Investigation into alternative raw material for cement production

This paper presents an investigation into the use of water works and wastewater (W & WW) sludge as an alternative raw material for cement production. The goal of this research was to provide a preliminary evaluation of the cementitious properties of W & WW sludge when used in the production of concrete after being sintered at different temperatures (800°C and 1100°C). Heat-treated sludge was incorporated into the manufacturing stage of concrete mortar as a replacement for a percentage of Portland cement. A series of 50 mm cube concrete prisms were cast containing different concentrations of W & WW sludge, ranging from 0 to 10%. The prisms were tested for compressive strength after curing periods of 7, 28 and 56-days. The highest heat treatment level of 1100°C showed some improvement in compressive strength up to 7.5%, however the trends were not consistent since results fluctuated between the 2.5% and 10% replacement levels. Results of wastewater sludge treated at 800°C also fluctuated between those levels. Water works sludge treated at 800°C proved to have the most beneficial effect, with compressive strengths for all replacement levels higher than the control specimens. Additional prisms were then cast using 800°C waterworks sludge and the tensile strength of the concrete was determined after seven days by means of a double-punching test. This study contributes to the increasing body of research regarding the use of W &WW in building materials, and suggests the potential benefits of its use in concrete for the purpose of sustainable infrastructure renewal.