Construction Chemicals

The discussion so far has been centered on the modification of the properties of concrete using admixtures. Other chemicals that are used to enhance the performance are discussed in this section. Such chemicals are referred to as construction chemicals or building chemicals.

Concrete-curing Compounds

The measure adopted to prevent the loss of water from the surface due to evaporation or any other means and to ensure retention is called curing. Surface loss of water from concrete depends upon air temperature, relative humidity, fresh concrete, temperature and wind velocity.

Liquid membrane-forming curing compounds are used. Curing compounds are made with bases such as synthetic resin, wax, acrylic and chlorinated rubber.

Resin and wax-based compounds effectively seal the concrete and prevent surface evaporation. After 28 days of curing, these compounds peel off.

Acrylic-based membrane compounds have the additional advantage of better adhesion of plaster. The membrane does not need to be removed, but the plastering can be done over it. Because of the acrylic emulsion the bonding of the plaster is better.

Chlorinated rubber-curing compounds form a thin film on the surface of the concrete, which prevents drying and at the same time fills the pores on the surface of the concrete. The surface film will wear out.

Polymer-bonding Agents

Many a times new concrete is required to be placed over an old concrete surface. In such cases a perfect bond is required. By providing a bond coat between the new and old surface of concrete a bond can be achieved. A mixing of a bonding agent with the new concrete helps to provide a better bond. Such mixtures also improve the workability and reduces shrinkage. Many types of commercial products such as Roof-Bond ERB, Nitobond PVA, etc., are available.

Polymer-modified repair materials are available for the repair of concrete work. Such repair works include ceiling of concrete roof, hydraulic structures, prefabricated members, pipes, poles, etc.

Waterproofing Chemicals

Many of the admixtures discussed in the previous section directly or indirectly reduce the permeability of concrete thereby making the material waterproof. However, waterproofing of roofs, walls, bathrooms, toilets, kitchens, basements, swimming pools, and water tanks, etc., still poses some problems.

Different materials are available to make the concrete perfectly waterproof. They are integral waterproofing compounds, acrylic-based polymers, mineral-based polymers, chemical DPC, waterproofing adhesives for tiles, silicon-based water-repellent materials, injection grouts, joint sealants and protective and decorative coatings.