PSI - Issue 70

Ravi Malik et al. / Procedia Structural Integrity 70 (2025) 682–689

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1. Introduction Cement is the most used material after water on Earth. A significant and more expensive component of concrete is the cement binder, which is produced by the cement manufacturing sector. About 400 million metric tons of cement are produced annually in India, with China coming in second. Cement output is increasing annually to meet the demand for construction. For every ton of cement produced, the cement industry releases thousands of kilograms of carbon dioxide into the atmosphere (Davidovits, 1994), and this amount is rising daily. This results in global warming by creating an atmospheric imbalance. However, increasing carbon footprints in cement production motivated researchers and industrialists to replace it with other sustainable materials (Glavind, 2009)(Sonebi et al., 2016)(Hafizyar & Dheyaaldin, 2019). Researchers have been trying to replace cement with fly ash, Ground Granulated Blast-Furnace Slag (GGBFS), Silica Fume (Microsilica), Rice Husk Ash (RHA), Metakaolin, Natural Pozzolans, Agricultural Waste Products, and many more. There are several benefits to using other materials in place of or in addition to cement in concrete, including lessening the environmental impact, increasing durability, and promoting the sustainability of building methods. Materials like metakaolin, fly ash, slag, and silica fume are frequently employed and have been shown to enhance concrete's mechanical qualities and chemical resistance. Although it cannot replace cement in every application, several other materials and technologies have the potential to either completely replace cement or drastically reduce its use in the manufacturing of concrete. Alkali-activated slag, magnesium-based binders, and geopolymer concrete are some of the most practical alternatives for completely substituting cement, especially regarding sustainability. Limestone is not used for geopolymer cement, thus its carbon footprint is far smaller. (Davidovits, 1994 & Duxson et al., 2007) highlighted that geopolymers, alkali-activated aluminosilicates from industrial byproducts like fly ash, offer a greener alternative to OPC. They reduce CO₂ emissions by up to 80% by eliminating energy-intensive clinker production while maintaining high compressive strength and durability against fire, acids, and chlorides. Key advantages include low shrinkage, thermal stability, and waste encapsulation capabilities. However, barriers like lack of long-term durability data, regulatory hurdles, and industry resistance hinder widespread adoption. For broader use, standardized testing, performance-based regulations, and optimized mix designs are needed. Geopolymers demonstrate strong potential to revolutionize sustainable construction if technical and market challenges are addressed. With an emphasis on cement and auxiliary materials, (Glavind, 2009) examines the environmental effects of concrete from a life cycle viewpoint. The paper identifies ways to lessen these effects, like employing cements that have been blended with fly ash, slag, or silica fume to lower emissions and clinker content. As sustainable substitutes, recycled aggregates and cutting-edge materials like sewage sludge ash or rice husk ash are also mentioned. In order to improve durability and lessen environmental impacts, the article focuses on optimizing concrete mix designs while taking into account the full life cycle, from the extraction of raw materials to demolition and recycling. In order to gradually balance emissions, it highlights the significance of CO₂ uptake during concrete carbonation. Examples of real-world uses include energy-efficient structures that take advantage of the thermal mass of concrete and environmentally friendly bridge designs that use stainless steel reinforcement or no asphalt. Future developments include performance-based standards, comprehensive life cycle assessments, and more studies on recycled materials and CO₂ uptake. The report promotes ongoing innovation and industry cooperation to achieve sustainable construction practices by highlighting concrete's potential to address environmental issues while preserving its structural advantages. 2. Mechanical Properties The ability of concrete to withstand failure under external forces is indicated by its compressive strength. For the buildings to be safe, the concrete's strength must satisfy the specifications. Hewayde et al. (2006) has investigated the impact of geopolymer cement on the microstructure and compressive strength. The study reveals that a 50% replacement of OPC with geopolymer cement increased 28-day compressive strength by approximately 50%. He recommended it for practical applications in sewer pipe manufacturing. Fly ash-based geopolymer concrete is examined by (Rangan, 2009) as a sustainable substitute for Portland cement. Low-calcium (Class F) fly ash is combined with an alkaline solution (sodium silicate and sodium hydroxide) to create geopolymer concrete. The study emphasizes important facets of geopolymer concrete, such as mechanical qualities, curing techniques, and mix design. To improve polymerization, heat-curing is advised; 60°C for 24 hours yields the best results. Similar to conventional