Dolomitic aerated concrete and method for its production

Abstract

The application discloses dolomite aerated concrete, raw materials and weight fractions of the dolomite aerated concrete, and the weight fractions of the raw materials comprise the following: cement 25-35 parts, dolomite powder 50-60 parts, quartz powder 15-20 parts, sodium sulfate 0.2-0.5 parts, water 30-40 parts, water reducing agent 0.05-0.1 parts and foaming agent 0.08-0.12 parts. The application can realize high-mixing application of dolomite industrial solid waste in the aerated concrete, greatly reduce the amount of high-silicon materials under the premise of good mechanical properties, heat preservation performance and shrinkage performance, and the like. The curing method is short in preparation period and is suitable for popularization and application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of building materials, and particularly relates to dolomite aerated concrete and a preparation method thereof. BACKGROUND

[0002] At present, the siliceous raw materials of autoclaved aerated concrete mainly include high-silicon sand (river sand, river sand, etc.) and fly ash, and the strength is from the hydration of calcium materials (cement, lime) and siliceous materials in the curing process to generate hydrated calcium silicate, tobermorite and ettringite. However, with the increasing scarcity of high-quality high-silicon sand, it has become a development trend in the industry to use other materials with wide distribution, high reserves and low price to partially or completely replace high-silicon sand to prepare autoclaved aerated concrete.

[0003] At present, many autoclaved aerated factories use industrial high-silicon solid waste to replace part of high-silicon sand, and have achieved certain results, but there are still some significant problems. The impurities introduced in the processing of raw materials are not conducive to the quality control of production.

[0004] Dolomite deposit resources are abundant, and the proven reserves can meet the needs of economic construction. However, the magnesium content in dolomite is high, and considering that high magnesium content may cause poor volume stability of building materials, the use range of dolomite raw materials in the field of building materials is very limited. For example, the magnesium content is strictly limited in the product quality standards of ordinary Portland cement and lime, and there is little research on the preparation of autoclaved aerated concrete using dolomite materials. SUMMARY

[0005] The main purpose of the present application is to solve the problems and deficiencies in the prior art, and to provide a dolomite aerated concrete and a preparation method thereof. Under the premise of greatly reducing the amount of high-silicon materials, good mechanical properties, thermal properties and shrinkage properties are considered. The curing method has a shorter preparation period and is suitable for popularization and application.

[0006] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0007] A dolomite aerated concrete, the raw materials and the weight percentage thereof include: cement 25-35 parts, dolomite powder 50-60 parts, quartz powder 15-20 parts, sodium sulfate 0.2-0.5 parts, water 30-40 parts, water reducing agent 0.05-0.1 parts, and foaming agent 0.08-0.12 parts.

[0008] In the above scheme, the cement is ordinary Portland cement, and the grade is above 42.5.

[0009] In the above scheme, the dolomite powder contains 65-95wt% CaMg(CO3)2, 0-35wt% SiO2, 0-10wt% CaCO3, and 0-10wt% clay minerals; and the fineness is 5-15% of 80μm residue.

[0010] In the above scheme, the quartz powder contains 85-100% SiO2 and 0-5% clay minerals; and the fineness is 5-10wt% of 80μm residue.

[0011] In the above scheme, the effective component of the sodium sulfate is more than 95%.

[0012] In the above scheme, the water-reducing agent is polycarboxylic acid superplasticizer, and the water-reducing rate is 35-45%.

[0013] In the above scheme, the foaming agent is preferably a physical foaming agent, and the pH value is 6-8; after being diluted 45-60 times with water, the water discharge amount of the foam produced by the foaming machine is less than 40ml, the sedimentation distance is less than 10mm, and the density is 30-50kg / m 3 ; and the protein foaming agent can be specifically selected.

[0014] The above method for preparing dolomite aerated concrete comprises the following steps:

[0015] 1) Measure the cement, dolomite powder, quartz powder, sodium sulfate, water-reducing agent, and water according to the proportions, and perform stirring treatment to obtain a neat slurry;

[0016] 2) Measure the physical foaming agent according to the proportions, dilute it (45-60 times) with water (extra water, not included in the formula), and produce foam by foaming;

[0017] 3) Mix the neat slurry with the foam, and perform stirring treatment to obtain a finished slurry;

[0018] 4) Pour the obtained finished slurry into a mold frame, and perform static standing, gasification hardening, demolding, and cutting to obtain an aerated concrete blank, and perform steam pressure curing to obtain a dolomite aerated concrete product.

[0019] In the above scheme, the stirring treatment step of step 1) comprises: first slow stirring at a speed of 90-120r / min for 2-4min, and then fast stirring at a speed of 900-1200r / min for 1-2min; and the stirring treatment step of step 3) comprises: first slow stirring at a speed of 60-90r / min for 2-4min, and then fast stirring at a speed of 120-250r / min for 1-2min.

[0020] In the above scheme, the temperature used in the static standing and gasification hardening step is 45-55℃, the relative humidity is not less than 80%, and the static standing time is 3-4h.

[0021] In the above scheme, in the autoclaved curing process, vacuum is first extracted, the vacuum degree is -0.04 to -0.06 MPa, then saturated water vapor is filled to rise the temperature to the target curing temperature (150 to 180 DEG C), constant temperature curing is carried out, finally, exhaust and cooling are carried out to obtain the autoclaved aerated concrete product.

[0022] Further, the saturated water vapor temperature is 150 to 200 DEG C, and the pressure is 0.5 to 1.4 MPa.

[0023] In the above scheme, in the aeration process, first, the temperature in the kettle is raised to 130 to 150 DEG C at a rate of 1 to 1.5 DEG C / min, and then the temperature in the kettle is raised to 150 to 180 DEG C at a rate of 2 to 3 DEG C / min for 3 to 4 h. After the curing is completed, exhaust and cooling are carried out to end the curing.

[0024] Further, in the cooling step, first, the temperature is lowered to 80 to 100 DEG C at a rate of 1.5 to 2.5 DEG C / min, and then the kettle is opened.

[0025] The dolomite aerated concrete prepared according to the above scheme has a compressive strength of 4.0 MPa or more, a bulk density of 620 to 650 kg / m 3 , a dry shrinkage of 0.19 to 0.21 mm / m, and a thermal conductivity of 0.13 W / (m*K) or less.

[0026] The performance optimization mechanism of the aerated concrete according to the application includes:

[0027] 1) The application is directed to a two-stage autoclaved curing process using dolomite powder, cement and quartz powder as the main raw material system. In the first stage (130 to 150 DEG C), the main reaction process is that the cement first reacts to generate hydrated calcium silicate and calcium hydroxide and other hydration products; then the dolomite powder reacts with the calcium hydroxide to generate calcium carbonate, magnesium hydroxide and other minerals; in addition, the addition of sodium sulfate increases the alkalinity in the liquid phase and promotes the reaction process of the dolomite; in the second stage (150 to 180 DEG C), the main reaction process is that the dolomite reaction product magnesium hydroxide reacts with the quartz powder to generate hydrated magnesium silicate; the hydrated calcium silicate crystallizes to generate tobermorite; the dolomite powder no longer exists only as an inert filler in the autoclaved aerated concrete, but has reactivity and generates different reaction products in the first and second stages, thereby promoting and improving the strength of the product.

[0028] 2) The dolomite reaction product magnesium hydroxide is partially dissolved in the hydrated calcium silicate crystals, making the crystals thicker and thicker, and also promoting the formation of C-S-H gel and the crystallization of tobermorite. The improvement of the morphology of the hydration products and the promotion of the formation of the hydration products by the magnesium hydroxide are beneficial to improving the mechanical properties of the obtained aerated concrete.

[0029] 3) The first stage of the autoclaved curing described in the application can generate a large amount of structural loose and strong expansibility magnesium hydroxide, but in this stage, since the quartz powder basically does not participate in the reaction, the capillary porosity is large, which can effectively solve the problem of poor volume stability caused by the enrichment of magnesium hydroxide in this stage; further combined with the second stage of autoclaved curing, magnesium hydroxide further reacts with quartz to form magnesium silicate hydrate, which can effectively improve the amount of hydration product while reducing the weak point of strength, and promote the strength development of aerated concrete.

[0030] Compared with the prior art, the application has the following beneficial effects:

[0031] 1) The dolomite powder is used to replace a large amount of siliceous material in the application, and combined with the stage autoclaved curing process, the reaction product magnesium hydroxide of dolomite is formed in the first stage and further forms magnesium silicate hydrate in the second stage, which solves the negative impact of the reaction product magnesium hydroxide of dolomite on the performance of aerated concrete, and provides a new technical solution for the resource utilization of dolomite powder.

[0032] 2) During the autoclaved curing process, a large amount of calcium carbonate is generated by the reaction of dolomite powder, which has high strength and no gel pores, and can effectively inhibit the shrinkage problem caused by capillary tension during the dehydration process of capillary pores and gel pores, which is beneficial to reduce the drying shrinkage value of aerated concrete.

[0033] 3) The reaction product magnesium hydroxide of dolomite can promote the formation of C-S-H gel and the crystallization of tobermorite, which is beneficial to shorten the curing time and reduce the curing temperature compared with conventional autoclaved aerated concrete, and promote the production efficiency and reduce the steam consumption. DETAILED DESCRIPTION

[0034] The application will be further described in detail below in combination with examples, so that the application can be more clearly understood, but they do not constitute a limitation on the application.

[0035] In the following examples and comparative examples, the cement used is P·O42.5 ordinary portland cement. The dolomite powder CaMg(CO3)2 content is 81%, the SiO2 content is 6%, the CaCO3 content is 7%, the clay mineral content is 4%, and the fineness is 8% of 80 μm residue. The quartz powder SiO2 content is 94%, the clay mineral content is 4%, and the fineness is 6% of 80 μm residue. The effective ingredient of sodium sulfate is 97%. The water-reducing rate of polycarboxylic acid water reducer is 40%. The physical foaming agent used is HTW-1 plant protein composite foaming agent provided by Henan Huatai New Material Technology Co., Ltd., with pH value of 6.5. The foam bleeding amount prepared after dilution of 50 times is 25 ml, the sedimentation distance is 6 mm, and the density is 43 kg / m 3 The high-temperature saturated steam temperature used in the autoclaved curing process is 200℃, and the pressure is 1.4 MPa.

[0036] Example 1

[0037] A preparation method of dolomite aerated concrete, comprising the following steps:

[0038] (1) Take cement 30 parts, dolomite powder 55 parts, quartz stone powder 15 parts, sodium sulfate 0.3 parts, water 35 parts, water reducing agent 0.08 parts, and first slowly stir at a speed of 90 r / min for 4 min, and then quickly stir at a speed of 1200 r / min for 1 min to obtain a neat slurry;

[0039] (2) Take 0.1 parts of foaming agent, dilute with water 50 times, and then use a foaming machine to make foam;

[0040] (3) Mix the neat slurry with the foam, and first slowly stir at a speed of 60 r / min for 4 min, and then quickly stir at a speed of 120 r / min for 1 min to obtain a finished slurry;

[0041] (4) Pour the obtained finished slurry into a mold frame and stand still to harden, the standing still chamber temperature is 50℃, the relative humidity is 85%, and after standing still for 3.5h, demold and cut to obtain an aerated concrete blank;

[0042] (5) After the aerated concrete blank is autoclaved and cured, the finished product is obtained; during the curing process, first vacuumize to-0.05MPa, then fill in saturated water vapor (temperature 200℃, pressure 1.4MPa), first increase the temperature to 140℃ at a rate of 1.2℃ / min and keep for 3h, then increase the temperature to 160℃ at a rate of 2.5℃ / min and keep for 3h, exhaust and cool, decrease the temperature to 100℃ at a rate of 2.0℃ / min, and after opening the autoclave, the aerated concrete finished product is obtained.

[0043] Example 2

[0044] A preparation method of dolomite aerated concrete, the preparation method is substantially the same as that of Example 1, except that during the curing process, first vacuumize to-0.05MPa, then fill in saturated water vapor (temperature 200℃, pressure 1.4MPa), increase the temperature to 140℃ at a rate of 1.2℃ / min and keep for 4h, then increase the temperature to 180℃ at a rate of 2.5℃ / min and keep for 4h, after the curing is completed, exhaust and cool, decrease the temperature to 100℃ at a rate of 2.0℃ / min, and after opening the autoclave, the aerated concrete finished product is obtained.

[0045] Example 3

[0046] A preparation method of dolomite aerated concrete, which is substantially the same as that of embodiment 1, except that 35 parts of cement, 50 parts of dolomite powder, 15 parts of quartz powder, 0.3 parts of sodium sulfate, 35 parts of water and 0.08 parts of water reducing agent are taken, and the mixture is stirred at a speed of 90 r / min for 4 min and then at a speed of 1200 r / min for 1 min to obtain a net slurry.

[0047] Comparative example 1

[0048] A preparation method of dolomite aerated concrete, which is substantially the same as that of embodiment 1, except that during the curing process, the vacuum is first extracted to-0.05 MPa, then saturated water vapor is filled, the temperature is increased to 160℃ at a rate of 1.2℃ / min, and the temperature is kept for 6 h, the exhaust is extracted at a rate of 2.0℃ / min to reduce the temperature to 100℃, and the aerated concrete product is obtained after the kettle is opened.

[0049] Comparative example 2

[0050] A preparation method of dolomite aerated concrete, which is substantially the same as that of embodiment 1, except that 30 parts of cement, 55 parts of dolomite powder, 15 parts of secondary fly ash, 0.3 parts of sodium sulfate, 35 parts of water and 0.08 parts of water reducing agent are taken, and the mixture is stirred at a speed of 90 r / min for 4 min and then at a speed of 1200 r / min for 1 min to obtain a net slurry.

[0051] Comparative example 3

[0052] A preparation method of dolomite aerated concrete, which is substantially the same as that of embodiment 1, except that no sodium sulfate is introduced in step 1).

[0053] The autoclaved aerated concrete obtained in examples 1-3 and comparative examples 1-3 is subjected to performance testing according to standard GB / T 11969-2008, and the results are shown in table 1.

[0054] Table 1: Performance testing results of autoclaved aerated concrete

[0055]

[0056] The present application is not limited to the above-described embodiments, and those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements are also considered to be within the scope of protection of the present application. The contents not described in detail in the specification are the existing technology known to those skilled in the art.

Claims

1. A dolomite aerated concrete, characterized in that: The raw materials and their weight proportions include: 25-35 parts of cement, 50-60 parts of dolomite powder, 15-20 parts of quartz powder, 0.2-0.5 parts of sodium sulfate, 30-40 parts of water, 0.05-0.1 parts of water reducing agent, and 0.08-0.12 parts of foaming agent; The preparation method of the dolomite aerated concrete comprises the following steps: 1) Measure cement, dolomite powder, quartz powder, sodium sulfate, water reducer, and water according to the proportion, stir, and obtain a slurry; 2) Measure the physical foaming agent according to the ratio and dilute it with water to make foam; 3) Mix the clean slurry with the foam and stir to obtain the finished slurry; 4) Casting the obtained finished slurry, stopping the gas generation and hardening, demoulding to obtain an aerated concrete body, and autoclaving and curing to obtain a finished dolomite aerated concrete product; The autoclave curing step includes: first, vacuuming, then filling with saturated water vapor and heating to the target curing temperature, performing constant temperature curing, and finally exhausting and cooling; The heating and constant temperature maintenance steps of filling with saturated water vapor include: firstly, heating the temperature in the kettle to 130-150°C at a rate of 1-1.5°C / min and keeping it warm for 3-4 hours, and then heating the temperature in the kettle to 150-180°C at a rate of 2-3°C / min and keeping it warm for 3-4 hours.

2. The dolomite aerated concrete according to claim 1, characterized in that: The dolomite powder has a CaMg(CO3)2 content of 65-95wt%, a SiO2 content of 0-35wt%, a CaCO3 content of 0-10wt%, and a clay mineral content of 0-10wt%; and a fineness of 80μm sieve residue of 5-15%.

3. The dolomite aerated concrete according to claim 1, characterized in that: The quartz powder has a SiO2 content of 85-100% and a clay mineral content of 0-5%; and the fineness requirement is 5-10% of the residue on an 80 μm sieve.

4. The dolomite aerated concrete according to claim 1, characterized in that: The cement is ordinary Portland cement, grade 42.5 or above.

5. The dolomite aerated concrete according to claim 1, characterized in that: The water reducer is a polycarboxylic acid high-efficiency water reducer with a water reduction rate of 35-45%.

6. The dolomite aerated concrete according to claim 1, characterized in that: The foaming agent is a physical foaming agent.

7. The method for preparing dolomite aerated concrete according to any one of claims 1 to 6, characterized in that: The steps include: 1) Measure cement, dolomite powder, quartz powder, sodium sulfate, water reducer, and water according to the proportion, stir, and obtain a slurry; 2) Measure the physical foaming agent according to the ratio and dilute it with water to make foam; 3) Mix the clean slurry with the foam and stir to obtain the finished slurry; 4) The finished slurry is poured, aerated and hardened, and demoulded to obtain an aerated concrete body, which is then autoclaved and cured to obtain a finished dolomite aerated concrete product.

8. The preparation method according to claim 7, characterized in that The temperature of the saturated water vapor is 150-200° C., and the pressure is 0.5-1.4 MPa.

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