4 - Properties of Latex-Modified Systems

Abstract

This chapter reveals the properties of latex-modified systems. The properties of the latex-modified mortar and concrete are markedly improved over conventional cement mortar and concrete. The properties of the fresh and hardened mortar and concrete are affected by a multiplicity of factors such as polymer type, polymer-cement ratio, water-cement ratio, air content, and curing conditions. Generally, latex-modified mortar and concrete provide a good workability over conventional cement mortar and concrete. This is mainly interpreted in terms of improved consistency due to the ball bearing action of polymer particles and entrained air and the dispersing effect of surfactants in the latexes. In most latex-modified mortars and concretes, a large quantity of air is entrained compared to that in ordinary cement mortar and concrete because of an action of the surfactants contained as emulsifiers and stabilizers in polymer latexes. Latex-modified mortar and concrete have markedly improved water retention over ordinary cement mortar and concrete. The water retention is dependent on the polymer-cement ratio. The reasons for this can be probably explained in terms of the hydrophilic colloidal properties of latexes themselves and the inhibited water evaporation due to the filling and sealing effects of impermeable polymer films formed. In contrast to ordinary cement mortar and concrete, which are apt to cause bleeding and segregation, the resistance of latex-modified mortar and concrete to bleeding and segregation is excellent in spite of their larger flow ability characteristics. This is due to the hydrophilic colloidal properties of latexes themselves and the air-entraining and water-reducing effects of the surfactants contained in the latexes.