What is it about?
This paper describes a study on creating an environmentally-friendly alternative to regular concrete using industrial waste materials. We developed a "one-part" concrete mix using: Ground granulated blast furnace slag (GGBFS) as the main ingredient Silica fume as an additive Combination of Soda ash and hydrated lime instead of caustic chemicals. To design the mix we used two optimization techniques: Packing density approach to design the concrete mix Taguchi-Grey Relational Analysis to find the best combination of ingredients The optimal mix contains 10% equivalent NaOH, 5% silica fume replacement, 0.50 water-to-solid ratio, and 32% excess paste content. This approach reduces greenhouse gas emissions by 80-90% compared to traditional cement while maintaining good strength and durability properties.
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Why is it important?
This research is groundbreaking for several important reasons: Environmental Crisis Solution Cement production is responsible for 5-7% of global CO2 emissions, making it one of the largest industrial contributors to climate change. This study offers a concrete alternative that reduces greenhouse gas emissions by 80-90%, which could significantly impact global warming if widely adopted. Waste-to-Resource Innovation The research transforms industrial waste into valuable construction material. India alone generates 24 million tonnes of blast furnace slag annually, which typically ends up in landfills. This approach converts waste into high-performance concrete, solving two problems simultaneously. Practical Industry Application Unlike previous "two-part" systems requiring specialized handling of corrosive chemicals, this one-part system works like traditional concrete . Construction workers can use conventional mixing methods without special training or safety equipment, making it commercially viable. Scientific Breakthrough The study addresses a critical gap - no established methods existed for designing one-part mixes. Using advanced optimization techniques, they reduced experimental trials from 256 to just 16, making the research process dramatically more efficient. Real-World Impact The optimized concrete achieves comparable strength to traditional concrete while being more durable. This means existing infrastructure standards can be maintained while dramatically reducing environmental impact.
Perspectives
This study presents a one-part blend using ground granulated blast furnace slag (GGBFS) as the primary aluminosilicate precursor, with silica fume (SF) as an additive, activated by an equivalent NaOH achieved by balancing powdered industrial-grade soda ash (SA) and hydrated lime (HL). Conventional concreting methods are used, with mix design proposed using the packing density approach. Taguchi-Grey Relational Analysis optimizes control factors, including equivalent NaOH content, SF amount, water-to-solid ratio (w/s), and excess paste content. The study investigates their effects on fresh concrete properties like setting time, compactibility, and mobility, as well as hardened concrete properties like compressive strength and sorptivity. Findings reveal that setting time is mainly influenced by the w/s ratio, compactibility improves with higher equivalent NaOH content, and excess paste content affects particle friction. Initial strength gain is influenced by equivalent NaOH content, while later-age strength development is controlled by the w/s ratio. Higher w/s ratios increase sorptivity, and SF usage beyond 5 % negatively impact sorptivity. Mechanical properties are influenced by Ca/Si, Al/Na and Na/Si ratios. Grey Relational Analysis was utilized to ascertain the optimal mixture proportions, taking into account the interdependencies among multiple responses. The analysis resulted in recommending 10 % equivalent NaOH, 5 % replacement of SF, a water-to-solid (w/s) ratio of 0.50, and an excess paste content of 32 %. The study also demonstrates the rational evaluation of mix design through an illustrative example.
Jayashree Sengupta
Indian Institute of Technology Kharagpur
Read the Original
This page is a summary of: Efficient mix design of one-part alkali-activated concrete using packing density method and its optimization through Taguchi-GRA, Construction and Building Materials, August 2024, Elsevier,
DOI: 10.1016/j.conbuildmat.2024.136869.
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