‘Sand for construction from desilting of lakes and reservoirs’

Ramani KANGARAARACHCHI

Sri Lanka’s future requirement of sand could be easily obtained from methodical desilting , washing and cleaning the excavated material, provided taking care of uncovered pits which could be dangerous. General Manager State Engineering Corporation T Wijenayake said at the Chamber of Construction Industry in Colombo.

He said this would give rise to better quality sand enabling the manufacture of higher strength concrete with lower cement content saving foreign exchange to the country.

The extra cost of washing and cleaning would be off-set by the reduced usage of cement. desilted lakes and reservoirs with enhanced storage would enable to produce more electricity and give more water for irrigation purposes.

Referring to Sri Lankan river sand, he said rivers are comparatively short and the sand recovered from the rivers has traveled over the river bed for a shorter length, have not rounded off their edges and are contaminated with heavy mud ,which gets washed after few days of water flow, leaving fine sand used mostly for plaster work.

Dry periods yield coarse sand used mostly for concreting. Pit sand obtained from excavating old river coarse yield a material heavily contaminated with dust were unsuitable for the construction industry unless washed he said.

However, with sand becoming scarcer and prices increasing quarry dust is an excellent alternative for sand, but with limitations.

The cement block manufacturers are already using quarry dust instead of sand which contains a higher percentage of finer material, therefore in concreting , up to half the sand quantity could be replaced with quarry dust. But it may not be possible to find large quantities as most of the current production is already consumed in producing ABC Aggregate Base Coarse , a major component in modern road construction, Wijenayake said.