Influence of limestone and slag on the pore structure of cement paste based on mercury intrusion porosimetry and water vapour sorption measurements

Abstract

The objective of this study is to evaluate the responsiveness of mercury intrusion porosimetry (MIP) and dynamic water vapour sorption (DWVS) experiments to reflect changes to the pore structure of cement paste due to the influence of cementing material type. The DWVS isotherms are used to evaluate the pore size distribution and specific surface area. The MIP test is used to characterize the threshold diameter, and total porosity of the specimens. This study examines the influence of four cement paste mixture designs, namely 100% general use (GU) Portland cement, 50% GU+50% ground granulated blast furnace slag (GGBFS), 100% Portland limestone cement (PLC), and 50% PLC+50% GGBFS. The specimens were aged for one year in saturated limewater. The results indicate that DWVS is sensitive to changes in microstructure resulting from GGBFS and PLC inclusions. The Barrett Joyner Halenda (BJH) pore size distributions indicate that the effect of GGBFS and PLC inclusions have a marked effect on pores smaller than 4nm diameter and a slight effect on pores between 4 and 10nm in diameter. Characterization of the paste microstructure using both DWVS and MIP techniques provide a description of pores ranging from less than 1nm in diameter to up to 8μm. Both methods are well suited to detect changes due to moisture-binder and the cementing material type (GGBFS and PLC).