Seawater-mixed concretes containing supplementary cementitious materials: compressive strength, e-modulus, electrical resistivity, and life cycle assessment Sundar Rathnarajan, Joao Nuno Pacheco, Francisco Capucha, Javier Valencia, Mateusz Techman, et al. Archives of Civil and Mechanical Engineering, 2025 Water and concrete are the materials humans consume the most on earth. By 2040, several countries are expected to face extreme water stress and the need for significant growth in their infrastructure simultaneously. Water is a fundamental ingredient for concrete production, and the need for infrastructure growth can further increase the water demand for concrete production and thus affect these regions facing water scarcity. Including supplementary cementitious materials (SCMs), non-metallic fibres, and coated/polymer reinforcements can increase the feasibility of producing concrete with seawater (SW). There is a lack of information on the long-term strength and durability properties of SW-mixed concretes (SWC) produced with SCMs. This paper optimises binder compositions with CEM I, fly ash, ground granulated blast furnace slag (slag), and metakaolin suitable for adapting SWC based on performance indicators. Binary and ternary blended concretes of similar binder content (360 kg/m3) and w/b (0.45) were designed and cast with the SCMs mentioned above. Compressive strength, surface resistivity, and accelerated carbonation tests were conducted on the concrete produced with freshwater (FW) and seawater (SW). SWC produced with 30% slag and 15% metakaolin had higher electrical resistivity and an improvement in compressive strength (up to 30%) than other combinations used for producing SWC. Life cycle assessment identified that the concretes produced with fly ash, and ternary combination of fly ash and metakaolin had the least water depletion potential (WDP) compared to other SW-mixed concretes. Also, the replacement of FW by SW reduces the WDP up to 50%.
Report of RILEM TC 281-CCC: insights into factors affecting the carbonation rate of concrete with SCMs revealed from data mining and machine learning approaches A. Vollpracht, G. J. G. Gluth, B. Rogiers, I. D. Uwanuakwa, Q. T. Phung, et al. Materials and Structures Materiaux Et Constructions, 2024 The RILEM TC 281–CCC ‘‘Carbonation of concrete with supplementary cementitious materials’’ conducted a study on the effects of supplementary cementitious materials (SCMs) on the carbonation rate of blended cement concretes and mortars. In this context, a comprehensive database has been established, consisting of 1044 concrete and mortar mixes with their associated carbonation depth data over time. The dataset comprises mix designs with a large variety of binders with up to 94% SCMs, collected from the literature as well as unpublished testing reports. The data includes chemical composition and physical properties of the raw materials, mix-designs, compressive strengths, curing and carbonation testing conditions. Natural carbonation was recorded for several years in many cases with both indoor and outdoor results. The database has been analysed to investigate the effects of binder composition and mix design, curing and preconditioning, and relative humidity on the carbonation rate. Furthermore, the accuracy of accelerated carbonation testing as well as possible correlations between compressive strength and carbonation resistance were evaluated. One approach to summerise the physical and chemical resistance in one parameter is the ratio of water content to content of carbonatable CaO (w/CaOreactive ratio). The analysis revealed that the w/CaOreactive ratio is a decisive factor for carbonation resistance, while curing and exposure conditions also influence carbonation. Under natural exposure conditions, the carbonation data exhibit significant variations. Nevertheless, probabilistic inference suggests that both accelerated and natural carbonation processes follow a square-root-of-time behavior, though accelerated and natural carbonation cannot be converted into each other without corrections. Additionally, a machine learning technique was employed to assess the influence of parameters governing the carbonation progress in concretes.
Comprehensive evaluation of early-age hydration and compressive strength development in seawater-mixed binary and ternary cementitious systems Sundar Rathnarajan, Krzysztof Cendrowski, Daniel Sibera, Pawel Sikora Archives of Civil and Mechanical Engineering, 2024 Seawater-mixed concrete (SWC) is a proposed solution for catering to the needs of developing nations facing extremely severe water stress. Recent research works advocate the feasibility of producing SWC by adding supplementary cementitious materials (SCMs) and alternative reinforcements without reducing the engineering properties of the same. However, limited information is available for optimising the type and amount of SCMs in binary and ternary blended SW-mixed cementitious systems for achieving desirable strength development and early-age hydration. A comprehensive study to understand the evolution of heat of hydration and strength up to 28 days was conducted on 31 binder compositions mixed with both fresh water (FW) and seawater (SW). Fly ash, slag, metakaolin, and limestone are the supplementary cementitious materials used with CEM I as a primary binder at a replacement level between 10 and 70%. Isothermal calorimetry results revealed an increase in total heat of hydration and a reduction in setting time with SW-mixed cement pastes compared to their FW-mixed counterparts. Similarly, a significant increase in strength between 0 and 50% was observed in SW-mixed cement pastes. Suitable binder combinations showing an increase in compressive strength and not a significant reduction in strength compared to the CEM I reference mix were identified using the strength improvement factor approach. Binary and ternary blended cementitious, consisting of fly ash, slag, and metakaolin at different replacement levels, are amongst the chosen binder combinations.
Seawater-Mixed Lightweight Aggregate Concretes with Dune Sand, Waste Glass and Nanosilica: Experimental and Life Cycle Analysis Pawel Sikora, Levent Afsar, Sundar Rathnarajan, Morteza Nikravan, Sang-Yeop Chung, et al. International Journal of Concrete Structures and Materials, 2023 The use of alternative and locally available materials is encouraged in the construction industry to improve its sustainability. Desert regions with shortages in freshwater and river sand as fine aggregates in concrete have to search for alternative materials such as seawater, dune sand, and waste glass powder to produce lightweight concretes. The potential negative effects of adding these alternative materials can be reduced by adding nanosilica to the cementitious system at very low quantities. This study evaluates the feasibility of using these alternative materials and nanosilica (NS) in producing lightweight aggregate concretes (LWACs). A systematic study was carried out to understand the synergistic effect of nanosilica and seawater in improving the hydration characteristics of the developed cementitious systems. Also, the effect of these alternative materials on the fresh properties of the cementitious system was assessed by slump flow tests. The evolution of compressive strength at early ages was investigated after 2, 7, and 28 days of moist curing and an improvement in the strength development in concretes with seawater was observed. Furthermore, the integrity of the developed LWACs was analyzed using oven-dry density, thermal conductivity, water porosity and shrinkage measurements. Moreover, the capillary porosity and sorptivity measurements revealed the denser microstructure in the nano-modified seawater lightweight concretes. In the end, the life-cycle assessment study calculated the benefit of alternative materials in terms of carbon footprint and water consumption. As an outcome, a sustainable solution for producing LWACs containing seawater, dune sand or glass powder was proposed.
Service life and life-cycle assessment of reinforced concrete with fly ash and limestone calcined clay cement 6th International Conference on Durability of Concrete Structures Icdcs 2018, 2018
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