Effects of cold weather concreting: 1. Due to cold weather, concrete shows reduced rate of hardening, which results delay in removal of formwork. 2. Water added in concrete mix gets frozen quickly, which results in difficulty in mixing showing less workability of concrete. 3. Snow fall during concerting increases the w/c ratio, which may lead to segregation and bleeding in concrete. 4. Ordinary method of curing becomes unsuitable in such humid conditions. 5. Due to freezing and thawing effect, concrete may results in contraction cracks. 6. Due to excessive moisture, lumps get formed in cement bag. 7. During transportation, concrete becomes hard due to ice formation of water added.
Precautions of cold weather concreting: 1. Concrete work should be done during day time or on sunny days. 2. Warm water should be added for mixing of ingredients of concrete. 3. Before placing of concrete, the formed ice, snow or frost should be removed from formwork. 4. The accelerating admixtures should be used to increase hardening of concrete. 5. A protective cover should be used over casted concrete to avoid cold winds and snow fall. 6. Aggregates (fine and coarse) should be heated before its use.
Effects of hot weather concreting: 1. Due to hot weather, concrete shows rapid rate of hardening, which results difficulty in transportation of concrete. 2. Water from concrete mix gets evaporated fastly, which results on w/c ratio and less workability of concrete. 3. Water may get absorbed by formwork, aggregate or ground due to excessive heat. 4. More shrinkage cracks get developed on concrete surface due to incomplete hydration with less water in concrete. Hence, early finishing becomes more essential. 5. Continuous curing is required to keep humidity and to avoid further development of cracks. 6. Air entrained in concrete may get expelled due to temperature, hence workability may reduce additionally.
Precautions of hot weather concreting: 1. During hot weather, transportation of concrete should be done quickly, without delay to avoid hardening of concrete. 2. Concrete should be covered with polythene before and after concreting work to minimize defects. 3. Before placing, water should be sprinkled on ground and formwork to avoid water absorption from concrete mix. 4. Concreting work should be done during night time only. 5. Retarding admixtures should be used to reduce rate of setting. 6. Low heat cement should be preferred to minimize heat evolution. 7. High w/c ratio and ice crystals should be used to maintain workability.