Question

Discuss the suitability of the following rock types in terms of their potential for Alkali Silica Reaction (ASR) when used as aggregates in concrete mix

. i) Granite

ii) Rhyolite

Answer 1

1) Granite:

Granite aggregates are crushed hard rock of granular structure which is common in the earth. In terms of technical characteristics granite is solid (800-1200) highly solid (1400-1600) frost resistant (grade 300-400) with low flakiness.It is a best aggregate for high grade concrete.

0.2mm -0.5mm

Smallest grade granite aggregates used for various reinforced concrete structures. Dayar used for decreasing slip coefficient.

2 - 5 mm

Mainly used for pavment slab and similar construction product

3 - 10mm

Used for road construction and making concrete

5-10mm

Is the common fraction of aggregate mainly used for constructing building,roads,bridges,drainage etc.

Use of granite as aggregate reduce the initial and final setting time of concrete. It also affect the compressive strength and abrasion resistance of concrete. Granite aggregates can be used to improve Mechanical properties , workability chemical resistance of conventional concrete mixture.

2) Rhyolite:

Rhyolite is extrusive rock. It is used as an aggregate in construction and road industries. It bears striking resemblance characteristics to granite. It has a fine grained structure. It not much as used as in construction like granite. Rhyolite as and hardness of 6 according to mohr circle.