Properties of Fly ash based Controlled Low Strength Material

Abstract

Rapidiindustrialization and use of coal power plant has led to the formation of large amount of coal ashes. Every year a large amount of quarry dust waste is dispose into the landfills. This quarry dust waste is a by-product generated during the production of aggregates in rubble crusher units through the crushing process of rocks. The huge increase in the amount of these wastes cause significant impact on health of living beings as well as the environment. Thus in the present time, the disposal of these harmful wastes is one of the major problem that is to be solved. A new innovative idea which would be efficient, effective and environmental friendly is necessary to overcome this problem of disposal. Recycling of such wastes by incorporating them into construction materials is one of the best practical solutions for resolving the problem.
Controlled low strength material (CLSM) is a self-levelling and self-compacting material that can be used as a backfill material in place of compacted soils. Flowable fills requires no tamping or compaction to achieve the strength and can be excavated easily at later ages. CLSM can be used in places where compaction equipment cannot be mobilized. In general, CLSM mixtures consist of standard materials such as Portland cement, fly ash, fine aggregate and water. Other industrial by-products and recycled materials are also can be used for the production of CLSM.
The present study aims to investigate the fresh and hardened properties and durability characteristics of fly ash based controlled low strength material. Various CLSM mixtures were prepared by using fly ash, quarry dust, blast furnace slag and cement. The quarry dust or slags content in the mix were increased from 0% to 100% as a replacement to fly ash at the rate of 20%. For all the mixes the cement content was kept constant at 5% of total mix. The amount of mixing water was chosen in order to provide a flowability value of 250 mm. The mixtures were inspected for series of tests in fresh state and hardened state. Properties like flowability, bleeding, fresh density and compressive strength were studied. Compacted samples were prepared with same material composition and compressive strength was measured at different curing ages to compare the same with flowable fills. Apart from the short-term performance, long-term performance of CLSM samples was studied by conducting durability tests.