Filling cracks with injection grout is a useful procedure that helps provide waterproofing and corrosion protection for structural purposes.
A variety of grouts are available on the market with different characteristics, properties and uses. Generally, grouts used for crack repair should have low viscosity, high bond strength, low shrinkage and high stability at the repair temperature.
The main types of grout used for injection are cementitious grouts, epoxy resins, polyurethane resins and acrylic resins. A particular grout may be ideal for one purpose but inappropriate for another. It is therefore important to understand the characteristics of the different types of injection grout before selecting it.
Main types of injection grout
Cementitious grouts are composed of a combination of cement and water, plus admixes or additives to alter their properties.
Epoxy resins contain resin and hardener, which react to form a nonfoaming elastic grout that doesn't bond as well to wet surfaces. They adhere well to metals, concrete and ceramics, show little volume change during and after curing, are mechanically strong and resistant to chemicals.
Polyurethane resins can be used for a range of different applications. Their properties can vary markedly in terms of their liquid or hardened phases, viscosity, thixotropy, foaming reaction (in the case of hydrophilic resins), and mechanical strength. In general, they have a notably low viscosity, cure rapidly and are flexible. Polyurethane resins are also selected for their ability to seal against water inflows.
Acrylic resins are formed from a polymerisation reaction between resin and hardener. The grout forms a permanent gel, which has low adhesive and compressive strength, but high tear strength. Different types of additive may be added to the mix to hasten or prolong the reaction.