Many polymers after their polymerization can be converted into a water-based emulsion form which are microfine solids suspended in liquids. After appropriate use and loss of water, the same can be brought to a solid polymer state. However, while they are in the aqueous phase they render many useful properties to cement when mixed with it.

Cement itself has good compression properties but lacks flexural properties, which can be very effiectively increased with polymers. The solvent-based polymers cannot become compatible with cementitious matrix, though the same polymers when used in latex form can be totally compatible with cement and offer improved results. There are several such latexes used for modifying cement properties as given in table 1.

Generally, the polymer latexes are copolymer systems of two or more different monomers and their total solid contents vary between 40-50 percent by weight.

The commercial latexes widely used in the world are styrenebutadiene rubber (SBR), Polychloroprene rubber (PCR), Polyacrylic ester (PAE), Polyethylene-vinyl acetate (PEVA) and Poly vinylidene chloride-vinyl chloride (PVDC) copolymers. However, acrylates and SBRs are more popularly used.

There are many advantages of such polymer latex-cement comatrix systems over pure solvent based epoxy/polyurethane grouting systems. There are as follows :

  • Polymer latex-cement comatrix being water-based, it is quite compatible with cement and can work in wet conditions.

  • Since it is a polymer and cement together, it can display the properties of both cement and polymer i.e. one can have the desirable compression properties from cement and flexural properties from the polymer.

  • It is already polymerized system and hence on drying there would not be a volume change due to shrinkage.

  • Cement is structurally a good material and if dispersed properly with the right water-cement ratio it can give excellent results. However, in plain cement injections, water-cement ratio has to be kept very high to provide workability and this adversely affects all structural properties of grouts. In case of polymer latexes, water-cement ratio can be controlled without loss in workability. Hence, grouted areas get an additional parameter of compression along with mere filling of the voids.

  • The incorporation of polymer gives good adhesion to the surface even if the same is damp. On a smooth surface like polished granite or marble top also these systems stick so well that the experimental results on axial pull-out have shown that the tiles break but the bond cannot be separated.

  • The total comatrix has excellent flexural and tensile parameters which will additionally reinforce the grouted area.

  • Finally, as compared to any other grout with similar parameters these systems are very economical since they use cement as one of the components.

Table 1 : Popularly used polymer latexes:

SBR : Styrene butadiene rubber
PAE : Polyacrylic ester
PCR : Polychlorprene rubber
PEVA : Poly Ethylene - Vinylacetate
NBR : Acrylonitrile-Butadiene rubber
PVDC : Polyvinylidene chloride
RA : Rubberised asphalt
PVAC : Polyvinylacetate
Pa : Paraffins
PVP : Polyvinyl propionate
EP : Epoxy
PP : Polypropylene