Influence of alkaline on electrical resistivity, pore structure and microstructure of fly ash cement at hydration early age

The relationship curves between electrical resistivity and hydration time were measured by the non-contact electrical resistivity method, and the rules of changes in early hydration time in fly ash cement with the addition NaOH and Na₂SO₄ were investigated. The results show that after the addition of NaOH, in the earlier hydration period, the electrical resistivity decreased, however, in the later period, the electrical resistivity increased. The addition of Na₂SO₄ followed a similar rule. Through the electrical resistivity curves of different hydration times, the absorption effect of fly ash on alkaline can be studied. The hydration structure was studied by a mercury intrusion pore test and scanning electron microscopy. The results indicated that with the addition of the appropriate amount of NaOH, the cumulative pore volume and total porosity in fly ash cement decreased and the hydration structure was more compact.