The Preparation Of High Quality Aerated Concrete And Matched Specialized Thin-layer Motar For Dry Construction

The autoclaved aerated concrete is a kind of single insulation wall material which can meet the energy conservation of buildings up to 50%(mostly requiring sandwich wall materials). With the advantages of lightweight, waste ulitization, heat insulation, long service life, machinability, it has been playing a more and more important role in the construction. However, due to the instability of raw material, improper mix proportion design, and non-standard production technology, the blocks have lower strength, larger size deviation and unstable performance. Therefore, its application is confined to non bearing structure, rarely in bearing structure; In the meanwhile, these all bring difficulties of masonry which not only increase the consumption of mortar, but also influence the thermal performance of the entire wall. In response to these problems, this paper studied the influence of raw material and some vital techniques on the performance of autoclaved aerated concrete, then optimized. Searched appropriate mixture ratio design method of producing high imposeaerated concrete, starting from the raw material chemical composition and pore structure. Researched high performance thin-layer mortar specifically for aerated concrete and realized dry construction of thin layer. This paper has important practical value.Firstly, the impact of raw materials was researched. To acquire high strength autoclaved aerated concrete, it is suggested that as for lime, the content of MgO in it should not be more than 2%, the fineness should not exceed 15% residue of 80μm square sieve and the content should be in 15%- 20%; as for fly ash, the fineness should not exceed 15% residue of 45μm square sieve and ratio of SiO2/Al2O3 should not exceed 1.8; as for sand, the fineness should not exceed 18% residue of 45μm square sieve. Then the influence of some vital manufacture techniques was discussed. The results show that the composite gas-entraining agent enhanced the strengths more significantly than the single one, under the same amount of gas former. When C/S is 0.51, the matching effect of gas forming in slurry and multiviscosity rate is better, compared with 0.41 and 0.48 of C/S. Improved mortar consistency meter was used to measure the sinking values in order to confirm demould time. When the value is 15-19 mm, it is easy for demoulding and cutting. The blocks obtain better performance when the constant temperature is 190℃ and the period time is 7 hours.Secondly, In order to prepare a dry density of 600 kg / m3, compressive strength of 5.0MPa fly-ash and sand autoclaved aerated concrete, based on the relationship equation of hydration products and strength and of pore structure and strength, the raw material chemical composition and basic slurry proportion of aerated concrete was respectively designed. the results show that the C/S range of raw material should be 0.50~0.55. When the C / S is 0.51, the number of torbomorite has been generated was 38%, and the appropriate amount of torbomorite with bulky crystal is interspersed with C- S- H gel, therefore, the structure is more compact and the intensity is highest. If aerated concrete meet the above performance, the basic slurry strength should be 21 MPa and the pore shape coefficient should be 1.7. When the strength of basic slurry meets the design requirements, if the pore shape coefficient is greater than 1.7, the strength of aerated concrete can’t meet the design requirements, because of poor pore structureIn addition, the thin-layer dry mortar specifically for aerated concrete was studied.The appropriate mix was obtained: Cement: fly-ash: sand=21%:5%:74%; the admixture was added by the percentage of mass of cementing materials: Cellulose ether is 0.135%, redispersible emulsion powder is 0.5%, fiber is 0.5%, expanding agent is 6%; the ratio of water to material is 0.18. The performance of this mortar is excellent, the water-retention rate greater than 95%, bonding strength greater than 0.5MPa, 28 d drying shrinkage value less than 0.80mm/m, and thermal conductivity is less than 0.5W/(m?K).Finally, the matching effect between high strengrh precise aerated concrete and thin-layer dry mortar was studied. The results show that bonding strength is 0.5MPa; modulus of elasticity is same order of magnitude; drying shrinkage value are not more than 0.5mm/m and 0.8mm/m respectively, the difference between them is small; thermal conductivity is not more than0.16 W/(m ? K) and 0.5 W/(m ? K), which thermal insulation properties is favorable. Therefore, the phenomenon of hollowing and cracking wall is reduced. Practical application shows that 65 to 70 percent amount of mortar can be saved, comprehensive construction efficiency of 10 to 15 percentbe promoted, and the comprehensive cost of 20% be reducted by using this wall.