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Industrial silica sand is a by-product obtained from the industries like paint, paper, rubber etc. It has a similar property with river sand and& M sand. This study explores the effect of high content of silica sand as a partial replacement for fine aggregate for concrete making in construction purpose. In this present research four types of silica sand from two different industrial units (coarser silica sand (VC and TC) and finer silica sand (VF and TF)) were used. The physical classification and morphology observation of silica sand through scanning electron microscope (SEM), energy-dispersive X-ray (EDAX), X-ray fluorescence (XRF) is examined. Fresh and hardened concrete properties were performed for the six sand samples, with two grades (M20 and M30) of concrete. No new compositions or phases were identified in silica sand concrete. Both fine and coarse silica sands were finer than river sand and M sand, as evaluated from the physical classification. The workability of silica sand mix at a fresh state improves the concrete performance up to 40%. The mix, which contains 80% coarser silica sand (TC) with 20% river sand, attained the maximum compressive strength of 34.5 Mpa and tensile strength of 3.5 Mpa at 28 days, which was the greatest of all the mixes. The combination of silica sand and river sand or M sand showed the superior impact of the concrete over the discrete concrete. SEM images showed the well-developed hydrated products like calcium silicate hydrate (CSH), calcium hydroxide (CH) and ettringite in all concrete mixes. It was observed from the XRD pattern that all concrete mixes containing silica sand have a high peak of quartz (SiO2), and calcium silicate hydrate (CSH) exhibits the formation of hydration products in the concrete. Similar stretching and bending patterns of silica sand concrete relates the pattern of nominal sand concrete as observed from Fourier-transform infrared spectroscopy (FTIR).

A mixture of hydraulic lime and pozzolanic material can be used as a binder in making concrete and mortar for energy-efficient construction purposes. Generally, lime possesses lower strength and higher setting time. By introducing pozzolans in the lime mortar, their cementitious properties could be increased and could compete with the cement mortars. The use of pozzolan-lime binder in mortar reduces the utilisation of cement, and hence reduces the environmental problem originating from cement production. This study mainly deals with the mechanical and microstructural properties of lime and lime composite mortars made up of hydraulic lime, silica fume and rice husk ash. Three composite mortars were made with the following combination such as hydraulic lime-silica fume (LSF), hydraulic lime-rice husk ash (LRA) and hydraulic lime-silica fume-rice husk ash (LSR). Further, their properties were compared with the pure lime mortar. Preliminary investigations were made on the lime reactivity and pozzolanic reactivity tests. It was understood that silica fumes have a (15%) better reactivity than rice husk ash. The introduction of pozzolans in the lime mortar promotes fresh, hardened and microstructural properties. The 28 days’ compressive strength of lime composite mortars achieved more than 16 Mpa, while the lime mortar attained 4 Mpa. The combined effect of pozzolanic reaction, hydration and carbonation in the lime composite mortars achieved four times the strength of lime mortar at 28 days. A high peak of calcium carbonate was detected in lime mortar as a result of carbonation. The well-developed microstructure of calcium silicate hydrate and calcium hydroxide exhibits the formation of hydration products in the lime composite mortars as observed from a scanning electron microscope (SEM), energy-dispersive X-ray (EDX) and X-ray diffraction (XRD). Similar graphs of Fourier transform infrared spectroscopy (FT-IR) showed the presence of equivalent functional elements in all lime composite mortars.

This research tests energy optimised furnace (EOF) steel slag as substitution for natural coarse aggregate in concrete. Steel slag’s usefulness as a substitute for natural coarse aggregate in concrete is the primary goal of this research. According to IS:2386-1963, the characterization of EOF steel slag, as coarse, is done by examining the shape and size of a particle, mechanical properties, physical properties, soundness, and alkali-aggregate reactivity. Tests for detection of staining material in steel slag and hardness of inter-facial transition zone in hardened cement paste were also carried out. The chemical analysis of the steel slag reveals the stability of oxides present in the steel slag. Microstructural characterization by SEM (scanning electron microscope) analysis of steel slag aggregate was also employed to support the characterization and XRD analysis, and it was found that the EOF steel slag is crystalline. The digital image processing technique (DIP) is adopted to study the shape indices, circularity, sphericity, shape factor, and roundness of natural and EOF steel slag aggregate. According to the characterization and strength investigation, steel slag aggregate outperforms natural coarse aggregate.