Tartaric acid effects on hydration development and physico-mechanical properties of blended calcium sulphoaluminate cements

The fast setting of calcium sulphoaluminate (CSA) cement-based systems is typically controlled using set-retarding admixtures, despite the notable efficiency of tartaric acid (TA) in adjusting CSA-based mixtures setting times, its use has only been marginally investigated, with an almost exclusive focus on the early age properties of TA manufactured mortars. This paper aims at evaluating the effect of the addition of tartaric-acid retarder on the hydration mechanism and physical properties of CSA-based mixtures from 4 h to 84 days. Macro- and microstructural properties were investigated using X-ray diffraction and differential thermal-thermogravimetric analyses, mercury intrusion porosimetry measurements, mechanical tests and analyses at fresh and hardened state. The experimental results reveal that the use of TA delays the formation of ettringite, modifies the porosity of hardened mixtures and strongly reduces strength in the short term. Nevertheless, the addition of TA slightly influences the properties at longer periods.