Maharashtra Engineering Research Institute, Nashik, India
Mass works are generally constructed in UCR masonry. It was observed that in this masonry, the voids in the rubbles are not filled up properly with cement mortar which led to heavy seepages through the body of dam after commissioning. This was mainly due to the fact that placement of mortar was not done properly by unskilled inexperienced masons. Colgrout masonry is found to be a best replacement to conventional masonry. Colgrout mortar is a flowy mortar and gets filled in each and every void in rubbles providing dense, strong and impermeable masonry at w/c ratio as high as 0.85. This technique has built in quality control.
Fly ash is a wasteful material available in abundant quantity. Generation of fly ash is increasing day by day for want of more & more electricity from thermal power stations. Fly ash is posing stacking, disposal and serious environmental problems. Use of fly ash in mortar/concrete slow down the process of heat of hydration, thereby, strength gain is at later days, generally up to 90 days. Thus, use of fly ash is the need o the day in mass works.
Mass works are of the nature of not fully loaded even after 90 days. As they utilize large amount of cement, there is scope of large scale utilization of fly ash as part cement replacement without impairing the properties of masonry. This can economise the cost of project considerably. It improves the impermeability of the structure which is the main requirement for water retaining structures. Thus, use of fly ash is the need of the day in mass works.
Therefore, Studies conducted to evolve the suitable % of cement replacement by fly ash in colgrout masonry indicated that fly ash to extent of 20% can be conveniently utilized in colgrout masonry. These results were also compared well with the test results of cores drilled from the blocks of fly ash colgrout masonry, specially constructed at Wan Project, Dist. Akola for the study.
