Abstract
The typical South African cementitious material used in industry today differs from what was commonly used in the past. With the move toward reducing carbon emissions in the cement manufacturing industry, extenders have now become a staple part of nearly all binder type materials. Along with this shift in cement type manufacturing, it is imperative that the effect of these common modern cement types be assessed in terms of their influence on the Elastic Modulus (E) of concrete.
This study includes the assessment of 36 different concrete mixes where each mix differed in strength, aggregate type and cement type. A total of four cement types were utilized and chosen according to the type and proportion of extenders used. These cements were CEM I 52.5N, CEM II A-M 42.5N (15 % FA), CEM II A-M 42.5N additionally extended with 30 % FA, and CEM III A 32.5N (60 % GGBS). The E of concrete was determined for each mix and the results of specimens were grouped according to curing age and cement type for analytical purposes. Specimens were cast for 7, 28 and 56 day tests.
The presence of FA had a slight influence on concrete E at early ages whereas GGBS concrete showed no significant differences in E compared to the CEM I concrete, for all ages included in this study. In general, the effect of FA and GGBS can be regarded negligible, except in the case where the E at an early ages is of vital concern.