Chemical Admixture Types

IS 9103:1999 / IS 456:2000 Cl. 5.5 · Chemical admixtures — classification, dosage, and performance requirements

Chemical admixtures for concrete classified per IS 9103:1999 (reaffirmed 2018). IS 456 Cl. 5.5 permits admixture use provided they are certified to IS 9103. Dosage is by weight of cementitious material unless stated otherwise. All admixtures must be tested for compatibility with the specific cement and supplementary cementitious materials before site use.

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19 items shown

Plasticizers (Type A)

Water-reducing admixtures. Most common type on Indian sites. Based on lignosulphonates or hydroxycarboxylic acids.

Type	IS Type	Effect	Dosage	Water Reduction
Lignosulphonate-based	Type A	Water reduction while maintaining workability; slight retardation	0.2–0.5% by wt of cement	5–15%
Hydroxycarboxylic acid-based	Type A	Water reduction with controlled set retardation	0.1–0.3% by wt of cement	8–15%
Modified lignosulphonate	Type A	Water reduction with minimal air entrainment	0.2–0.5% by wt of cement	8–12%

Superplasticizers (Type G/F)

High-range water-reducing admixtures. Essential for M40+ grades and self-compacting concrete (SCC).

Type	IS Type	Effect	Dosage	Water Reduction
Sulphonated Naphthalene Formaldehyde (SNF)	Type F	High water reduction without retardation	0.5–2.0% by wt of cement	15–25%
Sulphonated Melamine Formaldehyde (SMF)	Type F	High water reduction; very low air entrainment	0.5–2.0% by wt of cement	15–25%
Polycarboxylate Ether (PCE)	Type G	Very high water reduction with extended slump retention	0.3–1.2% by wt of cement	25–40%
Modified PCE (slump-retaining)	Type G	Extended workability retention for long transit/pumping	0.4–1.5% by wt of cement	20–35%

Retarders (Type B/D)

Delay initial setting time. Used in hot weather, long-distance RMC, and mass concrete pours.

Type	IS Type	Effect	Dosage	Water Reduction
Sugar-based retarder	Type B	Delays setting by controlled sugar chemistry	0.05–0.10% by wt of cement	Nil
Hydroxycarboxylic acid retarder	Type B	Retardation with mild water reduction	0.1–0.4% by wt of cement	5–10%
Retarding plasticizer	Type D	Combined water reduction and retardation	0.2–0.6% by wt of cement	10–15%
Phosphonate-based retarder	Type B	Strong retardation for mass pours and slip-form work	0.05–0.15% by wt of cement	Nil

Accelerators (Type C/E)

Speed up setting and/or early strength gain. Used in cold weather and repair work.

Type	IS Type	Effect	Dosage	Water Reduction
Calcium chloride	Type C	Accelerates setting and early strength gain significantly	1.0–2.0% by wt of cement	Nil
Calcium nitrite / calcium nitrate	Type C	Accelerates setting; also acts as corrosion inhibitor	1.0–3.0% by wt of cement	Nil
Triethanolamine (TEA)	Type C	Accelerates early strength; mild effect on setting time	0.02–0.05% by wt of cement	Nil
Calcium formate	Type E	Accelerates hardening with moderate setting acceleration	1.0–2.5% by wt of cement	5–8%
Sodium thiocyanate	Type C	Accelerates setting in cold weather concreting	1.0–3.0% by wt of cement	Nil

Air-Entraining (Type H)

Introduces microscopic air bubbles (25–250 μm) for freeze-thaw resistance and improved workability.

Type	IS Type	Effect	Dosage	Water Reduction
Vinsol resin-based	Type H	Entrains 4–7% stable air; improves cohesion and pumpability	0.02–0.10% by wt of cement	Nil (may increase water demand slightly)
Synthetic detergent-based	Type H	Entrains 3–6% air; improves workability of lean mixes	0.01–0.05% by wt of cement	Nil
Fatty acid salt-based (sodium oleate)	Type H	Entrains 3–5% air; mild water-repelling effect	0.02–0.08% by wt of cement	Nil

Notes

• IS 456 Cl. 5.5.2: Total chloride content in concrete shall not exceed 0.6 kg/m³ for RC and 0.4 kg/m³ for prestressed — effectively bans calcium chloride in reinforced work

• Always conduct compatibility test (IS 9103 Annex A) — mix the admixture with the project-specific cement and check setting time, strength, and slump retention before site use

• Shelf life of most liquid admixtures is 12 months from date of manufacture; check for sedimentation or colour change before use

• Overdose of superplasticizer causes segregation, bleeding, and excessive retardation — never exceed manufacturer's recommended maximum

• Overdose of retarder (especially sugar-based) can prevent concrete from setting at all — a 'dead' mix that must be removed and replaced

• Admixtures should be added to the mix with the gauging water, not directly on dry cement — direct contact with dry cement causes flash set

• In hot weather (>35°C), retarding plasticizer Type D is recommended per IS 7861 Part 1; increase dosage by 25% over normal-weather dosage

• Never mix two admixtures in the same container before adding to concrete — always add sequentially via the batching plant dispenser

• PCE-based superplasticizers are sensitive to clay content in fine aggregate — wash sand if clay > 3% to avoid dosage escalation

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