Durability of Soil Blended with Flyash

Abstract

Coal-based thermal power plants are the main source for electricity generation in India which leads to the production of huge quantities of flyash and later its disposal problems. To solve this problem many researchers have used soil–flyash mix as a smart material for the construction of roads and embankments. The researchers have proposed different quantities of flyash in the soil to get the engineering behaviour in terms of better stability but a few of them have taken into account the durability consideration. The present project deals with the durability of various mixes of soil and flyash. Locally available soil and flyash obtained from CRRI, New Delhi was mixed at different proportions. Index properties of these materials were determined initially. Heavy Proctor Compaction Tests were performed on these mixes to get the OMCs to be considered for the determination of CBR values. The durability of these mixes was determined in the form of CBR values passing through five weathering cycles to simulate five years in actual. To simulate the Delhi climate, the CBR moulds were kept for 4 days at 50 °C (representing summer season) → 1 day at room temperature → 4 days submerged in water (representing monsoon season) → 3–4 days at room temperature → 4 days at 0 °C (representing winter season) → 1 day at room temperature as one weathering cycle. After five weathering cycles, CBR values were determined for the mixes. It is found that the CBR values before weathering cycles decrease with respect to that of pure soil up to 10% flyash. The soil + 15% flyash mix got more CBR value. For the soil, the CBR value decreases after passing through the five weathering cycles. The CBR values after five weathering cycles increase with increasing percentage of flyash. This shows that the use of flyash in the soil not only increases the CBR but increases the durability of the mix.