Does adding a waterproofing compound lower the compressive strength of concrete?

It can, but IS 2645 mandates that the compressive strength must not be less than 85% of the untreated control mix.

How effective must the waterproofing compound be according to the code?

The water permeability of the treated concrete/mortar must be less than 50% of the plain untreated mix.

Will the compound affect the setting time of cement?

The setting time must remain within standard limits: Initial setting time >= 30 minutes, and Final setting time <= 600 minutes.

IS 2645

: 2003

Integral cement waterproofing compounds - Specification

CurrentFrequently UsedSpecificationMaterials Science · Admixtures and Chemical Products for Concrete

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This standard lays down the specification and testing methods for integral cement waterproofing compounds added to cement mortar and concrete. It ensures that the admixture effectively reduces water permeability without unacceptably degrading the concrete's setting time and compressive strength.

Specifies requirements for integral cement waterproofing compounds to be added to cement or concrete mixes to reduce permeability.

Quick Reference Values

minimum initial setting time30 minutes

maximum final setting time600 minutes

minimum compressive strength85% of plain control mix at 3, 7 and 28 days

maximum water permeability50% of plain control mix

maximum chloride contentAs specified (often 0.2% max for RCC) to prevent corrosion

Practical Notes

Integral waterproofing compounds are not a substitute for proper concrete mix design, adequate compaction, and curing.

Always verify the chloride content of the waterproofing compound before using it in reinforced concrete to avoid steel corrosion.

The compound must be thoroughly mixed; uniform dispersion is critical for effective waterproofing.