WO1995027685A1

WO1995027685A1 - Filler for concrete and similar building material

Info

Publication number: WO1995027685A1
Application number: PCT/NL1995/000133
Authority: WO
Inventors: Hendrikus Arnoldus Wilhelmus Cornelissen
Original assignee: N.V. Kema
Priority date: 1994-04-08
Filing date: 1995-04-10
Publication date: 1995-10-19
Also published as: NL9400564A; JPH09511482A; EP0758308A1; CA2186248A1

Abstract

The invention relates to a filler for concrete or similar building material comprising: physically comminuted particles of ash, such as fly ash and or fuel ash.

Description

FILLER FOR CONCRETE AND SIMILAR BUILDING MATERIAL

This invention relates to a filler for concrete and similar building material and more specifically to a filler suitable for, high performance, durable, strong and highly fluid concrete. Concrete is a conglomerate of sand, gravel and broken stones for example which together are called an aggregate, whereby this aggregate is embedded in a matrix such as Portland cement or blast furnace cement. Concrete is one of the most important building materials and is used in great quantities.

Constructions which are made of high performance, durable, strong and highly fluid concrete are stronger, more stable, have a high workability and can be built more slim- lined. Such concrete offers a greater compressive strength, in the region of 80-120 Newton/mm², and a greater durability compared to normal concrete.

At this moment most high performance, durable, strong and highly fluid concrete is produced with microsili- ca as filler material. A problem with this, is that such filler material is expensive however, the high performance, durable, strong and highly fluid concrete is in turn expen¬ sive, making it uneconomical to use for a lot of construc¬ tion work.

The present invention concerns the utilization of microminiaturized ash for the production of high perfor¬ mance, durable, strong and highly fluid concrete, which can be utilized on a much greater scale than presently.

Ash, such as fly ash and fuel ash, in particular coal fly ash, strongly resembles microsilica with respect to composition and qualities, with the exception of particle size. The particle size of coal fly ash lies mainly in the range of 10-300 μm, whilst the particle size of microsilica is mostly less than 1 μ. Coal fly ash with a particle size within this range improves the characteristics of concrete and similar building materials when used as a filler. However for the _^utilization as filler for high performance, durable, strong and higly fluid concrete, it is desirable that the coal fly ash particles are reduced in size, because the particles are too coarse in order to realize an ideal stacking of the particles and dense cement structure such as occurs with microsilica. The utilization of fly ash in building materials is already known, for instance the GB patent specification GB 1 362 372 teaches a cement comprising a particulate mate¬ rial derived from pulverised fuel ash by attrition and/or fragmentation of the particles by mutual bombardment; Chemi- cal Abstracts volume 117 No. 4 teaches a steel bar reinfor¬ ced concrete with high strength and improved concrete steel adhesion, whereby the concrete contains fine sieved parti¬ cles of fly ash from coal combustion; and a report of the fourth CONMET/ACI International Conference on Fly Ash, Silica Fume, Slag and Natural Puzzolanes in Concrete (1992) May, Istanbul, Turkey, gives attention to concrete strength enhancement due to classified fly ash obtained by air sepa¬ ration methods.

The methods for obtaining fly ash particles detai- led in the prior art are however relatively inefficient and uneconomical.

According to a first aspect, the present invention provides a filler for concrete or similar building material, comprising physically comminuted ash particles, wherein the ash is, preferably, coal fly ash.

Coal fly ash is a fine powder which substantially consists of ball shaped glass like particles. The powder mainly consist of Si0₂ and A1₂0₃. Coal fly ash is obtained in great quantities by means of electrostatic or mechanical separation of material particles from the waste gas of furnaces stoked with coal powder. Such coal fly ash can be roughly 100 times cheaper produced than micro-silica which is presently used as filler material for concrete and simi¬ lar building materials.

The grain size of coal fly ash thus obtained lies between 10-500 μm, with a D(50) of roughly 20-50 μm and a D(90) of roughly 80-300 μm. (This means that 50 % of the particles have a diameter smaller than 20-50 μm and that 90 % of the particles have a diameter smaller than 80-200 μm.) Coal fly ash has puzzolane qualities. This means that the material develops hydraulic qualities when it is activated in a basic environment (pH > 12) . Under hydraulic qualities is understood the ability of a material to react with water with the formation of insoluble in water stable compounds.

Coal fly ash also serves as filler material. This means that the material fills up the hollow cavities in the concrete (pores) . Besides this, coal fly ash improves the workability of concrete.

It appears from studies that the qualities of concrete improve, the finer the coal fly ash is. In practi- cal experiments, coal fly ash was physically comminuted, in order to yield a super fine product (reduced coal fly ash) . This physically comminuted coal fly ash preferably has a grain size of between 0-5 μm, and more preferably a D(50) of between 0.5-3 μm. This physically communited fly ash has the advan¬ tage that it is more reactive since its specific surface and the puzzolanity is greater. The filler qualities of the reduced coal fly ash are also improved, whereby the smaller pores in the concrete can now be filled. Accordingly a high performance, durable, strong and highly fluid concrete is yielded with a high initial strength which is easy to pro¬ cess and pour with little compaction energy. This yields the advantage that the construction time for a certain project, utilizing this concrete, is substantially shorter than with projects wherein such concrete is not used.

It is noted that the ash is preferably coal fly ash obtained from the waste gasses of an installation stoked with powder charcoal, but it will be obvious that ash can also be obtained from other processes, such as ash collected with electrostatic filters from burning municipal waste and sludge, and other fuel ashes.

The present invention further provides, according to a second aspect, concrete or similar building material comprising as filler material, physically comminuted ash, particularly coal fly ash, particles, preferably with a diameter substantially of 5 μm or smaller; the use of physi¬ cally comminuted ash, particularly coal fly ash, as a filler for concrete and a method for production of concrete or similar building material comprising bringing together physically comminuted ash particles, particularly coal fly ash particles, with relatively small diameters with the basis composition of the concrete or similar building mate- rial.

According to a further aspect of the present invention, there is provided a method for the production of a filler material for concrete or similar building material. Micronization of ash can preferably occur with known mechanical mill methods, such as ball mills (dry or wet pulverization) , jet stream mills (dry pulverization) and vibration mills, and most preferably can be carried out in a pearl mill (wet pulverization) , for optimum results, in order to yield a product of physically, comminuted fly ash which can be supplied both in the form of a slurry and as a solid. This product is cheaper to produce than known concre¬ te filler materials, whereby high performance, durable, strong and highly fluid concrete, having physically comminu¬ ted ash as filler material, can be utilized on a larger scale than is at present.

Furthermore the present invention provides for the use of pulverizing mills for physically comminuting ash particles, particularly coal fly ash particles, and the use of concrete, or similar building materials with physically comminuted ash filler, particularly physically comminuted coal fly ash particles, in the construction industry. The following experimental descriptions, results and examples air.; to clarify the present invention, but are not meant to limit its range.

Coal fly ash was selected from a low N0_χ furnace from the Maasvlakte-centrale in the Netherlands. The chemi¬ cal and physical composition of this coal fly ash is given below in table 1.

Table 1

The particle size distribution of this start material is given in figure 1.

100 kg of coal fly ash start material was mechanically pulverized in a DRAIS pearl mill (PMC 5 TEX) .

The material was pulverized in an aqeous suspensi¬ on with a solid material content of 35 %. The average pulve- ration time for a loading of 30 kg was 5 hours. The particle size of the comminuted fly ash, is given in figure 2. The comminuted ultra fine fly ash particles so obtained, were characterized by the inventors in order to obtain an impression of their qualities with respect to microcilica. In this comparison, the finest fraction of fly ash particles, separated out from the start material by means of air separation, the physically comminuted in the pearl mill fly ash particles and microsilica particles were taken, the results of which are shown in Table 2.

Table 2 start air physically micro¬ material separated comminuted silica

(SM) particles particles (MS)

(AS) (PC)

D(50) μm 21.6 9.9 1.6 0.2

D(90) μm 99.0 36.0 3.1 0.5

Grading 525 994 5390 modulus 1/mm specific 1.0 1.5 6.3 20.2 surface m²/g form round round broken round

Figure 3 shows an overview of the particle size distribution of these materials used for comparison.

The final result of this pulverization experiment yielded an end product with a D(50) = 1.6 μm and a D(90) = 3.1 μm.

Figures 4 and 5 show electron micrographs of the coal fly ash particles obtained after comminution with the pearl mill, taken at 10 μm and 3 μm respectively.

Figure 15 shows an electron micrograph of air separated fly ash particles taken at 10 μ for comparison. In order to further refine the pulverization process, a pre-pulverization step can be incorporated. This comminuted, ultra fine coal fly ash, obtained via the pearl mill, was used for a laboratory research program carried out into mortar and concrete compositions.

Design, production and testing of mortar compositions

In order to obtain a better insight into the influence of comminuted, ultra fine fly ash on the hydration of cement, laboratory research was carried out, by the inventors, into the strength development and binding time development of mortar samples.

The mortar for the strength development was produ¬ ced according to DIN-IN 196 part 1, and had the following composition:

- cement type: 22 weight % ENCI Portland cement A - sand: 67 weight % Normen sand according to DIN

- water: 11 % water/cement ratio 0.50

- filler material: 5/10/15 weight %

- consistancy: Hagermann 170 ± 10 mm.

The filler material was added to the above compo¬ sition in a slurry form.

As filler material, the comminuted, ultra fine coal fly ash obtained by the pearl mill was used, and micro- silica, and a mixture of the comminuted, ultra fine coal fly ash obtained via the pearl mill and the microsilica were also used for comparison.

Compressive strength tests were carried out on the following four mortar mixtures: l) Portland cement A (Reference material)

2) Portland cement A 4- 5, 10, 15 weight % physi¬ cally comminuted, ultra fine coal fly ash particles.

3) Portland cement A + 5, 10, 15 weight % micro silica. 4) Portland cement A + 5, 10, 15 weight % of a mixture of 50 weight % microsilica and 50 weight % physi¬ cally comminuted ultra fine coal fly ash particles. Table 3 gives the results of the compressive strength at intervals of 3, 7, 28 and 91 days of the mortar samples. In order to obtain the desired consistancy, a superplastifier was added to some of the samples.

Table 3 sample SP Hager- strength strength strength sσength density code (g) mann 3 days 7 days 28 days 91 days kg/m^J mm N/mm² N/mm² N/mm² N/mm²

REF 0 174 27.6 373 51.2 65.9 2300

PC05 0 170 31.1 41.8 56.0 71.4 2280

PC10 0.5 173 33.2 44.3 603 77.2 2266

PC15 1.1 169 33.8 483 63.4 79.6 2263

MS05 1.7 173 31.0 40.8 59.2 70.5 2235

MS10 3.4 173 31.2 42.3 61.7 75.5 2214

MS 15 5.1 172 323 46.2 68.7 80.2 2221

PCMS05 0.9 174 30.6 41.9 593 70.2 2250

PCMS10 2.0 174 31.9 43.0 64.2 783 2242

PCMS15 3.0 173 32.8 42.4 66.9 81.7 2227

REF = reference ; MS = microsilica

PC = physically comminuted, ultra fine coal fly ash particles; SP = Superplastifier

PCMS = 50 weight % physically comminuted, ultra fine coal fly ash particles / 50 weight % microsilica

From these measurements it can be concluded that the compressive strength of the samples increases on the addition of physically comminuted ultra fine fly ash. The more physically comminuted, ultra fine fly ash is added, the greater the compressive strength becomes. Figures 6 and 7 show graphically the compressive strength results.

Binding time development tests were carried out on _^the following three mortar mixtures: 1) Portland cement A (Reference)

2) Portland cement A plus 2-4-6-8-10-12-14 weight % air separated fly ash

3) Portland cement A plus 2-4-6-8-10-12-14 weight % physically comminuted fly ash obtained in the pearl mill. Table 4 gives an overview of the binding type measurements of the mortars.

Table 4 sample start end sample start end (h) binding binding binding binding

(time.hours) (time,hours) (time, hours) (time.hours)

AS-02 2.15 2.45 PC-02 2.15 3.00

AS-04 2.15 3.00 PC-04 2.15 3.00

AS-06 2.00 2.45 PC-06 2.15 3.00

AS-08 2.30 3.00 PC-08 2.15 3.00

AS-10 2.30 3.00 PC-10 1.45 2.45

AS-12 2.30 3.15 PC-12 1.45 2.30

AS-14 2.30 3.15 PC-14 1.45 2.30 reference 2.00 2.30

AS = air separated coal fly ash D(50) = 10 μm;

PC = physically comminuted ultra fine coal fly ash particles 02-14 = weight % filler; D(50) = 1,5 μm

From these measurements it can be concluded that air separated fly ash, at all the percentages (2-14) , had a slowing down effect on the hydration of cement. With percentages of greater than 8 %, it can be seen that physically comminuted, ultra fine fly ash parti¬ cles had an accelerating effect on the hydration of cement. This shows the reactivity of physically comminuted, ultra fine fly ash particles as a filler material.

Design, production and testing of cement mixtures

Three concrete mixtures were designed and produ¬ ced, using physically comminuted (in the DRAIS Pearl mill) ultra fine fly ash particles.

These concrete mixtures were as follows:

1. Cement type : Portland cement A ^D _max ^{of tne} mineral aggregates : 31,5 mm additional material : sand/river aggregate

2. Cement type : Portland cement A ^D _max ° -^ne mineral aggregates : 16 mm additional material : sand/river aggregate

3. Cement type : Portland cement C ^D _max ° ^tne mineral aggregates : 16 mm additional material : sand/river aggregate

(this mixture having a composition equivalent to that of high strength concrete which has been practically tested in former research projects)

Comparison tests are also to be carried out by the inventors into the cement mixture composition used in the building of a construction from high quality concrete in Breda, the Netherlands.

A summary of the concrete mixture samples upon which tests were carried out is given in table 5. Table 5 mixture 1 mixture 2 mixture 3 cement type PC-A PC-A PC-C content kg/πv⁵ 360 360 450 addition sand/ sand/ sand/ aggregate aggregate aggregate

D- 313 16 16

WCF 032 032 032

WBF (k=0.2) 0.28-031 0.28-031 0.28-030

% filler matenal 1 (AS) 05/10/15 05/10/15 -

% filler matenal 2 (PC) 05/10/15/20 05/10/15/20 10/20

% filler matenal 3 (MS) 05/10/15 05/10/15 -

% filler matenal 4 (PC/MS) 05/10/15 05/10/15 -

% auxiliary substance (SP) 2.5 2.5 2.5 BV 80/20

AS = air separated fly ash particles D(50) = 10 μm;

PC = physically comminuted, ultra fine coal fly ash particles D(50) = 1.5 μm

MS = microsilica D(50) = 0.2 μm; PC/MS = 50/50 mixture air separated fly ash particles/physically comminuted, ultra fine coal fly ash particles

% filler matenal = weight % of the cement

% auxiliary substance = superplast weight % of the cement weight (Cugla)

WCF = water/cement ratio WBF = water/binder ratio k = 0.2 means that 20 % of the filler material weight is a binder

Concrete mixtures using air separated fly ash particles, microsilica and a mixture thereof were used for comparison. Filler material was added as an aqueous slurry after the slurry had been well mixed five minutes before addition. 100 mm cubes were made from the three different concrete mixtures, which were stored, after form stripping in a "wet" room at 20°C ± 2°C at a relative humidity of > 95%.

Two reference mixtures were chosen for both mixtu¬ re 1 and mixture 2, namely REF1 with an equivalent water/ce¬ ment ratio and REF2 with a workability similar to the worka- bility of the mixtures with 5-10 weight % physically commi¬ nuted, ultra fine coal fly ash particles (pearl mill) .

In order to test whether physically comminuted, ultra fine coal fly ash particles could be used as a suit¬ able filler material in concrete, tests were carried out on both the concrete mortar and the hardened concrete. In order to do this, a number of aspects had to be taken into consi¬ deration, namely:

- the workability and stability of the concrete mortar,

- the compression strength development of the concrete, - the durability of the concrete.

In order to make a judgement on these, a number of tests were carried out, namely for:

1. workability and stability - slump

- flow measurement

- vibration measurement

- bleeding

2. compressive strength development

- the compression strength was measured after 1-2-3- 7-28-91 days

3. durability - water penetration after 28 days

- mercury porosimetry

- temperature development All the tests were carried out according to the NEN, ISO or DIN regulations apart from the fluid measure¬ ment, mercury porσsimetry and temperature development.

Results of the concrete tests

1. Workability and stability

Tables 6 and 7 show the results of the slump, fluid measurement, vibration measurement and bleeding of the mixtures l and 2 respectively. The slump was determined according to NEN 5956, the vibration measurement according to NEN 5957 and the bleeding according to NEN-EN 480. The fluid measurement was determined substantially according to NEN 5957.

Table 6 sample slump flow vibration bleeding code mm measurement measurement % mm mm

REF1 170 320 420 < 1

REF2 220 470 540 9

AS05 190 330 420 < 1

AS10 230 430 520 < 1

AS15 250 500 570 < 1

PC05 230 420 520 < 1

PC10 240 540 600 < 1

PC15 270 610 700 < 1

PC20 250 510 610 < 1

MS05 220 400 500 < 1

MS10 220 350 470 < 1

MS15 190 320 440 < 1

PC/MS05 230 490 580 < 1

PC/MS10 260 600 700 < 1

PC/MS15 270 600 700 < 1

Filler material: AS = air separated fly ash particles; PC = physically comminuted, ultra fine coal fly ash particles; MS = microsilica; PC/MS = mixture 50 weight % / 50 weight % physically commi¬ nuted, ultra fine coal fly ash particles/microsilica REF1/2 = reference concretes; ^D _max mineral aggregate = 31,5 mm Conclusions from Table 6:

From the workability derived from the flow measu¬ rement, it can be concluded that the samples with a high percentage of physically comminuted ultra fine coal fly ash particles are highly fluid.

The fluidity of the microsilica samples, reduced when more filler material was added.

The samples with a mixture of microsilica and ultra fine coal fly ash particles had the same workability as samples with physically comminuted ultra fine coal fly ash particles alone.

All the samples with filler material showed virtu¬ ally no bleeding. Table 7 shows the workability and stability of mixture 2, maximum diameter (D^) of the mineral aggregates = 16 mm

Table 7 sample slump flow vibration bleeding code mm measurement measurement % mm mm

REF1 140 - - 2

REF2 170 330 490 8

AS05 < 10 - - < 1

AS10 180 370 450 < 1

AS15 195 400 480 3

PC05 160 340 480 8

PC10 210 390 530 < 1

PC15 220 400 610 < 1

PC20 250 380 610 < 1

MS05 200 400 490 4

MS10 200 380 490 < 1

MS15 200 380 510 < 1

PC/MS05 180 360 430 < 1

PC/MS10 230 430 530 < 1

PC/MS15 230 430 550 < 1

Filler material: AS = air separated fly ash particles; PC = physically comminuted, ultra fine coal fly ash particles MS = microsilica; PC/MS = mixture 50 weight % / 50 weight % physically commi¬ nuted, ultra fine coal fly ash particles/microsilica 05, 10, 15, 20 = weigth % filler D (mineral aggregates) = 16 mm Conclusions from Table 7:

The mixtures with a D^ of 16 mm had a lower workability -* than the mixtures with a D_mma_=>x_v of 31.5 mm.

Figure 8 and 9 graphically represent the flow measurement, (an indication of workability) for mixtures l and 2.

2. Development of compressive strength The compression strength was measured according to

NEN 5968 and concerned an average of three compression tests. Tables 9, 10 and 11 show the compressive strength development for the mixtures 1, 2 and 3, carried out at 1, 2 , 3, 7, 28 and 91 days respectively.

Table 9 sample strength strength strength strength strength strength code 1 day 2 days 3 days 7 days 28 days 91 days (N/mm²) (N/mm²) (N/mm²) (N/mm²) (N/mm²) (N/mm²)

REF1 30.4 46.1 53.9 68.7 81.8 90.6

REF2 8.8 32.1 40.8 49.2 64.2 69.3

AS05 24.7 41.5 46.9 64.9 83.6 923

AS 10 23.6 42.1 49.7 64.9 81.6 93.7

AS15 20.4 43.0 50.1 623 79.8 92.4

PC05 31.4 45.90 50.5 653 80.0 85.9

PC10 36.0 50.4 58.9 66.2 86.2 96.0

PC15 22.5 45.4 53.2 69.6 95.8 105.9

PC20 26.0 47.6 53.5 - - -

MS05 323 49.1 57.5 69.4 94.0 953

MS10 35.1 49.0 55.9 70.6 96.6 103.9

MS 15 353 48.8 57.4 793 993 104.8

PC/MS05 28.6 45.0 54.2 66.7 86.5 92.9

PC/MS 10 28.0 47.6 54.8 71.4 93.2 993

PC/MS 15 32.0 50.7 59.2 73.9 97.1 103.4

Filler material: AS = air separated fly ash particles; PC = physically comminuted, ultra fine coal fly ash particles MS = microsilica; PC/MS = mixture 50 weight % / 50 weight % physically commi¬ nuted, ultra fine coal fly ash particles/microsilica 05, 10, 15, 20 = weight % filler D (mineral aggregates) = 31,5 mm Table 10

sample strength strength strength strengdi strength code 1 day 3 days 7 days 28 days 91 days

(N/mm²) (N/mm²) (N/mm²) (N/mm²) (N/mm²)

REF1 17.7 49.7 61.8 75.1 84.4

REF2 12.2 43.1 55.0 68.5 783

AS05 213 58.2 70.0 84.4 95.5

AS 10 10.2 49.0 62.2 75.7 90.4

AS 15 9.8 47.4 593 74.9 91.1

PC05 7.1 503 62.1 78.1 89.2

PC10 15.9 51.0 633 58.0 96.9

PC15 26.4 60.7 753 100.2 113.5

PC20 26.9 58.4 73.9 100.8 113.9

MS05 27.7 57.4 73.6 96.0 107.5

MS 10 303 59.8 75.4 105.9 115.1

MS 15 30.7 58.9 76.7 106.0 114.9

PC/MS05 13.8 51.7 64.1 84.4 95.0

PC/MS 10 18.7 54.8 71.5 97.0 106.9

PC/MS 15 22.9 58.5 76.7 104.6 116.5

Filler material: AS = air separated fly ash particles; PC = physically comminuted, ultra fine coal fly ash particles MS = microsilica;

PC/MS = mixture 50 weight % / 50 weight % physically commi¬ nuted, ultra fine coal fly ash particles/microsilica 05, 10, 15, 20 = weight % filler D (mineral aggregates) = 16 mm Table 11

sample strength strength strength strength strength code 1 day 3 days 7 days 28 days 91 days

(N/mm²) (N/mm²) (N/mm²) (N/mm²) (N/mm²)

PC10 613 82.1 89.4 1043 113.6

PC20 54.5 74.7 86.1 100.8 111.5

Filler material:

PC = physically comminuted, ultra fine coal fly ash particles;

Conclusions from Tables 9, 10, 11:

- The compressive strengths after 28 days of the mixtures with a D_maχ of 31.5 mm and 15 % filler material PC, MS and PC/MS are 10 to 20 % higher than that of reference 1;

- The same mixtures with a Dm„.a-_γx of 16 mm have com- pressive strengths 30 to 40 % higher than reference 1;

- The filler material function of AS does not yield any increase in compressive strength; - The optimum percentage of filler material for a

^D _max ^of 31.5 mm was for ultra fine fly ash, 15 %, microsilica 15 % and for PC/MS 15 %; and

- For D_max - 16 mm, the optimal filler material percentage was 10 %; - The end strength, after 91 days of the mixture with a D-^_j. = 16 mm is roughly 10 % higher than that of the mixtures with a D-m„a₌x_v of 31.5 mm.

The results of mixture 3 show that with a higher cement content, the filler material has a positive influence on the initial strength. The initial strength was twice as high as the comparable mixture 2. A filler material percen¬ tage of 20 % clearly yields lower compressive strength results than a filler material percentage of 10 %.

Figures 10, 11 and 12 show graphically the com- pressive strength results. 3. Durability

The durability of concrete is described as the resistance against environmental influence, whereby the concrete has a long life span. For a long life span of concrete, good design and a good realization are of great importance. The design of a concrete mixture begins with an optimal mixing of the different components in order to achieve concrete with a very closed structure. In order to predict life span and durability, a number of tests were carried out by the inventors, namely - the water penetration test for determining permeability,- mercury porosimetry for determining porosity and the pore distribution of the concrete, -petrography for visualizing the components after hardening and temperature development for predicting crack formation as a result of thermal stress.

Water penetration Water penetration was determined on cube samples of mixtures 1 and 2, after 28 days hardening according to DIN 1048 part 5, the results of which are reproduced in table 12.

Table 12 Water penetration in mm

sample code mixture 1 mixture 2

REF1 - 44

REF2 - 42

AS05 3 8

AS10 0 10

AS15 3 30

PC05 5 27

PC10 2 31

PC15 1 10

PC20 - 11

MS05 0 10

MS10 2 2

MS15 6 10

PC/MS05 3 21

PC/MS10 4 4

PC/MS15 5 6

Filler material: AS = air separated fly ash particles; PC = physically comminuted, ultra fine coal fly ash particles MS = microsilica; PC/MS = mixture 50 weight % / 50 weight % physically commi¬ nuted, ultra fine coal fly ash particles/microsilica 05, 10, 15, 20 = weight % filler D (mineral aggregates) = 16 mm - Mercury porosimetry

Mercury porosimetry was used to determine total _^porosity, pore size and pore distribution of sawn off sample pieces, and was determined by means of the intrusion of mercury into the pores under a strength of 2000 bar. This yielded information about the total pore system of the sample and was therefore usefull in estimating durability. Porosimetry measurements were carried out on mixture 2, Ω_mx = 16 mm, the results of which are given in table 13.

Table 13

samples pore pore pore porosity specific average volume volume volume ≤ 15 μm surface radius

≤ 15 μm > 15 μm total % pore pore run mπrVg m Vg mπvVg m²/g

REF2 193 0.9 20.2 4.7 2.10 19.9

AS15 15.8 0.9 16.8 3.9 1.85 19.9

PC15 20.8 0.5 213 5.0 2.64 15.7

MS 15 15.7 1.7 17.4 3.8 1.73 15.6

PC/MS 15 16.9 0.4 173 4.1 2.29 15.8

Filler material: AS = air separated fly ash particles;

PC = physically comminuted, ultra fine coal fly ash particles

MS = microsilica;

PC/MS = mixture 50 weight % / 50 weight % physically commi¬ nuted, ultra fine coal fly ash particles/microsilica

(where total pore volume = pore volume + pore volume) (< 15 μm) (> 15 μm)

15 = weight % filler material From these measurements it can be concluded that the total porosity does not decrease after adding physically comminuted ultra fine fly ash particles. The size of the process became smaller.

Temperature development

Temperature development is a measurement of the amount of heat released from cement during hydration.

For a managable temperature gradient of the harde- ned concrete it was desirable that the heat release took place gradualy.

The temperature development of the mixtures was measured with thermo couples in sample cubes.

The results are quantified in table 14.

Table 14

Filler material: AS = air separated fly ash particles; PC = physically comminuted, ultra fine coal fly ash; MS = microsilica; PC/MS = mixture 50 weight % / 50 weight % physically commi¬ nuted, ultra fine coal fly ash particles/microsilica mixt.3-10/20 = mixture 3 10/20 weight % physically comminu¬ ted ultra fine coal fly ash particles

Conclusion from Table 14:

T_totat yielded information about the total amount of released heat and is a quantification of the average tempe¬ rature per hour. The start temperature of D_maχ 16 mm was higher than that of D_ιnaχ 31.5 mm, because this measurement was taken in a period in which the environmental temperature was higher. The effect of this on the T_total was on average 10 %.

From the temperature measurements it appears that the heat development with mixture 2, D.^-. = 16 mm is greater than with mixture 1, Ω_mx = 31.5 mm.

Mixture 3 had a higher temperature development and a higher heat development.

From these results, it can be seen that in general the heat development reduces as the filler material percen¬ tage is increased. On comparing the reference concrete without filler material, the heat development of the mixtu¬ res 1 and 2 with a filler material percentage of 15 % physi¬ cally comminuted, ultra fine fly ash particles (pearl mill) is more favourable, so that it can be concluded that a large temperature gradient of the designed mixtures is not to be expected.

Figures 13 and 14 graphically show the temperature development for the mixtures with a D_rπaχ of 31.5 mm and a D of 16 mm.

The present invention is not limited by the above description, but is rather determined by the scope of the following claims.

Claims

1. Filler for concrete or similar building materi¬ al comprising:

- physically comminuted particles of ash, such as fly ash and or fuel ash.

2. Filler according to claim 1, wherein the fly ash is coal fly ash.

3. Filler according to claims 1 or 2, wherein the fly ash particles have a diameter of 5 μm or smaller.

4. Concrete or similar building material compri- sing as filler material physically comminuted particles of ash, such as fly ash and or fuel ash.

5. Concrete or similar building material according to claim 4, wherein the physically comminuted ash particles originate from coal fly ash, and have a diameter of 5 μm or smaller.

6. Concrete or similar building material according to claims 4 or 5 having a compressive strength of at least 80 N/mm².

7. Method for producing filler for concrete or a similar building material comprising physically comminuting particles of ash, such as fly ash and or fuel ash.

8. Method according to claim 7, wherein the ash particles, in particular coal fly ash particles, are physi¬ cally comminuted by pulverization in a pearl mill.

9. Use of physically comminuted ash particles, such as fly ash and or fuel ash particles, as filler for concrete or a similar building material, wherein the parti¬ cles have a diameter of 5 μm or smaller.

10. Method for producing concrete or similar building material comprising bringing together ash parti¬ cles, such as fly ash and or fuel ash, physically comminuted according to claims 7 or 8, with a base composition of the concrete or similar building material.

11. Ash particles, such as fly ash and or fuel ash particles, characterized in that they have been physically comminuted by pulverization, in particular in a pearl mill.

12. Use of a pearl mill for comminuting ash parti¬ cles, in particular coal fly ash particles.

13. Use of concrete or similar building material obtained by the method according to claim 10, for building constructions.