Development and Evaluation of Clinker Stabilized Fly Ash Based Composite Material for Haul Road Application

Abstract

India is expected to generate more than 2, 50, 000 MW during 12th five year plan period. The coal production would be 1000 MT per year. Opencast mining plays a major role in meeting the demand of fossil fuel for thermal power generation. Mine activities have to be expanded to meet this demand. It would lead to use of large capacity haul trucks. Carrying capacity of trucks/dumpers used in opencast mines has grown from 10 T to 200 T in recent years, with higher capacity being considered at places. Introduction of large capacity haul trucks demands well-designed haul roads. At present design of new haul roads is based on past experience and empirical methods. Opencast mines displace large amount of overburden as waste material. The sub-grade, sub-base and/or base of haul road typically uses those overburden materials. This investigation wants to focus on replacing a part of overburden material with another suitable and better material. There are about 170 opencast coal mines and many are near to thermal power stations. Problems associated with vehicular breakdown and poor performances as well as low morale work force of manpower have been attributed to the poor condition of haul road. The current fly ash production is about 180 MT that will rise to about 600 MT by 2030. The usage percentage of fly ash is about 50% leaving the rest as plant waste occupying huge land area and creating environmental problems. Dumped fly ash adversely affects land, air and water resources. So its gainful bulk utilization is a major challenge to India’s growing power sectors.

The investigation has characterized fly ash, mine overburden material as well as clinker. Data pertaining to existing practice and layout of haul road were reported. Geo technical properties of untreated fly ash, mine overburden, fly ash-mine overburden mixes and clinker treated fly ash-mine overburden mixes were determined. Numerical analyses were carried out to determine stress and strain of haul road for both conventional material and developed FCMs. Clinker percentage, curing period as well as fly ash percentage were observed to have strong bearing on the strength parameters of the developed FCMs. The best material obtained was 62% FA+30%O/B+8% CL with highest CBR and UCS values. Existing dimension was evaluated and found to be inadequate. A few different dimensions for haul road pavement have been proposed. Model equations have been developed to correlate between different variables. Micro structural analyses as well as ultrasonic pulse velocity measurement were carried out to confirm the values. Maximum Dry Density, Optimum Moisture Content, CBR, UCS, BTS and P-wave velocity of best developed material is 1559 kg/m3, 16.9%, 140%, 1.4 MPa, 150 kPa and 1785 m/s respectively.