In this article, we explained various concrete chemicals used in concrete construction and concrete
repair work
List of Concrete
Construction Chemicals and Repair Chemicals
The following is a short
list of chemicals used in concrete construction and repair, as listed in the
CPWD handbook.
1. Injection grouts
2. Rust removers for
reinforcement
3. Corrosion inhibitors
(for concrete and mortar)
4. Bond coats for reinforcement
5. Bonding coats for concrete
6. Plasticisers for reducing necessary water–cement
ratio up to 15%
7. Superplasticisers for reducing necessary water–cement
ratio up to 30%
8. Shrinkage-reducing compounds
9. Viscosity modifying admixtures (for self-compacting
concrete)
10. Polymer/epoxies for concrete
11. Quick-setting compounds
12. Retarders
13. Curing compounds
14. Deshuttering oils
15. Floor hardeners
16. Waterproofing compounds
17. Air entraining agents
18. Anticarbonation protective coatings for concrete (to
protect fully exposed structures like bridges, water tanks etc. from
carbonation and atmospheric chlorination)
19. Protective coat on a steel
20. Acid resistance enhancer
21. Anchoring agents
Description of the Chemicals
Each of these chemicals is
briefly described here. It is very interesting to note that from the same basic
chemical, we get chemicals for different purposes.
Injection grouts
These are repair chemicals
used to seal cracks in concrete and other materials by injection under
pressure. They can be epoxy-based, acrylic polymer-based, lignosulphonate-based
and polyester-based.
Corrosion inhibitors as admixtures
Corrosion inhibitors are the admixtures in
concrete/mortar for inhibiting corrosion on embedded reinforcement. These
admixtures also make concrete waterproof.
Bonding coats for reinforcement
These increase bonds and
protect the reinforcement from corrosion, chloride attack etc. They are based
on the following compounds:
1. Epoxy-based
2. Acrylic Polymer-based
3. Styrene butadiene rubber (SBR)-based
4. Lingosulphate-based
Bonding coats for concrete
Bonding coats are used to
bond the new concrete to the old concrete. In old practice, to bond new
concrete to ageing, we used to hack the old surface with chisel paint, and cement
grout and then, place mortar or concrete. The modern practice is to coat the
old concrete surface with a paste of special bond coat chemicals. The basic
chemical will be epoxy or polymer or SBR-based cement and sometimes, sand may
be also added to it. We place the polymer-modified mortar (or concrete) before
this bonding paste hardens. The bonding coats are mostly acrylic polymer or SBR
or epoxy-based.
Plasticisers
These chemicals reduce
water demand for making concrete up to 15% for the same workability. These can
be acrylic polymer-based, melamine-based, naphthalene-based and
lingosulphate-based.
Superplasticisers
These reduce water demand
more than plasticisers up to 30% for the same level of workability. These can
be melamine-based, naphalene-based and lingosulphate-based. This is the most
popularly used one.
Shrinkage compensating compounds
These can be any of the following types:
1. Acrylic polymer-based
2. SBR-based
3. Nepthalene-based
4. Lingosulphate-based
Quick setting compounds
These help in quickening the setting of concrete/mortar and give early high strength. They can be epoxy-based acrylic polymer-based, melamine-based, naphthalene-based and lingosulphate-based.
Retarders
These extend the initial and final setting time of mortar and concrete. They can be SBR-based melamine-based, napthalene-based and lingosulphate-based.
Free flow self-compacting non-shrink micro concrete
These are used for
structural repairs like jacketing, patch repair grouting foundations, anchor
bolts etc. This has very high early strength and ultimate strength.
Rust removers for reinforcement
One such chemical is acrylic polymer-based. There are also many others. When applied to rusted steel, it converts rust into chemically stable compounds. This forms deposits on steel. This may slightly reduce the bond strength of steel to some extent.
Polymers
Polymers are the most often
used chemicals for making repair mortar. Polymer-modified mortars (PMMs) are
prepared by first making a mortar mix of 1:3 or 1:2 (cement and sand) to which we add polymer in a quantity of 5% to 20% of the weight of cement. We use a
water-cement ratio of 0.3 to 0.6 according to the required workability. This is
to be applied in thin layers.
Polymer mortar (without the
term modified) is a mortar made of polymer, sand and water only.
Polymer-modified concrete
(PMC) is usually made by adding polymer with usual concrete ingredients
(usually with smaller size coarse aggregate) but with less water-cement ratio
than PMM.
Curing compounds
They prevent premature loss
of water in cast concrete so that it can get cured without external watering.
They are mostly lingosulphate-based.
Deshuttering oils
These are mostly lignosulphonate-based.
Floor hardeners
These are used for making
hard industrial floors. They can be epoxy-based, acrylic polymer-based and
lignosulphonate-based.
Waterproofing compounds
These can be the surface
coating type or the integral waterproofing type. In the second type, we add the
product to the mix like cement. They are based on or derived from one of the
following compounds:
1. Epoxy-based
2. Acrylic polymer-based
3. SBR-based
4. Melamine-based
5. Naphthalene-based
6. Lingosulphate-based
Protective coatings for steel structures
One coat of zinc-rich epoxy primer and two coats of tar
epoxy paint are usually specified for coatings of steel sections against
corrosion.
Acid resistance enhancer
The epoxy-based coating is prescribed for concrete and
steel to enhance resistance towards acids.
Anchoring agents
It is an epoxy-based construction chemical used for
anchoring anchor bolts. We drill the hole and anchor the bolt in the hole by
using this chemical.
Air-entraining agents
These are used for frost resistance in cold areas.
Anti-carbonation protective coatings on concrete
These are used to protect exposed concrete structures like water tanks, bridges, flyovers etc. This must be a breathable, anti-carbonation, crack-bridging UV-resistant protective coating to concrete. It can be acrylic polymer-based, SBR-based, lignosulphonate-based and epoxy-based
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