FI92580B - Method for the production of light crushed stone and its use - Google Patents

Description

92580

The present invention relates to a process for the production of light crushed stone by forming a mixture of fly ash, which may optionally contain other power plant ash or fine industrial by-products and waste, a calcium-containing binder such as cement and / or lime, water and a porosifier. .

10 Fly ash is generated in large quantities, especially in coal-fired power plants. Its storage and disposal has become a serious problem and therefore considerable resources have been devoted to developing the further recovery of fly ash. It is e.g. proposed for use either as such or as a mixture with a binder such as cement or lime, e.g. as a soil filler as a binder for concrete, cement and mortar, as a raw material for the production of sintered light aggregates, etc.

20 FI publication 81 559 describes a mass intended for landfill and its production method, which is characterized by its easy flowability and thus fills well-filled cavities and gaps around cables and pipes, for example, but on the other hand can be easily removed with an excavator or even with a shovel even after a long time. Such a mass is obtained by mixing 7-15% of cement and 95-85% by weight of fly ash with possibly small amounts of other waste products, as well as 400-500 l of water / m3 and a foaming agent in an amount so that the air content of the finished product becomes 5-25% by volume. The pulp is usually prepared at the place of use, or during transport to the place of use, so that it is ready to be pumped immediately after mixing.

Methods are also known for using fly ash as a raw material for the production of pelletized and sintered light gravel-type aggregates and for using them as 2,92580 as a aggregate in building elements. The disadvantages of this method are, above all, the energy required for pelletization and combustion, as well as the low residual activity of the pelletized product for some uses.

5

Although the solutions proposed above are able to recover some of the fly ash produced, they are far from sufficient, and one of the major problems for coal-fired power plants has been the environmentally sound disposal of unused fly ash and 10 other ashes. Fly ash is generated in large quantities during the cold season when demand is at its lowest. The unused ash is now exported as such, or mixed with water, to the so-called 15 disposal area, which is usually demarcated near the power plant.

Also known is the method ("The Use of Fly Ash in the Production of Bricks, Mortars and Lightweight Aggregates for Concretes", Drojlc, S. et al., First International Confe-20 rence for the Use of Fly Ash, Silica Fume, Slag and other Mineral By-Products in Concrete, July 31-August 5, 1983, Montebello, Quebec, Canada) where power plant ash has been used directly in the power plant storage area. In this case, the fly ash is first applied in the storage area in 25 layers, on top of which slaked lime in the form of powder is applied in an amount of 17% by weight, based on the ash, and these are mixed with a tractor. More water is added to the already wet mass and the mass is compacted. Fly ash is re-applied to this layer, then lime and the mixing and compacting process is repeated. After hardening for three months, the mass is crushed into an aggregate, for example for concrete. The local mixing technique used in this method is e.g. uneconomical due to its labor intensity and gives a highly inhomogeneous 35 and product of varying strength. It also cannot take advantage of the heat contained in the newborn fly ash and because of its slow and

II

92580 3 evenly it is difficult to make optimal use of the method so that the production rate of fly ash is in balance with the production rate of the finished unit.

5

According to the invention, a method has now been developed which enables the optimal year-round utilization of power plant ashes, in particular fly ash, on site immediately in connection with the generation of the ash in a manner which is both technically simple and labor-intensive. The method makes it possible to produce lightweight crushers with very good strength properties, which are particularly suitable as aggregates for building elements, but also, for example, for the rehabilitation and filling of road bases. The properties of the produced crushed stone can be well utilized when used as a aggregate for lime sand elements, so-called light blocks, whereby the final strength of the finished lime sand element is many times higher than the strength of the raw material.

These objects are achieved by the process according to the invention, characterized in that the mixture is formed immediately during ash formation, in particular in connection with a power plant, and that 1-50% by weight of calcium-containing binder is used, based on the total ash or ash component and binder, and on this dry powder mixture. 20-50% by weight of water and 0.01-1% by weight of poroser, stirring is continued to porate the mass to an air content of 20-50% by volume, after which the mass is cast and allowed to harden and the hardened mass is crushed and possibly fractionated.

• ·

The grain or material density of the light crushed material according to the invention, when no additional foam or other additives increasing the proportion of air 35 are used in the pulp, is about 700-1300 kg / m3.

4,92580

Preferably, a mixture of 90-99% by weight of fly ash 1-10% by weight of calcium-containing binder 5 25-30% by weight of water in the dry matter and 0.05-0.25% by weight of a poroser in the dry matter is used.

As the calcium-containing binder, for example, various CaO-containing binders can be used, such as cements, cement-blast furnace slag mixtures, alkali-activated slag, filter dusts from the cement and lime industry, lime or slaked lime, etc.

The ash may contain any power plant ash having latent hydraulic properties. A portion, for example up to about 50% by weight, such as 5-50% by weight of the ash, may be replaced by, for example, desulfurization product or finely divided industrial waste, such as flotation waste from the mineral or metal industry, or recycled finely divided light crushed material.

By porosifier is meant a substance or mixture of substances which promotes the formation, strengthening and retention of air pores in the mass produced. All suitable substances for this purpose, such as surfactants (surfactants, soaps), can be used. A suitable pore for the purposes of the invention is a product sold under the trade name Ekoste (ed. Partek Sementti Oy), which is a mixture of synthetic surfactants. The amount used, 0.01 to 1%, is based on 100% active ingredient content, although the blowing agent is generally used as an aqueous dilution.

As the blowing agent, it is also possible to use suitable gas-forming substances, for example substances known from the production of aerated concrete, such as aluminum powder.

li • 92580 5

To prepare the pulp, all the substances are mixed vigorously together in a mixer so that sufficient air can be incorporated into the pulp to achieve the desired density. Prior to curing, the pulp can also be mixed with a pre-stabilized foam to produce a lighter product (density can be as low as about 300 kg / m3), for example surfactant or protein foams known from the production of foamed concrete, which can be added up to 800-900 1 / m3, whereby after mixing 10 foams the final air content can be about 700-800 1 / m3. The amount of foam is usually in the range of 400-700 1 / m3.

When the lightweight crushed stone to be produced is to be used, for example, as a road base, lightweight plastic beads, for example expanded polystyrene polymer beads (styrox beads), can also be added to the pulp in an amount of 300-900 l / m 3 to allow better road holding and faster commissioning. The beads can be added as such or, for example, together with light crushed stone.

After mixing, the pulp is transported or pumped to a suitable storage or disposal area for curing. The consistency of the pulp is after mixing. 25 suitable, it is not too loose to spread or drain, nor too rigid to be pumped, but the accumulated mass remains in its shape.

In the production of the pulp, it is also possible to utilize the possible excess heat of the power plant, which can help to harden the ash activated by the binder and water. The resulting mass does not need to be protected or covered, but the mass can be allowed to be exposed to outside air until it has reached its final strength, which normally takes about 1 to 6 months, depending on the temperature and the amount of binder.

^ 2580 6

Thus, with the method according to the invention, the activity of the by-products of the power plant as well as the by-heat can be utilized immediately on site, which is of course of great economic and ecological significance.

Preferably, however, the cured mass is first granulated into light crushed material using suitable crushing equipment, for example crushing rollers. A suitable grain size for most purposes is about 3-30 mm. It is also advantageous to fractionate the light crumb into suitable fractions so that the finest fraction (usually about <10% of the total material) can be returned to the process. Fractionated light crushed stone is easy to transport out of the storage area to its destination and no waste products are generated.

According to the invention, the optionally fractionated light crushed stone can be further cured as such, whereby, for example when the crushed stone has been prepared using 10% cement, its strength can even be doubled by autoclaving or steam treatment.

According to a preferred embodiment of the invention, optionally 25 fractionated crushed stone is used as a aggregate for the production of very light building elements or blocks. For example, when preparing lime sand type light ingots in a manner known per se, the quicklime is preferably mixed with suitably fractionated light crush 30 and possibly with a filler such as sand. The light crusher does not need to be dried, but a little water may be added to the mixture. The mixture is compressed and the moisture released extinguishes all lime. Extruded pieces already have good raw strength after pressing. The pieces of press-35 n 92580 7 are then steam autoclaved at a vapor overpressure of a few pressures and at a temperature of about 150-170 ° C, usually for about 5-8 hours. The strength of the pieces continues to multiply during autoclaving.

5

The production of lightweight ingots containing light crushed material takes place in a manner known per se, in which case about 60-90% by weight of light crushed stone, 6-15% by weight! a calcium-containing binder, preferably 10 lime, optionally with the addition of a filler of up to about 30% by weight, and water. The total amount of water is generally at most about 30% by weight.

Good results have been obtained, for example, by using light crumb-15 kke about 75-90% by weight, lime about 10% by weight and filler up to 15% by weight.

The cross-sections of the pieces show that the pore structure of the light crushed stone is very uniform, for example compared to similar bodies made of similarly prepared expanded clay granules (Leea). The lightweight ingots according to the invention are considerably stronger than known ingots having approximately the same density. This is because light crushed stone made from fly ash is still somewhat active in the production of light crumbs, in contrast to expanded clay.

Due to the porous structure of the crushed stone according to the invention, it, or preferably its smaller fractions, can also be used in refractory masses and lightweight fillers, whereby the crushed stone can pass through without cracking any water vapor that may be formed.

The following examples illustrate the invention without limiting it in any way.

8 92530

Example 1

Crushed stone production 5 1800 kg of fly ash, 200 kg of Portland cement, 3 kg of Ekoste porosifier and 550 kg of water were fed to the mixer from the power plant storage silo. The mixture was stirred for a few minutes so that the density of the pulp became 1150 kg / m3. The air content of the pulp was 39.8% by volume.

10

The pulp was allowed to cure at + 20 ° C and> 90% relative humidity, and samples were taken after 4, 7, 28 and 91 days. The following compressive strengths and densities were obtained for the pulp (average of three samples):

Age (d) Compressive strength (MPa) Density _f 150x150x150 mm) _ka / m3 4 0.5 1220 7 1.1 1210 20 28 6.4 1170 91 8.2 1140

When the strength of the mass is sufficient, usually preferably more than 2 MPa, it is crushed to a grain size of about 0-30 mm. The 0-3 mm fraction can be returned to the mixer as starting material, and the remainder is fractionated to the appropriate grain sizes.

Example 2 30 When the procedure of Example 1 was repeated, but using 1200 kg of fly ash, 400 kg of cement and 400 kg of desulfurization product, a fresh pulp with a density of 1310 kg / -? m, with an air content of 32.3%. The pulp was maintained as above to give the following compressive strength and ti-3 heys.

92580 9

Age (d) Compressive strength (MPa) Density _ (150x150x150 mml_ka / m3 4 2.0 1340 7 2.8 1340 5 28 8.1 1270 91 13.0 1250

Example 3 10

The procedure of Example 1 was repeated but using 1500 kg of fly ash, 200 kg of cement, 300 kg of a fine fraction of crushed light from the previous preparation into a 0-3 mm filler, 6 kg of Ekoste porosifier, and 547 kg of water. 15 This pulp had a liter weight of 1028 kg / m3 and a compressive strength of 1.95 MPa after 91 days.

Example 4 Preparation of light crushed stone containing 20 Styrox beads.

The procedure was as in Example 1, but 1350 kg of fly ash, 600 kg of cement, 3 kg of Ekoste porosifier, and either 700 kg of water (mass 4.1) or 25,800 kg of water (4.2) were mixed. In addition, 30 kg of styrofoam beads, grade 20 kg / m3 'and 30 kg of styrofoam beads, grade 40 kg / m3, were added to the mass 4.1 in each case. The corresponding additions to the mass 4.2 were in each case 50 kg. The liter weights of the products obtained were 696 (4.1) and 462 (4.2) kg / m3, respectively. The 28-day strengths 30 were 1.7 (4.1) and 1.0 (4.2) MPa, and the 91-day strengths were 2.8 (4.1) and 2.15 (4.2) MPa.

• ·

By increasing the amount of cement to 900 kg, and using 1,050 kg of fly ash, 3 kg of Ekoste porosity and 770 kg of water, 35 and 50 kg of styrofoam beads (1-3 mm), the liter weight was 773 kg / m3 and the 7-day strength was already 3 .5 MPa.

10 92580

Example 5

Preparation of foam-containing light crushed material The procedure was as described in Example 1, but 870 kg of 740 kg of fly ash, 100 kg of 200 kg of cement P40 / 3, 30 kg and 60 kg of desulfurization product, respectively, and 360 kg of resp. 375 kg of water. In addition, about 700 l / m3 of protein foam was added to the mixture. 10 Liter weights (dry) were 860 kg / m3 and 708 kg / m3, respectively, and the 28-day compressive strengths were 2.6 MPa and 1.4 MPa, respectively.

Example 6 15

The pulps of Examples 1 and 2 were field tested in the spring of 1991.

After 34 days, the pulp 20 of Example 1 had an average compressive strength of 6.6 MPa, a density of 1250 kg / m 3 (moisture 26.9%). The corresponding values for the pulp according to Example 2 were 3.6 MPa, 1160 kg / m3 (humidity 19.7%).

Example 7 25

Manufacture of ingots

Two different grades of light crushed material were used as the aggregate for the production of light ingots, namely the crushed pulp according to Examples 1 and 2, marked E1, E2, respectively. Three fractions of each grade were screened, namely 0-3 mm, 3-6 mm, and 6-12 mm. The moisture and bulk densities of these grades are given in Table 1.

35 11 92580

table 1

El and E2 aggregates. Moisture and bulk densities of different fractions 5

El E2

Size Moisture Density Moisture Density% kg / m3% kg / m3 0-3 mm 23 1000 25 1000 10 3-6 mm 21 790 27 750 6-12 mrn 22 740 27 750

Said light crumbs were mixed with lime ("Kiikala" quality, Pargas) and possibly with filler (filler-15 sand, Naarajärvi, dried) in a Hobart-type mixer for 10 minutes, after which the mass was allowed to stand in a closed plastic bag for two hours. The recipes used for the light crushed material E1 and E2 are given in Table 2. In addition to the added water, the table shows the total amount of water, taking into account the moisture in the aggregate.

25 t 30 35 92 58 ϋ 12

Table 2 Light crushed stone El

Res. Fraction Lime Filler Water 5 £ _0-3_3-6_lis. National Coalition Party.

TH1 67 0 11 22 10 30 TH2 0 67 11 22 10 28 TH3 61 0 13 26 10 28 TH4 33.5 33.5 11 22 10 29 10 TH5 0 61 13 26 10 26 TH6 30.5 30.5 13 26 10 27 TH6K 30.5 30.5 13 26 0 15 TH7 73 0 9 18 10 32 TH7K 73 0 9 18 0 20 15 TH8 0 73 9 18 10 29 TH8K 0 73 9 18 0 18 TH9 36.5 36.5 9 18 10 31 TH9K 36.5 36.5 9 18 0 19 TH10 45 45 10 0 5 31 20 TH10K 45 45 10 0 0 24 TH11 30 60 10 0 5 30 TH11K 30 60 10 0 0 24 TH12 15 75 10 0 5 29 TH12K 15 75 10 0 0 23 25 TH13 0 90 10 0 5 29 TH13K 0 90 10 0 0 23 TH14 0 75 10 15 5 24 TH14K 0 75 10 15 0 18 3 0 Light crushed stone E2

Res. Fraction Lime Filler Water .1_0-3 3-6_lis. National Coalition Party.

TH10 45 45 10 0 5 37 TH10K 45 45 10 0 0 31 35 TH11 30 60 10 0 5 37 TH14 0 75 10 15 5 32

Test specimens were then prepared from the pulp as follows: 40 • · a) Pieces with a diameter of 50 mm and a height of 40 mm were made with a hand-operated LIDR press. The amount of raw material / piece varied between 90-140 g. These pieces were used to determine the dependence of strength and density on the compression pressure.

li 92580 13 b) The Tonindustrix press was used to make pieces measuring 102 x 102 x 43.5 mm. These pieces were tested for frost resistance.

5 RAW STRENGTH

Based on experience from previous projects, it is known that the crude strength is sufficient when a compressive strength of about one MPa is achieved.

10

Crude strengths were determined immediately after compression of the pieces. The masses of 90 to 140 g used in the test pieces were tried to be compressed to a constant volume (78.5 cm 3). The compressive pressure was recorded and the compressive strength was determined. 15 For example, for recipe E1 / TH14, the following results were obtained (Table 3)

Table 3 20 Mass (g) Density Compressive pressure Crude strength _ (Hq / rc3) _ (MPaJ_ (MPa) 90 1146 5.0 0.2 100 1273 7.3 0.5 110 1401 12.4 1.0 25 120 1528 23 , 4 1.8 130 1615 31.1 1.6

Similar experiments were performed for all El recipes.

30

Crude strength is most strongly affected by grain distribution and total water volume. Therefore, the effect of filler and water content on the compressive strength and density of the raw samples was further investigated. The results obtained at a compression pressure of 20 MPa 35 show that the crude strength decreases with increasing amount of water. In addition, it appears that the use of filler reduces the crude strength. The compressive force of 5 MPa does not achieve sufficient strength and the amount of water and the use of filler are irrelevant. Correspondingly, 14,92580 was found that the density also increases with the amount of water with a compressive force of both 20 MPa and 5 MPa. When using the filler, the density increases to about 2 kg.

5 Experiments show that the best raw strength / density values are obtained without filler and using relatively little water. The grain size has a much smaller effect on the properties of the workpiece, but both the grain strength and the density increase as the grain size decreases. 10 In addition, it has been found that the drier mass is both stronger and lighter than the wetter mass.

Similar experiments were performed with recipes E2-TH10, TH10K, TH11, and TH14, but no significant difference was observed compared to E1 light crushed stone.

autoclaving

The recipes that gave the 20 best raw properties were selected for autoclaving. It was also wanted to study how the total amount of water affects the properties of the autoclaved product. Recipe TH14 was included to determine the effect of the filler in the autoclaved product. A relatively normal run was selected for the autoclave, i.e. run-up to a pressure of 25 16 bar for 1 hour 15 min, hold at 16 bar for 4 hours, run-down for 50 min. temperature 150-170 ° C.

The autoclaved pieces were allowed to cool before weighing. The pieces were then dried (80 ° C, 20-30 h), reweighed and tested. The densities given are calculated from the dried pieces. The test speed was 0.25 kN / sec. Based on the drying results, it appeared that the pieces after autoclaving contain about 15-20% water.

35 The following Table 5 shows the breaking strengths and final densities of light ingots for the recipes E1 TH10, -TH11 and TH14.

I) * 2580 15

Table 5 Recipe E1 / TH10 Sample Mass Compressive pressure Density Tensile strength 5 g MPa kg / m3 MPa 1 90 4.6 886 2.2 2 100 6.8 990 7.2 3 110 13.3 1094 13.9 4 120 23.4 1165 18.0 10 5 130 31.1 1190 18.1

Recipe E1 / TH11 15 1 90 4.6 876 1.7 2 100 6.4 1006 7.5 3 110 11.9 1096 11.5 4 120 26.1 1212 15.1 5 130 31.1 1244 14.7 20 _

Recipe E1 / TH14 1 90 4.6 932 3.7 25 2 100 5.9 1028 6.3 3 110 11.0 1144 10.1 4 120 22.0 1255 17.8 5 130 31.1 1308 18.5 30

The results show that as the proportion of fine aggregate (0-3 mm) increases, the final strength increases but the effect on density is relatively small, and that the use of filler does not • significantly increase the strength, but the density increases.

35 A comparison of the results obtained from the tests carried out shows that the light crushed E2 gives a slightly lighter and also weaker end product. The use of Filler significantly improves strength with E2 crushed light. 1

Claims (13)

1. Process for producing light crushing g enoin to form a mixture containing 5. fly ash which may contain other power plant ash, comminuted industrial side products and waste, - calcium containing binder, such as cement and / or limestone, 10. water, and - pore forming agent, characterized in that the mixture is formed immediately upon the ash burning, preferably in connection with a power plant and using 1-50% by weight of calcium-containing binder calculated on the total amount of ash or ash-containing component and binder, and calculated on the amount of this dry powder mixture, 20-50 wt% water and 0.01-1 wt% pore forming agent, the mixing is continued to make the pulp porous to an air content of 20-50 vol%, the mass is deposited and cured and the cured mass is crushed and possibly fractionated. Method according to claim 1, characterized in that a mixture containing 90-99 wt.% Fly ash 1-10 wt.% Calcium-containing binder 25-30 wt.% Water of the dry material, and 0.05-0. 25 wt% pore forming agent of the dry material. A process according to claim 1, characterized in that a portion, at most about 50% by weight of the ash is replaced with a desulphurisation product or finely divided industrial side products or waste, or with ether circulated finely divided lightweight crusher. * 2580 20 4. A method according to claim 1, characterized in that a mixture containing 90-99% by weight of a mixture containing at least about 50% by weight fly ash is used and the remainder is a desulphurisation product or finely divided into industrial residue products or waste, or with ether circulated finely divided light crusher, 1-10 wt.% calcium-containing binder 25-30 wt.% water of the dry material, and 0.05-0.25 wt.% pore forming agent of the dry material. Process according to any of claims 1-4, characterized in that the cured mass is crushed to a grain size of 0-30 mm. 6. A process according to any one of the preceding claims 1-5, characterized in that stabilized foam, such as surfactant or protein foam, is preferably added in the amount of 400-700 l / m1 to the uncured mixture. Process according to any one of the preceding claims 1-6, characterized in that non-swollen polystyrene beads are added to the uncured mixture, preferably in an amount of 300-900 l / m1. 8. A process according to claim 3 or 4, characterized in that the ether circulated light crusher is a fraction below 3 mm and that its amount is preferably not more than 20% by weight of the ash or ash mixture. Method according to any of claims 1-6 and 8, characterized in that the obtained product is cured in an autoclaving or meadow treatment. Process for the production of building elements, characterized in that, as a ballast, light crusher manufactured according to any one of claims 1-9 is used. 11. A process according to claim 10, characterized in that about 60-90% by weight of light crusher, 6-15% by weight of calcium-containing binder, preferably lime, about -10% by weight of filler, and possibly water, is then cured. at elevated temperature in a meadow autoclave. Use of lightweight crusher manufactured according to any one of claims 1-9, in road foundations as crusher or as a ball load in lightweight concrete to improve load carrying capacity. Use of lightweight crusher manufactured according to any one of claims 1-6, 8 and 9 in refractory and light curing masses.