IS 8043 : 1991Hydrophobic Cement - Specification

IS 8043:1991 is the specification for hydrophobic cement — Portland cement inter-ground with a water-repellent film-forming admixture so that, in storage, it resists deterioration from atmospheric moisture. Its purpose is preserving cement quality during prolonged storage or transport in humid/wet conditions (monsoon, coastal, remote sites), not changing the hardened concrete.

It sits in the cement family:

• IS 269 — OPC (the cement it protects in storage) · IS 4082 — site stacking & storage of cement (the practice it complements)
• IS 4031 Part 1 — physical tests · IS 456 — concrete · IS 3535 — sampling of cement

Ordinary cement deteriorates in damp storage: it absorbs moisture, air-sets/lumps, loses strength and gains 'false set' tendencies. Hydrophobic cement adds a thin water-repellent coating on the cement grains so:

• In storage: the film repels atmospheric moisture, so the cement keeps its strength and setting characteristics far longer than OPC under humid conditions — the entire point of the cement
• In the mixer: the film is broken down by the mechanical mixing action, after which it hydrates essentially as normal Portland cement
• It typically has a slightly retarded set / marginally lower early strength from the admixture, but the hardened concrete is broadly OPC-like

The engineering point: hydrophobic cement is a storage/logistics solution, not a waterproofing or special-performance concrete cement. It does *not* make the concrete water-repellent and is *not* a substitute for proper mix design, low W/C or waterproofing measures. Its value is entirely in protecting cement quality before it reaches the mixer in conditions where OPC would degrade.

Scenario: a coastal/monsoon or remote project where cement must be stored long before use and OPC would deteriorate.

Step 1 — identify the storage risk: prolonged storage in high humidity / poor shelter where OPC lumps and loses strength.

Step 2 — specify hydrophobic cement (IS 8043): for its storage life advantage — alongside, not instead of, good IS 4082 storage practice.

Step 3 — design the concrete normally: treat it as ≈ OPC for mix design (IS 10262), allowing for slightly retarded set / marginally lower early strength.

Step 4 — adequate mixing: ensure mixing fully breaks the hydrophobic film (don't under-mix) so normal hydration proceeds.

Step 5 — don't expect waterproofing: durability/water resistance of the concrete still comes from low W/C, curing and any specified waterproofing — the cement name is about *storage*, not the structure.

Used for its real purpose it prevents a quality loss that would otherwise be invisible until weak concrete appears; misunderstood as a 'waterproof cement' it disappoints.

1. Expecting it to make concrete water-repellent. The hydrophobic action protects the *cement in storage*, not the hardened concrete — it is not waterproofing.

2. Using it as a substitute for low W/C / curing / waterproofing. Concrete durability is unchanged — design it normally.

3. Under-mixing. The water-repellent film must be broken by adequate mixing; insufficient mixing impairs hydration.

4. Ignoring slight set retardation / lower early strength. Allow for it in scheduling and mix design.

5. Using it where storage isn't the problem. It is a logistics solution; with good fresh-cement supply and storage there's no need for it.

• IS 269 — OPC (the cement it protects) · IS 4082 — stacking & storage of materials at site
• IS 3535 — sampling of cement · IS 4031 Part 1 — physical tests (set/strength effect)
• IS 456 — concrete (durability unchanged — design normally) · IS 10262 — mix design
• IS 8041 / IS 7328 — other special cements (rapid-hardening / high-alumina)

IS 8043 is reaffirmed and is the special cement most often misunderstood by its name: 'hydrophobic' refers to a storage-protection film on the cement grains, not to making concrete water-repellent. Its genuine value is logistical and real — on humid, coastal, monsoon or remote projects where cement may be stored for long periods, OPC silently lumps and loses strength, and hydrophobic cement preserves quality until it reaches the mixer (where the film is broken and it hydrates ≈ normally). The practitioner discipline: specify it for the storage problem, still follow good IS 4082 storage, design the concrete as ordinary OPC (allowing slight set retardation), ensure adequate mixing, and never present or rely on it as a waterproofing or special-durability cement. Right tool for a logistics problem; wrong tool for a durability requirement.