely adjacent thereto, the backfilling allows easy installation due to its flowable natuxe without any personnel being physically required within the trenches during the backfilling operation. The backfilling material may be very beneficially utilized under and around conduits, i~~~~..~~:
to fill essentially large size trenches having a significant depth. Obviously, small trenches may also be readily filled with the backfi.lling material, The overlying wearing course of paving material may be compacted over the backfilling material such as by a powered roller or truck tires depending upon the surface area of the backfilling material which is preferably laid down having an exterior surface area nearly parallel in grade to the existing roadway. The overlaid paving material may have a thickness varying from 3 to 9 inches or thicker, a$ desired, the backfilling material being fully compatible with and capable of supporting a wide variety of conventional paving materials.
The subject method of backfilling excavated trenches in roadways essentially comprises the steps of intimately combining and intermixing the backfilling material comprising the combined mixture as aforesaid with sufficient water to react with said Class C fly ash and the filler material. The backfilling material is installed in self-leveling relation into the excavated areas of roadways to withstand placement of the paving course overlay and subsequent exposure to normal roadway traffic loads, the backfilling material having an initial unconfined compressive strength of about 20 psi within about 4 hours. The flowable backfill material is measured and intermixed immediately prior to its installation in the excavated areas to substantially fill such areas, the backfilling material being capable of initially curing to approximately 25 to 40 percent of its 28-day unconfined compressive strength gain within about 4 hours and to a maximum compressive strength of. about 150 psi to permit ready reexcavation of the material.
The average trench in some utility maintenance work in certain cities is 4 feet by~6 feet by 3 feet deep which would require an average of about 2.7 cubic yards or 3.3 tons of flowable backfill material to fill such average trench size. Rockport fly ash which is economically available to a ~~~~.a~~~
broad geographic area of North America is a Class C fly ash meaning that it is a cementitious material as well as a pozzolanic material. A pozzolan is a siliceous or a siliceous and aluminous material which when combined with lime in the presence of water will produce a cementitious material with excellent structural properties. The quick-setting characteristic of the Rockport fly ash (Class C) makes it particularly valuable for use in the subject invention although other types of Class C fly ash from other sources may be readily used. Pickway fly ash which is available in the midwest USA is a Class F fly ash meaning that it is strictly a pozzolanic material. Picway fly ash is a pozzolanic fly ash material which is known to be available in central Ohio in large tonnages and is a particularly valuable filler material for use in the subject composition.
The subject flowable backfill.material made from coal ashes and boiler operation by-products allows road trench repairs to be made.faster, easier and more economical. The material is unique in that it utilizes no cement or chemical additives and achieves sufficient early strength to allow repaving operations to be undertaken quickly and permanently.
The subject backfilling material is especially valuable for backfilling trenches for utility work on water lines, sewer lines, gas lines, and buried electrical cable. The use of such readily available fly ashes reduces the cost of disposal or storing of such materials from coal-fired power plants.
The subject backfill meets all of the engineering requirements for a fast--setting backfill material for road repair work.
The basic criteria far such materials are:
1. Be readily flowable to perfectly form around pipes, cables, or other embedments in utility trenches;
2. Achieve a quick initial set to' permit paving within about 4 hours;
3. Achieve an initial strength capable of bearing traffic within about 4 hours; and 4. Achieve an ultimate strength of not more than about 150 psi so that the material can be reexcavated when necessary.
The preferred Class C and Class F fly ashes in a ratio of about 1 to 3 with the prescribed amount of water were proportionally blended to arrive at a combined mixture which satisfies all of the aforesaid criteria. Cube samples and cylinder samples were cast in order to measure compressive strength at 2 hours, 4 hours, 24 hours, 7 days and 28 days.
Tests were performed after mixing was complete to measure flow characteristics and unit weight.
To simulate field applications of the backfill material, a pad 4 feet by 2 feet by 6 inches deep was cast and a truck tire was driven on it at the various stated time intervals. Basically the material supported the weight associated with a light-duty pickup truck at 2 hours and is capable of carrying the weight associated with a 27,500 1b.
truck at 4 hours caith only minor deformation of the surface.
Penetrometer readings were taken on companion pads to develop a correlation between truck pad results and compressive strength results in quantifiable fashion.
Full scale field tests have been made of the backfill material. A backfilled trench filled with the material was tested to determine how long after placement it could safely carry traffic loads. The test involved filling a trench 4 feet wide by 8 feet long by 5 feet deep with the subject preferred backfil.l material discharged from a volumetric mobile mixer. A volumetric batch truck was used since preliminary tests indicated that prolonged mixing as would be experienced in a standard transit mixer would delay the initial set and early strength gain. The dry weight proportions necessary to meet the aforesaid criteria with a sufficient safety factor have been met. Exact proportions were adjusted depending upon specific results desired. The process is unique in that the material utilizes no cement and ~~941.~~~
achieves early strength gain in less than 4 hours with no chemical additives. Virtually all of the strength is achieved in the early phases of curing with approximately 60 to 75 percent of the 28-day strength being achieved prior to 7 days.
Ultimate strength gain does not prevent reexcavation at a later date.
Other comparable processes normally rely on cement for strength. The Class F fly ash primarily provides bulk for such mixtures. One known mixture and process, in particular, cannot be directly paved over for 16 to 24 hours while it gains sufficient strength. In such applications where quicker turnaround is needed, a high early-strength concrete overlay is placed over the backfill.
The flowable fly ash backfill of this invention is intended for use as a trench backfill mostly for road repair, but may also be utilized in any backfill situation by electric, gas, telephone, water and sewer utilities. A
primary advantage is that it provides a high quality backfill with very economical materials utilizing only minimal labor since it may be poured into a trench and is self-leveling, there being no labor intensive compaction of materials around pipes or conduits. Only approximately 4 hours are needed for the backfill material to gain sufficient strength to be paved over. The flowable fly ash backfill provides the desirable objective of reopening streets and highways to traffic more quickly. Safety objectives are also enhanced since personnel are required to be physically present in the trench only for a sufficient time period to perform repairs and installations and not during the backfilling operation.
The designated Rockport and Picway fly ashes (Class C and F respectively) are only set forth by way of example materials which may be beneficially used in the practice of this invention. Obviously, other fly ashes having these broad classifications may be employed. It is not contemplated or required in practicing this invention that the referenced fly ~~~4~.~~~' ashes conform strictly to the ASTM specifications employed in defining such fly ash classes, but may deviate therefrom in certain respects depending upon their source and method of production in coal-fired power generation stations. The aforesaid fly ashes are stated as representative of their class designations, but may differ therefrom in certain minor characteristics but still reside generally within the broad definitions of the particular classes.
Accordingly, the improved backfill material and method of its installation are simplified providing a effective, safe, inexpensive and efficient backfilling material and method of use which achieves all the enumerated objectives and solves the enumerated problems and obtains new results in the art.
~,5 In the foregoing description, certain terms have been used for brevity, clearness and understanding. but no unnecessary limitations are to be implied therefrom beyond the requirements of the. prior art, because.such terms are used for descriptive purposes and are intended to be broadly construed.
Having now described the features, discoveries and principles of the invention, the manner in which the improved backfilling material and method of installation are formulated and used in several forms, the characteristics of the construction, and the advantageous, new and useful results obtained; the new and useful structure, devices, elements, arrangements, parts and combination, are set forth in the appended claims.
Chemical Analysis ASTM C-618CLASS F % BY WEIGFIT
Silica 42.3 Aluminum Oxide 25.2 Iron Oxide 20.8 Combined 1,2 & 3 Min 70a 882 Titanium Dioxide 1.6 Calcium Oxide 0.7 Sodium Oxide 0.3 Potassium Oxide 1.5 Sulfur Trioxide Max 50 1.1 Phosphorus Pentoxi.de 0.2 Other Constituents 4.7 Total % 99'9 ph @ 26C, 1% slurry Available Alkalies, o Max 1.50 0.46 Sp. Cond. , @ 21C
Llmho of 1% Slurry 255 Physical Tests Moisture Content, ~ Max 30 0.1 Net Ignition Loss,.% Max 60 5.32 Retained on No. 325, (wet-sieved) Max 340 22.29 Specific Gravity 2.30 Autoclave Expansion Max 0.80 0.18 Water Requirement, o Control Max 105% 105 Strength Activity Index with Cement at 28 days Control Min 750 75 with Lime at 7 days, psi Min 800 psi 913 a~~'~~,~i~s~
A typical Class C fly ash from the Rockport, Indiana power plant of Indiana Michigan Power Co. has the following representational analysisand properties:
physical TABLE
IT
Chemical Analysis ASTM-C Class C o by Weight Silica 37.6 Aluminum Oxide 18.0 Iron Oxide 5'9 Combined 1,2, & 3 Min 500 61.5 Titanium Dioxide 1.5 Calcium Oxide 25.2 Magnesium Oxide 5.3 Sodium Oxide 1.9 Potassium Oxide 0.4 Sulfur Trioxide Max 50 1.9 Phosphorus PentoXide 1.3 Other Constituents 0.2 Total % 99.2 ph @ 26~C, 1% Slurry 11.6 Available Alkalies, % Max 1.50 1.26 sp. Cond, @ 21~ 1218 Umho of 1o Slurry Physical Tests Moisture Content, % Max 30 0.04 Net Ignition Loss, % Max 6a 0.30 Retained on No. 325, o (wet-sieved) Max 340 19.05 Specific Gravity 2.68 Autoclave Expansion Max 0.80 0.007 Water Requirement, Control Max 105% 93 Strength Activity Index with cement at 28 days, Control Min 750 99 with lime at 7 days, NA NA
psi The Class C fly ash must be maintained in a dry condition and the filler materials are normally maintained in an essentially dry condition prior to their being intermixed with a prescribed reactive amount of water, preferably at the ~~~.a~~~
backfilling site for installation within the excavated area or areas. A preferred ratio of total solids to water is about 2.3 to 1 parts by weight, although the water content may be varied slightly from such precise ratio depending upon the given characteristics of the particular Class C fly ash used and the preferred characteristics of the backfill material end product. A preferred combined mixture comprises about 52% by weight Class F fly ash, about 17o by weight Class C fly ash, and about 31% by weight water.
The following components are employed in the preferred backfill composition in the indicated amounts:
PREFERRED LOWER RANGE
500 1b. class 330 1b. class 600 1b. class C ash C ash C ash 1550 1b. class 1620 lbs. class 1470 1b. class F ash F ash F ash 870 lbs. water 870 lbs. water 850 lbs. water The amount of water is critical and must be sufficient for flowability and essentially self-leveling;
excess water will retard adequate early strength gain. The composition is formulated in the range of 1 part Class C fly ash to 10 parts Class F fly ash (about 200 lbs. Class C to about 2000 lbs. Class F) and from 1 part Class C to 2 parts Class F (about 700 lbs. Class C to about 1400 lbs. Class F).
The material is not a paving material but is a fill material to be overlain with a wearing course of paving material at a relatively short time period (e. g. 4 hours or less).
After the coal combustion by-products are intimately intermixed with water, such as by a rotary mixer, the backfilling composition is placed within the excavated areas in a flowable self-leveling condition. The excavations are substantially filled to near roadway level following which a roadway wearing course of paving material such as asphalt or concrete is installed thereover to provide a durable wear-resistant roadway surface.
~~4~.~~:
The paving course can be placed over the backfill within a period of from about 2 to 4 hours depending upon the rate of strength gain. Where the overlay is comprised of asphalti.c material, the roadway can be opened to traffic almost immediately. Where the overlay is concrete, a longer period is required depending upon its thickness and specific hardening properties. High early-strength concretes are available and known in the art to form such paving course.
The backfill material is capable of obtaining an unconfined compressive strength of about 20 psi within about 4 hours following which time period the pavement course overlay may be placed and the roadway surfaces may be opened to traffic without enforcing reduced traffic loads. The roadway surface may be impacted by such rolling traffic thereover without undue settlement or the formation of wavy surfaces or potholes. The backfilling material is capable of curing to approximately 25 to 40 percent of its 28-day unconfined compressive strength within about 4 hours to be fully, capable of withstanding traffic loads which may vary from 2-20 tons of loading pressure without adverse effects on the backfilling material. The composition is capable of curing to approximately 60 to 75 percent of its 28-day strength gain within about 7 days, this progressive increase in compressive strength further strengthens the backfilling material during its permanent underlying of the roadway surfaces which are then in continuous traffic supporting use.
The composition is capable of curing to a maximum strength of about 150 psi over its lifetime to permit ready reexcavation of the material at a subsequent date as may be desired or required. It is not uncommon for the previously excavated and backfilled areas to again require reexcavation to facilitate further maintenance or repair work on the underlying conduits.
As stated, mixtures containing purely cementitious materials or those which contain Portland cements are undesirable in view of reexcavation difficulties which can and do occur with such materials.
A preferred backfill material comprising the intimately combined mixture of Class C and Class F fly ash's and water has the following representational physical properties:
~ASZE zzz Unit Weight (Fresh Weight)------------------- 105 lbs.ft3 Resistance to Penetration (Avr. At 4-Hours)-- 400 psi Coefficient Of Permeability------------------ 2.6 x 10-5cm/sec Unconfined Compressive Strength 4-Hours 30 psi (2.16 TSF)*
28 days 75 psi (5.4 TSF) 91 days <150 psi (10.8 TSF) Atterberg Limits----------------------------- Non-Plastic pH (At 1-Month)___-_________________________- g.52 Resistivity (At 1-Month)---------------------- 1160 ohm-cm Redox Potential (At 1-Month)------°---------_ + 150 mv.
Thermal Resistivity (At 24-Hours)------------ 100°C-cm/W
Color (Can Be Modified Within Limits)-------- Gray *TSF is defined as tons per square foot.
The backfill:ing material provides a superior material for use as a backfill in utilizing readily available and most economical constituents and avoids the difficulties of layered compacting which is frequently required with other common types of backfilling materials. The subject backfilling material is intimately mixed at the site of the excavation, or closely adjacent thereto, the backfilling allows easy installation due to its flowable natuxe without any personnel being physically required within the trenches during the backfilling operation. The backfilling material may be very beneficially utilized under and around conduits, i~~~~..~~:
to fill essentially large size trenches having a significant depth. Obviously, small trenches may also be readily filled with the backfi.lling material, The overlying wearing course of paving material may be compacted over the backfilling material such as by a powered roller or truck tires depending upon the surface area of the backfilling material which is preferably laid down having an exterior surface area nearly parallel in grade to the existing roadway. The overlaid paving material may have a thickness varying from 3 to 9 inches or thicker, a$ desired, the backfilling material being fully compatible with and capable of supporting a wide variety of conventional paving materials.
The subject method of backfilling excavated trenches in roadways essentially comprises the steps of intimately combining and intermixing the backfilling material comprising the combined mixture as aforesaid with sufficient water to react with said Class C fly ash and the filler material. The backfilling material is installed in self-leveling relation into the excavated areas of roadways to withstand placement of the paving course overlay and subsequent exposure to normal roadway traffic loads, the backfilling material having an initial unconfined compressive strength of about 20 psi within about 4 hours. The flowable backfill material is measured and intermixed immediately prior to its installation in the excavated areas to substantially fill such areas, the backfilling material being capable of initially curing to approximately 25 to 40 percent of its 28-day unconfined compressive strength gain within about 4 hours and to a maximum compressive strength of. about 150 psi to permit ready reexcavation of the material.
The average trench in some utility maintenance work in certain cities is 4 feet by~6 feet by 3 feet deep which would require an average of about 2.7 cubic yards or 3.3 tons of flowable backfill material to fill such average trench size. Rockport fly ash which is economically available to a ~~~~.a~~~
broad geographic area of North America is a Class C fly ash meaning that it is a cementitious material as well as a pozzolanic material. A pozzolan is a siliceous or a siliceous and aluminous material which when combined with lime in the presence of water will produce a cementitious material with excellent structural properties. The quick-setting characteristic of the Rockport fly ash (Class C) makes it particularly valuable for use in the subject invention although other types of Class C fly ash from other sources may be readily used. Pickway fly ash which is available in the midwest USA is a Class F fly ash meaning that it is strictly a pozzolanic material. Picway fly ash is a pozzolanic fly ash material which is known to be available in central Ohio in large tonnages and is a particularly valuable filler material for use in the subject composition.
The subject flowable backfill.material made from coal ashes and boiler operation by-products allows road trench repairs to be made.faster, easier and more economical. The material is unique in that it utilizes no cement or chemical additives and achieves sufficient early strength to allow repaving operations to be undertaken quickly and permanently.
The subject backfilling material is especially valuable for backfilling trenches for utility work on water lines, sewer lines, gas lines, and buried electrical cable. The use of such readily available fly ashes reduces the cost of disposal or storing of such materials from coal-fired power plants.
The subject backfill meets all of the engineering requirements for a fast--setting backfill material for road repair work.
The basic criteria far such materials are:
1. Be readily flowable to perfectly form around pipes, cables, or other embedments in utility trenches;
2. Achieve a quick initial set to' permit paving within about 4 hours;
3. Achieve an initial strength capable of bearing traffic within about 4 hours; and 4. Achieve an ultimate strength of not more than about 150 psi so that the material can be reexcavated when necessary.
The preferred Class C and Class F fly ashes in a ratio of about 1 to 3 with the prescribed amount of water were proportionally blended to arrive at a combined mixture which satisfies all of the aforesaid criteria. Cube samples and cylinder samples were cast in order to measure compressive strength at 2 hours, 4 hours, 24 hours, 7 days and 28 days.
Tests were performed after mixing was complete to measure flow characteristics and unit weight.
To simulate field applications of the backfill material, a pad 4 feet by 2 feet by 6 inches deep was cast and a truck tire was driven on it at the various stated time intervals. Basically the material supported the weight associated with a light-duty pickup truck at 2 hours and is capable of carrying the weight associated with a 27,500 1b.
truck at 4 hours caith only minor deformation of the surface.
Penetrometer readings were taken on companion pads to develop a correlation between truck pad results and compressive strength results in quantifiable fashion.
Full scale field tests have been made of the backfill material. A backfilled trench filled with the material was tested to determine how long after placement it could safely carry traffic loads. The test involved filling a trench 4 feet wide by 8 feet long by 5 feet deep with the subject preferred backfil.l material discharged from a volumetric mobile mixer. A volumetric batch truck was used since preliminary tests indicated that prolonged mixing as would be experienced in a standard transit mixer would delay the initial set and early strength gain. The dry weight proportions necessary to meet the aforesaid criteria with a sufficient safety factor have been met. Exact proportions were adjusted depending upon specific results desired. The process is unique in that the material utilizes no cement and ~~941.~~~
achieves early strength gain in less than 4 hours with no chemical additives. Virtually all of the strength is achieved in the early phases of curing with approximately 60 to 75 percent of the 28-day strength being achieved prior to 7 days.
Ultimate strength gain does not prevent reexcavation at a later date.
Other comparable processes normally rely on cement for strength. The Class F fly ash primarily provides bulk for such mixtures. One known mixture and process, in particular, cannot be directly paved over for 16 to 24 hours while it gains sufficient strength. In such applications where quicker turnaround is needed, a high early-strength concrete overlay is placed over the backfill.
The flowable fly ash backfill of this invention is intended for use as a trench backfill mostly for road repair, but may also be utilized in any backfill situation by electric, gas, telephone, water and sewer utilities. A
primary advantage is that it provides a high quality backfill with very economical materials utilizing only minimal labor since it may be poured into a trench and is self-leveling, there being no labor intensive compaction of materials around pipes or conduits. Only approximately 4 hours are needed for the backfill material to gain sufficient strength to be paved over. The flowable fly ash backfill provides the desirable objective of reopening streets and highways to traffic more quickly. Safety objectives are also enhanced since personnel are required to be physically present in the trench only for a sufficient time period to perform repairs and installations and not during the backfilling operation.
The designated Rockport and Picway fly ashes (Class C and F respectively) are only set forth by way of example materials which may be beneficially used in the practice of this invention. Obviously, other fly ashes having these broad classifications may be employed. It is not contemplated or required in practicing this invention that the referenced fly ~~~4~.~~~' ashes conform strictly to the ASTM specifications employed in defining such fly ash classes, but may deviate therefrom in certain respects depending upon their source and method of production in coal-fired power generation stations. The aforesaid fly ashes are stated as representative of their class designations, but may differ therefrom in certain minor characteristics but still reside generally within the broad definitions of the particular classes.
Accordingly, the improved backfill material and method of its installation are simplified providing a effective, safe, inexpensive and efficient backfilling material and method of use which achieves all the enumerated objectives and solves the enumerated problems and obtains new results in the art.
~,5 In the foregoing description, certain terms have been used for brevity, clearness and understanding. but no unnecessary limitations are to be implied therefrom beyond the requirements of the. prior art, because.such terms are used for descriptive purposes and are intended to be broadly construed.
Having now described the features, discoveries and principles of the invention, the manner in which the improved backfilling material and method of installation are formulated and used in several forms, the characteristics of the construction, and the advantageous, new and useful results obtained; the new and useful structure, devices, elements, arrangements, parts and combination, are set forth in the appended claims.
Claims (25)
1. A rapid-setting self-hardening flowable backfill composition consisting essentially of a combined mixture of filler material in major amount, Class C
fly ash in minor amount, said filler ranging in amount from about 2 to 10 parts by weight to about 1 part by weight Class C fly ash, and sufficient water to react with said Class C fly ash and said filler material to form a self-leveling non-settling flowable material for backfilling introduction into excavated areas of roadways having sufficient early strength to withstand placement of a paving course overlay and subsequent exposure to normal roadway traffic loads within about four (4) hours.
fly ash in minor amount, said filler ranging in amount from about 2 to 10 parts by weight to about 1 part by weight Class C fly ash, and sufficient water to react with said Class C fly ash and said filler material to form a self-leveling non-settling flowable material for backfilling introduction into excavated areas of roadways having sufficient early strength to withstand placement of a paving course overlay and subsequent exposure to normal roadway traffic loads within about four (4) hours.
2. A rapid-setting self-hardening flowable backfill composition in accordance with claim 1, wherein said filler material in major amount is selected from the group consisting of Class F fly ash, coal combustion bottom ash, and coal combustion boiler slag.
3. A rapid-setting self-hardening flowable backfill composition in accordance with claim 1, wherein said filler material in major amount is comprised of Class F fly ash.
4. A rapid-setting self-hardening flowable backfill composition in accordance with claim 1, wherein said composition is capable of self-hardening to an initial unconfined compressive strength of greater than about 20 psi within about four (4) hours.
5. A rapid-setting self-hardening flowable backfill composition in accordance with claim 1, wherein said composition is capable of curing to approximately 25 to 40 percent of its 28-day strength gain within about four (4) hours.
6. A rapid-setting self-hardening flowable backfill composition in accordance with claim 1, wherein said composition is capable of curing to approximately 60 to 70 percent of its 28-day strength gain within about 7 days.
7. A rapid-setting self-hardening flowable backfill composition in accordance with claim 1, wherein said composition is capable of curing to a maximum strength of about 150 psi to permit ready reexcavation of the material at a subsequent date.
8. A rapid-setting self-hardening flowable backfill composition in accordance with claim 1, wherein said composition is measured and intermixed immediately prior to its installation within utility trenches.
9. A rapid-setting self-hardening flowable backfill composition comprising a combined mixture of Class F fly ash in major amount and Class C fly ash in minor amount, said Class F and Class C fly ashes ranging from about 2 to 10 parts by weight Class F fly ash to about 1 part by weight Class C fly ash, and sufficient water to react with both said Class F
and Class C fly ashes, the ratio of said total solids to water being about 2.3 to 1 parts by weight, said composition being measured and intimately intermixed immediately prior to self-leveling flowable introduction of said composition into excavated roadway areas as a non-settling backfill material having an initial unconfined compressive strength of about 20 psi within about 4 hours.
and Class C fly ashes, the ratio of said total solids to water being about 2.3 to 1 parts by weight, said composition being measured and intimately intermixed immediately prior to self-leveling flowable introduction of said composition into excavated roadway areas as a non-settling backfill material having an initial unconfined compressive strength of about 20 psi within about 4 hours.
10. A rapid-setting self-hardening flowable backfill composition in accordance with claim 9, the ratio of said Class F fly ash to said Class C fly ash being about 3 to 1 parts by weight.
11. A rapid-setting self-hardening flowable backfill composition in accordance with claim 9, wherein said combined mixture comprises about 52 percent by weight Class F
fly ash, about 17 percent by weight Class C fly ash, and about 31 percent by weight water.
fly ash, about 17 percent by weight Class C fly ash, and about 31 percent by weight water.
12. A rapid-setting self-hardening flowable backfill composition in accordance with claim 9, wherein said backfill composition having sufficient early strength to being overlaid with a separate wearing course of paving material to provide a durable load-bearing roadway surface within about four (4) hours.
13. A rapid-setting self-hardening flowable backfill composition in accordance with claim 9, wherein said composition is capable of curing to approximately to 40 percent of its 28-day compressive strength gain within about four (4) hours.
14. A rapid-setting self-hardening flowable backfill composition in accordance with claim 9, wherein said composition is capable of curing to approximately 60 to 75 percent of its 28-day strength gain within about seven (7) days.
15. A rapid-setting self-hardening flowable backfill composition in accordance with claim 9, wherein said composition is capable of curing to a max strength of about 150 psi to permit ready reexcavation of the material at a subsequent date.
16. A rapid-setting self-hardening flowable backfill composition in accordance with claim 9, wherein said composition is measured and intermixed immediately prior to its backfilling installation within excavated roadway trenches to withstand paving course overlays.
17. The method of backfilling excavated trenches in roadways comprising the steps of intimately combining and intermixing a rapid-setting self-hardening flowable backfill composition, said composition consisting essentially of filler material in major amount, Class C fly ash in minor amount, said filler material ranging in amount from about 2 to 10 parts by weight to 1 part by weight Class C fly ash, and sufficient water to react with said Class C fly ash and said filler material to form a flowable non-settling backfilling material having sufficient early strength to withstand placement of a paving course overlay and subsequent exposure to normal roadway traffic loads, and introducing said flowable backfilling material in self-leveling relation into excavated areas of roadways, said backfilling material having an initial unconfined compressive strength of about 20 psi within about four (4) hours.
18. The method of backfilling excavated trenches in roadways in accordance with claim 17, includes the step of overlaying the backfilled excavated areas with a separate wearing course of paving material to form a durable roadway surface.
19. The method of backfilling excavated trenches in roadways in accordance with claim 17, includes the step of intimately combining and intermixing said backfill composition immediately prior to introducing same into said excavated areas to substantially fill such areas.
20. The method of backfilling excavated trenches in roadways in accordance with claim 17, wherein said filler material is comprised of Class F fly ash, said Class F fly ash and said Class C fly ash being combined in a ratio of about 3 to 1 parts by weight, the ratio of total solids to water being about 2.3 to 1 parts by weight.
21. The method of backfilling excavated trenches in roadways in accordance with claim 17, said backfill composition is self curing to a maximum compressive strength of about 150 psi to permit ready reexcavation of the material at a subsequent date.
22. The method of backfilling excavated trenches in roadways in accordance with claim 17, wherein said backfill composition is capable of curing to approximately 25 to 40 percent of its unconfined 28-day compressive strength within about four (4) hours.
23. The method of backfilling excavated trenches in roadways in accordance with claim 17, wherein said backfill composition is capable of self-curing to approximately 60 to 75 percent of its 28-day strength gain within about 7 days.
24. The method of backfilling excavated trenches in roadways in accordance with claim 17, wherein said backfill composition comprises about 52 percent by weight Class F fly ash, about 27 percent by weight Class C fly ash and about 31 percent by weight water.
25. The method of backfilling excavated trenches in roadways in accordance with claim 17, wherein said filler material in major amount is selected from the group consisting of Class F fly ash, coal combustion bottom ash and coal combustion boiler slag.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US643,894 | 1991-01-18 | ||
| US07/643,894 US5106422A (en) | 1991-01-18 | 1991-01-18 | Rapid-setting flowable backfill composition and method of using |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2041322A1 CA2041322A1 (en) | 1992-07-19 |
| CA2041322C true CA2041322C (en) | 2002-10-01 |
Family
ID=24582604
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2041322 Expired - Lifetime CA2041322C (en) | 1991-01-18 | 1991-04-26 | Rapid-setting flowable backfill composition and method of using |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US5106422A (en) |
| CA (1) | CA2041322C (en) |
Families Citing this family (46)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA2068362C (en) * | 1991-05-24 | 1994-05-31 | Clinton Wesley Pike | Asphaltic roofing material and method with fly ash filler |
| US5484479A (en) * | 1991-12-03 | 1996-01-16 | American Fly Ash Company | Method of manufacturing synthetic aggregate |
| US5766338A (en) * | 1991-12-03 | 1998-06-16 | American Fly Ash Company | Road base material containing fly ash |
| US5299692A (en) * | 1993-02-03 | 1994-04-05 | Jtm Industries, Inc. | Method and apparatus for reducing carbon content in particulate mixtures |
| US5436227A (en) * | 1993-05-27 | 1995-07-25 | Shell Oil Company | Soluble/insoluble alcohol in drilling fluid |
| US5361841A (en) * | 1993-05-27 | 1994-11-08 | Shell Oil Company | Drilling and cementing with blast furnace slag/polyalcohol fluid |
| US5361842A (en) * | 1993-05-27 | 1994-11-08 | Shell Oil Company | Drilling and cementing with blast furnace slag/silicate fluid |
| US5358044A (en) * | 1993-05-27 | 1994-10-25 | Shell Oil Company | Drilling and cementing with blast furnace slag/soluble/insoluble alcohol |
| US5337824A (en) * | 1993-06-28 | 1994-08-16 | Shell Oil Company | Coal slag universal fluid |
| US5439056A (en) * | 1993-06-28 | 1995-08-08 | Shell Oil Company | Coal slag solidification of drilling fluid |
| US5363918A (en) * | 1993-08-04 | 1994-11-15 | Shell Oil Company | Wellbore sealing with unsaturated monomer system |
| US5654352A (en) * | 1995-05-16 | 1997-08-05 | Maxflow Environmental Corp. | Air-entraining agent and method of producing same |
| NZ507156A (en) * | 1998-03-20 | 2002-04-26 | Anglo Operations Ltd | Method of producing a thickened slimes fraction blended with a tailings fraction |
| TR200003604T2 (en) * | 1998-06-05 | 2001-05-21 | Pirelli Cavi E Sistemi S.P.A. | A low thermal thermal resistance composition and a method for laying underground cables for carrying electrical energy. |
| US6644891B2 (en) | 1998-06-05 | 2003-11-11 | Pirelli Cavi E Sistemi S.P.A. | Composition having low thermal resistivity and method for laying underground cables for carrying electrical energy |
| US6334895B1 (en) * | 1998-07-20 | 2002-01-01 | The University Of Wyoming Research Corporation | System for producing manufactured materials from coal combustion ash |
| US6398848B1 (en) | 1999-04-26 | 2002-06-04 | American Electric Power Service | Method of separating a low density fly ash fraction from an overall group of fly ash |
| US6277189B1 (en) | 1999-08-31 | 2001-08-21 | The Board Of Trustees Of Southern Illinois University | Coal combustion by-products-based lightweight structural materials and processes for making them |
| US6485503B2 (en) * | 2000-05-19 | 2002-11-26 | Coapt Systems, Inc. | Multi-point tissue tension distribution device, a brow and face lift variation, and a method of tissue approximation using the device |
| US6916863B2 (en) * | 2000-11-14 | 2005-07-12 | Boral Material Technologies, Inc. | Filler comprising fly ash for use in polymer composites |
| US6428107B1 (en) | 2000-11-28 | 2002-08-06 | Inco Limited | Heat added to underground cemented fill to obtain both early and long term strength increases |
| KR100398076B1 (en) * | 2000-12-28 | 2003-09-26 | (주)청석엔지니어링 | Filling composition with a high fluidity containing bottom ash, and method for preparing the same |
| US6461424B1 (en) | 2001-02-21 | 2002-10-08 | Wisconsin Electric Power Company | Electrically conductive concrete and controlled low-strength materials |
| US6645290B1 (en) * | 2001-10-09 | 2003-11-11 | Ronald Lee Barbour | Settable composition containing cement kiln dust |
| WO2003070655A1 (en) | 2002-02-20 | 2003-08-28 | Flowable Fill, Ltd. | Controlled low strength flowable fill composition |
| AU2003252138A1 (en) * | 2002-08-02 | 2004-03-29 | Charles Edgar Price | Cementitious composition comprising bottom ash, methods of making and use thereof |
| ATE331353T1 (en) * | 2002-12-18 | 2006-07-15 | Cit Alcatel | METHOD AND SYSTEM FOR PROCESSING DATA BETWEEN A CIRCUIT ARRANGEMENT FOR RECOVERING A CLOCK SIGNAL AND A DATA SIGNAL AND A DATA PROCESSING UNIT IN ASYNCHRONOUS NETWORKS |
| WO2004108627A1 (en) * | 2003-06-04 | 2004-12-16 | Isg Resources, Inc. | Cementitious mixtures and methods of use thereof |
| US6821336B1 (en) | 2003-08-15 | 2004-11-23 | Wisconsin Electric Power Co. | Electrically conductive concrete and controlled low strength materials having carbon fibers |
| US7716901B2 (en) * | 2004-05-27 | 2010-05-18 | Price Charles E | Packaging for particulate and granular materials |
| US7914618B1 (en) * | 2004-07-28 | 2011-03-29 | VCNA Prairie IP, Inc. | Flowable cement-based material and methods of manufacturing and using same |
| US7381177B2 (en) * | 2005-09-22 | 2008-06-03 | C & D Waste, Ltd. | Flowable fill and flowable fill method for disposal of recovered waste |
| US7578881B2 (en) * | 2006-04-12 | 2009-08-25 | Wisconsin Electric Power Company | Electrically conductive concrete and controlled low strength materials having spent carbon sorbent |
| US7581903B1 (en) | 2006-06-08 | 2009-09-01 | Thermoforte, Inc. | Method of manufacture and installation flowable thermal backfills |
| US8377197B2 (en) | 2009-10-21 | 2013-02-19 | Reco Cement Products, LLC | Cementitious compositions and related systems and methods |
| US8882905B1 (en) | 2010-05-20 | 2014-11-11 | Flashfill Services, Llc | Recycled compositions for construction, and methods of utilizing and producing the same |
| US8747547B1 (en) | 2010-05-20 | 2014-06-10 | Flashfill Services, Inc. | Foamed compositions for reducing freeze-thaw heave risk, and methods of utilizing and producing the same |
| AU2012318528A1 (en) | 2011-10-07 | 2014-05-22 | Boral Ip Holdings (Australia) Pty Limited | Inorganic polymer/organic polymer composites and methods of making same |
| US8864901B2 (en) | 2011-11-30 | 2014-10-21 | Boral Ip Holdings (Australia) Pty Limited | Calcium sulfoaluminate cement-containing inorganic polymer compositions and methods of making same |
| US9932457B2 (en) | 2013-04-12 | 2018-04-03 | Boral Ip Holdings (Australia) Pty Limited | Composites formed from an absorptive filler and a polyurethane |
| AU2015301229A1 (en) * | 2014-08-04 | 2017-02-16 | Vac-Tron Equipment, Llc | Method and system to manufacture native soil flowable fill |
| US9802863B1 (en) | 2016-03-09 | 2017-10-31 | Flashfill Services, Llc | Accelerating set times of flowable fill compositions with dry calcium chloride, and methods of utilizing and producing the same |
| US10322971B1 (en) | 2016-04-21 | 2019-06-18 | MK1 Construction Services | Fast-setting flowable fill compositions, and methods of utilizing and producing the same |
| US10851016B1 (en) | 2017-02-28 | 2020-12-01 | J&P Invesco Llc | Trona accelerated compositions, and methods of utilizing and producing the same |
| US11434169B1 (en) | 2018-04-25 | 2022-09-06 | J&P Invesco Llc | High-strength flowable fill compositions |
| US10919807B1 (en) | 2018-04-25 | 2021-02-16 | J&P Invesco Llc | High-strength flowable fill compositions |
Family Cites Families (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2987411A (en) * | 1957-11-19 | 1961-06-06 | Corson G & W H | Light weight aggregate and method of making same |
| US3141857A (en) * | 1960-01-27 | 1964-07-21 | H Negendank Dr Ing | Foaming agent for making cellular concrete, and method of making same |
| DE2120775C2 (en) * | 1971-04-28 | 1979-11-22 | Wasag-Chemie Ag, 4300 Essen | Construction lightweight concrete |
| US4050950A (en) * | 1974-06-03 | 1977-09-27 | K-Krete, Inc. | Controlled density fill material containing fly ash |
| US4101332A (en) * | 1976-02-02 | 1978-07-18 | Nicholson Realty Ltd. | Stabilized mixture |
| US4321243A (en) * | 1980-08-05 | 1982-03-23 | Cornwell Charles E | Method of producing stabilized aqueous dispersions of silica fume |
| US4472198A (en) * | 1982-01-29 | 1984-09-18 | American Fly Ash Company | Process and system of wasting fly ash and product produced thereby |
| US4429456A (en) * | 1982-02-01 | 1984-02-07 | Irwin Zahn | Apparatus for inserting elements into a workpiece |
| US4501830A (en) * | 1984-01-05 | 1985-02-26 | Research One Limited Partnership | Rapid set lightweight cement product |
| US4815891A (en) * | 1984-10-26 | 1989-03-28 | Thermal Power Corporation | Method for repairing an opening formed in and below a section of pavement |
| US4624711A (en) * | 1984-11-07 | 1986-11-25 | Resource Technology, Inc. | Light-weight aggregate |
| NL8501137A (en) * | 1985-04-18 | 1986-11-17 | Aardelite Holding Bv | METHOD FOR PRE-TREATING FLYES |
| US4859344A (en) * | 1986-05-08 | 1989-08-22 | The Dow Chemical Company | Method for underground support and removal of hazardous ions in ground waters |
| US4741834A (en) * | 1986-05-08 | 1988-05-03 | The Dow Chemical Company | Method for underground support and removal of hazardous ions in ground waters |
| US4804147A (en) * | 1987-12-28 | 1989-02-14 | Waste Management Energy Systems, Inc. | Process for manufacturing aggregate from ash residue |
| US4917733A (en) * | 1988-11-14 | 1990-04-17 | Hansen David L | Pozzolanic mixture for stabilizing landfill leachate |
-
1991
- 1991-01-18 US US07/643,894 patent/US5106422A/en not_active Expired - Lifetime
- 1991-04-26 CA CA 2041322 patent/CA2041322C/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| US5106422A (en) | 1992-04-21 |
| CA2041322A1 (en) | 1992-07-19 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA2041322C (en) | Rapid-setting flowable backfill composition and method of using | |
| Ling et al. | Global perspective on application of controlled low-strength material (CLSM) for trench backfilling–An overview | |
| Pierce et al. | Potential of scrap tire rubber as lightweight aggregate in flowable fill | |
| US10913688B2 (en) | Flowable compositions and methods of utilizing and producing the same | |
| US9139475B2 (en) | Grout for filling a micro-trench | |
| US4050950A (en) | Controlled density fill material containing fly ash | |
| US4062195A (en) | Method of bedding a conduit using controlled density fill material | |
| CN113636809A (en) | Collapsible loess aggregate filling material | |
| WO2007026977A1 (en) | Soil rock layer's composition, constructing method thereof and road construction method thereby | |
| Moulton et al. | Utilization of ash from coal burning power plants in highway construction | |
| Dockter | Comparison of dry scrubber and class C fly ash in controlled low-strength material (CLSM) applications | |
| US4050258A (en) | Method of building embankments and structure supports of backfilling | |
| Kaneshiro et al. | Controlled Low Strength Material for Pipeline Backfill— Specifications, Case Histories and Lessons Learned | |
| Radhakrishna | Fluidized cable thermal backfill | |
| Riggs et al. | Specifications and use of controlled low-strength material by state transportation agencies | |
| Brewer | Controlled low strength materials (CLSM) | |
| Abdel-Halim et al. | Rehabilitation of the spillway of Sama El-Serhan dam in Jordan, using roller compacted concrete | |
| Rossow | Fly ash facts for highway engineers | |
| SU1673677A1 (en) | Method for building antifiltration screen of dam | |
| Ghataora et al. | Use of pulverized fuel ash in trench backfill | |
| Lundvall | Mitigation of roadway settlement above buried culverts and pipes | |
| Howard¹ | Proposed standard practice for installing buried pipe using flowable fill | |
| Du | Laboratory investigations of controlled low-strength material | |
| JPH0790272A (en) | Super-plasticizable back-filling material and back-filling process | |
| Ghataora et al. | Assessment of the performance of trial trenches backfilled with cementitious materials |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed | ||
| MKEC | Expiry (correction) |
Effective date: 20121202 |