Autoclaved aerated concrete prepared from filter pressing waste slurry and preparation method of autoclaved aerated concrete

Abstract

The invention relates to the field of building materials, in particular to autoclaved aerated concrete prepared from filter-press waste slurry and a preparation method of the autoclaved aerated concrete. The autoclaved aerated concrete is prepared by replacing part of cement and fine sand in traditional aerated concrete with the filter-pressing waste slurry and the modified residual slurry, the manufacturing cost of the autoclaved aerated concrete can be greatly reduced, the waste slurry and the residual slurry contain rich active SiO2 and active CaO, and when the waste slurry and the residual slurry are applied to aerated concrete blocks, the autoclaved aerated concrete has the advantages that the autoclaved aerated concrete is prepared, and the utilization rate of the autoclaved aerated concrete is increased. In addition, the waste slurry, the residual slurry, the fly ash and the like are used, so that the reutilization of wastes is realized, the green and environment-friendly requirements are met, the material cost is greatly reduced, and the national industrial requirements are met.

Description

Technical Field

[0001] The invention relates to the field of building materials, and in particular to autoclaved aerated concrete prepared from filter press waste slurry and a preparation method thereof. Background Art

[0002] The aerated concrete industry has a history of more than 40 years in my country. So far, it has formed a complete system including production, equipment manufacturing, supporting material production and scientific research and design. The aerated concrete industry has become an important force in my country's building energy conservation and wall material innovation, and has made great contributions to the circular economy and low-carbon life. The production and use of aerated concrete can not only save energy, save land, reduce resource consumption, protect the ecological environment, but also promote the modernization of the construction and housing industries. Aerated concrete has the advantages of high strength-to-weight ratio, load-bearing, heat preservation, fire resistance and mildew resistance. Its early application form was mainly aerated concrete blocks.

[0003] In the preparation process of autoclaved aerated concrete, sand plays an important role as fine aggregate. However, the distribution of sand resources in my country is uneven, mainly distributed in several large river basins. There is less sand with an SiO2 content of more than 80%, and the large-scale development of infrastructure requires a large amount of sand, resulting in a shortage of construction sand. Therefore, without affecting the basic properties of autoclaved aerated concrete, a new material is needed to replace sand to prepare autoclaved aerated concrete in order to save sand resources. In the prior art, concrete waste slurry is used to replace coarse and fine aggregates and fillers in cement concrete, but the quality of aggregates will be reduced, and studies have shown that the compressive strength of mortar will decrease with the increase of the amount of concrete waste slurry. Summary of the invention

[0004] In order to solve the technical problem of how to use a new material to replace sand without affecting the basic properties of autoclaved aerated concrete, the present invention provides an autoclaved aerated concrete prepared with filter press waste slurry and a preparation method thereof.

[0005] The autoclaved aerated concrete prepared by using filter press waste slurry provided by the present invention is characterized in that: in parts by weight, it comprises 150-300 parts of cement, 200-400 parts of lime, 50-100 parts of fly ash, 2000-3000 parts of filter press waste slurry, 150-220 parts of modified residual slurry, 100-300 parts of desulfurized gypsum, 5-10 parts of polycarboxylate water reducer and 1.6-2.0 parts of aluminum powder; The mass ratio of the filter press waste slurry to the modified residual slurry is 200-300:15-22; In the filter press waste slurry, the mass ratio of waste slurry, dispersant and water is 100-150:1-2:150-200; In the modified slurry, the mass ratio of slurry, water glass, water reducing agent and dispersant is 150-210:20-60:5-9:3-7.

[0006] Preferably, the autoclaved aerated concrete prepared with filter press waste slurry includes, by weight, 180-260 parts of cement, 220-380 parts of lime, 60-80 parts of fly ash, 2200-2800 parts of filter press waste slurry, 160-200 parts of modified residual slurry, 120-280 parts of desulfurized gypsum, 6-8 parts of polycarboxylic acid water reducer and 1.7-1.9 parts of aluminum powder.

[0007] More preferably, the autoclaved aerated concrete prepared with filter press waste slurry includes, by weight, 220 parts of cement, 300 parts of lime, 70 parts of fly ash, 2500 parts of filter press waste slurry, 180 parts of modified residual slurry, 200 parts of desulfurized gypsum, 7 parts of polycarboxylic acid water reducer and 1.8 parts of aluminum powder.

[0008] The waste slurry can be waste residue generated during the production, transportation and hopper flushing of concrete, which is formed by sand and gravel separation and then filter pressing. It should be noted that waste slurry generated by other methods can also be used, including but not limited to the above scheme.

[0009] The residual slurry can be the residual slurry produced by the pipe pile centrifugal device. It should be noted that the residual slurry can also be produced by other methods, including but not limited to the above-mentioned scheme.

[0010] On the basis of the above scheme, further, the dispersant is sodium tripolyphosphate or aminosulfonic acid dispersant.

[0011] Preferably, the dispersant is sodium tripolyphosphate.

[0012] On the basis of the above scheme, further, the water reducing agent is lignin sulfonate or polycarboxylate.

[0013] Preferably, the water reducing agent is lignin sulfonate.

[0014] On the basis of the above scheme, further, the bulk density of the filter press waste slurry is 1.5-1.7 g / ml, and the diffusion degree is 28-35 cm.

[0015] On the basis of the above scheme, further, the modified slurry has a bulk density of 1.6-1.8 g / ml and a solid content of 55%-64%.

[0016] On the basis of the above scheme, further, the cement is one or two of PO 42.5R ordinary Portland cement, PC32.5 composite silicate, and PC32.5 cement.

[0017] On the basis of the above scheme, further, the fly ash is grade 3 fly ash with a fineness of 4.1%-5.7% and a density of 1.1-2.3 g / cm³.

[0018] On the basis of the above scheme, further, the water reduction efficiency of the polycarboxylate water reducer is 30%-36%.

[0019] The purpose of adopting the above technical scheme is that the polar groups (such as carboxyl, hydroxyl, amine, etc.) in the polycarboxylic acid molecules can provide dispersion and flow properties to cement particles through surface active effects such as adsorption, dispersion, wetting, and lubrication. These groups can also reduce the free energy of the interface between cement particles and water, thereby accelerating the hydration reaction and improving the strength.

[0020] The present invention also provides a method for preparing autoclaved aerated concrete using filter press waste slurry as described above, characterized in that it comprises the following preparation steps: S1, weighing and mixing the filter press waste slurry, the modified residual slurry and the desulfurized gypsum in proportion to obtain a mixture A, and then placing the mixture A in a mixer and stirring it evenly; S2, adding polycarboxylate water reducer to the mixture A, stirring to obtain a mixture B; S3, weighing and mixing cement, lime and fly ash in proportion, adding them to mixture B and stirring continuously to obtain mixture C; S4. Add aluminum powder to mixture C and stir continuously to obtain autoclaved aerated concrete.

[0021] On the basis of the above scheme, further, in step S1, the stirring time of mixture A is not less than 3 minutes; in step S3, the stirring time of mixture C is not less than 2 minutes; in step S4, the time of adding aluminum powder and continuously stirring is not more than 2 minutes.

[0022] Compared with the prior art, the present invention provides an autoclaved aerated concrete prepared with filter press waste slurry and a preparation method thereof. By using filter press waste slurry and modified residual slurry to replace part of the cement and fine sand in traditional aerated concrete to prepare autoclaved aerated concrete, the production cost of autoclaved aerated concrete can be greatly reduced. Moreover, the waste slurry and residual slurry contain rich active SiO2 and active CaO. Applying them to aerated concrete blocks is conducive to generating a large amount of hydration products such as tobermorite, thereby improving the compressive strength of aerated concrete blocks. In addition, the present invention uses waste slurry, residual slurry and fly ash, etc., realizes the reuse of waste, meets green environmental protection requirements, and greatly reduces material costs, which meets national industrial requirements.

[0023] In the preferred embodiment, the use of polycarboxylate water-reducing agent and sodium tripolyphosphate is beneficial to improving the fluidity and saturated solubility of autoclaved aerated concrete, and is helpful to improving the volume stability and durability of aerated concrete. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention is clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Example 1 A kind of autoclaved aerated concrete prepared by using filter press waste slurry, the raw materials include: 200kg cement; 300kg lime; 70kg fly ash; 2000kg filter press waste slurry; 160kg modified residual slurry; 200kg desulfurized gypsum; 7kg polycarboxylate water reducer; 1.8kg aluminum powder; In the filter press waste slurry, the ratio of waste slurry, sodium tripolyphosphate and water is 125:2:175; In the modified waste pulp, the ratio of waste pulp, water glass, lignin sulfonate and sodium tripolyphosphate is 180:40:7:5, and the components are stirred for 20-40 minutes to prepare the modified waste pulp; The filter press waste slurry has a bulk density of 1.6 g / ml and a diffusion degree of 30 cm; The modified slurry has a bulk density of 1.7 g / ml and a solid content of 60%; The cement is PO 42.5R ordinary Portland cement; The fly ash is grade 3 fly ash with a fineness of 4.5% and a density of 1.6 g / cm³; The polycarboxylate water-reducing agent used has a water-reducing efficiency of 32%; The method for preparing autoclaved aerated concrete using filter press waste slurry is characterized by comprising the following steps: S1. Weigh and mix the filter press waste slurry, modified residual slurry and desulfurized gypsum in proportion to obtain a mixture A, and then place the mixture A in a mixer and stir for 3 minutes; S2, adding polycarboxylate water reducer to the mixture A, stirring to obtain a mixture B; S3, weighing and mixing cement, lime and fly ash in proportion, adding them to mixture B and stirring continuously for 2 minutes to obtain mixture C; S4. Add aluminum powder to mixture C and stir continuously for 1 min to obtain autoclaved aerated concrete.

[0026] Example 2 The difference between Example 2 and Example 1 is that the weight of the filter press waste slurry is replaced from 2000 kg to 2300 kg, and the other components and operating steps are the same as those of Example 1.

[0027] Example 3 The difference between Example 3 and Example 1 is that the weight of the filter press waste slurry is replaced from 2000 kg to 2500 kg, and the other components and operating steps are the same as those of Example 1.

[0028] Example 4 The difference between Example 4 and Example 1 is that the weight of the filter press waste slurry is replaced from 2000 kg to 2800 kg, and the other components and operating steps are the same as those of Example 1.

[0029] Example 5 The difference between Example 5 and Example 1 is that the weight of cement is replaced from 200kg to 180kg, the weight of filter press waste slurry is replaced from 2000kg to 2300kg, the weight of modified residual slurry is replaced from 160kg to 180kg, and the remaining components and operating steps are the same as those in Example 1.

[0030] Example 6 The difference between Example 6 and Example 1 is that the weight of cement is replaced from 200kg to 160kg, the weight of filter press waste slurry is replaced from 2000kg to 2300kg, the weight of modified residual slurry is replaced from 160kg to 200kg, and the remaining components and operating steps are the same as those in Example 1.

[0031] Comparative Example 1 The difference between Comparative Example 1 and Example 3 is that the filter press waste slurry in the raw material is replaced by an equal amount of fine mortar, and the fine mortar is made by mixing fine sand and cement in a weight ratio of 2-3:1, and then adding water and stirring evenly. The other components and operating steps are the same as those in Example 3.

[0032] Comparative Example 2 The difference between Comparative Example 2 and Example 3 is that no polycarboxylate water-reducing agent and dispersant sodium tripolyphosphate are added to the raw materials, and the other components and operating steps are the same as those of Example 3.

[0033] Comparative Example 3 The difference between Comparative Example 3 and Example 3 is that no modified residual pulp is added to the raw material, only filter press waste pulp is added, and other components and operating steps are consistent with Example 3.

[0034] Comparative Example 4 The difference between Comparative Example 4 and Example 3 is that only modified residual pulp is added to the raw material, and no filter press waste pulp is added. Other components and operating steps are consistent with Example 3.

[0035] Comparative Example 5 The difference between Comparative Example 5 and Example 3 is that the cement in the raw materials is completely replaced by modified residual slurry, and the other components and operating steps are consistent with Example 3.

[0036] Comparative Example 6 The difference between Comparative Example 6 and Example 3 is that the filter press waste slurry and modified residual slurry in the raw material are replaced by waste slurry and residual slurry without any treatment, and the rest is consistent with Example 3.

[0037] Test methods and standards: The autoclaved aerated concrete prepared above was subjected to a performance test according to the standard: GB / T 11969-2020 "Autoclaved Aerated Concrete Performance Test Method", and the results are shown in Table 1 below: Table 1

[0038] From Table 1, we can see that: From the data of comparative examples 1-4, it can be seen that as the amount of filter press waste slurry added increases, the compressive strength, drying shrinkage and frost resistance of autoclaved aerated concrete first increase and then decrease. When the amount of filter press waste slurry added is 2500kg, the performance reaches the best. This may be because the solid particles in the filter press waste slurry have different amounts and dispersion of solid phase hydration products at different ages. There must be solid particles in the waste slurry at a certain age that are most conducive to the deposition of hydration products. The waste slurry also contains a certain proportion of unhydrated cement and admixtures and other hydration-active components, including a certain amount of SiO2 and Al2O3. During the stirring and later hydration and hardening process, they react with alkaline components to generate CSH gel and aluminate, which is one of the reasons for the early strength improvement of autoclaved aerated concrete. At the same time, since the cement will be fully hydrated in the end, the active substances in the waste slurry are getting less and less, and the strength is gradually reduced.

[0039] By comparing the data of Example 3, Example 5, Example 6 with Comparative Example 3 and Comparative Example 5, it can be seen that by replacing part of the cement with the modified residual slurry, the compressive strength gradually decreases, but the strength is still greater than the standard value and meets the use requirements.

[0040] By comparing Example 3 with Comparative Example 1, it can be seen that the filter press waste slurry can perfectly replace fine sand to make autoclaved aerated concrete, and the performance of Example 3 is better than that of Comparative Example 1.

[0041] By comparing Example 3 with Comparative Example 2, it can be seen that after the addition of polycarboxylic acid water-reducing agent and sodium tripolyphosphate, the compressive strength and fluidity performance are improved. This may be because the polar groups (such as carboxyl, hydroxyl, amine, etc.) in the polycarboxylic acid molecules provide dispersion and fluidity performance to cement particles through surface active effects such as adsorption, dispersion, wetting, and lubrication. These groups can also reduce the free energy of the interface between cement particles and water, thereby accelerating the hydration reaction and improving the strength.

[0042] By comparing Example 3 with Comparative Example 3 and Comparative Example 4, it can be seen that when filter press waste slurry is added alone without adding modified residual slurry or modified residual slurry is added alone without adding filter press waste slurry, its compressive strength, thermal conductivity and other properties are weaker than those in Example 3. The possible reason is that the filter press waste slurry and the modified residual slurry have a synergistic effect, which improves the performance of autoclaved aerated concrete.

[0043] By comparing Example 3 and Comparative Example 6, it can be seen that when waste slurry and residual slurry are directly added without any treatment, the compressive strength and thermal conductivity of the autoclaved aerated concrete are worse than those of Example 3. This may be because the active substances contained in the untreated filter press waste slurry and residual slurry cannot be stimulated to promote the formation of hydration products, resulting in performance inferior to that of Example 3.

[0044] In summary, by adding a certain proportion of filter press waste slurry and modified residual slurry, the compressive strength of the autoclaved aerated concrete prepared in the present invention is improved compared with traditional fine sand, and the autoclaved aerated concrete prepared has good fluidity, durability, compressive strength, etc., and has excellent comprehensive performance.

[0045] Although the terms such as autoclaved aerated concrete, filter press waste slurry, modified residual slurry and polycarboxylate water reducer are used more frequently in this article, the possibility of using other terms is not excluded. The use of these terms is only for more convenient description and explanation of the essence of the present invention; interpreting them as any additional limitation is contrary to the spirit of the present invention.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An autoclaved aerated concrete prepared from filter press waste slurry, characterized in that: In parts by weight, it includes 150-300 parts of cement, 200-400 parts of lime, 50-100 parts of fly ash, 2000-3000 parts of filter press waste slurry, 150-220 parts of modified residual slurry, 100-300 parts of desulfurized gypsum, 5-10 parts of polycarboxylate water reducer and 1.6-2.0 parts of aluminum powder; The mass ratio of the filter press waste slurry to the modified residual slurry is 200-300:15-22; In the filter press waste slurry, the mass ratio of waste slurry, dispersant and water is 100-150:1-2:150-200; In the modified slurry, the mass ratio of slurry, water glass, water reducing agent and dispersant is 150-210:20-60:5-9:3-7.

2. The autoclaved aerated concrete prepared from filter press waste slurry according to claim 1, characterized in that: The dispersant is sodium tripolyphosphate or aminosulfonic acid dispersant.

3. The autoclaved aerated concrete prepared from filter press waste slurry according to claim 1, characterized in that: The water reducing agent is lignin sulfonate or polycarboxylate.

4. The autoclaved aerated concrete prepared from filter press waste slurry according to claim 1, characterized in that: The bulk density of the filter press waste slurry is 1.5-1.7 g / ml, and the diffusion degree is 28-35 cm.

5. The autoclaved aerated concrete prepared from filter press waste slurry according to claim 1, characterized in that: The modified slurry has a bulk density of 1.6-1.8 g / ml and a solid content of 55%-64%.

6. The autoclaved aerated concrete prepared from filter press waste slurry according to claim 1, characterized in that: The cement is one or two of PO 42.5R ordinary silicate cement, PC32.5 composite silicate, and PC32.5 cement.

7. The autoclaved aerated concrete prepared from filter press waste slurry according to claim 1, characterized in that: The fly ash is grade 3 fly ash with a fineness of 4.1%-5.7% and a density of 1.1-2.3 g / cm³.

8. The autoclaved aerated concrete prepared from filter press waste slurry according to claim 1, characterized in that: The water reducing efficiency of the polycarboxylate water reducer is 30%-36%.

9. A method for preparing autoclaved aerated concrete using filter press waste slurry according to any one of claims 1 to 8, characterized in that: The method comprises the following preparation steps: S1, weighing and mixing the filter press waste slurry, the modified residual slurry and the desulfurized gypsum in proportion to obtain a mixture A, and then placing the mixture A in a mixer and stirring it evenly; S2, adding polycarboxylate water reducer to mixture A, stirring evenly to obtain mixture B; S3, weighing and mixing cement, lime and fly ash in proportion, adding them to mixture B and stirring continuously to obtain mixture C; S4. Add aluminum powder to mixture C and stir continuously to obtain autoclaved aerated concrete.

10. The method for preparing autoclaved aerated concrete using filter press waste slurry according to claim 9, characterized in that: The stirring time of the mixture A in the step S1 is not less than 3 minutes; the stirring time of the mixture C in the step S3 is not less than 2 minutes; the time of adding aluminum powder and continuously stirring in the step S4 is not more than 2 minutes.

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