Infrastructure development and urbanization have created a demand for the prime construction material—"Concrete." The manufacture of concrete has pressurized the aggregate supply chain for over-exploitation of natural resources leading to eco-detrimental impacts besides environmental regulations. The auxiliary sectors of the construction industry are creating a vast quantum of by-products and waste, causing environmental degradation, which concerns governing bodies. Developing aggregates artificially using these by-products and waste materials would be an eco-friendly and economical solution. This article provides an overview of the ingredients, production methods, and factors influencing the characteristics of such sustainable building materials, which can substitute conventional aggregates in the near future.

In the construction sector, the material supply chain of aggregates is frequently disturbed due to seasonal unavailability, quarrying issues, and environmental norms. The production of artificial aggregates has gained prominence to conserve natural resources and promote green construction practices. The current study encompasses the production of alkali-activated artificial aggregates through cold-bonding pelletization technique using three different raw materials, including fly ash, ground granulated blast furnace slag, and seashell powder in binary and ternary blending combinations. The cold bonding was achieved by alkali activation of binders with the aid of a sodium-based alkaline solution, which acts as an activator and hydrating liquid. The fresh artificial aggregates were subjected to surface treatment using the same alkaline solution to enhance their characteristics. The mechanical properties of artificial aggregates confirmed their potential as a substitute for conventional aggregates by exhibiting crushing and impact values of 18.19–27.53% and 12.06–18.85%, respectively. The microstructural and mineralogical characteristics depicted dense microstructure and compact matrix. The study concludes that artificial aggregates can effectively replace natural coarse aggregate in making structural concrete with many economic, environmental, and technical advantages.

Geopolymer concrete with time is gaining recognition as a sustainable alternative to Portland cement concrete, offering lower carbon emissions and utilising industrial by-products. While prior research focussed on its mechanical properties for structural purposes, this study explores its potential for paving applications. A unique geopolymer concrete mixture suitable for paving, referred to as paving quality geopolymer concrete (PQGC), was developed by incorporating slag sand (SS) as a substitute for river sand (RS). The investigation primarily assessed fatigue life PQGC mixes. The findings demonstrate that the inclusion of SS in PQGC has no significant impact on its setting times or workability. However, PQGC formulated with 100% SS, w.r.t PQGC containing RS, exhibited enhanced mechanical strength of 7% in compression, 16.7% in flexure and 8.3% in split tensile tests at 28 days of open-air curing. Following a 14-day period of curing, PQGC achieved a compressive strength of 46 MPa, surpassing the minimum requirement of 40 MPa as per IRC:58 2015 for pavement quality concrete (PQC) by 15%. To evaluate fatigue performance, PQGC beam specimens were subjected to repeated loading at stress levels ranging from 0.9 to 0.6. The resulting fatigue data were employed to develop stress-fatigue life (SN) and Weibull two-parameter fatigue failure models. Comparative analysis with fatigue failure models such as Indian Road Congress (IRC) and Darter revealed that PQGC exhibits superior fatigue resistance and longer life expectancy compared to PQGC. In conclusion, this study confirms that PQGC incorporating SS is an efficient and eco-friendly choice for constructing rigid pavements with advantages such as curing without water, enabling early opening of roadways to traffic, and excellent resilience under cyclic loads.

The excessive use of natural aggregates raises mining activity. Further, it leads to environmental damage, which can be reduced using artificial aggregates produced from waste powdered materials. This study discussed the production process of alkali-activated artificial coarse aggregates and how their use affects the behavior of concrete. The different concrete mixtures were designed by replacing natural aggregates with artificial ones at different percentages. Various tests were conducted to determine concrete’s fresh, hardened, permeability, and microstructural characteristics. The result showed that concrete incorporated with artificial aggregates can achieve higher workability and lower density than natural aggregate concrete. The mechanical strengths were slightly decreased as the percentage addition of artificial aggregates in a mix increased. However, adding up to 50% showed comparable results to natural aggregate concrete. The water permeability and chloride ion penetration were within the standard limits for all the mixes. The scanning electron micrographs showed a solid and compact ITZ between the phases. XRD pattern revealed that the addition of artificial aggregates had not changed the mineralogical composition of the concrete; the formation of hydrated products helps concrete obtain strength. The study concluded that artificial aggregates could effectively replace natural coarse aggregate in producing structural concrete with many advantages.

The present study concentrates on the performance evaluation of calcined and uncalcined cashew nut-shell ash (UCCNA and CCNA) with treated total recycled concrete aggregate (TRCA) in self-compacting concrete. The achievement of sustainable self-compacting concrete (SCC) is possible by the implication of four stages, which includes TRCA treatment process, gradation selection process through Bailey aggregate grading technique, by considering TRCA replacement percentage with an increment of 25% and up to 100% and by considering UCCNA or CCNA replacement with an increment of 5% and up to 20%. Hardened and fresh properties of SCC have been performed and analyzed based on the compliance requirements of SCC. In addition finding results through microstructure assessment was in line with the findings of the hardened and fresh properties of SCC. In addition, quality and dynamic instability assessments of SCC were analyzed through ultrasonic pulse velocity and drying shrinkage aspects. Besides CO₂, the emission rate and the efficiency rate of SCC, composites were analyzed in detail. Overall findings revealed that CCNA-based SCC mixes performed effectively than UCCNA-based SCC; specifically, incorporation of 75% of TRCA with 15% CCNA was found to be optimal. But with regard to shrinkage performance UCCNA found to be better by imputing less shrinkage compared to CCNA-based SCC mixes. Further with regard to efficiency rate of SCC composites revealed the gain of maximum efficiency of about 0.156 MPa/kg CO₂/m³ and 0.160 MPa/kg CO₂/m³ for 15% and 20% CCNA-based SCC mixes.

Concrete has become a versatile material by adapting itself to user needs, from pavers to skyscrapers. Escalated demand for concrete is the prime reason for the exploitation of resources and increased carbon emissions. This research focuses on reducing the environmental impact of cement manufacturing by partly replacing cement with 40% ground granulated blast furnace slag (GGBS) and 20% fly ash (FA). Waste management is also uplifted by fractional replacement of manufactured sand (M-sand) with granulated blast furnace slag (GBFS) at various intervals. Results of mechanical properties prove that this triple-blend M25 concrete with 60% GBFS and 40% M-sand as a fine aggregate would exhibit optimum mechanical properties and a maximum density of 2.58 g/cc. Tests on durability properties assure that, at the same replacement level, the percentage of weight loss due to acid attack was the lowest, with a value of 1.9, and the percentage of weight gain due to sulfate attack was as low as 0.12. The end product obtained with 40% M-sand and 60% GBFS as fine aggregates will be cost-effective and eco-friendly, making triple-blended concrete dense, durable, and sustainable and promoting waste management.