Sulphate resistance of concrete with partial replacement of hydraulic binder by pozzolanic material: Fid-Bau Portal

Sulphate resistance of concrete with partial replacement of hydraulic binder by pozzolanic material

Bazantova, Z. / Modry, S. / Dobias, D.

The object of the current study is to determine the manner in which pozzolanic replacement of portland cement (OPC) in mortars influences the properties of the cement mortars with regards to sulphate resistance. The materials used in this study were two types portland cements (with relatively high and low C3A content), and two types of fine grained fired clay bricks ('acid' character and 'lime' one). Replacement levels of OPC by the pozzolanic material were 10, 20, 30 and 40% wt. and the water to binder ratio (w/b) used was 0.50. Tested specimens were also characterised by measurement of the pore structure. As a model of sulphate environment, 5 % wt. solution of Na2SO4 was used. Behaviour of specimens was characterised by determination of the expansion and by weight changes. Pore structural characteristics of mortars show that in the control mixes, in general, have smaller values in comparison with samples where blended cements were used. The porosity of the samples increased with increased replacement levels. In general, increase in ground brick content of mortars increases its pore volume, specific surface area, and total porosity. It can be concluded that replacement of some portion of the binder by pozzolanic additive positively influences sulphate resistance. Generally, the higher the replacement, the higher is the sulphate resistance. Mentioned consequences of cement replacement are more pronounced in the case of specimens, where cement with higher C3A content was used.