Influence of various ion chelators on mechanical, transport and microstructure properties of cement-based materials

Influence mechanism of various ion chelators on the mechanical, transport, and microstructure properties of cement-based materials was explored. The ion chelators included pentasodium diethylenetriamine pentaacetate, tetrasodium ethylenediaminetetraacetate, sodium hexametaphosphate and tetrasodium glutamate diacetate, with a dosage of 1 % of the cement mass. The effect of ion chelators on the mechanical, transport, and pore structure properties was evaluated by compressive, sorptivity, and mercury intrusion porosimetry (MIP) tests. The composition and microstructure of hydration products were studied by scanning electron microscope (SEM) and Xray diffractometer (XRD). Test results indicated that four ion chelators reduced the mechanical and transport properties, and increased the porosity of specimens at 3 d and 7 d. And four ion chelators improved the mechanical and transport properties, and reduced porosity at 28 d and 56 d. The fundamental reason for the differences in the basic properties of cement-based materials caused by the types of ion chelators is that different ion chelators possess various calcium chelating capacities and stability of calcium complexes, which leads to different impact on the complexation substitution reaction process. Moreover, compared to the stability of calcium complexes, the influence of calcium chelating ability on the basic properties of specimens is more significant in the early curing ages.