•Creep behavior of basalt fiber reinforced polymer is similar to other types of FRP bars.•The creep rupture time and creep strain of basalt FRP bars depend mainly on the initial stress level.•Fiber ...volume fraction of basalt FRP bars has significant effect on the long-term creep behavior.•The residual tensile properties of basalt FRP bars are barely affected due to creep up to 1000 h.•Basalt FRP bars are recommended to be used in prestressing application.
One of the main properties that affects the use of fiber reinforced polymer (FRP) composites in prestressing application is the long-term creep behavior. In this study the long-term creep behavior of basalt fiber reinforced polymer (BFRP) bars was investigated. The initial stress level and the fiber content presented in different diameter are the variables considered in this study. The creep rupture stress, the creep strain, and the residual properties of BFRP were experimentally studied. Moreover, the ratio of creep rupture stress after million-hour (114 years) to the initial ultimate strength of BFRP bars was extrapolated based on statistical analysis of the experimental results to be 62.3% and 57.7% for 6 and-10 mm diameters of BFRP bars, respectively. The test results showed that the creep rupture stress of BFRP bars under different sustained stresses have linear relationship with logarithm of time similar to other types of FRP bars. Additionally, the creep behavior of BFRP bars follows the three stages of creep strain similar to glass and aramid FRP bars. Moreover, based on the test results, the fiber content had proved to have a significant effect on the long-term creep behavior of BFRP bars, since the 6 mm diameter of higher fiber content exhibit lower creep strain and higher extrapolated creep rupture stress than 10 mm diameter. Finally, BFRP bars are recommended to be used in prestressing application.
AbstractThis paper presents an experimental study that investigated the physical, mechanical, and durability characteristics of three different types of fiber-reinforced polymer (FRP) bars made of ...basalt and glass fibers with vinylester and epoxy resins, namely basalt/vinylester (B/V) FRP bars, glass/vinylester (G/V) FRP bars, and basalt/epoxy (B/E) FRP bars. First, their physical and mechanical properties were assessed. Then, a comparative durability study was performed on the three types of FRP bars under alkaline exposure simulating a concrete environment. The alkaline exposure was achieved by immersing the bars in an alkaline solution for up to 5,000 h at 60°C. Thereafter, the properties were assessed and compared with the unconditioned (reference) values. The test parameters were (1) fiber type (basalt or glass); (2) resin type (vinylester or epoxy); and (3) conditioning time (1,000, 3,000, and 5,000 h). The test results reveal that the G/V composite had the best physical and mechanical properties and lowest degradation rate after conditioning in alkaline solution. The B/E composite ranked second, while the B/V composite evidenced the lowest physical and mechanical properties and exhibited significant degradation of its physical and mechanical properties after conditioning.
•Increasing the modulus of silicate, the workability increased and the compressive strength decreased.•Low workability Geopolymer mortar reaches high early and late comp. strength of 50 and 77 MPa, ...respectively.•Self-compacted Geopolymer mortar has a considerably high strength of 40.2 MPa.•Adding water to geopolymer concrete decreased compressive strength significantly.•Based on the statistical analysis, i the mixture of 1.7 MS is the optimum mixture.
Recently, the application of green concrete as an alternative for conventional concrete has become popular worldwide. The innovative green concrete can be produced using waste materials as one of its components. Therefore, recent years witnessed a huge increase in the studies that investigate geopolymer’s fresh and hardened properties. The previous studies show that workability loss, rapid setting time and the need for heat curing are the main constraints that restrict the production of cast in place geopolymer concrete. This study aims to reach the optimum activator modulus which achieves the maximum compressive strength with acceptable workability. Nine different mixtures were blended using industrial by-products, such as Ground Granulated Blast Furnace Slag (GGBS) and Metakaolin (MK). Two main materials mixtures were used; either slag or 50/50 slag/MK. Sodium hydroxide and sodium silicate were used as an activator. The main variables were the base material (GGBS and MK), water/binder ratio (0.0, and 15.0%), and modulus of silicate (1.1, 1.3, 1.5, and 1.7). Fresh and hardened properties were examined using the flow table test, and compressive strength test, respectively. It has been observed that by increasing the modulus of silicate, the workability increased and the compressive strength decreased. Adding water decreased compressive strength significantly, as well. Based on the statistical analysis, it was concluded that the mixture of 1.7 modulus of silicate is the optimum mixture. It worth mentioning that the compressive strength of the optimum mixture after 7, 28 and 90 days of water curing were 19.6, 33.4 and 35.6 MPa, respectively, and its flowability was about 150%.
Abstract Alkali Activated Slag Concrete (AASC) has been a sustained research activity over the past two decades. Its promising characteristics and being environmentally friendly compared to Ordinary ...Portland Cement made AASC of exceptional interest. However, there is still no firm mix design, for the AASC, that can provide desirable fresh and hardened properties based on the composition of the binder and activator. This research specifically aims to investigate the affecting parameters on the slump and compressive strength of alkali-activated slag/lime-based concrete and provide a better understanding of the potential reasons for these characteristics. The experimental program consisted of two stages; the first stage studied the effect of different binder and activator compositions, and the second stage studied the water-to-binder ratio and binder content effects on the slump and compressive strength of alkali-activated slag/lime-based concrete. The binder and activator compositions were defined through two main parameters, the hybrid factor (HF = CaO/Si 2 O + Al 2 O 3 ) and the solution modulus (Ms = SiO 2 /Na 2 O). The compressive strength, initial slump, and slump loss were measured to evaluate the different mixes and specify the optimum range of compositions. Based on the studied parameters, the effective range to achieve desirable slump and concrete compressive strength is from HF 0.6 up to 0.8 at Ms 1.5, this would achieve a compressive strength of more than 30 MPa and a slump of 100 mm after 90 min.
This research aims to evaluate the tensile properties of basalt textile-reinforced mortar. The tension test was carried out on nineteen sets of pin action specimens. The variables studied in the ...current research are textile mesh size, number of plies, and mortar type, as well as coating some of the textiles with epoxy. The results indicated that increasing the number of plies resulted in an increase in the ductility and the ultimate load of specimens. The polymer modified cementitious mortar reinforced with glass fibers is the most efficient in enhancing the strength and ductility among the different types of mortars used in the study. Moreover, coating textiles with epoxy enhanced the ultimate load by about 25% compared to the uncoated specimens. The experimental results were compared with the corresponding values predicted by a model reported in the literature. The experimental results were in good agreement with those predicted using the model.
Several challenges faced the carbon footprint reduction of concrete production. Recycling waste materials from different industries to produce green concrete would be a proper solution due to their ...low cost and space-saving for landfill purposes. One of these industries is manufacturing vitrified clay pipes used for sewage, which show high resistance to the aggressive environment. However, vastly deteriorated pipes are disposed of as waste in landfills while processing. Additionally, the vitrified clay pipes are sourced from the kaolin burnt at a temperature above 800 °C while processing; no literature introduces the disposal wastes as supplementary cementitious material (SCMs). Nevertheless, other wastes such as ceramic sourced by metakaolin were introduced. This paper studies the grounded vitrified clay pipe (GVCP) as SCMs for producing green concrete. The methodology encountered examining the durability and mechanical properties of concrete using GVCP. Two group sets suggested; normal and high concrete strength with 0, 5, 10, 15, 20, and 25% cement replacement by GVCP. Slump, compressive and flexural strengths, and abrasion were assessed while microstructure analysis handled. The results showed that the optimized values would be 10% and 20% for normal and high concrete strength in which mechanical properties are provided. The study also suggested a coefficient of 1.52 and 0.7 for ACI 318 and EN 1992-1 flexural provision. The GVCP showed higher resistance to chloride ingress of fewer than 1000 coulombs even at a high water-to-cement ratio of 0.64. The X-ray diffraction (XRD) revealed that GVCP provided more CSH gels, increasing compressive strength at later ages.
•NSM and prestressed NSM are effective techniques that greatly enhanced the flexural behaviour of strengthened RC beams.•BFRP bars showed superior performance in strengthening of RC beams using NSM ...and prestressed NSM techniques.•The initial prestressing level greatly influence the flexural behavior of strengthened RC beams.•The high creep rupture strength of BFRP bars offers it a priority for strengthening RC beams using prestressed NSM technique compared to GFRP bars.
This research aimed at studying the flexural behavior of RC beams strengthened with near surface mounted (NSM) technique using basalt FRP (BFRP) bars to assess their efficiency for strengthening RC beams in order to be introduced as an alternative to other types of FRP bars. Moreover, this study investigated a new type of strengthening technique, named prestressed near surface mounted (PNSM) technique, which is expected to offer lots of advantages owing to combining two well-known “external prestressing” and “NSM” techniques. The variables considered in this study were the strengthening effect (unstrengthened and strengthened), the type of the FRP bars (BFRP and GFRP), the strengthening technique (NSM and PSNM), the initial prestressing level (30% and 50% of ultimate tensile capacity of BFRP bars), and the position of NSM FRP bars (bottom and side). The test results demonstrated the efficiency of using BFRP bars for strengthening RC beams with NSM and PNSM techniques. Additionally, BFRP bars offered additional advantage compared to GFRP bars when strengthened with PNSM technique owing to its higher creep rupture strength. Moreover, the test results proved that strengthening of RC beams with PNSM technique offers superior enhancement in the pre-cracking stage compared to NSM technique while sacrificing a great portion of beam’s ductility.
•Physical and mechanical characterization of newly developed basalt FRP bars for concrete members.•Durability of BFRP bars in harsh alkaline conditions simulating the concrete environment.•Discussion ...of BFRP characterization and durability results and compare them against the requirements of FRP standards.
This paper introduces an experimental study that investigated the physical, mechanical, and durability characteristics of basalt fiber-reinforced polymer (BFRP) bars. Durability and long-term performance were assessed by conditioning the BFRP bars in an alkaline solution simulating the concrete environment (up to 3000h at 60°C) to determine their suitability as internal reinforcement for concrete elements. Thereafter, the properties were assessed and compared with the unconditioned (reference) values. In this study, three types of BFRP bars were investigated. The test results revealed that the BFRP bars had good mechanical behavior and could be placed in the same category as grade II and grade III GFRP bars (according to tensile modulus of elasticity). Their tensile strength, however, was higher than that provided by CAN/CSA S807-10 for CFRP bars. On the other hand, the BFRP bars showed poor alkali resistance and exhibited a remarkable reduction in mechanical properties due to the resin–fiber interface issues, which needs to be remedied to achieve the desired durability characteristics.
AbstractRecently, basalt fiber–reinforced polymer (BFRP) reinforcement emerged as a new FRP type. Research is needed, however, to understand the behavior of BFRP bars in concrete members. This paper ...presents an experimental study aimed at investigating the flexural behavior and serviceability performance of concrete beams reinforced with ribbed BFRP bars. A total of eight concrete beams measuring 3,100 mm in length×200 mm in width×300 mm in depth were constructed and tested up to failure. Six beams were reinforced with 8-, 12-, and 16-mm BFRP bars with ribbed surfaces and two reference beams were reinforced with 10M and 15M steel bars. The beam specimens were designed in accordance with Canadian standards, and tested under four-point bending over a clear span of 2,700 mm until failure. The test results are presented and discussed in terms of cracking behavior, deflection, and failure modes. The test results yielded an average bond-dependent coefficient (kb) of 0.83, which is lower than 1.0 recommended by Canadian standards for ribbed FRP bars. Moreover, comparing the test results to the design provisions showed that American Concrete Institute (ACI) Committee 440 Guide underestimated the deflections at service load for the beams reinforced with ribbed BFRP bars, while Canadian standards for design and construction of building structures with FRP yielded reasonable and conservative deflections.
This experimental research aims to reduce the joint length between the precast concrete elements reinforced with GFRP bars. The experimental work was divided into two stages. Stage (I) consists of ...twelve specimens made from GFRP bars and jointed together using GFRP or steel sleeves filled with epoxy resin. The specimens were tested under tension up to failure to investigate the tensile capacity of splice bars taking into consideration different parameters such as sleeve type, embedment length, bar size, and sleeve radial stiffness. While Stage (II) consists of ten reinforced concrete beams measuring 200 × 350 × 3300 mm. All beams were tested under a four-point bending load up to failure. The connection types for GFRP bars were investigated using two methods; (i) the optimum sleeve connector selected from stage I, (ii) using lap splice with different parameters such as splice length, joint compressive strength, and confinement lap-splice region with GFRP sheets. The test results show that an adequate bar embedment length and sleeve radial stiffness are required to achieve bar tensile strength. Whereas lap splice length can be reduced by increasing confinement of lap splice region with GFRP sheets. Finally, precast elements' joint length can be minimized by using a sleeve connector with adequate radial stiffness and embedment length equal to 15-times bar diameter or by confinement of the lap splice region to minimize its length to 40-times bar diameter.
•The tensile capacity of spliced bars increases by increasing radial stiffness of the GFRP sleeve connector.•The tensile capacity of steel sleeve spliced bars improved by increasing the bar embedment length, regardless of bar diameter.•Increasing confinement of the lap splice region with GFRP sheets can reduce the lap splice length.•The joint length of precast elements can be minimized by using a sleeve connector with adequate radial stiffness or by confinement of the lap splice region.
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