Fly Ash Concrete

Anil Banchhor, Chief Executive- Concrete Business, ACC Limited, Mumbai

This paper discusses the suitability of HVFAC in road Construction by demonstration project wherein 30m long road constructed with embedment of 63 nos vibrating wire type strain gauges to measure the temperature and load stresses under actual load conditions. Panels of different lengths, thickness, with/without polythene sheet between DLC & PQC etc were cast for evaluation. The benefits of using fly ash in concrete pavements have been evaluated in the above demonstration projects, in terms of fresh concrete properties and the hardened concrete properties with respect to strength and durability. With the improved properties of HVFAC, the initial cost also comes down because of reduced pavement thickness and the cost difference with the bitumen road also gets reduced coupled with the improved life cycle cost.

The design of concrete pavement in India is being done as per standard code of IRC-58–2002, wherein load stresses as well as temperature stresses are predominant and have a cumulative effect due to extreme heat in the summer. The design is based on the empirical formulae of Bradbury's coefficient and Westergaard's equations. With this background, ACC has taken up an experimental study project at Noida to study the effect of Temperature and Load stresses in the HVFA concrete panels and compare the stresses with that of control concrete made with the similar materials & workmanship at the same locations by measuring the actual stresses by inserting the strain gauges (vibrating wire type) at various depths and locations of concrete pavement. CANMET has supported the project and testing & analysis was done with the help of "National Centre for Cement Building Materials" and Dr. L. R. Kadiyali, convenor of the rigid pavement committee of IRC-58.

The use of Portland pozzolana cement in concrete construction improves the properties of fresh and hardened concrete and imparts better long-term performance as compared to OPC, because of pore filling effect and Pozzolanic property of fly ash. Use of PPC would also solve the problem of non-availability of facilities of testing of fly ash at many construction sites, where the processed fly ash as per IS 3812-2003 is not available but the user wants to derive the benefits of good quality processed fly ash present in the cement.

NBMCW September 2014