TABLE OF CONTENTS As well as emulsions, latexes are also available in a solid form termed redispersible polymer powders [1, 8, 9, 14-16, 29, 32]. The redispersible polymer powder incorporated into the cementitious material subsequently polymerises upon contact with water [12, 14, 15, 29, 32, 46]. Research into this area has shown that the incorporation of such polymer powders into cement-based materials inherently improves the flexural strength but has a much greater impact on the tensile strength of the resultant hardened composite [1, 12, 14-17]. However, their effect upon the compressive strength is much less pronounced and analysis has shown a slight reduction in this parameter to be common. It should be noted that the water to cement ratio, and porosity of the hardened cementitious structure principally governs the compressive strength [1, 5, 9, 47]. A heightened degree of workability is achieved by adding polymers to the mix, thus less water is effectively required to obtain the desired consistency [9, 14, 47].
Today, redispersible polymer powders are commonly used in the manufacture of one-pack polymer modified cementitious floor screeds, underlayments and repair mortars [8, 18, 29, 48]. These systems basically comprise a blended cementitious material (cements, aggregates, superplasticers, antifoamers etc) which generally contain 1-3% redispersible polymer powder to improve the flexural/tensile strength and bond adhesion [48, 49].
Certain techniques are utilised during the manufacturing process of redispersible polymer powders [9, 14, 15, 29, 32, 46, 50]. Initially, emulsion polymerisation of the latex occurs which can be either...
