Quality Assurance Handbook for Rural Roads Volume-I - pmgsy

Appendix-1
(ii) Workability: Take a handful of concrete in left hand and make a round ball with both hands.
If a ball can be maintained for a while, it is indicative of a ‘workable mix’. Any low or high
content of water cannot make a good ball of concrete.
(iii) Alkali Silica Reaction (ASR):
Alkali Silica reactivity is noticed in aggregates crushed with siliceous rock. When aggregates are
immersed in water, a slight increase in volume occurs. If alkali content in Portland cement is less
than 0.6 percent by weight, no harmful reaction occurs.
The Basalt rocks found in parts of Deccan plateau, Madhya Pradesh, Kathiawar peninsula of
Gujarat, Jammu & Kashmir, Jharkhand and West Bengal should be viewed with caution. Similarly,
some lime-stones containing chert modules occurring in Madhya Pradesh, Rajasthan, Punjab and
Assam are reactive.
Due to ASR, normally damp patches are visible at the junction of cracks, the edges of cracks often
appear light in colour, the concrete often has an uncharacteristic pinkish appearance in the affected
areas. There will be negligible spalling of concrete but exudation may occur from some of the
cracks.
If aggregates are suspect of likely positive ASR on the basis of past performance or any evidence,
it is always recommended that the aggregates are tested as per IS:2386 part 7 before they are
approved for use in making concrete.
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