Research on the methods for improving the compressive strength of solid waste-based high-strength autoclaved aerated concrete

Three methods were used to improve the compressive strength of autoclaved aerated concrete (AAC), namely, 1) raw material carbonation modification enhancement, 2) pressurized foam enhancement, and 3) immersion of product in alkali and then enhanced by carbonation curing enhancement. The experimental results showed that the optimal weight ratio of fly ash (FA):carbide slag (CS) was 7:3, that is, the calcium:silicon ratio was 4:5. When the CS amount was 2.5 %, after the raw material was modified by carbonation, the compressive strength of the test block reached the maximum of 4.7 MPa, which was 52 % higher than that of the ordinary test block, and the density increased by 10 %. When the foaming pressure was 1.0 x 103 Pa, the compressive strength of the test block reached 10.4 MPa, which was 236 % higher than that of the ordinary test block, and the density also increased by 34 %. When the carbonation curing time was 6 h after alkali immersing, the compressive strength of the test block was the best, reaching 4.4 MPa, which was 42 % higher than the ordinary test block, and the density increased by 4 %. The use of carbonation modification and alkali immersion carbonation together reduced the compressive strength of the test block. The test block prepared by carbonation modification and pressurized foam had the highest strength, which was 12.3 MPa, and the dry density was 857 kg/m3. The orders of the three methods to increase the compressive strength were pressurized foam > alkali immersion carbon-ation > carbonation modification. This study realized the coupling of AAC preparation and CO2 utilization.