Effect of anionic emulsifier on cement hydration and its interaction mechanism

Cement-asphalt mortar (CA mortar) is an inorganic-organic composite, which combines both advantages of the mechanical property of cement and flexibility of asphalt. Therefore, it has been widely applied in high-speed railway and used as a kind of semi-flexible pavement material. Cement hydration process can affect the rheological property of fresh cement-asphalt paste as well as the mechanical and durability properties of the hardened cement-asphalt paste. Whereas, the interaction of emulsifier and cement particles will significantly affect the hydration process. Hence, the influence of emulsifier on cement hydration was investigated though measuring of setting time, hydration heat, ions concentration and electrical resistivity. It is indicated that the cement hydration process was retarded with the addition of emulsifier according to the results of the setting time and the hydration heat, and meanwhile, the hydration process was delayed gradually with the increasing dosage of emulsifier. The mechanism of the retardation effect can be attributed to the occupation of emulsifier at the active sites of cement particles, therefore, the delaying of cement hydration was further confirmed by the results of the lower ions concentration of the paste mixed with emulsifier. More specifically, for the cement mixed with emulsifier, a protective layer formed around the cement particles and this protective layer hindered the releasing of ions. As is well known, electrical resistivity is an indicator parameter which can indicate the cement hydration process and the formation of micro-structure effectively, thus, the variation law of the electrical resistivity can also reflect well the retardation effect of emulsifier on cement hydration. (C) 2015 Elsevier Ltd. All rights reserved.