Reactivity and performance of blastfurnace slags of differing origin

The performance of an Algerian blastfurnace slag has been assessed by examining the parameters influencing reactivity in a comparative study of two slags from different origins. These parameters include chemical composition, glass content, particle size distribution, heat of hydration and microstructural development. Three cement paste systems were investigated; OPC as a control, and two blended cements; 50% OPC-50% Algerian slag and 50% OPC-50% UK slag. All samples were made with a water/binder ratio of 0.4 and cured at 20 °C for up to 90 days. The specimens were tested using calorimetry, thermogravimetry, X-ray diffraction, selective dissolution, back-scattered electron microscopy and compressive strength. The chemical composition of the slag has a profound influence on strength development. The heat evolved appears to be proportional to the strength development and may be used as an important indicator of the reactivity of slag. A relationship was established between the amount of calcium silicate hydrate formed and compressive strength.