PERFORMANCE OF INDUSTRIAL BY- PRODUCTS IN CONCRETE

Abstract

The present study is aimed to evaluate the performance of industrial by-products as a partial replacement material to sand and cement in concrete, and to compare it with the base control mix. Di ammonium phosphate (paper industry), product lime (paper industry), unsaturated wood chippings and saturated wood chippings were used to replace sand in the concrete mixes by 1%, 3%, 5% and 8%. In case of fly ash, owing to its pozzolanic nature, a high volume fly ash concrete mix (HVFAC consisting of Flyash content 50% to cement or higher) was attempted. Stone dust was further used to substitute 1% and 3% sand in the 50% fly ash mix. Compressive strength and split tensile strength were studied at 3, 7, 28, 56 and 90 days, while stress- strain relations were documented at 28 days age. The time — dependent properties of concrete were subjected to statistical analysis. The trend for gain of strength was obtained by `chi square minimization' method' of minimizing errors. A linear function was obtained between the values found from this method, and the logarithm of time. The "goodness of it" of the proposed models to the data was tested by the `chi-square test'. A Confidence envelope of 95 percent has been generated for each material. X-Ray Diffraction was used to analyse the predominant chemical composition of the materials. Also, for samples obtained from the paper industry, as well as wood chippings, a UV spectrophotometric analysis was conducted to ascertain the presence of lignin. The microstructure of the materials and the concrete mixes was studied illustrating the important features of hydrated cement paste (HCP), Interfacial transition zone and various products of hydration as seen in backscatter mode scanning electron microscopy (SEM).The approach employed is purely qualitative.