Study of high performance autoclaved shell-aggregate from propylene oxide sludge

This study focuses on the comprehensive utilization of propylene oxide sludge (POS). High performance propylene oxide sludge aggregate (POSA), whose main hydrated phase is tobermorite, was prepared by the hydrothermal synthesis of POS and silica materials under the condition of 180 °C saturated steam. The factors affecting the performance of the aggregate were investigated systematically by orthogonal experiments, thus aggregate with cylinder compressive strength between 6.14 and 13.52 MPa, bulk density between 882 and 1163 kg/m3, apparent density between 1515 and 1916 kg/m3, 1 h water absorption rate between 4% and 14%, 24 h water absorption rate between 11% and 19%, the mass loss of freezing and thawing between 1.63% and 3.92% was achieved. By single-factor analysis, it was shown that cylinder compressive strength and specific strength of propylene oxide sludge shell-aggregate (POSS-A) increases by 21.3% and 13.9%, respectively, in contrast to the POSA with no shell. At the same time, 1 h water absorption rate and 24 h water absorption rate decreases by 57% and 20%, respectively. The compressive strength of the concrete with POSS-A as coarse aggregate reaches 80 MPa, which is 8.1% higher than that of the crushed stone concrete. In addition, the density gets lowered by 17%. The HVEP results of analysis of the aggregate imply that heavy metals are solidified inside aggregate and the POSA thus fabricated is non-hazardous for construction use.

Research highlights
► Non-hazardous propylene oxide sludge shell-aggregate (POSS-A) could satisfactorily be produced under the hydrothermal synthesis and autoclave curing process.
► Cylinder compressive strength of these aggregate increased by 21.3% in contrast to the propylene oxide sludge aggregate with no shell.
► The compressive strength of the POSS-A concrete reached 80 MPa, which is 8.1% higher than the common concrete.
► The density of the POSS-A concrete was found to be lower by 17% than the common concrete.