Field investigation of sustainable green concrete incorporating ultra-high volumes of coal ash – a case study

Coal-fired thermal power plant ash (CTPA) has been widely used in construction works not only as a partial replacement to conventional cementitious binders but also as a substitute to fine aggregates. However, higher volumes of CTPA in concrete typically lead to non-satisfactory performance of concrete in terms of strength and durability. This was remedied by incorporation of hyper-plasticizers which offset the negative effects of loss of workability, segregation, bleeding, and strength reduction. This study describes three field studies undertaken with ultra-high volumes of CTPA in terms of Class-F fly ash (FA) and coarse bottom ash (BA) in M40 grade sustainable pavement quality concrete (PQC) at NTPC Khargone, Khargone, India, NTPC Mouda, Nagpur, India, and DIL Tadali, Chandrapur, India. Core samples of 100mm diameter and varying slenderness ratio were drawn from casted segments at site after 28 days curing and the results in terms of compressive strength and durability characteristics were evaluated against the results of laboratory investigation. Statistical analysis was also conducted using student’s t-test to analysis the variance in the results. Effects of H/D ratio of core samples on the compressive strength of cores were also analyzed. The results indicate a non-significant difference in the values of means of compressive strength of the batches for H/D = 1 indicating the field applicability of the developed mix designs for severe exposure conditions.