Applications of heterogeneous photocatalytic processes based on semiconductor particles in cement-based materials have received great attention in recent years to enhance the aesthetic durability of buildings and reducing global environmental pollution. Amongst all, titanium dioxide (TiO2) is the most widely used semiconductor particle in structural materials with photocatalytic activity because of its low cost, chemically stable nature, and absence of toxicity. Utilization of TiO2 in combination with cement-based materials would plunge the concentration of urban pollutants such as NOx. In fact, cementitious composites containing TiO2 have already found applications in self-cleaning buildings, antimicrobial surfaces, and air-purifying structures. This paper aims to present a comprehensive review on TiO2-based photocatalysis cement technology, its practical applications, and research gaps for further progression of cementitious materials with photocatalytic activity.
In this study, the fresh and hardened state properties of heavyweight self-compacting concrete (HWSCC) and heavyweight high strength concrete (HWHSC) containing heavyweight magnetite aggregate with 50, 75, and 100% replacement ratio, and their performance at elevated temperatures were explored experimentally. For fresh-state properties, the flowability and passing ability of HWSCCs were assessed by using slump flow, T500 mm, and J-ring tests. Hardened-state properties including hardened density, compressive strength, and modulus of elasticity were evaluated after 28 days of mixing. High-temperature tests were also performed to study the mass loss, spalling of HWSCC and HWHSC, and residual mechanical properties at 100, 300, 600 and 900 °C with a heating rate of 5 °C/min. Ultimately, by using the experimental data, rational numerical models were established to predict the compressive strength and modulus of elasticity of HWSCC at elevated temperatures. The results of the flowability and passing ability revealed that the addition of magnetite aggregate would not deteriorate the workability of HWSCCs and they retained their self-compacting characteristics. Based on the hardened densities, only self-compacting concrete (SCC) with 100% magnetite content, and high strength concrete (HSC) with 75 and 100% magnetite aggregate can be considered as HWC. For both the compressive strength and elastic modulus, decreasing trends were observed by introducing magnetite aggregate to SCC and HSC at an ambient temperature. Mass loss and spalling evaluations showed severe crack propagation for SCC without magnetite aggregate while SCCs containing magnetite aggregate preserved up to 900 °C. Nevertheless, the mass loss of SCCs containing 75 and 100% magnetite content were higher than that of SCC without magnetite. Due to the pressure build-up, HSCs with and without magnetite showed explosive spalling at high temperatures. The residual mechanical properties analysis indicated that the highest retention of the compressive strength and modulus of elasticity after exposure to elevated temperatures belonged to HWSCC with 100% magnetite content.
Heavyweight concrete (HWC) is produced by replacing natural aggregates in a concrete mix design with heavyweight aggregates of a higher specific gravity. HWC is mainly used for the prevention of leakage from radioactive containing structures and is hence primarily used in the medical and nuclear energy industries where this property is of particular benefit and importance. Also, high‐strength concrete (HSC) has been increasingly employed in both civil structures, such as high rise buildings and bridges and defense applications. This study makes attempt to develop and evaluate different concrete mixes, which are considered as high‐strength, heavyweight and highly workable in nature. Such mixes use magnetite as the primary aggregate. The three‐mentioned properties of these concrete types have been thoroughly investigated individually; however, there is a limited numbers of literature on the analysis of mix designs dealing with the three‐mentioned properties simultaneously, in which the water/cement ratio variation, and/or variation of the magnetite content have been assessed. In this study, nine highly workable high‐strength HWC mixes have been developed and fresh and hardened properties are discussed. The overall result indicates that the developed mixes satisfied the required high‐strength, heavyweight and highly workable criteria, as well as, compressive strength would increase by increasing the heavyweight aggregate content.
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