Przeglądaj wg Autor "Rathnarajan, Sundar"

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  • Miniatura
    PozycjaOpen Access
    Seawater-mixed concretes containing natural and sea sand aggregates – A review
    (Elsevier BV, 2023) Rathnarajan, Sundar; Sikora, Paweł; West Pomeranian University of Technology in Szczecin. Faculty of Civil and Environmental Engineering; West Pomeranian University of Technology in Szczecin. Faculty of Civil and Environmental Engineering
    In light of global warming and the rising urban population across the world, freshwater is becoming a scarce commodity. Freshwater consumption in the production of concrete makes up a significant (9%) share of total freshwater withdrawal for industrial purposes. Among the alternative sources of water for concrete production, seawater involves minimal processing, besides screening debris with filters. Other options, such as the use of wastewater from industrial effluent or desalination of hard waters, require a significant amount of energy, which add to overall concrete production emissions. Many efforts have been made by researchers in the last decades to understand the behaviour of seawater-mixed and sea sand concretes (SW-SS). The present work evaluates the early-age hydration, fresh, mechanical, and durability performance of SW-SS concretes and the corrosion characteristics of embedded reinforcement in them. The authors also summarize mitigation measures recommended in the literature for improving the anti-corrosion performance of SW-SS concretes, by partial substitution of supplementary cementitious materials (SCMs), the inclusion of alternative reinforcements (such as stainless steel and fibre reinforced polymer bars), the incorporation of corrosion inhibitors, and the adaptation of cathodic prevention measures. Finally, the article highlights the possible challenges to, opportunities for and potential applications of SW-SS concretes in the near future, so as to combat the freshwater crisis in nations suffering severe water stress.
  • Miniatura
    PozycjaOpen Access
    Seawater-mixed concretes containing supplementary cementitious materials: compressive strength, e-modulus, electrical resistivity, and life cycle assessment
    (Springer, 2025) Rathnarajan, Sundar; Pacheco, Joao Nuno; Capucha, Francisco; Valencia, Javier; Techman, Mateusz; Sikora, Pawel
    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%.
  • Miniatura
    PozycjaOpen Access
    Seawater-Mixed Lightweight Aggregate Concretes with Dune Sand, Waste Glass and Nanosilica: Experimental and Life Cycle Analysis
    (Springer Nature, 2023-08-01) Sikora, Pawel; Afsar, Levent; Rathnarajan, Sundar; Nikravan, Morteza; Chung, Sang-Yeop; Stephan, Dietmar; Abd Elrahman, Mohamed; Technische Universität Berlin, Germany; West Pomeranian University of Technology in Szczecin, Poland; Technische Universität Berlin, Germany; West Pomeranian University of Technology in Szczecin, Poland; Technische Universität Berlin, Germany; Yonsei University, Seoul, South Korea; Technische Universität Berlin, Germany; Mansoura University, Mansoura, Egypt
    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.