General Construction Problems on Site
Getting fine aggregate free from dust, clay, salts etc.
- Silt clay and silt (sizes below 70M)
- (sizes below 4-5M)
Being small, they absorb lot of water. Water available for cement hydration is less, leaves pores. Clay and silt affect the gel formation. As it does not participate in gel formation, denser cone is not formed. Durability is reduced.
Clay particles tend to flocculate due to cohesion and under stress, may tend to break resulting in voids, therefore weak concrete. These clay particles coat the coarse aggregate, thus presetting the bond between the coating of cement and coarse aggregate. This seriously affects the strength.
Therefore, sand containing silt and clay should be summarily rejected or through washing of sand but expensive.
Quality of water
- Many it is hard water that is available at site. For food concreting job, it requires portable soft water, as the salt contents in hard water may affect the gel formation.