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The production of cement is a carbon dioxide-intensive process. Replacing ordinary Portland cement (OPC) with industrial by-products can bring down the carbon footprint associated with cement production. Various industrial residues are currently used as alternative cementitious materials in this regard. However, developing a low carbon dioxide composite cement with different pozzolans alters the packing density, which influences its properties. Although studies have been conducted on the use of fly ash and slag at lower cement replacement levels, studies on the packing density and strength of ternary and quaternary composite cements with higher replacement levels are limited. In this study, fly ash, blast-furnace slag, ultra-fine fly ash and ultra-fine slag are used as a partial replacement for cement in various proportions. Out of the 51 mixtures tested in the study, 11 combinations were selected, based on the maximum packing density, for further investigations on fresh and hardened properties to arrive at the best trade-off between cement reduction and desired properties. The early-age strength is influenced by the packing density of composite cements, whereas the later-age strength is found to be highly governed by the amount of OPC and the pozzolanic potential of the industrial by-products. [ABSTRACT FROM AUTHOR]

Studies on the characterization and performance of residual sugarcane bagasse ash (SCBA) obtained from high-temperature cogeneration boilers in concrete are highly limited. This study investigated the pretreatment process and optimization of SCBA collected from high-temperature boilers by various physicochemical methods. The effect of recalcination and grinding on the physical and mineralogical properties of SCBA were also examined. The percentage replacement of cement with SCBA was optimized using packing density and flow. The performance of optimized binder with combinations of cement and SCBA was validated through compressive strength of mortar specimens. From the results, it was observed that SCBA from high-temperature boilers can be used as a supplementary cementitious material with minimal processing efforts, and a 15% level of replacement is suggested as the optimum level for SCBA-blended cement. Based on the investigation, a framework with a step-by-step procedure including pretreatment and optimization methods is suggested for the use of SCBA. [ABSTRACT FROM AUTHOR]

As stated in the European Commission's waste framework directive, the geographic proximity of wastes to the potential recovery/disposal site is of paramount importance in attaining an effective resource recycling paradigm. The global interest in achieving an end-of-waste scenario encourages the recovery of useful products/secondary raw materials from locally available waste materials. Sugarcane bagasse ash is an abundantly available waste (44,200 tonnes day–1) from sugar plants in India which has the potential to be used as a partial replacement to cement in ready-mix concrete plants. Although pozzolanic performance of sugarcane bagasse ash and its ability in reducing the carbon emissions associated with concrete production have been reported in earlier research studies, its use in concrete is hindered due to the lack of availability and accessibility data. In this study, the geographical distribution of sugar plants and the available quantity of sugarcane bagasse ash in India have been determined. In addition, a detailed network analysis using a geographic information system was conducted to quantify the geographic proximity of bagasse ash, fly ash and slag sources to ready-mix concrete plants. The study results indicate that for most of the ready-mix concrete plants in India, the probability of having a bagasse ash source in proximity is higher than the probability of encountering slag/fly ash sources. [ABSTRACT FROM AUTHOR]

Pretreatment processes on rice husk ash (RHA) influence its properties and in turn, the performance of concrete. However, most of the available literature captures only the influence of the RHA usage in concrete without focusing on the systematic pretreatment process and optimization of RHA dosage on physical and chemical perspective. Further, the replacements were done on weight basis, leading to higher binder volume and inaccuracies in the performance evaluation. The main objective of the present study is to adopt adequate pretreatment process and to systematically optimize the RHA dosage (vol. %) towards better strength and durability properties. Hence, the current study focuses on understanding the nature of RHA through characterization, followed by suitable pretreatment processes for enhancing the properties of RHA. The enhancement in the chemical activity of the treated RHA was assessed through pozzolanic activity tests (strength activity index, lime consumption test, and soluble silica). Based on the physical properties (particle size, surface area, and packing density), chemical characteristics (strength activity index) and the energy required, the grinding time (30 min) was optimized rationally. The optimized dosage of RHA (20% by vol.) was evaluated for its performance through fresh, mechanical, and durability properties. From the results, it is evident that adequate pretreatment, along with systematically optimized RHA dosage yields enhanced performance in concrete properties. [ABSTRACT FROM AUTHOR]