Construction chemicals are used on hardened concrete either as surface application, coating or as repair materials. We look at 5 types of commonly used construction chemicals:
1.Concrete curing compound
Concrete curing compound is a construction chemical compound which helps to prevent the loss of moisture content from the concrete. So, concrete is properly cured which results the full development of strength of concrete.
Types of Concrete Curing Compounds
- Synthetic resin compound
- Acrylic compound
- Wax compound
- Chlorinated rubber compound
Synthetic Resin Concrete Curing Compound
Synthetic resins will seal the concrete by forming membrane. If we want to provide plastering, the membrane can be removed by washing it with hot water.
Acrylic Concrete Curing Compound
Acrylic is made of polymers of acrylic acid. It also seals the concrete in good manner. It is having property of adhesion to the subsequent plaster. No need to wash the surface of acrylic with hot water if we want to provide plastering.
Wax Concrete Curing Compound
Wax compound have similar properties like resin compound. The wax membrane will lose its efficiency with time increment.
Chlorinated Rubber Curing compound
Chlorinated rubber type curing compound will form thick layer when we applied. It seals the concrete tightly and also fills the minute pores present in the concrete. But the film cannot stay for longer period. It is wear out in the long run.
2.Polymer Bonding Agents
Polymer Bonding Agents are an aqueous emulsion of a polymer and chemical admixtures. It is designed for use as a bonding agent with concrete and cement-based products in interior or exterior applications.
Polymer Bonding Agents are also designed for use as a polymer modifier in mortars and concretes to develop increased tensile, flexural and bond strengths. The use of Polymer Bonding Agents in concretes and shotcretes also gives significant improvements in resistance to penetration by chlorides and de-icing salts. After curing Polymer Bonding Agents are not re-emulsifiable.
USES
Polymer Bonding Agents are designed for uses such as the following:
Bonding slurry coats or primers applied to existing concrete before placing
overlays or patches.
As an integral component of mixes such as:
Concrete or mortar overlays, patches and levelling coats
Shotcrete or gunite
Bonding mortars such as tile setting mortars.
Pointing mortars, stucco and Portland cement plaster.
Parge coats for concrete.
3.Mould releasing agents
Mold releasing agentor simply release agent is a chemical used to prevent other materials from bonding to surfaces. It can provide a solution in processes involving mold release, die cast release, plastic release, adhesive release, and tire and web release.
Release agents provide the critical barrier between a molding surface and the substrate, facilitating separation of the cured part from the mold. Without such a barrier in place, the substrate would become fused to the mold surface, resulting in difficult clean-up and dramatic loss in production efficiency.
Even when a release agent is used, factors such as irregular applications or improper release agent choice may have a dramatic effect on the quality and consistency of the finished product.
Types of Releasing agents
Cosolvent
Volatile organic compound (VOC) reduction along with the elimination of health and safety concerns surrounding solvent-based release agents were primary drivers in the development of cosolvent mold release. Cosolvent based release agents combine the benefits of a solvent based system and the safety of water-based release agents.
Semi-permanent
One of the key attributes of a release agent is its degree of permanence: how long will it last before reapplication is necessary. A semi-permanent release agent does not need to be reapplied for every cycle of a molding operation and even works better when it is not over-applied to the mold surface.
How many releases can be achieved before reapplication is necessary varies by process, material, and application method. In order to achieve multiple releases per application, the semi-permanent release coating generally must be applied to a clean, dry surface free of dirt, rust, grime or previous coatings. This allows the release agent to properly bond to the mold and mold tooling, improving durability and longevity of the coating.
Sacrificial
Sacrificial coatings must be applied before every cycle of a molding operation and are therefore considered more labor intensive. Most molders will prefer semi-permanent coatings to sacrificial coatings, especially when molding rubber and plastic parts. These coatings contain fewer solid ingredients, and thus do not last as long as semi-permanent coatings.
Water- or solvent-based
Release agents may be water or solvent-based and use of either will depend on the personal preference of the molder, plant safety regulations, hazardous materials shipping costs, state, local, or federal regulations, and/or desired drying times of the release coating.
Water-based
Water-based die lubricant (WBD) has been used for about 40 years. All die casting machines have been designed with the use of WBD. Water-based release coatings generally dry slower than solvent-based release agents but present fewer health and safety concerns. Water-based release agents will be less expensive to ship because of their inherently non-flammable nature and satisfy most plant-safety goals.
Solvent-based
Solvent-based release coatings dry almost instantly but present serious health and safety concerns. Fumes from solvent-based release agents may be hazardous without proper ventilation of the work area. Most solvents used in release agents are flammable.
Non-flammable solvents
Non-flammable release agents are available and may or may not be classified as combustible.
4.Surface retarders and sealers
urface retarders, also called surface “deactivators,” are applied to fresh concrete to chemically delay the set of the surface mortar. Unlike concrete set retarders, they allow the rest of the concrete to cure normally, without affecting the setting rate or strength gain.
Because surface retarders work by stopping the hydration process down to a controlled depth, the underlying concrete will harden properly while allowing easy removal of the surface paste later.
When do you apply surface retarder?
The best time to apply surface retarder is after you’ve completed all finishing operations and the bleedwater has dissipated. Don’t seal the concrete first or apply curing compounds, which could prevent the retarder from doing its job.
Apply surface retarder evenly over the surface using a low-pressure sprayer or roller. Many surface retarders are designed to form a film over the surface that acts as temporary curing agent and protects the concrete from light rain and wind. However, if extreme wind or rain is expected, you should protect the surface with plastic sheeting.
Tip: The most important issue when applying surface retarder is to ensure complete, even coverage. An easy way to visually monitor where you’ve sprayed is to use a pigmented surface retarder, which contains a tracer dye that allows you to see your progress. The dye will decompose in time after drying.
5.Ready to use plaster
Ready Mix Plaster is a blend of portland cement, fine graded sand and water soluble, high quality polymer additives, in the right proportions. It isready to use by simply mixing water at the site and can be easily applied on brick, block and concrete surfaces.
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