Strain hardening behavior of lightweight hybrid polyvinyl alcohol (PVA) fiber reinforced cement composites

Experimental results on the strain hardening and multiple cracking behaviors of polyvinyl alcohol (PVA) fiber reinforced cementitious composites under bending are reported in this paper. Different hybrid combinations of PVA fibers with different lengths and volume fractions are considered to reinforce the mortar matrix. Among different hybrid combinations, the composite containing 2% thicker PVA fibers of 12 mm length and 1% thinner PVA fibers of 6 mm length and the composite containing 2% thicker PVA fibers of 24 mm length and 1% thinner PVA fibers of 6 mm length showed the best performance in terms of highest ultimate load, largest CMOD (crack mouth opening displacement) at peak load and multiple cracking behavior. The effects of four types of light weight sands on the strain hardening and multiple cracking behavior of hybrid fiber composites are also evaluated in this study. It has been observed that the ultimate load and CMOD at peak load for all light weight hybrid fiber composites are almost the same irrespective of volume fractions of light weight sand. The composites containing finer light weight sands exhibited higher ultimate load than those containing coarser light weight sands. It is also observed that the hybrid fiber composite containing normal silica sand exhibited higher ultimate load than the composites with light weight sands

Intolerance of uncertainty and mental wellbeing: serial mediation by rumination and fear of COVID-19

The novel coronavirus-2019 (COVID-19) pandemic has become globally widespread with millions of confirmed cases and many countries implementing various levels of quarantine. Therefore, it is important to investigate the psychological consequences of this process, given the unique situation that has been experienced globally. Therefore, the present study examined whether intolerance of uncertainty was related to mental wellbeing and whether this relationship was mediated by rumination and fear of COVID-19. The sample comprised 1772 Turkish individuals (aged between 18 and 73 years) from 79 of 81 cities in Turkey, who completed measures of mental wellbeing, intolerance of uncertainty, rumination, and fear of COVID-19. Results of serial mediation analyses showed that intolerance of uncertainty had a significant direct effect on mental wellbeing. Rumination and fear of COVID-19, in combination, serially mediated the association between intolerance of uncertainty and mental wellbeing. The findings are discussed within the framework of the psychological consequences of the COVID-19 pandemic and related literature

Iridoids and Anthraquinones from the Malaysian Medicinal Plant, Saprosma scortechinii (Rubiaceae)

A further investigation of the leaves and stems of Saprosma scortechinii afforded 13 compounds, of which 10 are new compounds. These were elucidated as the bis-iridoid glucosides, saprosmosides G (1) and H (2), the iridoid glucoside, 6-O-epi-acetylscandoside (3), and the anthraquinones, 1-methoxy-3-hydroxy-2-carbomethoxy-9,10-anthraquinone (4), 1-methoxy-3-hydroxy-2-carbomethoxy-9,10-anthraquinone 3-O-β-primeveroside (5), 1,3-dihydroxy-2-carbomethoxy-9,10-anthraquinone 3-O-β-primeveroside (6), 1,3,6-trihydroxy-2-methoxymethyl-9,10-anthraquinone (7), 1-methoxy-3,6-dihydroxy-2-hydroxymethyl-9,10-anthraquinone (8), 1,3,6-trihydroxy-2-hydroxymethyl-9,10-anthraquinone 3-O-β-primeveroside (9), and 3,6-dihydroxy-2-hydroxymethyl-9,10-anthraquinone (10). Structure assignments for all compounds were established by means of mass and NMR spectroscopies, chemical methods, and comparison with published data. The new anthraquinones were derivatives of munjistin and lucidin

Cover Cracking of Reinforced Concrete Beams Due to Corrosion of Steel

A finite element (FE) model is proposed to simulate the corrosion-induced cracking of reinforced concrete (RC) beams. The smeared cracking approach is used to model the cracking ofordinary concrete, ductile fiber-reinforced cementitious composites (DFRCC), and engineered cementitious composites (ECC). The model simulates the cracking of ordinary concrete beams and RCbeams containing ECC and DFRCC materials. The strains obtained from the FE models are compared with that measured by the fiber-optic strain sensor (FOSS) gauge, which is placed between longitudinal steel bars at midspan of RC beams during the accelerated corrosion test. The model could predict thecorrosion-induced damage tolerance of ECC and DFRCC materials and found that it is several times higher than that of ordinary concrete. The model predicted the uniform damage in the ECC and the DFRCC materials due to corrosion compared with localized damage in ordinary concrete. The model also predicted that the delamination of the cover of the RC beams containing ECC/DFRCC materials will occur at a higher level of steel loss compared with that of an ordinary concrete beam. The betterperformance exhibited by the RC beam containing ECC/DFRCC materials is due to their higher tensile strain capacity, strain hardening, and multiple cracking behavior

Corrosion Durability and Structural Response of RC Beams Containing Supplementary Cementing Materials

This paper reports the results of an experimental program on the effect of fly ash, slag and silica fume used as partial replacement of ordinary Portland cement (OPC) in retarding the corrosion of steel in medium-scale reinforced concrete beams. Eight reinforce concrete beams measuring 2.5 meters in length and 210 x 300 mm in cross-section were cast, four of which were subjected to accelerated corrosion. It was found that concrete containing fly ash, slag and silica fume showed better corrosion protection of steel in RC beams than OPC concrete. Among these, fly ash concrete showed the best performance in terms of lowest corrosion current (hence lowest steel loss), least visual damage and lowest tendency for delamination as measured by a concrete-embeddable fibre optic strain sensor. Corroded and un-corroded RC beams were tested under four point bending in order to evaluate the effect of corrosion damage on flexural behaviour of the beams. The results showed that corroded RC beam containing fly ash lost only 3% of its ultimate load capacity compared to 13% strength loss observed in the corroded OPC concrete beam