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Aerated concrete (AAC) or lightweight concrete is primarily used for non-load bearing structures in construction work. Generally, it is produced with cement as a main binding ingredient, and the production of cement is blamed to contribute 7 to 8% of CO 2 emission in the environment. In addition, the dumping of industrial wastes is also a great environmental concern. This research is an attempt to produce low-cost and sustainable aerated concrete utilizing silica fume and fly ash as partial substitution to cement without compromising the fundamental properties of aerated concrete. The current study was divided into two phases: in the first phase, the silica fume was substituted up to 20% with a variation of 5% in each mix. In the second phase, the fly ash was replaced with cement in three variations, i.e., 10%, 20%, and 30% containing an optimum proportion of silica fume obtained in phase 1. The aluminum powder was added at 0.4% by weight of binder to introduce aeration in concrete. Before testing, samples of aerated concrete were cured with steam in an autoclaving machine for 9 h at a pressure and temperature of 1.5 bars and 127 °C respectively and oven-dried at a temperature of 105 °C for 24 h after steam curing. From the experimental results, the highest compressive and split tensile strength of AAC was recorded when 15% of the cement was replaced with silica fume and 30% of the cement was replaced with fly ash combined. At this proportion the least density was also recorded which showed the lightweight of AAC without compromising the strength characteristics. In addition, the reduction of 42.64% and 32.4% of embodied carbon and cost was observed respectively., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Currently, recycling of waste materials in construction is being considered very important because waste generation is posing serious threats to our living environment. Hence, to induce sustainability in the ongoing urban development, researchers around the globe are using numerous wastes in concrete as partial substitutes of binders (cement, lime, etc.) and fillers (fine and coarse aggregates) with the aim of reducing the depletion of natural resources and cutting the carbon dioxide emissions emerging from increased demand and production of cement. This review paper has summarized the findings of literature relating to recycling of marble wastes and ceramic tiles wastes in production of concrete. The physical, fresh-state, and strength properties of concrete were reviewed from available extensive literature, and it was found that the concrete prepared from marble waste and ceramic waste as partial substitution of cement and aggregates is expected to perform at least comparable to conventional cement concrete and better if applicable. Both marble wastes and ceramic tiles wastes can be incorporated and recycled in concrete as cementitious materials and aggregate replacing materials. With such approach, the concrete can be made strong and durable, and the issues relating to depletion of natural resources and environmental degradation can also be solved without compromising sustainability in infrastructure development., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The production of cement releases an enormous amount of CO 2 into the environment. Besides, industrial wastes like silica fume and fly ash need effective utilization to reduce their impacts on the environment. This research aims to explore the influence of silica fume (SF) and fly ash (FA) individually and combine them as binary cementitious material (BCM) on the hardened properties and embodied carbon of roller compacted concrete (RCC). A total of ten mixes were prepared with 1:2:4 mix ratio at the different water-cement ratios to keep the zero slump of roller compacted concrete. However, the replacement proportions for SF were 5%-15%, and FA were 5%-15% by the weight of cement individually and combine in roller compacted concrete for determining the hardened properties and embodied carbon. In this regard, several numbers of concrete specimens (cubes and cylinders) were cast and cured for 7 and 28 days correspondingly. It was observed that the compressive strength of RCC is boosted by 33.6 MPa and 30.6 MPa while using 10% of cement replaced with SF and FA individually at 28 days, respectively. Similarly, the splitting tensile strength of RCC is enhanced by 3.5 MPa at 10% cement replaced with SF and FA on 28 days, respectively. The compressive and splitting tensile strength of RCC is increased by 34.2 MPa and 3.8 MPa at SF7.5FA7.5 as BCM after 28 days consistently. In addition, the water absorption of RCC decreased while using SF and FA as cementitious material individually and together at 28 days. Besides, the embodied carbon of RCC decreased with increasing the replacement level of SF and FA by the mass of cement individually and combined., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Research for alternative binders has become a necessity due to cement's embodied carbon, climate change, and depletion of natural resources. These binders could potentially reduce our reliance on cement as the sole binder for concrete while simultaneously enhancing the functional characteristics of concrete. Theoretically, the use of finer particles in the cement matrix densifies the pore structure of concrete and results in improved properties. To validate this hypothesis, current research was designed to investigate how the value-added benefits of nano-silica (NS) and metakaolin (MK) in fly ash (FA)-blended cement affect the mechanical and durability characteristics of concrete when used as ternary and quaternary blends. Additionally, the cost-benefit analysis and environmental impact assessment were conducted. It was observed that the synergy of MK and NS used in FA-blended cement had a greater impact on enhancing the functional characteristics of concrete, while 10% MK as ordinary Portland cement (OPC) replacement and 1% NS as an additive in FA-blended OPC concrete was the optimum combination which achieved 94-MPa compressive strength at the age of 91 days and showed more than 25% increment in the flexural and splitting tensile strengths compared to the control mix (MS00). The ultrasonic pulse velocity and dynamic modulus of elasticity were significantly improved, while a significant reduction in chloride migration of 50% was observed. In terms of environmental impact, MS100 (30% FA and 10% MK) exhibited the least embodied CO 2 emissions of 319.89 kgCO 2 /m 3 , while the highest eco-strength efficiency of 0.268 MPa/kgCO 2 ·m -3 with respect to 28-day compressive strength was exhibited by MS101. In terms of cost-benefit, MS00 was determined the cheapest, while the addition of MK and NS increased the cost. The lowest cost of producing 1 MPa was exhibited by MS01 with a merely 0.04-$/MPa/m 3 reduction compared to MS00., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)