There is always a need for more durable, ductile, and robust materials for buildings, bridges, and other infrastructure due to the drawbacks of existing construction materials. Some of the drawbacks are the corrosion of steel, the brittle failure of concrete, and the performance instabilities that are caused when exposed to different environments. Thus, an innovative system is required to improve the performance and retain the integrity of structures in a harsh environment. To alleviate the situation, Un-plasticized polyvinyl chloride (uPVC) tubes are used as a confining material and their performance was experimentally evaluated by testing uPVC confined equivalent cylinders. Accordingly, unconfined and uPVC confined equivalent concrete cylinders for five different concrete classes, four types of uPVC tube sizes, and the aspect ratios of two (h/D = 2) were prepared and tested under axial compression loads. The result shows that the uPVC confinement increased the strength, ductility factor, and energy absorption in between 1.28–2.35, 1.84–15.3, and 11–243 times the unconfined levels, respectively. The confinement performed well for lower concrete classes and higher thickness to diameter ratios (2t/D). The post-peak behavior of the stress-strain curve was affected by the 2t/D ratio and the absolute value of the slope decreased as the 2t/D ratio increased. Additionally, the uPVC tube has shown several advantages, such as acting as a permanent formwork, protecting the concrete from chemical attacks, preventing the segregation of concrete, preventing peeling, and taking off concrete cover, decreasing the cross-section, and resulting in lighter sections. The uPVC confinement provided a remarkable improvement on the strength, ductility, energy absorption, and post-peak behavior of concrete. Therefore, uPVC tubes can be used as confining material for bridge piers, piles, electric poles, and highway signboards, where the fire risk is very small, though additional research is required on fire resistance mechanisms, such as wire-mesh reinforced mortar cover.

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Abstract:This experimental research is focused on the development of self-compacting mortar incorporating recycled glass aggregate (SCM-RGA) as partial substitution of fine aggregate (wt 0%, 10%, 20%, 30%, 40% and 50%). The fresh and hardened mechanical properties as well as durability of SCM-RGA mixes were investigated. Limestone powder (LP) was used as filler that constitutes 20% of the powder volume to reduce the amount of cement. The SCM-RGA mixtures were designed based on Japanese mix design method. The experimental test results showed that the slump flow of SCM-RGA mixes decreased and V-funnel flow time increased when the content of recycled glass aggregate (RGA) increased. The bulk density, compressive strength, flexural strength, water absorption and sorptivity of SCM-RGA mixes were decreased as RGA content increased. Moreover, the accelerated mortar bar test results showed that the expansion due to alkali-silica reaction (ASR) of SCM-RGA mixes increased as the content of RGA increased although the expansion of all mixes were within acceptable limit and potentially innocuous. In conclusion, up to 30% of RGA can be successfully integrated in SCM mixes that offers comparable strength performance, sorptivity enhancement and without long term detrimental ASR effect, and thus, contributes towards sustainable solid waste management, conservation of natural resources and environmental protection.

The unprecedented damage to steel structures during the Hyogo-ken Nanbu Earthquake not only prompted the revision of the Japanese seismic code but also emphasized the need for a comprehensive understanding of seismic response, which in reality is complex and multi-directional, as opposed to the conventionally assumed urn-directional approach. Thus, this experimental study investigated the effects of multi-directional load histories on the response of tubular columns widely used in the construction of elevated highways and building structures. Test results indicate that, in comparison with uniaxial displacement paths, multi-directional displacement patterns lead to significant degradation of stiffness, strength and ductility of tubular columns.

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Background: There is an increased demand for high-performance materials in the construction industry due to the high cost, the difficulty of sourcing and shortcomings of the existing construction materials. Some of the deficiencies are corrosion of steel, brittle failure and rapid deterioration of reinforced concrete structures in a harsh environment. Nowadays, there is also a move from one material to another due to the difficulty of sourcing i.e. timber electric poles to concrete poles due to the difficulty of sourcing native hardwood. These situations have triggered the interest to develop an alternative structural system. Objective: This paper presents the behavior of unconfined concrete, Concrete-Filled Single Skin uPVC Tubular (CFSUT) and concrete-filled double skin uPVC tubular (CFDUT) members under axial compression loads. Method: The unconfined concrete cylinders, CFSUT and CFDUT specimens were prepared from a concrete class of C25 and tested using a UTM machine at a rate of 0.2MPa/s. The parameters considered where thickness to diameter ratio (2t/D), aspect ratio (h/D) and hollow ratio (d/D). Also, a model was developed to predict the peak strength of CFSUT and CFDUT specimens. Results: The result shows that both CFSUT and CFDUT specimens exhibited improved strength, ductility, and energy absorption capacity. For CFSUT and CFSUT specimens, the strength, ductility, and energy absorption capacity increased by more than 1.32, 3.75 and 14.75 times compared to the unconfined concrete specimens, respectively. It is found that the strength decreased as the h/D and d/D ratios increased. The result also shows that the strain of CFSUT and CFDUT at the peak strength increased by more than 3.16 times compared to the unconfined concrete specimens. The proposed model accurately predicted the peak strength with AAE of 2.13%. Conclusion: The uPVC confinement provided a remarkable improvement on the strength, ductility and energy absorption of concrete. Therefore, uPVC tubes can be used as confining material for bridge piers, piles, electric poles, and building columns to increase the strength, ductility and energy absorption of concrete structures.