Contact: Mr. Mao
Add: No. 31, Anxi Road, Chunjiang Town, Xinbei District, Changzhou City
As early as 1958, China began to study steam raised fly ash aerated concrete. After long-term exploration and practice, relatively mature preparation technology has been formed. Generally speaking, fly ash with Si02 content ≥40% and particle size of 180 mesh (80 μm square hole sieve size ≤25%) can be used to produce autoclaved aerated concrete products.
At present, the bulk production and application of fly ash aerated concrete is mainly B05-B07 grade products, its dry bulk density is larger (& GT; 500 kg/m³), low compressive strength (≥ 2.5mpa), high thermal conductivity (≥0.14W(M ˙K)), and there are poor freeze-thaw resistance, low carbonization capacity, easy cracking of the wall and other problems. Therefore, the research in recent years mainly focuses on the performance improvement and the development of aerated concrete products with high strength and low bulk density. Wang Ligang's research team tried to make various aerated concrete with superfine fly ash (5~15 um), and found that superfine ash has obvious enhancement effect on aerated concrete. However, due to the small particle size and large specific surface area of ultrafine ash, the filling effect of ultrafine ash is enhanced, which leads to the decrease of porosity and increase of bulk density. Because of its higher activity than the original ash, the slurry thickens faster and the pouring stability deteriorates. Chuanwei Du et al. explored the use of physical foams and coagulants to improve pore structure and the use of cement to improve product strength. The results show that the added foam is easy to be destroyed in the process of stirring and pulping, so the improvement of pore structure and product strength is not obvious. M.Serhat BaspinarE et al. studied the effect of cement on the properties of products and found that reducing the cement content actually increased the compressive strength of products. The reason is that when the cement content is high, ettringite phase will be formed in the early hydration reaction. Although ettringite phase is beneficial to improve the early strength of the body, it can cause cracking of the product and reduce its durability. They inhibited the formation of ettringite phase by adding silica powder, which improved the hydration reaction conditions to a certain extent and increased the strength of the product, but greatly increased the bulk density of the product. Zheng Huilin et al. developed B03 grade fly ash aerated concrete insulation block by adding a variety of additives and accurately controlling process parameters. However, its absolute dry compressive strength is only O.89 MPa(the national standard is 1.0 MPa), so its practical application value is not great.
In general, no breakthrough has been made in the research of fly ash aerated concrete, especially the basic problems such as the reaction mechanism of starting material and the relationship between phase, structure and performance of the product are lack of in-depth research.