Influence of high altitude on the strength of aerated concrete.

Aerated concrete specimens were prepared at Fuzhou and Lhasa with the same processing conditions. The compressive strengths of the specimens in Lhasa were lower than that in Fuzhou. We used SEM-EDS, XRD, FT-IR and MIP to study their microstructure in order to find the reasons made for differences in strength. Furthermore, the effect of the preparation process on the material strength was analyzed. The results showed that a low ambient temperature affected the autoclave curing process of the aerated concrete. A longer time was needed to reach the desired constant temperature, resulting in an insufficient degree of hydration, a low level of tobermorite generation, poor crystallinity, high porosity, an uneven pore size distribution, more harmful pore content above 200 nm and unsatisfactory strength. Under low environmental pressure, increasing autoclave pressure can promote the better formation of tobermorite to improve the strength of aerated concrete.