Concrete Quality During Site Execution - Part 2 of 11
Aggregates occupy much of the volume of concrete. An approved mix assumes a particular grading, shape, cleanliness and moisture condition. The site cannot treat all material sold under the same size or sand description as interchangeable.
Select fine and coarse aggregates against the project specification and IS 383. Check the approved source and relevant tests, including grading and deleterious material. Different coarse aggregate sizes may need to be combined in controlled proportions. A switch in quarry, crusher setting or fine aggregate source can change water demand, workability and the balance of the mix; review and trial the change before routine use.
Storage is part of quality control. Place aggregates on a clean, firm, drained base. Keep sizes and sources in separate stockpiles and prevent loader buckets from scraping soil into the batch. Protect fine aggregate from contamination and excessive loss by wind. Avoid stockpile practices that separate larger particles from smaller ones.
Moisture needs a daily response, especially during Kerala’s monsoon. Rain-wet sand carries surface water into the mixer. Absorptive, dry aggregate may take water from the mix. Both change the workability expected from the approved quantities. Check moisture and adjust the water added and aggregate masses in accordance with the approved batching procedure. If volume batching is exceptionally permitted, sand bulking needs a separate correction; informal gauge boxes do not make an uncontrolled mix reliable.
A site engineer should record source, stockpile condition, grading checks and moisture adjustments. Those simple observations explain why two batches made from the same paper mix may behave differently.
Key references: IS 383:2016; IS 2386 (relevant parts, especially Part 1 and Part 3); IS 4082; IS 456:2000, Clauses 10.2.1 and 10.2.5; IS 10262:2019.