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This study examines the flexural behavior of reinforced concrete (RC) one-way slabs strengthened with near-surface mounted (NSM) basalt fiber-reinforced polymer (BFRP) bars. Ten RC slabs were subjected to four-point loading until failure. Various parameters including the steel reinforcement ratio (0.48and 0.95%), the NSM-BFRP reinforcement ratio (0.17, 0.25, and 0.35%), and two types of epoxy adhesives (Sikadur-30 and NSM-Gel) were investigated. The experimental results demonstrated the remarkable efficacy of the NSM-BFRP bars in enhancing the flexural performance of the strengthened slabs, especially those with lower steel reinforcement ratios. Compared to the control slabs, the ultimate loads were increased by 51‐123% and 21‐44% for slabs with 0.48 and 0.95% steel reinforcement ratios, respectively, while the ductility indices were increased by 10‐53% and 29‐79%. The type of the epoxy adhesive used had minimal impact on the flexural behavior of the strengthened slabs. Failure primarily occurred due to steel yielding followed by the rupture of the NSM-BFRP bars or by concrete crushing, depending on the reinforcement ratio provided. The cracking, yield, and ultimate loads of the strengthened slabs were predicted using the formulations of ACI 440.2R [3] guideline. Good agreement between the predicted and the experimental results were obtained, with ACI formulations being on the conservative side. • NSM-BFRP increased slab load capacity by up to 124%. • Effectiveness of NSM-BFRP varied based on steel reinforcement ratios. • Strengthened slabs exhibited improved ductility with ductility indices increasing up to 79%. • Failure modes differed based on both steel and NSM-BFRP reinforcement ratios. • Experimental results aligned well with ACI 440.2 R (2017) predictions. [ABSTRACT FROM AUTHOR]

• BFRP bars' bond strength examined in harsh environments. • High-strength concrete achieves maximum bond strength. • Ribbed bars show higher bond strength in all environments. • SEM shows debonding and cracks due to seawater exposure. • BPE and CMR models correlate well with sand-coated bars. This study examines the bond durability behavior of basalt fiber-reinforced polymer (BFRP) bars in harsh environments. The effects of surface treatment, concrete compressive strength, exposure type, and period of exposure on bond strength were examined through an experimental program. The results of 42 pull-out samples show that the bond strength of sand-coated bars was not significantly affected by concrete compressive strength. However, specimens with high-strength concrete achieved most of or above their maximum bond strength after the descending stage, while those with normal-strength concrete showed a decrease in bond strength to an approximately constant value with continuous slip. Ribbed bars had significantly higher bond strength than sand-coated bars and were less affected by the surrounding environments. After 9 months, the bond strength retentions for sand-coated bars were 29.43, 63.93, and 67.43%, and 66.10, 94.94, and 80.44% for ribbed bars under the exposure to the 50 °C seawater, sulfuric acid, and freeze–thaw cycles, respectively. The failure in sand-coated bars was governed by a complete delamination of the outer surface from the core of the bar, whereas the ribbed bars failed due to bar rupture and interlaminar shear failure between bar layers. Both BPE and CMR models correlated well with experimental findings of the sand-coated bars, but CMR was more accurate for ribbed bars. [ABSTRACT FROM AUTHOR]

The ever-increasing utilization of fiber-reinforced polymer (FRP) bars has led to a surge in research regarding their bonding properties with concrete. In this study, the bond durability behavior between high-strength fiber-reinforced concrete (FRC) and sand-coated basalt FRP (BFRP) bars was examined under three different environmental conditions including immersion in seawater solution at 50 °C for 3, 6, and 9 months, immersion in the sulfuric acid solution for 3, 6, and 9 months with an ambient temperature range of 20 to 30 °C, and exposure to 270 freeze–thaw cycles. A total of 60 pull-out samples were prepared using either basalt (B) fibers or polypropylene (PP) fibers. Plain concrete pull-out samples were served as controls. Test results revealed that all exposures have degraded the bond, leading to pull-out failure in all of the specimens. Exposure to 50 °C seawater was found to cause the most significant degradation. However, the use of basalt fibers helped to mitigate the loss of bond strength in the specimens when compared to plain concrete specimens. For example, after 3, 6, and 9 months of exposure to 50 °C seawater, bond strength retentions of 73.58%, 56.04%, and 34.47% were observed for basalt FRC (BFRC) specimens, compared to 39.64%, 49.37%, and 29.61% for plain concrete specimens. On the other hand, a lower retention in bond strength of 16.28% was recorded for polypropylene FRC (PPFRC) specimens at 9 months of exposure to 50 °C seawater. The bond stress-slip relationship of the tested bars was accurately predicted using two calibrated analytical models: the Eligehausen, Popov, and Bertero (BPE) model and the Cosenza, Manfredi, and Realfonzo (CMR) model. Notably, both models showed a strong correlation with the observed bond stress-slip relationships in the experiments. [ABSTRACT FROM AUTHOR]

Abstract This research investigates experimentally and analytically a novel one-way slab system reinforced with either basalt fiber-reinforced polymer (BFRP) or glass fiber-reinforced polymer (GFRP) longitudinal bars embedded in fiber-reinforced concrete (FRC) incorporating basalt macro-fibers (BMF). Twelve one-way concrete slab strips were prepared and tested to failure under four-point loading configuration. The investigated parameters included the type of fiber-reinforced polymer bars (BFRP and GFRP), the longitudinal reinforcement ratio ρ f (1.4 and 2.8 ρ bf , where ρ bf is the balanced reinforcement ratio), and the volume fraction of the fibers added (0, 0.5, 1, and 2% per volume). The test results demonstrated the promise of BMF to enhance the flexural performance of the tested slab strips in terms of ductility and load-carrying capacities. The formulations of different available codes and design guidelines were used to predict the test results. Comparison between the experimental and predicted results showed the adequacy of the models to predict the flexural performance of the tested slab strips. The findings of this study demonstrated the potential of using the BMF as alternatives to conventional fibers in flexural concrete members. [ABSTRACT FROM AUTHOR]

This research paper investigates the physical, chemical and mechanical properties of steel slag aggregates (SSA), gravel aggregates (GLA), natural gabbro aggregates (NGA), and the different fresh and hardened properties of concrete mixtures prepared using SSA, GLA and NGA. Furthermore, this paper presents the compression and flexural test results of different concrete mixtures made with SSA or NGA combined with different volume fractions of basalt macro-fibre (BMF). The investigated parameters included the type of coarse aggregates, the replacement of the recycled aggregates (0, 25, 50, 75 and 100%) and the volume fraction of BMF (0·25% and 1·0%). Test results have shown that replacing NGA with GLA reduces both the compressive and tensile strength of the concrete. However, concrete made with SSA tends to result in a higher compressive strength than that made with NGA. In addition, the test results showed a considerable improvement in mechanical concrete properties with increasing BMF volume fractions. [ABSTRACT FROM AUTHOR]

It is well known that the Newmark's method is considered one of the most popular methods for structural dynamic analysis. In this study, starting from the basic Newmark's method, a new accurate method is investigated and developed. The basic idea of the proposed method is to use Richardson's extrapolation to improve the basic Newmark's method. To observe the accuracy of the proposed method, several numerical tests are performed for a single degree-of-freedom (SDM) dynamic system and the results are compared with results from Newmark's method and the exact solution. The results show that the proposed method improves the solution accuracy of the structural dynamic problems compared to the Newmark's method. Moreover, the results of the free oscillating case show that the modified Newmark's method has more computational efficiency compared to the Newmark's method. [ABSTRACT FROM AUTHOR]

This study investigates the effect of using recycled concrete aggregates (RCA) from construction and demolition (C&D) waste combined with basalt macro-fibers (BMF) on the flexural behavior and ultimate capacity of reinforced concrete (RC) beams experimentally and analytically. A total of 16 RC beam specimens were flexural tested to failure. The investigated parameters include the RCA replacement ratio and the volume fraction of the BMF. Furthermore, the experimental results were also compared against the existing analytical models and code-based equations for conventional concrete. The test results show that the flexural capacity of beams with the addition of BMF was improved. On the other hand, the use of RCA has no remarkable impact on the flexural strength of the tested beams. [ABSTRACT FROM AUTHOR]

The impact of flow rate and turbidity on the performance of multi-media filtration has been studied using an artificial neural network (ANN) based model. The ANN model was developed and tested based on experimental data collected from a pilot scale multi-media filter system. Several ANN models were tested, and the best results with the lowest errors were achieved with two hidden layers and five neurons per layer. To examine the significance and efficiency of the developed ANN model it was compared with a linear regression model. The R2 values for the actual versus predicted results were 0.9736 and 0.9617 for the ANN model and the linear regression model, respectively. The ANN model showed an R-squared value increase of 1.22% when compared to the linear regression model. In addition, the ANN model gave a significant reduction of 91.5% and 97.9% in the mean absolute error and the root mean square error, respectively when compared to the linear regression model. The proposed model has proven to give plausible results to model complex relationships that can be used in real life water treatment plants. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the shear behavior of high-strength one-way plain and basalt fiber reinforced concrete (BFRC) slabs reinforced with basalt fiber reinforced polymers (BFRP) bars. A total of 8 slabs having 2550 mm length, 600 mm width and 150 mm height were tested under four-point loading until failure. The main test variable was the BFRP longitudinal reinforcement ratio with two ratios of 0.792 % and 1.27 %. Also, two slabs were cast with basalt macro fibers (BMF) at a volume fraction (V f) of 0.75 % to explore the effect of the added fibers on the shear capacity of the tested one-way slabs. Following the experimental testing, the shear capacities of the BFRC-BFRP one-way slabs were evaluated analytically using two approaches. The first approach considers the individual contribution of concrete and BMF to shear strength, while the second takes into account a direct alteration to the concrete contribution owing to the addition of BMF. The experimental results showed that the shear capacity was enhanced by 25 % to 29 % when the reinforcement ratio was increased from 0.792 % to 1.27 %. In addition, the shear capacity of the slab containing 0.75 % of BMF was notably enhanced over the plain concrete slab, however, this enhancement was less notable when a higher reinforcement ratio was used. Based on the analytical investigation, a new model that accounts for the individual contribution of concrete and the BMF is proposed. The model has accurately and conservatively predicted the experimental data with a mean experimental to predicted shear capacity of 1.10 and a coefficient of variation of 7.95 %. [ABSTRACT FROM AUTHOR]

This paper reports on the experimental and analytical investigation of the shear performance of concrete beams cast with basalt fiber-reinforced concrete (BFRC) and longitudinally reinforced with basalt fiber-reinforced polymer (BFRP) bars. Fourteen hybrid (BFRC-BFRP) beams with no stirrups were tested to failure under a four-point loading setup. The investigated parameters included the volume fraction, V f , of the added fibers (0.75 and 1.5%), the reinforcement ratio of the BFRP bars, ρ , (0.31, 0.48, 0.69, 1.05, and 1.52%), and the shear span-to-depth ratios, a/d , of the beams (3.3 and 2.5 for slender and short beams, respectively). The tests results showed that adding 0.75% of basalt macrofibres (BMF) improved the shear capacity of the slender and short beams by 46 and 43 %, respectively, compared to 81 and 82% when 1.5% of BMF were added. The impact of adding the BMF on the shear strength of the beams diminished as the longitudinal reinforcement ratios increased. The existing models overestimated the shear strength of the tested beams with an average predicted-to-experimental ratio ranging between 1.15 ± 0.03 and 2.48 ± 0.29. A shear model that accounts for the type of the longitudinal reinforcement and the added fibers was proposed to predict the shear strength of the BFRC-BFRP beams. A good agreement between the predicted and experimental shear strength was evident with a predicted-to-experimental ratio that ranged between 0.98 ± 0.11 and 0.88 ± 0.02 for the slender and short beams, respectively. [ABSTRACT FROM AUTHOR]

• Concrete made with TWW, RCA, and FA was investigated. • FA considerably improved TWW and RCA concrete durability and interface properties. • Concrete mixes with TWW, RCA, and FA exhibited the lowest chloride permeability. • Aggregate and concrete morphological images and composition were investigated. This study evaluates the impact of using treated wastewater (TWW), recycled concrete aggregates (RCA), and fly ash (FA) on the mechanical, durability, and microstructural properties of concrete. A total of eight concrete mixes were manufactured and tested. Fresh mixing water and natural gabbro aggregates were completely replaced with TWW and RCA, respectively, whereas 20% of cement was substituted by FA. Test results revealed that TWW slightly reduced concrete mechanical properties by 6% to 12%, while it drastically reduced the chloride permeability by 77% in comparison with freshwater concrete. In addition, RCA decreased concrete compressive and flexural strengths by 21% and 10%, respectively, compared to natural aggregate concrete. Moreover, TWW concrete mixes with RCA had 16% to 42% lower porosity and chloride permeability than their counterparts with gabbro aggregates. Furthermore, concrete mixes with TWW, RCA, and FA exhibited the lowest chloride permeability among the investigated mixes. It was also shown that the interfacial transition zones between RCA and cement matrix were improved by replacing FA for 20% of cement. Analytically, aggregate and concrete morphological images and chemical composition were investigated to support the experimental results. [ABSTRACT FROM AUTHOR]

This paper investigates the bond between high-strength concrete (HSC) and tensile lap-spliced basalt fiber-reinforced polymer (BFRP) bars. Ten large-scale BFRP-reinforced concrete beams (300 × 450 × 3900 mm) were fabricated and tested under four-point loading until failure. The parameters investigated included the BFRP bar diameter (10, 12, and 16 mm), the splice length (400–1200 mm range), and the bar surface texture (sand-coated (SC) and helically wrapped (HW)). Test results demonstrated that the flexural capacity of the beams reinforced with SC-BFRP bars was almost similar to that of beams reinforced with HW-BFRP bars. However, SC-BFRP bars showed a slightly higher bond with concrete compared to that of helically wrapped counterparts. The bond strength of spliced BFRP bars was inversely related to the splice length. Also, BFRP bars with larger diameter bars require longer splice lengths to reach their maximum capacity. Finally, the experimentally estimated critical splice lengths were compared to those calculated by existing models and code-based equations. Both ACI 440.1R-15 and CSA S806-12 provisions were conservative in predicting splice length for BFRP bars. However, the CSA-S6-14 design code was more accurate in estimating the splice length for BFRP with bigger diameters. Though, it was not conservative with smaller diameters. [ABSTRACT FROM AUTHOR]

This study presents an experimental and numerical study on the structural behavior and moment redistribution of basalt fiber-reinforced concrete (BFRC) continuous beams with basalt fiber-reinforced polymer (BFRP) bars. A total of seven BFRP-BFRC two-span continuous beams were tested to failure under a five-point test setup. Three parameters were investigated: volume fractions (V f) of basalt macro-fibers (BMF), BFRP reinforcement ratio, and stirrups spacing. Test results indicated that compared to stirrups spacing, reinforcement ratio and V f of BMF were more significant in improving the structural performance and moment redistribution of the tested beams. Furthermore, nonlinear 2D finite element (FE) models were developed using the commercial ABAQUS software to predict the behavior of the tested beams. The FE analysis accounted for the tensile cracking and compressive crushing of concrete using the built-in concrete damaged plasticity model. Ayub's analytical model was employed to simulate the nonlinearity of BFRC in compression. The accuracy of the FE models was validated using the experimental load-deflection responses and crack patterns at failure. Good agreement was obtained between the experimental and numerical results with the experimental-to-predicted mean, standard deviation, and coefficient of variance values of 1.036, 0.041, and 3.95% for the ultimate loads and 0.993, 0.046, and 4.68% for the deflections, respectively. [ABSTRACT FROM AUTHOR]

This study investigated the shear performance of large-scale green concrete (GC) beams reinforced with basalt fiber reinforced polymer (BFRP) bars and stirrups. The GC concept was employed in this study by partially substituting the cement content with 35% by weight of industrial by-products (fly ash and silica fume). The main test variables were the reinforcement ratio, the shear span to depth ratio (a/d), and the spacing between stirrups. Three beams were transversely reinforced with steel stirrups to serve as a control. Experimental results indicated that the ultimate shear capacity was significantly increased at higher reinforcement ratios. Such effect was less pronounced in beams with reduced spacing between stirrups. In addition, the BFRP stirrups were effective in reducing the diagonal shear crack width and increasing the ultimate shear capacities of the tested beams. On the other hand, beams with a higher a/d ratio have shown higher deflection and reduced ultimate shear capacity. Comparing the experimental results of the current study with the current design codes and guidelines provisions, the CSA-S806-12 has shown the best predictions with a mean experimental to predicted shear (V exp /V pre) ratio of 1.43 ± 0.29. [ABSTRACT FROM AUTHOR]

Recently, researchers' efforts have been directed toward using fiber-reinforced concrete (FRC) in lieu of conventional concrete to improve the compressive strain, tensile strength capacity, cracking patterns, and ductility of fiber-reinforced polymer (FRP) reinforced concrete members. In this study, a numerical one-factor-at-a-time parametric study including 144 finite element (FE) models was performed using ABAQUS 6.14 software to deeply explore the influence of the volume ratios of basalt macro-fiber (BMF), reinforcement ratios of basalt FRP (BFRP) bars, and stirrups spacing on the moment redistribution of basalt FRC continuous beams reinforced with BFRP bars. It was shown that the most influential parameter on the moment redistribution was the longitudinal reinforcement configuration. While a higher moment redistribution was noticed with higher sagging reinforcement ratios and BMF, stirrups spacing showed no effect on the moment redistribution. It was also observed that the moments were inversely distributed for FE models having high hogging-to-sagging reinforcement ratios. The sagging-to-hogging reinforcement ratio is recommended to be at least 1.6 to ensure a uniform moment redistribution. Furthermore, a multiple linear regression model was developed using Minitab 17 software to establish a relationship between the investigated parameters and the beams' moment redistribution. The moment redistribution was accurately predicted using the developed regression model. [ABSTRACT FROM AUTHOR]

• The shear behavior of BFRP-BFRC beams was investigated experimentally and analytically. • The ultimate loading capacity and ductility of beams were improved with the addition of BMF. • The shear capacities of the tested beams were enhanced as their reinforcement ratios increased. • The GFRP stirrups resulted in lower ultimate strengths of beams than steel stirrups. • A modified shear equation incorporating CAN/CSA-S806-12 provisions was proposed. This study investigated the shear behavior of basalt fiber reinforced concrete (BFRC) beams reinforced with basalt (B) and glass (G) fiber-reinforced polymers (FRP) bars and stirrups, respectively. Fourteen beams were tested under four-point loading up to failure. The investigated parameters were the volume fractions (V f) of basalt macro-fibers (BMF), the reinforcement ratio, the shear-span-to-depth ratio, and the stirrup spacing. An enhancement in shear capacities of the tested beams was observed with the increase of the V f of the added BMF from 0 to 1.5%. The shear capacities of the tested beams were also improved as their reinforcement ratios increased. On the other hand, there was a significant reduction in the ultimate strengths and stiffnesses of beams with GFRP stirrups compared to their counterpart beams with steel stirrups. The experimental capacities of the tested beams and experimental results of 178 FRP-RC beams available in the literature were compared to those predicted by existing models and code equations. A good correlation between the predicted and experimental results was obtained using the equations of CAN/CSA-S806-12. A proposed modified shear equation incorporating CAN/CSA-S806-12 provisions and a model suggested by Al-Ta'an and Al-Feel predicted the shear design capacities of BFRP-BFRC reinforced concrete beams with reasonable accuracy. [ABSTRACT FROM AUTHOR]

This study presents an experimental investigation on the bond durability of helically wrapped basalt fiber reinforced polymer (BFRP) bars embedded in plain and steel fiber reinforced concrete (SFRC) under the combined effect of simulated oceanic environment and elevated temperatures. A total of sixty-three pullout specimens were tested to study the effect of concrete type (plain and SFRC), immersion temperature (35 °C and 60 °C), immersion duration (30, 60, and 90 days), and fiber volume fraction (V f) of steel fibers (0.5% and 1%). The bond durability of the used bars was examined based on the bond strength and mode of failure. The BFRP bars at the interface along the embedment length with concrete were analyzed using scanning electron microscopy. In addition, the BPE and CMR models for bond-slip behavior were calibrated considering the immersion temperature, concrete type, and exposure duration. The experimental results revealed that the pullout specimens with V f = 1% showed higher bond durability performance than specimens with V f = 0.5%, particularly at high temperatures. Furthermore, the CMR model showed better correlation with the experimental data than the BPE model. Moreover, the 50 years service life prediction showed bond strength retentions of BFRP bars that ranged from 54% to 86% depending on the type of concrete (plain and SFRC), surrounding mean annual temperature (5 °C to 35 °C), and degree of moisture (dry, moist, and moisture saturated). [ABSTRACT FROM AUTHOR]

• The addition of the BMF to concrete mixes improved their flexural tensile strength and ductility. • The ductility of BFRP-BFRC beams was improved by increasing the V f of BMF. • The moment redistribution of BFRP-BFRC beams was investigated experimentally. • Increasing Sagging-to-hogging reinforcement improved moment redistribution of the beams. • A proposed equation incorporating ACI 440.1R-15 guide and a model suggested by Rjoub is proposed. This study investigated the structural performance and moment redistribution of basalt fiber reinforced concrete (BFRC) continuous beams reinforced with basalt fiber reinforced polymers (BFRP) bars. A total of 10 reinforced concrete (RC) continuous beams over two equal spans of 1800 mm were tested under five-point loading until failure. The test variables were the type of main bars, sagging-to-hogging reinforcement ratio, volume fractions (V f) of basalt macro fibers (BMF), and stirrups spacing. Seven beams were longitudinally reinforced with BFRP bars, while the remaining three beams were reinforced with conventional steel bars and served as a control. Test results showed that BFRC-RC beams had higher crack widths, mid-span deflections, and strains than steel-RC beams. Furthermore, the ductility index, load-carrying capacities and moment redistribution of the tested beams considerably improved by increasing the V f of BMF and sagging-to-hogging reinforcement ratio, and decreasing stirrups spacing. However, increasing the reinforcement ratio and V f of BMF was more effective in improving the moment redistribution than reducing the stirrups spacing. Analytically, the experimental sagging and hogging moments were compared to the available existing models and codes equations. A modified equation incorporating ACI 440.1R-15 provisions and a model suggested by Rjoub provided the most accurate predictions of the tested beams' moment capacities. [ABSTRACT FROM AUTHOR]

Abstract: A novel hybrid fiber reinforced polymer (FRP)–concrete structural system was applied to bridge superstructures. The hybrid FRP–concrete bridge superstructure systems are intended to have durable, structurally sound, and cost effective hybrid system that will take full advantage of the inherent and complementary properties of FRP materials and concrete. The proposed hybrid FRP–concrete system consists of trapezoidal FRP cell units surrounded by an FRP outer shell forming a bridge system. A thin layer of concrete was placed in the compression zone. As a trial case, a prototype bridge superstructure was designed as a simply-supported single span one-lane bridge with a span length of 18.3m. Performance of this superstructure was examined both experimentally and computationally. A test specimen, fabricated as a one-fourth scale model of the prototype bridge, was subjected to a series of loading tests: nondestructive tests (flexure, off-axis flexure, and negative flexure), and destructive tests (flexure and shear). Results from both experimental and computational analysis confirmed that the proposed hybrid bridge superstructure system has an excellent performance from structural engineering point of view. Furthermore, it was shown that a detailed linear finite element analysis (FEA) could predict behavior of the test specimen under different service loading conditions. [Copyright &y& Elsevier]

Abstract: A hybrid FRP-concrete deck on steel girders specimen was subjected to a series of service flexural loading tests under seven different loading conditions to capture the global response of the specimen, and to investigate the composite action of the bridge. The experimental and finite element results demonstrated that the structural performance of the hybrid FRP-concrete bridge deck exceeds AASHTO specifications. In addition, it was observed that the hybrid deck and the steel girders are interacting in a partially composite action under service loading conditions. Effective width calculations of the hybrid deck showed that the effective flange width for hybrid decks are less than AASHTO prescribed effective width for concrete decks. [Copyright &y& Elsevier]

• The leaching of hazardous metal from SSA and RCA were well below the standard limits. • Compressive and flexural strengths of concrete are improved by using SSA. • BMF improved the mechanical properties of concrete made with RCA and NLA. • Both SSA and RCA showed promising potential as sustainable alternative aggregates. Demands to assess the feasibility of utilizing alternative sustainable aggregates in concrete have been raised because of the rapid depletion of virgin aggregates resources. In this study, a comparison of the physio-chemical properties of commonly used natural gabbro aggregates (NGA) and natural limestone aggregates (NLA) and their possible sustainable alternatives recycled concrete aggregates (RCA) and steel slag aggregates (SSA) is presented. The suitability of these alternate aggregates is assessed through several standardized tests. Chemical compositions, mineralogical and morphological properties of these aggregates are also reported. To determine the possible leachates of hazardous metals into the environment when used as concrete aggregates, the inductively coupled-plasma atomic emission spectroscopy was carried out on acid digestions of these aggregates. Additionally, basalt macro-fibers (BMF) were incorporated to improve the mechanical properties of concrete made with RCA and local NLA which are deemed as weak and unfit for use as aggregates in structural concrete. Experimental results revealed that both RCA and SSA could be used as sustainable alternative aggregates to have a cleaner production of structural concrete. They had acceptable leachate limits of the hazardous elements. The soundness test results and expansion under autoclave of SSA were well below the acceptable limits. The concrete made with SSA showed higher mechanical properties than the concretes made with other aggregate types. As expected, BMF improved the mechanical properties of concrete made with the low-strength NLA and RCA. [ABSTRACT FROM AUTHOR]

This study investigates the influence of basalt fiber reinforced concrete (BFRC) on the bond durability of helically wrapped basalt fiber reinforced polymers (HWBFRP) bars subjected to harsh saline environmental conditions. A total of 63 pullout specimens were fabricated and tested. Test parameters included conditioning duration (30, 60 and 90 days), conditioning temperature (35 and 60 °C), and the volume fraction of basalt macrofibers (BMF) added in the concrete mixture (0, 0.5 and 1%). Moreover, scanned electron microscopy (SEM) analysis was conducted to investigate the degradation of the HWBFRP bars. Additionally, two existing analytical models, the BPE and CMR models were calibrated using the experimental results for a better prediction of the bond-slip behavior of HWBFRP bars. The service life prediction of the bond strength after 50 years of service was also performed. Experimental results revealed that the addition of BMF to concrete improved the bond performance of HWBFRP bars and showed higher retentions in the bond strength compared to plain concrete specimens after 90 days of environmental conditioning, particularly at high temperatures. Moreover, the CMR model showed better reliability than the BPE model in describing the bond-slip behavior of HWBFRP bars in both plain and fiber reinforced concrete. [ABSTRACT FROM AUTHOR]

The prediction of the response of waveguides to time-harmonic base excitations has many applications in mechanical, aerospace and civil engineering. The response to base excitations can be obtained analytically for simple waveguides only. For general waveguides, the response to time-harmonic base excitations can be obtained using the finite element method. In this study, we present a wave and finite element approach to calculate the response of waveguides to time-harmonic base excitations. The wave and finite element method is used to model free wave propagation in the waveguide, and these characteristics are then used to find the amplitude of excited waves in the waveguide. Reflection matrices at the boundaries of the waveguide are then used to find the amplitude of the travelling waves in the waveguide and subsequently the response of the waveguide. This includes the displacement and stress frequency response transfer functions. Numerical examples are presented to demonstrate the approach and to discuss the numerical efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

This study investigated the flexural performance of one-way reinforced concrete (RC) slabs strengthened with two distinct strengthening systems: near – surface mounted (NSM) bars and externally bonded (EB) carbon fiber-reinforced polymer (FRP) strips. The NSM bars comprised four types: carbon FRP (CFRP), basalt FRP (BFRP), glass FRP (GFRP), and stainless – steel (SS) bars. The NSM – strengthened slabs showcased substantial enhancements in yield and ultimate load capacity, ranging from 20 % to 55 % and 59–123 %, respectively. In comparison, those strengthened with EB – CFRP strips displayed increases from 46 % to 107 % and 45–177 %, respectively, depending on the axial stiffness ratio of the strengthening system provided. Furthermore, the slabs reinforced with NSM–BFRP bars showed an 11–25 % improvement in their ductility indices. In contrast, the slabs reinforced with EB experienced a decrease in ductility ranging from 38 % to 50 %. This reduction was attributed to the differences in the modes of failure observed in both strengthening systems. The rupture of the NSM–FRP bars and the strain readings associated at the end of testing confirmed that the tensile strength of the NSM–FRP bars was fully exploited whereas the EB–CFRP strips utilized only 29–36 % of their ultimate tensile strain due to debonding. A finite element (FE) model was formulated to anticipate the behavior of the strengthened slabs. A strong correlation between the numerical predictions and the experimental outcomes was observed. The experimental–to–numerical ratios of the ultimate load ranged between 1.0 and 1.08 for the NSM–strengthened slabs and between 0.98 and 1.38 for the EB–strengthened slabs. This validated the FE models' ability to capture the nonlinear performance of the strengthened slabs. • Effectiveness of NSM-FRP varied based on the type of FRP bars. • NSM-FRP bars increased yield and ultimate loads up to 55 and 123 %, respectively. • NSM-strengthened slabs exhibited improved ductility with indices increasing up to 25 %. • EB-strengthened slabs failed due to debonding of the CFRP strips. • NSM-FRP systems are more effective in restoring the ductility of RC slabs. [ABSTRACT FROM AUTHOR]

This paper presents the results of an experimental and analytical study on the flexural behavior of corrosion–damaged reinforced concrete (RC) slabs strengthened with different near–surface mounted fiber–reinforced polymer (NSM–FRP) bars. An accelerated corrosion technique was used to induce corrosion in the steel reinforcing bars of the tested slabs. The investigated parameters comprised the number of NSM–FRP bars (two and four bars), the type of the NSM–FRP reinforcement (basalt B and glass G bars), and the mass loss in the steel rebars due to corrosion (10 and 20%). The yielding and ultimate capacity of the strengthened slabs was not only restored but surpassed those of the virgin control slab. Slabs strengthened with two and four NSM–BFRP bars showed 32–42% increase in their yielding load and 45–50% in their ultimate loads, respectively, as compared to the unstrengthened corroded slab. Similarly, the strengthened slabs showed 5–50% increase in their ductility index as compared to the virgin slab. The strengthened slabs failed due to the yielding of the steel reinforcing bars followed by compression concrete crushing. ACI–440 formulations reasonably predicted the performance of the strengthened slabs with conservative capacities when ACI strain limit of 0.7 ε fu was considered. [ABSTRACT FROM AUTHOR]

In order to design phononic crystals whose band-gaps are located in low-frequency ranges, researchers commonly adopt low stiffness polymeric materials as key constituents and exploit the high impedance mismatch between metals and polymers. However, there has been very little research on wave propagation at arbitrary angles in the sagittal plane of viscoelastic-elastic multilayered composites because there exist the intricate wave attenuation characteristics at the layer interfaces. The objective of our investigation is to obtain analytical dispersion relation for oblique wave motion in the sagittal plane of infinitely periodic multilayered composite composed of alternating viscoelastic and elastic solids, where the attenuation of harmonic plane waves is found to occur only in the direction perpendicular to the layers. By using this wave propagation characteristic, we directly apply the semi-analytical approach employed in elastic multilayered composites to calculate the dispersion relation of sagittal plane waves in alternating viscoelastic-elastic multilayered composites. Specifically, we consider a bilayered composite composed of alternating aluminum and polyurethane elastomer, whose complex-valued viscoelastic moduli are experimentally determined by performing dynamic mechanical analysis (DMA). The analysis shows that the alternating viscoelastic-elastic layered composite does not possess a phononic band-gap regardless of incident angles. In addition, wave motions at oblique angles are found to travel with a wide range of frequency contents compared to wave motions perpendicular to the layers. The presented analysis demonstrates that wave dispersion relation in viscoelastic-elastic layered composites is distinctly different from the corresponding elastic counterpart, and highlights the importance of the viscoelastic modeling of polymeric materials in wave dispersion analysis. [ABSTRACT FROM AUTHOR]

Fiber-reinforced polymer (FRP) composites are increasingly used in concrete structures owing to their superior corrosion resistance. However, FRP-reinforced concrete (RC) structures exhibit less ductile response compared to steel RC structures. Recently, the use of basalt fiber reinforced concrete (BFRC) reinforced with BFRP bars was investigated to achieve a reasonable level of ductility in BFRC-BFRP one-way slabs. The shear behavior of such a slab depends on different design parameters. This paper aims to identify the impact of each design parameter on the shear behavior of BFRC-BFRP one-way slabs using a fractional factorial design of experiment (DOE). A 3D finite element model was first developed and validated against available experimental results. The developed model is then used to conduct a sensitivity analysis considering five factors that influence the shear behavior of BFRC-BFRP one-way slabs. These factors are the longitudinal reinforcement ratio, shear span-to-depth ratio, effective depth, concrete compressive strength, and volume fraction of basalt macro fibers (BMF). Finally, a design equation that can predict the shear capacity of one-way BFRC-BFRP slabs was proposed based on genetic algorithm. The proposed model showed the best prediction accuracy compared to the available design codes and guidelines with a mean of predicted to experimental shear capacities (V pred / V exp ) ratio of 0.97 and a coefficient of variation of 17.91%. [ABSTRACT FROM AUTHOR]

• The bond performance of NSM-FRP bars are governed by the adhesive type. • The shear strength of the adhesive has a significant influence on the bond strength of the NSM-FRP bars. • The NSM-CFRP bars showed the highest bond strength as compared to their BFRP, GFRP, and SS counterparts. • The texture of the NSM-FRP bar dictates its mode of failure. • The BPE model can be used to describe the bond-slip relationship for the NSM-FRP bars. This paper presents the experimental and analytical results of a large study on the bond performance of near-surface mounted (NSM) fiber-reinforced polymer (FRP) bars. The investigated parameters included the bar material (basalt-FRP (BFRP), glass-FRP (GFRP), carbon-FRP (CFRP), and stainless steel (SS) bars), the bar surface configuration (deformed and sand-coated bars), the filling adhesive (NSM-Gel, Sikadur-30, and Sika Grout-214), and the bonded length of the bar (6, 12, and 24 times its diameter). Sixty-six C-shape concrete specimens were tested under direct pullout loading configuration. The bond strength, the free-end and loaded-end slip, the strains in the NSM bar, and the modes of failure of the tested specimens are reported and discussed. The NSM-Gel adhesive outperformed other adhesives in developing the bond strength of the tested specimens regardless of their bar material. Both the deformed and sand-coated NSM-BFRP and GFRP bars showed almost similar bond strengths while the NSM-CFRP bars showed the highest strengths. The images obtained from the scanning electron microscope confirmed the obtained results in terms of the modes of failure and the bond failure mechanism. Analytically, the BPE model was calibrated using the experimental results to describe the bond stress-slip relationships of the FRP bars. [ABSTRACT FROM AUTHOR]

A primary concern of conventional Portland cement concrete (PCC) is associated with the massive amount of global cement and natural coarse aggregates (NCA) consumption, which causes depletion of natural resources on the one hand and ecological problems on the other. As a result, the concept of green concrete (GC), by replacing cement with supplementary cementitious materials (SCMs) such as ground granulated blast furnace slag (GGBFS), fly ash (FA), silica fume (SF), and metakaolin (MK), or replacing NCA with recycled coarse aggregates, can play an essential role in addressing the environmental threat of PCC. Currently, there is a growing body of literature that emphasizes the importance of implementing GC in concrete applications. Therefore, this paper has conducted a systematic literature review through the peer-reviewed literature database Scopus. A total of 114 papers were reviewed that cover the following areas: (1) sustainability benefits of GC, (2) mechanical behavior of GC in terms of compressive strength, (3) durability properties of GC under several environmental exposures, (4) structural performance of GC in large-scale reinforced beams under shear and flexure, and (5) analytical investigation that compares the GC shear capacities of previously tested beams with major design codes and proposed models. Based on this review, the reader will be able to select the optimum replacement level of cement with one of the SCMs to achieve a certain concrete strength range that would suit a certain concrete application. Also, the analysis of durability performance revealed that the addition of SCMs is not recommended in concrete exposed to a higher temperature than 400 °C. Moreover, combining GGBFS with FA in a concrete mix was noticed to be superior to PCC in terms of long-term resistance to sulfate attack. The single most striking observation to emerge from the data comparison of the experimentally tested beams with the available concrete shear design equations is that the beams having up to 70% of FA as a replacement to OPC or up to 100% of RCA as a replacement to NCA were conservatively predicted by the equations of Japan Society of Civil Engineers (JSCE-1997), the American Concrete Institute (ACI 318-19), and the Canadian Standards Association (CSA-A23.3-14). [ABSTRACT FROM AUTHOR]

• The impressed current induces non-uniform corrosion based on the spatial location of the rebar. The reinforcement bar facing the cathode suffered a higher corrosion degree than the bar away from the cathode. • Single CFRP laminate regained the strength of a corroded RC beam with 35 to 37% steel weight loss up to the level of sound control beams. • Hybrid CFRP-GFRP laminates showed 42% and 62% higher yield and ultimate load, respectively, compared to the counterpart beams with 37% steel weight loss. • The CFRP and hybrid CFRP-GFRP laminates are efficient strengthening for the severally corroded RC beams. Steel corrosion is a major degradation factor for the reinforced concrete (RC) infrastructure and necessitates a costly repair after short service life. Predicting the strength of corroded and retrofitted structural elements while under service is a challenging task. For this purpose, the impressed current technique is frequently used to achieve the desired degree of corrosion in RC members in the laboratories. This study investigates the effectiveness of this technique on laboratory-scale RC beams and evaluates the behavior of severely corroded beams rehabilitated with carbon fiber-reinforced polymers (CFRP) and the hybrid of CFRP and glass-FRP (GFRP) laminates. Extensive literature is available on the behavior of sound RC members strengthened with FRPs, however, data are scarce on the behavior of corroded-strengthened RC beams. The RC beams were deteriorated by applying an impressed current of 750 µA/cm2 for 15 days. All the beams were tested under four-point bending till failure. The reinforcement mesh was non-uniformly corroded; the flexural bar facing the external cathode experienced a higher degree of corrosion than the opposite bar and the actual applied impressed current reached as high as 2388 µA/cm2. The flexural strength of the degraded beams, with 37 % weight loss on the main rebars, was 41 % less than counter-part sound beams. On the other hand, the CFRP strengthening regained the strength of degraded beams by 45 % compared to the unstrengthened-degraded beams. Whereas the CFRP-GFRP hybrid laminates regained strength up to 60 % compared to the counterpart-degraded beams and 12 % higher than the sound beams. This study demonstrated that a desired degree of corrosion could be achieved on a particular reinforcement portion with the impressed current technique. In addition, CFRP and CFRP-GFRP laminates are effective external strengthening techniques for rehabilitating degraded concrete infrastructure. [ABSTRACT FROM AUTHOR]

• High-chromium steel showed 1.5 times higher R p values than mild steel. • EIS is the most suitable technique to evaluate the corrosion performance of ECR. • High-chromium steel showed 48% less macrocell current than mild steel. An experimental study is carried out in this paper to evaluate the corrosion performance of mild steel reinforcing bars (MS), high strength steel reinforcing bars (HS), epoxy-coated steel reinforcing bars (EC), and high-chromium steel reinforcing bars (HC) under harsh environmental conditions. Reinforcing bars (rebar) of 16 mm diameter and 310 mm length were embedded in cylindrical concrete samples of 60 mm diameter and 350 mm length, and subjected to a Southern Exposure test for sixteen months. The open circuit potential (OCP) was monitored during the exposure period until corrosion initiation. The linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS), and Tafel plot techniques were employed to assess the corrosion rates on the rebar surfaces. The macrocell corrosion current was monitored by connecting the corroding rebar with an external stainless steel bar of the same size. The polarization resistance of the HC was found to be 1.5 times higher than that of the MS. The EIS technique showed that EC, even with damaged epoxy coating, has the highest resistance to chloride attack. The macrocell current of HC rebar was 48% less than that of MS during the active corrosion state. The LPR, EIS and Tafel plots analysis provided the current densities, which were close to each other; indicating the validity of these techniques to study the problem at hand. The corrosion rates from electrochemical methods were compared against the ones calculated by gravimetric methods. The quantitative results from this research may be used in service life prediction of concrete structures with different types of rebar. Extensive analysis of the results indicates that the corrosion resistance of the evaluated steels was in the following decreasing order: EC, HC, MS, and HS. [ABSTRACT FROM AUTHOR]