Hydration characteristics of cement for co‐sintered from washed‐fly ash and waste sludge

Abstract

The purpose of this study is to co‐sinter washed‐fly ash, limestone sludge, stone sludge, and iron‐oxide sludge to fabricate 4 types of eco‐cement clinkers. The compound raw materials were burned for 2 h at 1400°C to form the eco‐cement clinkers, all of which met the toxicity characteristic leaching procedure requirements. The results show that the major components of ordinary Portland cement (OPC), C3S, C2S, C3A, and C4AF, were present in the eco‐cement clinkers. The compressive strength development indicated that the EcoA pastes were similar to those of commercial OPC products. The compressive strength in the EcoG pastes decreased because of the amount the α‐C2S increased. The mercury intrusion porosimetry results showed that the pore volume in the pastes gradually decreased when the curing time increased. Additionally, from the X‐ray diffraction results, all the eco‐cements produced Ca(OH)2 during hydration, which also increased with curing age. The scanning electron microscopy images of OPC and EcoA pastes showed that the pore volume decreased and the denser structural increased with the curing time increased. In addition, adding higher amounts of 1% washed‐fly ash caused to increase the content of α‐C2S. The result show that this co‐sintered process from 1% washed‐fly ash and 99% waste sludge (77% limestone sludge, 19.51% stone sludge and 2.49% iron‐oxide sludge) to produce eco‐cement with excellent mechanical characteristics. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 964–972, 2015