Slake durability and microscopic analysis of rocks used as aggregate for concrete

The rocks are being used extensively as construction material from very early part of the human history as building stones, road metal, rail ballast and as aggregate for concrete. The concrete has become the most important construction material with reinforcement and is using almost 70-75 percent of coarse aggregate with fine aggregate, cement, water and recently different admixtures. As concrete is being made as mass concrete at batching plants, the quality control at raw material level is very important. The important physio-mechanical properties of rock aggregate include size, grading, shape, crushing strength, resistance to abrasion and attrition etc. The most common rocks in use as aggregate include quartzite and granite in north India, basalt and dolerite in central India, laterite and gneisses in peninsular India and mixed ones in hilly states of India depending upon its availability in nearby areas. The best in the lot are quartzite, granite and basalt owing to their strength and chemical stability. Due to restrictions on mining by Honorable Supreme Court of India, for ban on mining around Rajasthan bordering UP and Haryana due to environmental concerns, the good quality rock material is not available easily. Also, along many river stretches coming out of Uttrakhand and Himachal Pradesh, blanket restriction has been imposed to save river morphology. Due to this, aggregate suppliers are supplying crushed rocks from locations having poor quality rocks.