Effects of synthetic CSH-tartaric acid nanocomposites on the properties of ordinary Portland cement

Abstract

Synthetic nano CSH is well known to serve as crystal nuclei in ordinary Portland cement. In this paper, tartaric acid was used as a stabilizer to prepare nano CSH by a separate nucleation and growth steps method. The acquired samples were tested by XRD, FT-IR, TG-DSC, total organic carbon (TOC) and dynamic laser scattering (DLS) and their effect on hydration and hardening of ordinary Portland cement were investigated. The results indicated that tartaric acid intercalated the interlayer regions of CSH, and swelled the interlayer spacing from 1.288 nm to 1.398 nm. The average particle size of the CSH-tartaric acid nanocomposites（CTNs）were in the range of 60–160 nm, and increasing the concentration of tartaric acid in composites caused a smaller CTNs particle size. When present in the alkaline solution of pH 13, tartaric acid can be released from CTNs, and the higher concentration of tartaric acid in the CTNs, the more tartaric acid was released. Due to the synergistic effect of nanocrystal nucleus and tartaric acid released from CTNs, the total hydration heat declined at first and then increased and the pore structure of hardened pastes was adjusted, resulting in the increase of compressive strength at all ages.