An investigation was conducted into the characteristics of two different slag materials, ground granulated blastfurnce slag (GGBS) and ground granulated Corex slag (GGCS), which are used as supplementary cementitious materials (SCM). GGCS has been found to be more reactive when in combination with CEM I 42.5 N Portland cement (PC). The higher reactivity has resulted in superior concretes, with improvements in both strength and durability.

 

Due to the exothermic nature of the cementitious reaction in the formation of hardened concrete, the thermal profies of cement samples were assessed by means of semi-adiabatic calorimetry at early age in order to evaluate relative reactivity.

 

Apart from assessing the degree of reactivity through thermal profiles the setting times of the cement paste samples were evaluated through a physical penetration test (SANS 50196-3:2006). A relationship between the thermal profiles and the calculated setting times was then analyzed using the fractions method.

 

Finally a comparative analysis is done between thermal profiles produced during experimentation and the thermal profiles produced with concrete samples by Alexander et al. (2003). Although the thermal profiles differ by the following:

 

• Cement pastes were measured as opposed to concrete mixtures

• CEM I 52.5 N was used as opposed to CEM I 42.5 N

• A lower w/b ratio was used

• The calorimetric system used was classified as semi-adiabatic as opposed to 'fully' adiabatic

• Smaller volume samples were measured