Analysis of pore structure development of alkali-activated slag cement at early age

This study describes the results of a laboratory study dealing with changes in pore structure of AASC at early age. In order to achieve this, porosity, electrical conductivity of pore solution, electrical resistivity of hardened paste samples were determined and these data were further analysed to estimate tortuosity. Water absorption tests were also carried out to verify conclusions derived from the indirect method. Two AASCs with 0.35 and 0.5 liquid/solid ratios were tested at the age of 3, 7, 14 and 28 days along with pure Portland cement (PC) pastes for a purpose of comparison. The results show that the value of tortuosity decreases as the age increases, and for a given liquid/solid ratio, electrical resistivity and capillary porosity of AASC are lower than PC system, while an opposite trend is found for pore solution conductivity due to significantly higher ion concentration in AASC. More importantly, capillary pores in AASC are less tortuous than PC. In order to achieve comparable tortuosity as PC pore network, AASC needs to be cured for a longer duration.