Study On Preparation And Properties Of Non-autoclaved Aerated Concrete

Nowadays, the construction energy consumption is increasing rapidly and the wall thermal insulation is becoming more important. As a new type of building thermal insulation material, aerated concrete can greatly improve the thermal preservation performance of the palisade structure and the building energy efficiency. But the wall materials proportion of aerated concrete in our country is low, and the development region is unbalanced. This is because the production technology requirement of aerated concrete is very high. The equipment, energy and safety inputs of autoclaved curing are higher. These factors have restricted the development of aerated concrete in our country. Therefore, non-autoclaved curing is adopted to prepare aerated concrete, and non-autoclaved aerated concrete (NAAC) must have the same mechanical properties and thermal insulation performance of autoclaved aerated concrete (AAC).Firstly, the process parameters, mix proportion, dosage of admixture and curing system were studied by the research method of the control variables. The results showed that the proper pore formation temperature was 60 ℃. The weight proportion of cement, lime, gypsum, fly ash, sodium sulfate, TEA and water glass were 28%,22%,2%,48%,0.5%,0.03% and 0.1%. The water material ratio was 0.54. The ratio of stable foam agent and aluminum powder was 2:1. The stream curing temperature was 60℃. In the end, the B05 to B06 NAAC were obtained by changing the dosage of aluminum powder, they all met the strength requirement ofAAC.Secondly, the fiber reinforced NAAC was studied, and the interface bonding of fiber and aerated concrete substrate was observed through SEM. The results showed that the optimum content of basalt fiber (BF) and polypropylene fiber (PF) is 0.4%. The basalt fiber and polypropylene fiber could improve the compressive strength of NAAC by 17.0% and 14.7% respectively, and improve the flexural strength by 58% and 80% respectively. After the NAAC was damage, the residual strength of NAAC without fiber was only 1 MPa, but the residual strength of NAAC which was reinforced by BF and PF was 2.25 MPa and 2.60 MPa respectively. After adding fiber, the NAAC porosity and the gas pore size is reduced, the micro hole (≤200 nm) volume was increased. The SEM analysis found that the combine of fiber and aerated concrete substrate was better. It could explain that the fiber could effectively prevent the propagation of the crack and increase the strength of aerated concrete.Lastly, the thermal and moisture performance of NAAC was studied. For the convenience of engineering application, the prediction functions of thermal conductivity coefficient were established. The moisture performance results showed that the equilibrium moisture content of aerated concrete increased with the increase of relative humidity. The capillary absorption of NAAC obeyed the simple t1/2 kinetics, but the overall water absorption process of NAAC didn’t obey the simple t1/2 kinetics. Moreover, the thermal insulation performance of NAAC was evaluated with other building materials, and the internal condensation of was NAAC was analyzed. It illustrated that NAAC wall had excellent thermal and moisture performance and could let us have a comfortable living environment.