阅读说明：本技术 一种加气混凝土用减缩剂及其应用方法 (Shrinkage reducing agent for aerated concrete and application method thereof ) 是由 张鑫 任鹏飞 贾虎琛 于 2020-06-11 设计创作，主要内容包括：本发明属于建筑材料技术领域,具体涉及一种加气混凝土用减缩剂及其应用方法,按重量份计包括如下组分：煅烧蛇纹石20-30份、改性松针凋落物13-19份,本发明的减缩剂能够填充在混凝土内部毛细孔中,抑制了加气混凝土孔隙率的增大进而保证了抗压强度,提高混凝土制品的耐久性能,具有抑碱性,低能耗、低成本,利用了废弃物,实现了资源最大化利用,还降低了工艺条件,减少了能耗和成本；属温控型,能够降低水化热。(The invention belongs to the technical field of building materials, and particularly relates to a shrinkage reducing agent for aerated concrete and an application method thereof, wherein the shrinkage reducing agent comprises the following components in parts by weight: 20-30 parts of calcined serpentine and 13-19 parts of modified pine needle litter, wherein the shrinkage reducing agent can be filled in capillary pores inside concrete, so that the increase of porosity of aerated concrete is inhibited, the compressive strength is further ensured, the durability of a concrete product is improved, the shrinkage reducing agent has the advantages of alkali inhibition, low energy consumption and low cost, wastes are utilized, the maximum utilization of resources is realized, the process conditions are also reduced, and the energy consumption and the cost are reduced; belongs to a temperature control type, and can reduce hydration heat.)

1. The shrinkage reducing agent for aerated concrete is characterized by comprising the following components in parts by weight: 20-30 parts of calcined serpentine and 13-19 parts of modified pine needle litter.

2. A shrinkage reducing agent for aerated concrete according to claim 1, which comprises the following components in parts by weight: 24 parts of calcined serpentine and 16 parts of modified pine needle litter.

3. A shrinkage-reducing agent for aerated concrete according to claim 1 or 2, wherein the calcined serpentine is produced by a method comprising: grinding serpentine by a ball mill until the serpentine passes through a 600-mesh sieve, then placing the serpentine under the condition of 160-320W for microwave irradiation for 10-20min, then uniformly mixing the serpentine with sodium hydroxide, adding the serpentine into a tube furnace, heating the serpentine to 420 ℃ at the speed of 15-20 ℃/min, preserving the heat for 10-15min, cooling the serpentine to room temperature, soaking the serpentine in 75-80 ℃ water for 20-25min, filtering, dehydrating the solid at high temperature, and cooling to obtain calcined serpentine; wherein the mass ratio of the serpentine powder to the sodium hydroxide is 1: (2.1-2.7).

4. A shrinkage reducing agent for aerated concrete according to claim 3, wherein the high-temperature dehydration is carried out by placing the solid into a tube furnace, heating to 220 ℃ at a rate of 10-15 ℃/min, and holding for 10-20min, and then heating to 400 ℃ at a rate of 20-30 ℃/min, and holding for 10-15 min.

5. A shrinkage reducing agent for aerated concrete according to claim 1 or 2, wherein the modification method of the modified pine needle litter comprises the following steps:

(1) loading the pine needle litters into a steam explosion tank for steam explosion to obtain steam explosion pine needle litters;

(2) and (3) treating the steam exploded pine needle litter through plasma, and mixing the treated pine needle litter with acetic acid at 45-60 ℃ for 10-15min to obtain the modified pine needle litter.

6. The shrinkage reducing agent for aerated concrete according to claim 5, wherein the steam explosion process in the step (1) comprises introducing steam with the temperature of 130-160 ℃ into the steam explosion tank until the pressure is 1.5-2.3MPa, maintaining the pressure for 120s, opening a valve of the steam explosion tank instantly, releasing the pressure to normal pressure, and taking out the steam explosion tank.

7. A shrinkage reducing agent for aerated concrete according to claim 5, wherein in the step (2), the plasma treatment is performed by using oxygen as a treatment atmosphere, the treatment power is 40-50w, the oxygen flow is 0.1-0.2L/min, and the treatment time is 120-.

8. The application method of the shrinkage reducing agent for aerated concrete according to claim 1 or 2, which is characterized by comprising the following steps: the modified pine needle litter is uniformly mixed with calcined serpentine, then the gelled material is added and mixed for 3-7min at room temperature, and then other auxiliary agents and water are sequentially added and fully mixed for construction.

9. The application method of the shrinkage reducing agent for aerated concrete according to claim 1 or 2, which is characterized by comprising the following steps: the shrinkage reducing agent for aerated concrete and the swill-cooked dirty oil are mixed according to the mass ratio of 1: (0.01-0.02) are co-incorporated into the cement.

10. The method for applying the shrinkage reducing agent for aerated concrete according to claim 8 or 9, wherein the shrinkage reducing agent for aerated concrete is used in an amount of 3 to 5% by weight based on the weight of the cement.

Technical Field

The invention belongs to the technical field of building materials, and particularly relates to a shrinkage reducing agent for aerated concrete and an application method thereof.

Background

Compared with common concrete, the aerated concrete has excellent performances of light weight, heat preservation, heat insulation, sound insulation, fire prevention, earthquake resistance and the like, so the aerated concrete is widely applied, but in practical application, the aerated concrete has the characteristics of lack of aggregate, high porosity and the like, the shrinkage of the aerated concrete is seriously larger than that of the common concrete due to structural difference, and the adverse phenomena of cracking, hollowing and the like caused by the severe shrinkage of the aerated concrete severely limit the popularization and application of the aerated concrete.

Drying shrinkage is the main shrinkage form causing shrinkage and cracking of the surface layer of the aerated concrete, and then the cracks caused by volume shrinkage provide quick channels for media such as erosive ions and the like during the service period of the concrete, finally, the deterioration of the concrete structure is accelerated, and further, the durability of the aerated concrete is not ideal. At present, the shrinkage reducing agent can change the capillary pore tension of the aerated concrete, reduce shrinkage, hydrate expansion components, expand volume and compensate shrinkage, so that the reasonable utilization of the shrinkage reducing agent is very important for the engineering application of the aerated concrete.

The shrinkage reducing agents developed and researched in the market at present mainly comprise NA-SP series shrinkage reducing agents, JM-SRA shrinkage reducing agents (the main component is alkyl polyoxyethylene ether) and JSJ type shrinkage reducing agents (the main component is polyether and aliphatic polymer composite organic matters), but the shrinkage reducing agents are only suitable for common concrete and can cause loss of the compressive strength of the concrete. Patent application No. CN201911026268.1 discloses that the shrinkage reducing agent for aerated concrete comprises polyoxyethylene ether and pentaerythritol, but the shrinkage reducing agent can only solve the problems of drying shrinkage and self-shrinkage, and can not solve the phenomena of cracking and the like caused by large temperature difference between the inside and the outside of the concrete and too high cooling rate.

Disclosure of Invention

The invention provides a shrinkage reducing agent for aerated concrete and an application method thereof, aiming at the defects of the prior art.

The method is realized by the following technical scheme:

in a first aspect, the invention provides a shrinkage reducing agent for aerated concrete, which comprises the following components in parts by weight: 20-30 parts of calcined serpentine and 13-19 parts of modified pine needle litter.

Preferably, the shrinkage reducing agent for aerated concrete comprises the following components in parts by weight: 24 parts of calcined serpentine and 16 parts of modified pine needle litter.

Further, the manufacturing method of the calcined serpentine comprises the following steps: grinding serpentine by a ball mill until the serpentine passes through a 600-mesh sieve, then placing the serpentine under the condition of 160-320W for microwave irradiation for 10-20min, then uniformly mixing the serpentine with sodium hydroxide, adding the serpentine into a tube furnace, heating the serpentine to 420 ℃ at the speed of 15-20 ℃/min, preserving the heat for 10-15min, cooling the serpentine to room temperature, soaking the serpentine in 75-80 ℃ water for 20-25min, filtering, dehydrating the solid at high temperature, and cooling to obtain calcined serpentine; wherein the mass ratio of the serpentine powder to the sodium hydroxide is 1: (2.1-2.7).

The high-temperature dehydration is to put the solid into a tube furnace, heat up to 220 ℃ at the speed of 10-15 ℃/min, preserve heat for 10-20min, then heat up to 400 ℃ at the speed of 20-30 ℃/min, and preserve heat for 10-15 min.

The modified pine needle litter modification method comprises the following steps:

(1) loading the pine needle litters into a steam explosion tank for steam explosion to obtain steam explosion pine needle litters;

(2) and (3) treating the steam exploded pine needle litter through plasma, and mixing the treated pine needle litter with acetic acid at 45-60 ℃ for 10-15min to obtain the modified pine needle litter.

The steam explosion process in the step (1) is to introduce water vapor with the temperature of 130-160 ℃ into the steam explosion tank until the pressure is 1.5-2.3MPa, and to maintain the pressure for 120-180 seconds to instantly open the valve of the steam explosion tank, and to release the pressure to the normal pressure and then take out.

And (2) performing plasma treatment, wherein oxygen is adopted as a treatment atmosphere, the treatment power is 40-50w, the oxygen flow is 0.1-0.2L/min, and the treatment time is 120-150 s.

And (3) the usage amount of the acetic acid in the step (2) is 3-7% of the quality of the pine needle litter.

The mixing in the step (2) is to stir and react for 15min at the speed of 200-300 r/min at the temperature of 70-80 ℃.

In a second aspect, the present invention provides a method for applying the shrinkage reducing agent for aerated concrete, which comprises: the modified pine needle litter is uniformly mixed with calcined serpentine, then the gelled material is added and mixed for 3-7min at room temperature, and then other auxiliary agents and water are sequentially added and fully mixed for construction.

Preferably, the shrinkage reducing agent for aerated concrete and the swill-cooked dirty oil are mixed according to a mass ratio of 1: (0.01-0.02) are co-incorporated into the cement.

Preferably, the shrinkage reducing agent for aerated concrete is 3-5% of the weight of the cementing material.

In the invention, serpentine is a natural magnesium-containing silicate mineral, is metamorphic rock of olivine and has a general formula of Mg₃Si₂O₅(OH)₄A layered phyllosilicate mineral formed by bonding a silicon-oxygen tetrahedral wafer and a magnesium hydroxide octahedral wafer; according to the invention, the serpentine is calcined by using alkali mixture, so that the silicon and the magnesium are effectively separated; before calcination, serpentine is subjected to mechanical activation-microwave irradiation treatment, so that the activity of serpentine is excited, and the method has the following advantages: firstly, the calcining temperature and time are reduced, and more importantly, the using amount of sodium hydroxide is also reduced, so that the problem of high cost of the traditional alkali-fused serpentine is solved; secondly, the process condition treatment is adopted, the silicon extraction rate is calculated after the content of the silicon element in the filtered filtrate is measured by adopting a sodium fluoride acid-base titration method, the silicon extraction rate is about 90.7 percent, the silicon extraction rate of the comparative example 1 is about 80.3 percent, the silicon extraction rate of the comparative example 2 is about 77.5 percent, and the filtrate can be processed to produce silicon products such as fumed silica, white carbon black and the like; the product after dehydration at high temperature (400 ℃) was subjected to phase analysis and component analysis, and the results showed that: the silicon element content in the calcined serpentine is reduced, the iron element is suddenly reduced, the magnesium element is enriched, and the active magnesium oxide content reaches 78.1 percent; and then, the steps of high-temperature dehydration and cooling are utilized to increase the grain size of the magnesium oxide, so that the activity of the magnesium oxide is passivated, the expansion time of the magnesium oxide is slowed, and the ineffective expansion is avoided.

According to the invention, the pine needle litter is utilized, so that the waste is recycled, and the accumulation pressure of the pine needle litter is relieved; according to the invention, the characteristics of low water-soluble substance content and high lignin content of the pine needle litter are utilized, a water reducing effect can be achieved, high-temperature and high-pressure steam is utilized to permeate and infiltrate the cell walls of the pine needle litter through a diffusion effect, the cells are expanded and broken by depressurization, a lignin wrapping effect and a cellulose crystal structure are broken, and then plasma treatment is carried out to generate hydroxyl active sites on the surface of the pine needle litter, so that the workability of a material system can be improved, and then acetic acid soaking is adopted to weaken hydrogen bond acting forces between molecules and in the molecules, increase steric hindrance, destroy the structure of a crystal region, and simultaneously enable the surface of the pine litter to contain carboxyl pine needle functional groups, so that the pine needle litter can also be used as a hydration heat inhibiting component, and further solve the problems of cracking and the like caused by excessive internal and external temperature difference due to more self heat release and; in addition, the low-water-solubility substances contained in the pine needle litter can play a supporting role, and the tensile stress generated by the lignin distributed in the aerated concrete is combined, so that the effect of reducing cracks is achieved. More importantly, the pine needle litter contains stable carbon, can adsorb alkaline substances, and prevents the concrete from returning to alkali.

Preferably, the waste oil is used, and C in the grease₃H₅(OOCR)₃Reacts with the hydroxide, and the resultant is filled in the concrete pores to reduce the shrinkage value of the concrete and prevent the occurrence of the saltpetering phenomenon.

Compared with other methods, the method has the beneficial technical effects that:

(1) the durability is high; the shrinkage reducing agent can be filled in capillary pores inside concrete, so that the increase of the porosity of the aerated concrete is inhibited, the compressive strength is further ensured, and the durability of a concrete product is improved.

(2) Inhibiting alkalinity.

(3) Controlling the temperature; the expanding agent can reduce the hydration heat.

(4) Low energy consumption and low cost. The invention not only utilizes the waste, realizes the maximum utilization of resources, but also reduces the process conditions and reduces the energy consumption and the cost.

Detailed Description

The following is a detailed description of the embodiments of the present invention, but the present invention is not limited to these embodiments, and any modifications or substitutions in the basic spirit of the embodiments are included in the scope of the present invention as claimed in the claims.

The composition of serpentine in the examples and comparative examples is as follows: SiO 2₂38.97％，MgO38.13％，Fe₂O₃13.15％，Al₂O₃0.38％，CaO0.11％，NiO0.35％，Cr₂O₃1.52％。