Quick-setting and quick-hardening fly ash foam concrete and preparation method thereof

Abstract

The invention discloses quick-setting and quick-hardening fly ash foam concrete and a preparation method thereof. The foam concrete comprises powder, water, a water reducing agent and a foaming agent, the powder material is prepared from the following components in percentage by mass: 26 to 30 weight percent of dicalcium silicate-lime composite cementing material, 5 to 12 weight percent of aluminate cement clinker, 5 to 12 weight percent of dihydrate gypsum and 50 to 60 weight percent of fly ash. The low-temperature calcined dicalcium silicate-calcareous composite cementing material, the aluminate cement clinker, the fly ash and the dihydrate gypsum are adopted as materials to prepare the foam concrete, and the foam concrete is high in setting and hardening speed and not prone to mold collapse.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, and in particular to a fast-setting and fast-hardening fly ash foam concrete and a preparation method thereof. Background Art

[0002] Foamed concrete refers to a lightweight microporous concrete made by physically making a foaming agent into foam, then adding the foam to a slurry made of cement, admixtures, additives and water, and then mixing, pouring, molding and curing. Foamed concrete has low deadweight, high fluidity, low aggregate dosage, controllable low strength and excellent thermal insulation performance. Ensuring the stability of bubbles in fresh foamed concrete is crucial to obtaining foamed concrete with excellent pore morphology and performance. The stability of bubbles in fresh concrete determines the pore morphology and distribution of hardened foamed concrete, which in turn affects the density, permeability, thermal insulation and mechanical properties of foamed concrete (especially at ultra-low density). However, in unstable fresh foamed concrete, bubbles will continue to lose stability until the slurry hardens. Bubble instability can cause foamed concrete to form rough and uneven pores, or even partial or complete collapse.

[0003] In order to shorten the setting time of fresh foam concrete and stabilize bubbles, the Chinese invention patent "A high-strength foam concrete and preparation method" (application number CN202211705709.2) uses sulphoaluminate cement as a cementitious material, mixes foam at an ultra-low water-cement ratio, and prepares high-strength foam concrete. The Chinese invention patent "A lightweight thermal insulation foam concrete and its preparation method" (application number CN202410145839.8) selects silicate cement, calcium magnesium phosphate cement, and calcium silicate cement with a compressive strength of 42.5 or above as the base material, and matches lightweight aggregates and optimized additives to effectively shorten the setting time of concrete and improve strength. The Chinese invention patent "A new type of foam concrete preparation method" (application number CN202210895977.9) uses new special cementitious materials and sulphoaluminate cement as cementitious materials to shorten the setting time. Although the above method can effectively shorten the setting time of foam concrete, the amount of special cement used is large and the economy is poor. Summary of the invention

[0004] The object of the present invention is to provide a fast-setting and fast-hardening fly ash foam concrete and a preparation method thereof, so as to solve the problems of slow setting time and low strength of the foam concrete.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] On the one hand, a fast-setting and fast-hardening fly ash foam concrete is provided, comprising powder, water, a water reducing agent and a foaming agent; the powder comprises the following components in percentage by mass: 26-30wt% of dicalcium silicate-lime composite cementitious material, 5-12wt% of aluminate cement clinker, 5-12wt% of dihydrate gypsum and 50-60wt% of fly ash; the amount of water is calculated according to a water-to-material ratio of 0.24-0.30; the amount of the water reducing agent is 0.8-1.2wt‰ of the mass of the powder; the foaming agent is used to configure foam, and the added volume of the foam is obtained based on the bulk density of the foamed concrete.

[0007] Furthermore, the dicalcium silicate-lime composite cementitious material comprises the following mineral components in percentage by mass: C2S: 50-62wt%, CaO: 30-36wt%, C3A: 5-10wt%, and C4AF: 3-4wt%.

[0008] Furthermore, the dicalcium silicate-lime composite cementitious material is prepared by calcining low-grade limestone and waste soil cakes at a high temperature, wherein the calcination temperature is 1200-1250° C. and the calcination time is 20-60 min. The calcined clinker is ground to obtain a specific surface area of ​​330-350 kg / m 2 The quality of the low-grade limestone and waste soil pressed cake ingredients is calculated based on the mineral composition of the dicalcium silicate-lime composite cementitious material and the Baugh formula.

[0009] Furthermore, the low-grade limestone has a loss on ignition of 40.13±2wt%, and includes the following mineral components in mass percentage: SiO2: 6.04±2wt%, Al2O3: 1.77±2wt%, Fe2O3: 0.73±2wt%, CaO: 49.00±2wt%, and MgO: 1.10±2wt%.

[0010] Furthermore, the waste soil has a loss on ignition of 17.00±2wt%, and includes the following mineral components in mass percentage: SiO2: 43.60±2wt%, Al2O3: 13.67±2wt%, Fe2O3: 21.51±2wt%, CaO: 1.85±2wt%, and MgO: 2.29±2wt%.

[0011] Furthermore, the aluminate cement clinker comprises the following mineral components in percentage by mass: CA: 31-49wt%, CA2: 23-36wt%, C2AS: 28-33wt%.

[0012] Furthermore, the basicity coefficient A of the aluminate cement clinker is m It is 0.9~1.0.

[0013] Furthermore, the slurry density of the foamed concrete is 1900-2000 kg / m 3 .

[0014] Furthermore, the water reducer is a polycarboxylic acid water reducer; and the foaming agent is one of silicone resin polyether emulsion, lauryl alcohol, and calcium stearate.

[0015] On the other hand, a method for preparing fast-setting and fast-hardening fly ash foam concrete is provided, comprising the following steps:

[0016] S1. According to the bulk density of the foamed concrete to be prepared, the powder, water, and water reducing agent are weighed in proportion, wherein the bulk density of the foamed concrete is the mass of the powder;

[0017] S2, adding the weighed powder and water reducing agent into a mixer and stirring to form a uniform mixture;

[0018] S3, adding a foaming agent and water required for foaming into a foaming machine to generate foam; wherein the water required for foaming is not included in the water weighed in S1, and the mass of the water required for foaming is determined according to the type of the foaming agent;

[0019] S4, adding the water weighed in S1 to the mixed material, stirring and mixing to form a slurry;

[0020] S5, according to formula V 泡 =1-M / ρ 料 Calculate the added volume V of the foam 泡 , the volume is V 泡 Add the foam into the slurry and stir for 3 to 4 minutes to obtain the foam slurry. M is the sum of the mass of powder and water in the foam concrete. 料 is the slurry density of foam concrete;

[0021] S5. Pour the foam slurry into the mold and cure it in the natural environment for 24 hours. After demoulding, cure it in the natural environment for 2 days.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The dicalcium silicate-calcium oxide composite cementitious material calcined at 1200-1250° C. of the present invention has a size of dicalcium silicate of 1 μm, while the size of dicalcium silicate in traditional silicate cement clinker exceeds 10 μm. The smaller size is conducive to the hydration and hardening of C2S, thereby improving the strength of foamed concrete; and the size of CaO in the dicalcium silicate-calcium oxide composite cementitious material is about 10 μm, with a fast digestion speed, generating Ca(OH)2 gel, releasing a large amount of heat, promoting slurry thickening, and stabilizing bubbles.

[0024] 2. Compared with traditional silicate cement, the dicalcium silicate-calcium oxide composite cementitious material of the present invention has a low calcination temperature, low energy consumption, and the production of foamed concrete is green and low-carbon.

[0025] 3. Usually in the presence of dihydrate gypsum, CA and CA2 in aluminate cement are hydrated to produce calcium sulfonate and aluminum gel, and the chemical reaction equation is as follows:

[0026] 3CA+3CaSO4·2H2O+nH2O→AFt(ettringite)+4Al(OH)3;

[0027] 3CA2+3CaSO4·2H2O+mH2O→AFt(ettringite)+10Al(OH)3.

[0028] Due to the presence of Al(OH)3, aluminate cement shrinks greatly in the later stage. In the present invention, since CaO in the dicalcium silicate-calcium oxide composite cementitious material will be rapidly hydrated to Ca(OH)2, in the presence of Ca(OH)2 and dihydrate gypsum, the aluminum gel produced by the hydration of aluminate cement will generate AFt, and its chemical reaction equation is as follows:

[0029] Al(OH)3+3CaSO4·2H2O+3Ca(OH)2+bH2O→AFt (ettringite).

[0030] The synergistic hydration of the dicalcium silicate-calcium oxide composite cementitious material and aluminate cement can fully utilize the aluminum-containing minerals to generate AFt, which can promote the coagulation and hardening of the foamed concrete on the one hand and reduce shrinkage on the other hand. In addition, due to the consumption of aluminum gel in the system, the hydration of CA and CA2 minerals can be promoted, thereby improving the strength of the foamed concrete.

[0031] 4. Since fly ash mainly contains Al2O3 and SiO2 glass, the depolymerization rate of fly ash glass is highly sensitive to temperature. The CaO in the dicalcium silicate-calcium oxide composite cementitious material will emit a lot of heat when it is decomposed. In addition, the rapid generation of AFt in the system is conducive to the depolymerization of AlO2 in the fly ash glass. - The fly ash glass network structure is easily activated, its volcanic ash activity is increased, and the strength of the foamed concrete is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a SEM image of the dicalcium silicate-lime composite cementitious material of the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0034] Example 1

[0035] As a preferred embodiment of the present invention, the fast-setting and fast-hardening fly ash foam concrete of this embodiment includes powder, water, a water reducing agent and a foaming agent.

[0036] In this embodiment, the powder includes, by mass percentage, 30wt% of dicalcium silicate-lime composite cementitious material, 5wt% of aluminate cement clinker, 5wt% of dihydrate gypsum, and 60wt% of fly ash.

[0037] In this embodiment, the water-to-material ratio is 0.3.

[0038] In this embodiment, the dosage of the polycarboxylate water-reducing agent is 0.8wt‰ of the powder mass.

[0039] In this embodiment, the slurry density of the prepared fast-setting and fast-hardening fly ash foam concrete is 1900 kg / m 3 .

[0040] In this embodiment, the mineral components of the dicalcium silicate-lime composite cementitious material include: C2S: 62wt%, CaO: 30wt%, C3A: 5wt%, and C4AF: 3wt%.

[0041] In this embodiment, the dicalcium silicate-lime composite cementitious material is prepared by calcining low-grade limestone and waste soil cakes at high temperature. The calcination temperature is 1230°C and the calcination time is 45 minutes. The calcined clinker is ground to obtain a specific surface area of ​​350 kg / m 2 The mass ratio of low-grade limestone to waste soil is 8:2 according to the mineral components C2S: 62wt%, CaO: 30wt%, C3A: 5wt%, C4AF: 3wt% in the dicalcium silicate-lime composite cementitious material; the mass ratio of low-grade limestone to waste soil is 8:2 according to the Baugh formula.

[0042] In this embodiment, the mineral components of aluminate cement clinker include: CA: 49wt%, CA2: 23wt%, C2AS: 28wt%, basicity coefficient A m is 1.0.

[0043] In this embodiment, the preparation method of fast-setting and fast-hardening fly ash foam concrete is as follows:

[0044] S1, preparation density M is 400kg / m 3 For foamed concrete, weigh the powder, water and water reducing agent according to the proportions;

[0045] S2, adding the weighed powder and water reducing agent into a mixer and stirring to form a uniform mixture;

[0046] S3, adding a foaming agent and water required for foaming into a foaming machine to generate foam;

[0047] S4, adding the water weighed in S1 to the mixed material, stirring and mixing to form a slurry;

[0048] S5, according to formula V 泡 =1-M / ρ 料 Calculate the added volume V of the foam 泡 0.73m 3 , 0.73m 3 Add the foam into the slurry and stir for 3 minutes to obtain foam slurry.

[0049] Step 6: Pour the obtained foam slurry into a mold and cure it in a natural environment for 24 hours. After demoulding, cure it in a natural environment for 2 days.

[0050] Example 2

[0051] As a preferred embodiment of the present invention, the fast-setting and fast-hardening fly ash foam concrete of this embodiment includes powder, water, a water reducing agent and a foaming agent.

[0052] In this embodiment, the powder includes, by mass percentage, 26wt% of dicalcium silicate-lime composite cementitious material, 12wt% of aluminate cement clinker, 12wt% of dihydrate gypsum, and 50wt% of fly ash.

[0053] In this embodiment, the water-to-material ratio is 0.24.

[0054] In this embodiment, the dosage of the polycarboxylate water reducer is 1.2wt‰ of the powder mass.

[0055] In this embodiment, the slurry density of the prepared fast-setting and fast-hardening fly ash foam concrete is 2000 kg / m 3 .

[0056] In this embodiment, the mineral components of the dicalcium silicate-lime composite cementitious material include: C2S: 50wt%, CaO: 36wt%, C3A: 10wt%, and C4AF: 4wt%.

[0057] In this embodiment, the dicalcium silicate-lime composite cementitious material is prepared by mixing low-grade limestone and waste soil cakes and calcining them at high temperature. The calcination temperature is 1250°C and the calcination time is 20 minutes. The calcined clinker is ground to obtain a specific surface area of ​​330 kg / m 2 The mass ratio of low-grade limestone to waste soil is 8:2 according to the mineral components C2S: 50wt%, CaO: 36wt%, C3A: 10wt%, C4AF: 4wt% in the dicalcium silicate-lime composite cementitious material; the mass ratio of low-grade limestone to waste soil is 8:2 according to the Baugh formula.

[0058] In this embodiment, the mineral components of aluminate cement clinker include: CA: 31wt%, CA2: 36wt%, C2AS: 33wt%, basicity coefficient A m is 0.95.

[0059] In this embodiment, the preparation method of fast-setting and fast-hardening fly ash foam concrete is as follows:

[0060] S1, preparation density M is 400kg / m 3 For foamed concrete, weigh the powder, water and water reducing agent according to the proportions;

[0061] S2, adding the weighed powder and water reducing agent into a mixer and stirring to form a uniform mixture;

[0062] S3, adding a foaming agent and water required for foaming into a foaming machine to generate foam;

[0063] S4, adding the water weighed in S1 to the mixed material, stirring and mixing to form a slurry;

[0064] S5, according to formula V 泡 =1-M / ρ 料 Calculate the added volume V of the foam 泡 0.752m 3 , 0.752m 3 Add the foam into the slurry and stir for 4 minutes to obtain foam slurry.

[0065] Step 6: Pour the obtained foam slurry into a mold and cure it in a natural environment for 24 hours. After demoulding, cure it in a natural environment for 2 days.

[0066] Example 3

[0067] As a preferred embodiment of the present invention, the fast-setting and fast-hardening fly ash foam concrete of this embodiment includes powder, water, a water reducing agent and a foaming agent.

[0068] In this embodiment, the powder includes, by mass percentage, 28wt% of dicalcium silicate-lime composite cementitious material, 9wt% of aluminate cement clinker, 9wt% of dihydrate gypsum, and 54wt% of fly ash.

[0069] In this embodiment, the water-to-material ratio is 0.27.

[0070] In this embodiment, the amount of polycarboxylic acid water-reducing agent added is 1.0wt‰ of the powder mass.

[0071] In this embodiment, the slurry density of the prepared fast-setting and fast-hardening fly ash foam concrete is 1950 kg / m 3 .

[0072] In this embodiment, the mineral components of the dicalcium silicate-lime composite cementitious material include: C2S: 56wt%, CaO: 33wt%, C3A: 7wt%, and C4AF: 4wt%.

[0073] In this embodiment, the dicalcium silicate-lime composite cementitious material is prepared by calcining low-grade limestone and waste soil cakes at high temperature. The calcination temperature is 1200°C and the calcination time is 60 minutes. The calcined clinker is ground to obtain a specific surface area of ​​340 kg / m 2 The mass ratio of low-grade limestone to waste soil is 8:2 according to the mineral components C2S: 56wt%, CaO: 33wt%, C3A: 7wt%, C4AF: 4wt% in the dicalcium silicate-lime composite cementitious material; the mass ratio of low-grade limestone to waste soil is 8:2 according to the Baugh formula.

[0074] In this embodiment, the mineral components of aluminate cement clinker include: CA: 40wt%, CA2: 30wt%, C2AS: 30wt%, basicity coefficient A m It is 0.97.

[0075] In this embodiment, the preparation method of fast-setting and fast-hardening fly ash foam concrete is as follows:

[0076] S1, preparation density M is 400kg / m 3 For foamed concrete, weigh the powder, water and water reducing agent according to the proportions;

[0077] S2, adding the weighed powder and water reducing agent into a mixer and stirring to form a uniform mixture;

[0078] S3, adding a foaming agent and water required for foaming into a foaming machine to generate foam;

[0079] S4, adding the water weighed in S1 to the mixed material, stirring and mixing to form a slurry;

[0080] S5, according to formula V 泡 =1-M / ρ 料 Calculate the added volume V of the foam 泡 0.739m 3 , 0.739m 3 Add the foam into the slurry and stir for 4 minutes to obtain foam slurry.

[0081] Step 6: Pour the obtained foam slurry into a mold and cure it in a natural environment for 24 hours. After demoulding, cure it in a natural environment for 2 days.

[0082] Comparative Example 1

[0083] In this comparative example, ordinary Portland cement clinker is used to completely replace the dicalcium silicate-lime composite cementitious material, with an admixture amount of 28wt%, and the proportions of other raw materials are consistent with those in Example 3. The preparation method of the foamed concrete is consistent with that in Example 3.

[0084] Comparative Example 2

[0085] In this comparative example, sulphoaluminate clinker is used to completely replace aluminate cement clinker, with an admixture amount of 9wt%, and the proportions of other raw materials are consistent with those in Example 3. The preparation method of foamed concrete is consistent with that in Example 3.

[0086] Test Case

[0087] The foamed concrete of Examples 1 to 3 and Comparative Examples 1 to 2 were tested for strength at various ages and 28d shrinkage. The test results are shown in Table 1.

[0088] Table 1 Test results of foamed concrete in various embodiments and comparative examples

[0089] serial number 3d strength / MPa 28d strength / MPa Shrinkage rate / % Example 1 1.3 2.3 0.15 Example 2 1.4 2.6 0.13 Example 3 1.3 2.5 0.13 Comparative Example 1 1.0 1.6 0.20 Comparative Example 2 0.8 1.4 0.21

[0090] From the results in Table 1, it can be seen that in Examples 1 to 3, the 3d and 28d compressive strengths are higher than those of the comparative example, and have the characteristics of early strength; from the shrinkage results, the shrinkage rates of each embodiment are less than 0.2%, while the shrinkage rates of the comparative example are higher or greater than 0.2%. Therefore, the fly ash foam concrete prepared by the dicalcium silicate-lime composite cementitious material, aluminate cement and dihydrate gypsum system can achieve early strength and low shrinkage.

[0091] Figure 1 : is a SEM image of the dicalcium silicate-lime composite cementitious material of the present invention. Figure 1 As shown, the calcium oxide (CaO) particles in the dicalcium silicate-lime composite cementitious material are popcorn-shaped, with a size of about 5 to 10 μm, and have a faster digestion rate; while the dicalcium silicate (C2S) has a size of about 1 μm and has good hydration activity.

[0092] Finally, it should be noted that the above embodiments are only preferred embodiments of the present invention to illustrate the technical solutions of the present invention, rather than limiting them, and certainly not limiting the patent scope of the present invention. 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 recorded in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention. In other words, any changes or modifications made to the main design concept and spirit of the present invention that have no substantive significance, and the technical problems they solve are still consistent with the present invention, should be included in the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention in other related technical fields is also included in the patent protection scope of the present invention.

Claims

1. A fast-setting and fast-hardening fly ash foam concrete, characterized in that: The invention comprises powder, water, a water reducing agent and a foaming agent; the powder comprises the following components in percentage by mass: 26-30wt% of dicalcium silicate-lime composite cementitious material, 5-12wt% of aluminate cement clinker, 5-12wt% of dihydrate gypsum and 50-60wt% of fly ash; the amount of water is calculated according to a water-to-material ratio of 0.24-0.30; the amount of the water reducing agent is 0.8-1.2wt‰ of the mass of the powder; the foaming agent is used for configuring foam, and the added volume of the foam is obtained based on the bulk density of the foamed concrete.

2. The fast-setting and fast-hardening fly ash foam concrete according to claim 1, characterized in that: The dicalcium silicate-lime composite cementitious material comprises the following mineral components in percentage by weight: C2S: 50-62wt%, CaO: 30-36wt%, C3A: 5-10wt%, and C4AF: 3-4wt%.

3. The fast-setting and fast-hardening fly ash foam concrete according to claim 1, characterized in that: The dicalcium silicate-lime composite cementitious material is prepared by mixing low-grade limestone and waste soil cakes and calcining them at high temperature. The calcination temperature is 1200-1250° C. and the calcination time is 20-60 min. The calcined clinker is ground to obtain a specific surface area of ​​330-350 kg / m 2 The quality of the low-grade limestone and waste soil cake ingredients is calculated based on the mineral composition of the dicalcium silicate-lime composite cementitious material and the Baugh formula.

4. The fast-setting and fast-hardening fly ash foam concrete according to claim 3, characterized in that: The low-grade limestone has a loss on ignition of 40.13±2wt%, and includes the following mineral components in mass percentage: SiO2: 6.04±2wt%, Al2O3: 1.77±0.5wt%, Fe2O3: 0.73±0.5wt%, CaO: 49.00±2wt%, MgO: 1.10±0.5wt%.

5. The fast-setting and fast-hardening fly ash foam concrete according to claim 3, characterized in that: The waste soil has a loss on ignition of 17.00±2wt%, and includes the following mineral components in mass percentage: SiO2: 43.60±2wt%, Al2O3: 13.67±2wt%, Fe2O3: 21.51±2wt%, CaO: 1.85±2wt%, and MgO: 2.29±2wt%.

6. The fast-setting and fast-hardening fly ash foam concrete according to claim 1, characterized in that: The aluminate cement clinker comprises the following mineral components in percentage by weight: CA: 31-49 wt%, CA2: 23-36 wt%, C2AS: 28-33 wt%.

7. The fast-setting and fast-hardening fly ash foam concrete according to claim 1, characterized in that: The basicity coefficient A of the aluminate cement clinker m It is 0.9~1.

0.

8. The fast-setting and fast-hardening fly ash foam concrete according to claim 1, characterized in that: The slurry density of the foamed concrete is 1900-2000 kg / m 3 .

9. The fast-setting and fast-hardening fly ash foam concrete according to claim 1, characterized in that: The water reducer is a polycarboxylic acid water reducer; the foaming agent is one of silicone resin polyether emulsion, lauryl alcohol and calcium stearate.

10. The method for preparing fast-setting and fast-hardening fly ash foam concrete according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. According to the bulk density of the foamed concrete to be prepared, the powder, water, and water reducing agent are weighed in proportion, wherein the bulk density of the foamed concrete is the mass of the powder; S2, adding the weighed powder and water reducing agent into a mixer and stirring to form a uniform mixture; S3, adding a foaming agent and water required for foaming into a foaming machine to generate foam; S4, adding the water weighed in S1 to the mixed material, stirring and mixing to form a slurry; S5, according to formula V 泡 =1-M / ρ 料 Calculate the added volume V of the foam 泡 , the volume is V 泡 Add the foam into the slurry and stir for 3 to 4 minutes to obtain the foam slurry. M is the sum of the mass of powder and water in the foam concrete. 料 is the slurry density of foam concrete; S5. Pour the foam slurry into the mold and cure it in the natural environment for 24 hours. After demoulding, cure it in the natural environment for 2 days.

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