The Effect of Mineral Admixtures such as Coal and Wood Ashes on the Compressive Strength of Concrete

Landfilling is becoming very restrictive due to shrinking landfill space and strict environmental regulations, CO2 emissions from cement industry must be reduced, thus substituting part of the cement clinker with by-products or waste materials such as coal/wood ashes is one of the solutions for these problems. Coal ash (CA) and wood ash (WA) are the residues generated due to combustion of coal/wood and coal/wood products. In present study coal/wood ashes and additionally ground coal/wood ashes for 30 min in laboratory planetary ball mill were used as partial substitution of cement at 3 levels 20, 30, and 40% in concrete mixes. Standard testing sample 100×100×100mm cubes were produced. Two days later the samples were dismantled. Standard curing conditions (temperature 20±2oC, RH > 95±5%) were provided during the process of concrete hardening. Compressive strength of hardened concrete samples was determined at the age of 7, 28 and 56 days. Compression testing machine with the accuracy of ±1% was used, the rate of loading was 0.7 MPa/s (according to LVS EN 12390-3:2009 standard).