Concrete Quality During Site Execution - Part 3 of 11
The cementitious system selected in a mix design affects water demand, setting, heat development and later strength. A certificate for a cement consignment is useful, but it cannot compensate for poor storage or an unexamined substitution at site.
Specify the cement type required by the mix and project conditions, and check that deliveries match it and the applicable product standard. Bags should be identifiable by source and date. Store them in a dry, weatherproof place above the floor and away from damp walls, following the stacking plan. Use stock in a controlled order. Cement that has become hard or lumpy from moisture exposure should be segregated for assessment, not quietly returned to the pour.
The word cement on two bags does not mean they are interchangeable in an approved mix. A change from ordinary Portland cement to a blended cement, or a change of source within one category, may affect admixture response, slump retention and early strength. Where supplementary cementitious materials are separately batched, their source and proportion are likewise part of the approved design. Proposed substitutions should be evaluated through the required tests and approval before production.
Storage records should connect each pour to the material used. This is particularly useful when strength development or setting differs from expectations. The site team should also plan curing for the selected cementitious system before concreting begins.
The practical test is straightforward: could the engineer identify exactly which approved cementitious materials entered a given pour, and whether they were in sound condition? If the answer is uncertain, material control needs strengthening.
Key references: IS 456:2000, material and batching provisions; IS 4082; IS 269:2015 for OPC, IS 1489 for PPC and IS 455 for PSC where applicable; IS 10262:2019. Check current editions and the selected cement specification.