Assessment of FlyAsh Based Geopolymer Concrete Paving Blocks for Sri Lankan Roads

Abstract

The coal fired thermal power plants generate solid waste in the form of fly ash and pond ash. Disposal of these wastes is a major engineering challenge. Since large amountjof raw materials is needed in the production of every tonne of Portland cement and at the same time about one tonne of carbon dioxide (CO2) is released into the environment during this production, the research attempts to see whether this solid waste Fly ash can be used in geo polymer concrete paving blocks, so that it will mitigate the adverse effects on the environment due to disposal while reducing the carbon footprint. In this research geo polymer concrete paving blocks were made from low calcium fly ash activated by alkaline solutions (NaOH or KOH) to liberate silicon and aluminium with an additional source of silica to assess whether these could satisfactorily be used in Sri Lankan roads satisfying the Sri Lanka Standard (SLS) requirements. Geo polymer concrete blocks with concentration of NaOH of 12M and 16M was prepared for three different strength classes, namely 30MPa, 40MPa, 50MPa. One set of series was cured in 80°C for 48hrs and the other series was cured in ambient temperature. The compressive strength, slip/skid resistance and water absorption of GPC paving blocks were determined and were compared with SLS 1425 part 1 and 2. GPC paving blocks for all strength classes which is cured in 80 °C ambient temperature is found to satisfy all SLS specifications while compressive strength of geo polymer concrete paving bocks cured in ambient temperature is found to be less than the design strength.