Types of Construction Chemicals: What Each Does and Where It Goes on Site

What are the types of construction chemicals?

The table lists all eleven families in the order they turn up on a typical building or road job. Fly ash and GGBS are left out on purpose: they are mineral materials that replace part of the cement, not chemicals, even though IS 456 calls them mineral admixtures.

Table 1: Types of construction chemicals and where each is used

Read down the third column and a pattern shows. The first two families go into the concrete. The next three work on its surface. The last six join, fill or seal it after it has hardened.

Figure 1: Where each chemical family enters the life of a slab

Which construction chemicals go into the concrete mix?

Two families go in with the water: admixtures and integral waterproofing compounds. Both are dosed by weight of cement, so they only work if the batch is measured properly.

Admixtures are the biggest family by far. IS 9103:1999, the Indian Standard for them, names five types: accelerating (sets faster), retarding (sets slower, useful in summer or on a long haul), water-reducing, air-entraining (tiny air bubbles that help concrete survive freezing) and superplasticising (makes concrete flow like a thick soup with little extra water). The same standard asks the maker to declare the chloride content and expects superplasticisers to be chloride free, because chloride rusts reinforcement steel. Accelerators are also what sprayed concrete relies on to stay up on a tunnel roof, covered in our guide to shotcrete. Doses, types and choice are set out in full in our guide to concrete admixture types.

Integral waterproofing compounds are a narrower group. IS 2645 covers them and caps the dose at 3 per cent of the cement’s weight. They slow water moving through the concrete but cannot close a crack, so on a roof or tank they work alongside a surface coat.

Getting the dose right is a machine question as much as a chemical one. A few self-loading mixers list an admixture dosing unit or admixture system among their features, including the AJAX ARGO 4500, the AJAX ARGO 3000 and the Schwing Stetter SLM 4300. On a transit mixer such as the Schwing Stetter AM 6 (C2), the maker lists an admixture option alongside the water tank. Compare the full range of self-loading concrete mixers if your site batches its own concrete.

Which chemicals work on the formwork and the fresh surface?

Three families act on the face of the concrete.

Mould release agents, sold on site as shuttering oil, go on the formwork before the pour. Fosroc’s India data sheet for its water-based Reebol Emulsion is a good picture of how they are meant to be used: diluted 1 part to 5 parts water, sprayed or wiped on as thin as possible, and allowed to dry fully before any concrete goes in. The same sheet warns that too much leads to surface dusting. A thin, even film is the whole skill.

Floor hardeners are dry powders shaken onto a fresh floor and trowelled into it, so they bond into one piece with the slab. Fosroc’s Nitoflor Hardtop, a non-metallic hardener built on aluminium oxide grit, is laid at 3, 5 or 7 kg per square metre for light, medium and heavy traffic. Its sheet also asks for base concrete with at least 300 kg of cement per cubic metre. A hardener cannot rescue a weak slab.

Curing compounds are sprayed on once the surface water has gone, forming a film that holds moisture inside the concrete. Indian makers certify them against ASTM C309. Coverage, timing and where not to use one are covered in our guide to curing compound. One clash is worth knowing in advance: a compound film on a floor that will later be tiled or coated has to come off first.

What is a bonding agent, and when do you need one?

A bonding agent makes fresh concrete, mortar or plaster stick to concrete that has already hardened. Without one, a new topping or patch often sounds hollow when tapped, and that is the first sign it is lifting away.

There are two common kinds. SBR latex (styrene butadiene rubber, a milky liquid) is mixed into the patching mortar and also brushed on as a slurry just before the new work goes on. Fosroc’s sheet for Nitobond SBR Latex gives that slurry as 1 volume of latex, 1 volume of water and 3 volumes of cement. The topping must go onto the slurry while it is still wet; if the slurry dries, it is scraped off and the surface primed again. For patch mortar it gives 5 to 9 litres of latex per 50 kg bag of cement with 150 kg of sand, laid 8 to 30 mm thick. In the maker’s own lab test, the latex lifted the 28-day flexural strength of a 1:3 mortar from 5.0 to 6.5 N/mm².

Epoxy bonding agents are two-part resins used where the bond has to be stronger than the old concrete itself, such as new concrete cast against an old bridge deck or a factory floor topping. Fosroc describes Nitobond EP as working on dry or damp surfaces. Each one has an overlay time, the window in which new concrete must be placed, and that window shrinks in hot weather. Check the hours on the data sheet before the formwork goes up.

Tile adhesives are close cousins: polymer-modified cement products that stick tiles in a thin bed. The Indian Standard for them is IS 15477. Vitrified tiles soak up very little water, so they grip a plain cement and sand bed poorly; that is the job tile adhesives are made for.

What is the difference between a grout and a repair mortar?

A non-shrink grout fills a gap. A repair mortar or micro-concrete rebuilds a missing piece of concrete. Both are factory-mixed bags that need only water, which is their main advantage over a site mix.

Non-shrink grouts go under base plates. Ordinary cement grout shrinks as it hardens and leaves a thin air gap under the plate, so the load sits on a few points and the bolts take the vibration. A non-shrink grout expands slightly while it is still fluid to make up for that. Fosroc’s Conbextra GP2 conforms to ASTM C1107, the American specification for packaged non-shrink cement grout, and is sold for gaps up to 100 mm. Its sheet gives a 28-day compressive strength of 65 to 68 N/mm² and a gas expansion that runs from about 20 to 120 minutes after mixing. Typical jobs are crusher and pump bases, bridge bearings and anchor bolts.

Repair mortars and micro-concrete replace concrete that has cracked off, usually because the steel inside has rusted and swelled. Hand-applied repair mortars suit thin patches. Micro-concrete is runny enough to be poured or pumped into a jacket of formwork around a column without vibration. Fosroc’s Renderoc RG, for example, is sold for sections up to 100 mm deep, with 5 to 12 mm aggregate added on site for bigger pours. Rusted steel has to be cleaned to bright metal and primed first. A repair laid over rust starts cracking again from the same bar.

Which sealant is used for expansion joints?

Polysulphide and polyurethane sealants are the two main types for expansion joints. They cure into a rubbery strip that stretches and squeezes as the joint opens in summer and closes in winter. A rigid filler such as cement mortar cracks out within a season.

India has two standards for polysulphide sealants. IS 12118 (Part 1):1987 covers two-part products mixed on site and splits them into a pouring grade for horizontal joints and a gun grade for vertical and sloping ones. IS 11433 (Part 1):1985 covers one-part gun-grade sealants that cure with moisture from the air. The joint shape matters as much as the product. Fosroc’s data sheet for its two-part Thioflex 600, which lists compliance with IS 12118, sets out the rules below.

Table 2: Sealant joint sizing from one two-part polysulphide data sheet

The width-to-depth rule surprises most contractors. A joint filled too deep turns stiff, and a stiff bead pulls away from the sides when the slab shrinks.

Which construction chemicals keep water out?

Waterproofing is a group of its own: cementitious coatings, acrylic and polyurethane coatings, bitumen products and crystalline treatments, plus the integral compounds that go into the mix. Which one fits depends on the location. A bare terrace needs a coat that stretches. A bathroom needs one that sits under tiles. A basement needs one that resists water pushing from the soil. A drinking-water tank needs one certified safe for potable water. The full location-by-location choice, with the IS 3067 and IS 3370 details, is in our guide to waterproofing chemicals.

Two other families on this page also help. Joint sealants close the gaps a coating cannot bridge, and SBR latex makes plaster and screeds less permeable.

How do you choose the right construction chemical?

Start with the stage of the job and the problem, then the product. A short checklist works on almost any site:

1. Name the stage: going into the mix, onto the formwork, onto fresh concrete, or onto hardened concrete.
2. Ask for the data sheet for the exact product and read the dose, the coverage per square metre and the cure or overlay time.
3. Ask which standard it meets: IS 9103 for admixtures, IS 2645 for integral waterproofers, IS 12118 or IS 11433 for polysulphide sealants, IS 15477 for tile adhesives, ASTM C1107 for non-shrink grout, ASTM C309 for curing compounds.
4. Check the products will work together. A curing compound film can stop a later coat or adhesive from bonding, so plan the sequence before the pour.
5. Count the packs against the area. A product spread at half the stated rate gives half the result.

Cement choice sits underneath all of this. A dense, well-cured slab made with the right cement needs fewer chemicals to fix later, and our guide to the best cement for each job covers that choice.

Planning the chemicals with the mixer and the pour

Most of these chemicals are cheapest to use while the building is going up. The admixture and waterproofer go into the batch, the release agent and hardener are planned into the pour, and joints are cut where the sealant will go. Compare concrete mixer models and prices if you are planning a slab or a road and connect with a dealer near you. The makers behind these products, with their plants by state, are listed in our post on construction chemical companies in India, and the rest of what goes into a building is in the building materials guides. The admixture types quoted here are published as IS 9103:1999, Concrete Admixtures: Specification, and the sealant grades as IS 12118 (Part 1):1987, Specification for Two-Part Polysulphide Based Sealants.

Prices, specifications and features are indicative, vary by variant, location and date, and should always be confirmed with the official OEM or authorised dealer before any purchase decision. DesiMachines is not liable for decisions taken on the basis of information that may have changed after publication. Product properties quoted on this page are as published by the makers named, read in October 2026; always follow the data sheet supplied with the pack you buy.