Concrete is a commonly used building material, used for its strength, durability and versatility. Concrete is made from a mixture of stone and sand particles (the term used to describe this is ‘aggregate’) and cement, which binds the material together.

Aggregate

The materials commonly used as the aggregate in concrete are sand and gravel. The ‘all-in aggregate’ or ‘ballast’ uses natural aggregate dredged or dug from riverbeds. However, accepted practice today is to make concrete from a separate mix of fine (sand) and course (gravel) aggregate. This is produced by washing, sieving and separating the fine from the coarse.

Reinforced Concrete

Plain concrete is weak in tension and good in compression, the placement of reinforcement will bear the tensile strength.

Steel reinforcement used in concrete can be in the form of:

• Rods

• Bard

• Mesh

• Fibres (the use of steel fibres as reinforcement)

Regardless of the type of reinforcement used, it is necessary to ensure a proper bond between the concrete and the reinforcement, as this will control the strength and durability of the concrete.

Polymer Concrete

Instead of the concrete being bound with cement, it is bound with a polymer. This helps reduce the volume of voids in the aggregate, thus reducing the amount of polymer that is necessary to bind the aggregates used. The aggregates are graded and mixed accordingly to achieve minimum voids, hence minimum density.

Characteristics of polymer concrete

• Improves strength and durability

• Resistance and permeability are increased

• The bond characteristics between old and new concrete can be improved

• The flow properties of fresh concrete can be modified based on the required specifications.

Commonly used polymers

• Urethanes

• Acrylics

• Vinyl

• Epoxies

• SBR (Styrene Butadiene Resins)

Applications of different polymers in concrete

• Polymer Impregnated concrete (PIC)

• Polymer-modified concrete (PMC)

• Polymer concrete (PC)

• Polymer as protective coating

• Polymer as bonding agent