Bond behavior of self-compacting mortar containing construction and demolition waste under elevated temperatures

Abstract

The aim of the current study is to provide useful data and information on the compatibility between self-compacting mortar (SCM) mixes containing recycled powder (RP) from construction and demolition waste (C&DW) and parent concrete under temperatures in excess of the current. For this purpose, four SCM mixes were prepared with replacement ratios of 0%, 10%, 20% and 30% RP, according to the EFNARC specifications. The compatibility was measured at 28-day curing age via slant shear test on composite cylindrical samples (half SCM/half concrete) cured in water curing tank and then held at different levels of elevated temperature: 200 °C, 400 °C and 600 °C for a duration of 2 h. The results of fresh mortar and also hardened unit weight, compressive strength and water absorption were assessed. The study concluded that the partial replacement of the cement with RP decreased both dry unit weight and compressive strength and increased water absorption of SCMs. In addition, the obtained data of slant shear test showed that mortars containing up to 20% RP exhibited sufficient adhesion with the concrete substrate (compatible mortar) at elevated temperatures (200–400 °C) during 2 h. Beyond 400 °C, only composites containing up to 10% RP could withstand this temperature.