Heat of hydration of concrete containing powdered scoria rock as a natural pozzolanic material

Specifications for mass concrete constructions typically mandate the use of pozzolanic materials with a low heat of hydration. In this paper, the influence of different powdered scoria rocks on reducing the heat of hydration and the associated temperature rise in mass concrete was investigated. Six paste mixtures, including a control and mixtures containing three sources of powdered scoria rocks (SR1, SR2, SR3), fly ash (FA) and ground silica flour (GS), were investigated using isothermal calorimetry. Also, the temperature rise due to the heat of hydration of their corresponding concrete mixtures cast in a semi-adiabatic block was recorded. The compressive strength development and microstructure of concrete mixtures were examined. The results show that powdered scoria rocks were as effective as FA in reducing the heat of hydration and peak temperature rise and can be used as a source of natural pozzolan for mass concrete applications.