Key Engineering Materials Vol. 880

Abstract: This paper presents a parametric study on the adsorptive property of NaOH-treated polyacrylonitrile (PAN)-kapok fibers for the removal of Pb (II) and Cr (VI) ions in aqueous solutions. Generally, the NaOH-hydrolyzed PAN-kapok favors the adsorption of Pb (II) compared to Cr (VI). The adsorption capacity was in the range of 41.67-83.33 mg/g as the initial Pb (II) concentration was increased from 50 to 100 ppm. Similarly, the adsorption capacity for Cr (VI) was from 8.24 to 15.81 mg/g as the initial concentration was raised from 50 to 150 ppm. The adsorption capacity was also enhanced by increasing the adsorbent dosage. Finally, uptake of Pb (II) at the early stages of the adsorption was fast, with adsorption capacity reaching ~120 mg/g.

Abstract: S-doped TiO₂ nanoparticles were fabricated by hydrothermal process and post-calcination, and their morphology, crystalline phase and chemical composition were characterized with transmission electron microscopy, powder X-ray diffraction and selected area electron diffraction. The results showed that S was successfully doped into the TiO₂. We investigated the photocatalytic reactions in a simulated environment in tandem with thermal desorption-gas chromatography-mass spectrometry determinations. The catalytic activity of S-doped TiO₂ was evaluated by monitoring the photodegradation of BTEX from wood-based panels, and 95% degradation rate in 75 min demonstrated efficient visible-light catalytic performance.

Abstract: The paper deals with the determination of nano, microstructural, and micromechanical properties of cementitious materials surface with self-healing agent based on calcium carbonate precipitation (calcite). This was done by means of electron microscopy with elemental microanalysis and nanoindentation. These methods can define parameters of individual phases within cementitious materials, which are important for the development of micromechanical models. Bacillus pseudofirmus in combination with culture medium 235 was chosen as a self-healing agent. Our study provides information about micromechanical properties of crystals resulting from spontaneous crystallization from the culture medium and from crystallization caused by bacteria.

Abstract: Pervious concrete pavement is a porous urban surface. It could reduce runoff capacity, decrease a storm-water detention, reduce the amount of requiring rain drainage pipes, and let rainwater filter into ground and allow groundwater resources to renew in time. Fire damage, could be one of important factors since European countries have been used pervious concrete in buildings construction. This study was conducted to assess the fire damage on pervious concrete with silica fume and steel fiber. The test results find that pervious concrete with 10% silica fume and 2% steel fibers showed the maximum increase in compressive and flexural strengths by 60% and 23% respectively over the control mix while maintaining adequate permeability. It also shows that the flexural strength of pervious concrete with 10% silica fume and 2% steel fiber could reach 45 kg/cm² strength specification. The high temperature exposure results find that pervious concrete could hardly be detected any crack at the temperature of 700 °Cor 800°C and fire duration of 2 hours. There is some damage on strength after the fire-attack test, the ratio of the residual strength can range from about 20%~60% and it depends on temperature, steel fiber, and silica fume content. By this study of pervious concrete will be valuable for fire safety design and construction of practice.

Abstract: Waterproof additives and bonding agent mixtures are commonly employed in the setting up of render mortars. This practice often shows beneficial results, enhancing the properties of the common mortars. Yet, the use of these additives does not seem to have a direct effect on the mechanical properties of the mortars. This study thus aims to evaluate the influence of the use of waterproof and adhesion additives on the mechanical properties of render mortars. Based on their chemical composition, three different types of mortar admixtures were evaluated, using fourfold additive-mortar weight ratios: 0%, 1.5%, 3%, and 5%. Compressive and flexural strength tests were conducted after 28 days. The results showed a negative impact on the mechanical properties of the mortars. The lowest flexural and compression strength values reported are 1.52 and 4.57 (MPa), respectively. However, all compressive and flexural strength values lied within the limit range recommended by the “Mortars applied on walls and ceilings” construction code (i.e., ABNT NBR 13281). It is compulsory to continue the experimental tests to determine render mortars mechanical properties with higher waterproof additive-mortar weight ratios since higher ratios might produce mortars with non-allowed mechanical properties.