Effect of electrical field on the stability of hydration products of cement paste in different liquid media

Abstract

Electrical fields accelerate the sulfate attack, which induces detrimental effects on the durability of cement-based materials. However, the role of the electrical field and aggressive liquid media in the degradation process is still unclear. Investigation of the role of the electrical field and aggressive liquid media during the degradation allows a better understanding of the mechanism of accelerated technique. Four different liquid media were used in this work to study the effect of the electrical field and liquid media in terms of the stability of hydration products. The evolution of hydration products was experimentally identified using multiple techniques, including X-ray diffraction (XRD), thermogravimetric analysis (TG), transmission electron microscopy (TEM), nitrogen adsorption/desorption (NAD), pH and CaO content measurements. The results indicated that the CSH structure was stable under the electrical field and saturated Ca(OH)2 solution. The calcium loss under the electrical field was more likely to leach out from portlandite even though the mixed Ca(OH)2-Na2SO4 solution was present. A severe degradation occurred under the electrical field and low-pH liquid media (pure water, Na2SO4-MgSO4 solutions). The Ca/Si ratio significantly decreased from 1.34 to 0.82 under the coupling effect of the electrical field and Na2SO4-MgSO4 solutions. Based on the fractal dimension results derived from NAD and TEM, the variations of pore structure and CSH gel morphology were quantitatively characterized. The coupled electrical field and low-pH liquid media dramatically altered the microstructure of hydration products, resulting in coarser pore networks and a shift to the disordered CSH gel.