Effects Of Additives And Mineral Admixtures On The Hydration Process Of Sulphoaluminate Cement Pastes

Suophoaluminat cement is an energy efficiency and low-carbon cement. To solve the problems of short setting time and large fluidity loss of the sulphoaluminate cement, superplasticizers and retarders are always used to get better workability. Besides, mineral admixtures are kinds of industrial waste with the characteristic of pozzolanic activity. The equivalent substitute cement by mineral admixture can not only reduce costs, but also get good economic and environmental benefits.In this study, the sulphoaluminate cement made by single minerals of anhydrous calcium sulphoaluminate(C4A3S?) and dicalcium silicate(β-C2S), gypsum(CS?H2) and limestone powder, and the content of each component was controlled according to the formula of manufactured sulphoalumiant cement. Superplasticizers of β-naphthalenelfonic acid-based superplasticizer(BNS) and polycarboxylate acid-based superplasticizer(PC), retarders of citric acid(CA) and sodium gluconate(SG), and mineral admixtures of slag and fly ash were chosen. The effects of different type of superplasitcizers, retarders and mineral admixtures on the setting time, strength of sulphoaluminate cement were studied. Besides, the adsorption amount of superplasticizer and the hydration process were investigated by ultraviolet spectrophotometry and X-ray diffraction analysis(XRD).The results show that:(1) with the superplasticizers increasing, the setting time slightly extended and the strength of the cement mortar slightly increased;(2) when the superplasticizers and retarders added into the cement pastes or mortar simultaneously, the setting time greatly extended but the strength of the cement mortar decreased significantly;(3) when slag and fly ash respectively added into the cement pastes, the initial setting time and the final setting time interval of the cement becomes longer and the effect of slag on setting time is more significant;(4) the dosage of 10% slag or fly ash equivalent alternative cement is optimum. At each age, the compressive strength of samples with slag slightly higher than that of fly ash at the same content.