Regulation of pore structure of Brick-concrete recycled sand powder autoclaved aerated concrete and its relationship with key properties

Abstract

RBCSP has a high content of SiO2 and Al2O3, which can be used as raw material to prepare AAC. However, due to the high water absorption of RBCSP, the fluidity of the slurry has been reduced. Further, the pore structure of RBCSP-AAC has been affected severely. Therefore, this paper aims to solve the problem of high water absorption in the use of RBCSP. The RBCSP-AAC samples with different dosages of water reducing agent and different content of aluminum (Al) powder paste were prepared. The relationship between the fluidity of the slurry and gas forming agent- pore structure parameters-dry density and compressive strength was established. The results showed that when the fluidity of the slurry is constant, with the increase of Al powder paste, the porosity, average pore size, and hole shape factor increased, the number of holes decreased, and the proportion of large holes increased. Meanwhile, when the content of Al powder paste is constant, with the fluidity of the slurry increased, the porosity, average pore size, and hole shape factor first increased and then slowly decreased, the number of holes first decreased and then slowly increased. The dry density and compressive strength of RBCSP-AAC decreased with the increase of porosity. It showed a positive correlation with the number of holes and a negative correlation with the average pore size and hole shape factor. Finally, the grey system theory was used to analyze the factors affecting the dry density and compressive strength of RBCSP-AAC. It is found that the hole shape factor has the most significant impact on the dry density of RBCSP-AAC, while the number of holes is the most significant factor affecting the compressive strength of RBCSP-AAC.