Sea-sand Concrete Beams Research Articles

Experimental investigations on the flexural behavior of compression-cast seawater sea-sand concrete beams reinforced with CFRP bars

To address the corrosion problems, environmental concerns, and achieve green and sustainable civil engineering practices, this study designed several compression-cast seawater sea-sand concrete (SSC) beams reinforced with corrosion-resistant carbon fiber-reinforced polymer (CFRP) bars (i.e., FRP-SSC beams) and their flexural behavior was experimentally investigated through four-point bending tests. Twelve FRP-SSC beams were designed, including three normal-cast and nine compression-cast ones. The critical parameters included the concrete casting forms, water-to-cement (w/c) ratios, and reinforcement ratios of CFRP bars (ρf). Effects of the concrete casting methods, w/c ratios, and ρf on the flexural responses of FRP-SSC beams were comprehensively studied. In addition, the flexural theorems were used to derive the prediction models of the equivalent stress block parameters (i.e., εcm, α1, and β1) and flexural strength (Mu) of compression-cast FRP-SSC beams. Moreover, based on the experimental results, effectiveness and accuracy of the proposed flexural strength design models were verified by using the existing design specifications. Finally, the results indicate that, (1) compression-cast FRP-SSC beams with the larger ρf (1.78 %) exhibited bending failure featured by compression concrete crushing, whereas that with the smaller ρf (0.75 %) shown splitting failure; (2) The cracking moments of compression-cast FRP-SSC beams increased significantly owing to the higher compressive strength and elastic modulus of compression-cast concrete (CCC); (3) Because of the pronounced brittleness of CCC, the improvement of the ultimate flexural capacity of compression-cast FRP-SSC beams was limited; (4) Under the same moment level, the maximum crack widths of compression-cast FRP-SSC beams were smaller than their normal-cast counterparts; and (5) the proposed flexural strength design models could yield more accurate, safer, and conservative predictions of flexural strength for both normal- and compression-cast FRP-SSC beams.

Durability of SFCB reinforced low-alkalinity seawater sea sand concrete beams in marine environment

Seawater sea-sand concrete (SWSSC) provides an alternative to normal concrete, while Steel-FRP Composite Bars (SFCB) offer corrosion resistance in offshore and marine structures. Despite their benefits, the long-term performance of SFCB-reinforced SWSSC structures remains under-explored. This study evaluated the durability of such beams, particularly focusing on the effects of using Portland cement versus low-alkalinity calcium sulphoaluminate (CSA) cement. The investigation involved tensile and pull-out tests conducted on SFCB, and flexural tests conducted on the beam components after accelerated marine environmental exposure over periods ranging from one to six months. Results highlighted that SFCB embedded in low-alkalinity CSA cement exhibited improved retention of tensile strength, elastic modulus, and bonding strength by 32.0 %, 39.1 %, and 56.7 % respectively, compared to that embedded in normal Portland cement concrete. Microstructural analyses showed much less hydrolysis of the resin matrix and shallower corrosion of the basalt FRP (BFRP) cover on the SFCB. Furthermore, flexural tests demonstrated superior cooperative performance between low-alkalinity CSA concrete with SFCB in beam components, showing only marginal degradation in crack density, crack strength, and yielding points. The ultimate failure load of beams made with CSA concrete was 1.89 times higher than those made with normal SWSSC after 6 months of exposure. These results underscore the potential of low-alkalinity concrete in improving the long-term durability and structural performance of SFCB-reinforced marine concrete infrastructures.

Flexural performance of seawater sea sand concrete composite beams enhanced by dual-functional C-FRCM jackets

The flexural performance of seawater sea sand concrete (SSC) composite beams enhanced by the dual-functional carbon-fabric reinforced cementitious matrix (C-FRCM) jackets was experimentally investigated. Five SSC composite beams were constructed and tested in flexure under four-point loading, including one control specimen, one C-FRCM enhanced beam without the presence of the impressed current cathodic protection (ICCP) system, and three C-FRCM jacketed beams implementing the ICCP system (three different current densities: 25, 75 and 125 mA/m2). The failure modes observed and the performance of the strengthened beams with the dual-functional C-FRCM jackets were discussed in details. The results indicated that the C-FRCM jacketing effectively increased the cracking load up to 46.43 % and delayed yielding. The C-FRCM jacket had a relatively small impact on the initial stiffness of the specimens but significantly increased the load-carrying capacity (up to 18 %) and improved ductility. With the increase in current density, the load-carrying capacity gradually decreased, the crack inhibitory effect gradually weakened, but the ductility coefficient increased notably (up to 98 %). Regarding the failure modes of the composite beams, both fiber fracture and fiber slippage coexisted, and with the increase of current density, the latter became more predominant. Based on the design guidelines provided by ACI 549.4R-13, an analytical formula for bending moment was proposed and compared with the experimental results, providing a reference for the design of such components.

Shear behavior of seawater sea-sand concrete beams reinforced with BFRP bars after seawater dry-wet cycling

The shear behavior of 27 basalt fiber-reinforced polymer reinforced seawater sea-sand concrete (BFRP-SSC) beams after seawater dry-wet cycling was comprehensively investigated. Parameters considered included stirrup diameter and spacing, shear span-to-depth ratio, stirrup surface treatment, cycling duration, concrete cover thickness, and seawater temperature. Results indicate that seawater dry-wet cycling increases cracking load and decreases bending stiffness in BFRP-SSC beams. Increasing shear span-to-depth ratio from 1.55 to 2.35 led to load reductions of 31.3 % and 49.7 % at 6.5 mm mid-span deflection. Seawater dry-wet cycling, particularly temperature and duration, significantly impacts the mechanical properties of stirrups. This results in diminished shear contribution and reduced efficacy in inhibiting diagonal crack propagation, leading to a shift in beam failure mode from diagonal compression failure to shear compression failure and diagonal tension failure. Increasing cycling duration from 60 to 120 days decreased tensile strength retention by 19.1 % and 33.3 % respectively. Based on experimental data, Arrhenius theory, and the time shift factor (TSF) method, a predictive model was developed for the shear capacity retention of beams subjected to seawater dry-wet cycling. Results indicate that after 100 years in a tidal environment (70 % and 90 % relative humidity), shear capacity damage factors of 0.77 and 0.52, respectively, can be applied to account for the impact of seawater dry-wet cycling on the shear capacity of BFRP-SSC beams.

Experimental Study of the Flexural Performance of GFRP-Reinforced Seawater Sea Sand Concrete Beams with Built-In GFRP Tubes.

The use of seawater sea sand concrete (SSSC) and fiber-reinforced polymer (FRP) has broad application prospect in island and coastal areas. However, the elastic modulus of FRP reinforcement is obviously lower than that of ordinary steel reinforcement, and the properties of SSSC are different from that of ordinary concrete, which results in a limit in the bearing capacity and stiffness of structures. In order to improve the flexural performance of FRP-reinforced SSSC beams, a novel SSSC beam with built-in glass FRP (GFRP) tubes was proposed in this study. Referring to many large-scale beam experiments, one specimen was used for one situation to illustrate the study considering costs and feasibility. Firstly, flexural performance tests of SSSC beams with GFRP tubes were conducted. Then, the effects of the GFRP tubes' height, the strength grades of concrete inside and outside the GFRP tubes, and the GFRP reinforcement ratio on the flexural behaviors of the beams were investigated. In addition, the concept of capacity reserve was proposed to assess the ductility of the beams, and the interaction between the concrete outside the GFRP tube, the GFRP tube and concrete inside the tube was discussed. Finally, the formulas for the normal section bearing capacity of beams with built-in GFRP tubes were derived and verified. Compared to the beam without GFRP tubes, under the same conditions, the ultimate bearing capacities of the SSSC beam with 80 mm, 100, and 200 mm height GFRP tubes were increased by 17.67 kN, 24.52 kN, and 144.42 kN, respectively.

Durability of glass FRP bar‐reinforced seawater–sea sand concrete beams under sustained loading in a subtropical coastal environment

AbstractThe replacement of conventional bars with fiber‐reinforced polymer (FRP) bars in seawater–sea sand concrete (SSC) structures is a promising method for sustainable construction. To promote the engineering application of the aforementioned structures, the primary objective of this study was to investigate the concerns regarding the durability of SSC beams reinforced with GFRP bars. For this purpose, three‐point bending tests were conducted on GFRP bar‐reinforced SSC beams to examine the coupled effects of sustained loading and exposure to a subtropical coastal environment on the flexural behavior of exposed SSC beams. The test results revealed that SSC beams reinforced with GFRP bars exhibited excellent durability in a subtropical coastal environment. The coupled effect of sustained loading and exposure to the subtropical coastal environment had an insignificant negative influence on the ultimate flexural capacity of GFRP bar‐reinforced SSC beams at 540 days of age. The failure mechanism of the exposed GFRP bar‐reinforced SSC beams was concrete crushing due to overreinforcement. Finally, the flexural capacity of the exposed beams was predicted by a function of the degradation in the tensile strength of the GFRP bars.Highlights The coupled effects of loading and environmental exposure on GFRP‐SSC beams were examined. The failure mechanisms of the exposed GFRP‐SSC beams was investigated. The long‐term flexural capacity of the GFRP‐SSC beams was predicted.

Parametric study, finite element analysis, and load capacity calculation for flexural behaviour of seawater and sea sand concrete beams reinforced with GFRP bars

This study sought to enhance the understanding of seawater sea sand concrete (SWSSC) structures reinforced with glass fiber-reinforced polymer (GFRP) bars. To achieve this, an experimental investigation was conducted involving the production and testing of 6 GFRP bar-reinforced SWSSC beams (GFRP beams) alongside 3 ordinary seawater sea sand concrete (OSWSSC) beams (Ordinary beams) to evaluate their flexural performance. Additionally, a subsequent analysis comprised the establishment of 11 full-scale finite element models aimed at parameter assessment on GFRP beams. The experimental and numerical findings revealed that an increase in sea sand replacement ratio in SWSSC beams, with a shear-span ratio of 2.2, led to varying degrees of shear-compression failure. Notably, owing to the superior crack resistance of SWSSC, the beams demonstrated outstanding structural coordination. Compared to OSWSSC beams, GFRP beams with a 100 % replacement ratio of sea sand or an increased in concrete strength to C55 had initial stiffness values that were 150 % and 106 % larger, respectively. Further investigation unveiled that a reduction in the shear-span ratio from 2.5 to 1.0 or an increase in the longitudinal reinforcement ratio from 1.27 % to 2.53 % significantly augmented the ultimate load-carrying capacity, resulting in increases of 88.0 % and 37.7 %, respectively. Based on these findings, several design recommendations are proposed: 1. Establish a deflection limit at l0/500 or implement more stringent measures for GFRP beams. 2. Consider reducing the diameter of GFRP bars while maintaining a 50 % sea sand replacement rate to mitigate crack formation. 3. An excessive longitudinal reinforcement ratio hampers the enhancement of specimen load-carrying capacity. 4. Consider utilizing Chinese specifications for flexural capacity calculations.

Experimental and numerical research on shear performance of GFRP bar reinforced seawater sea-sand concrete deep beams without stirrups

Using glass fibre-reinforced polymer (GFRP) bars to reinforce seawater sea-sand concrete (SWSSC) is a feasible way to replace traditional concrete structures. Thus, this paper aims to understand the shear response of GFRP bar-reinforced SWSSC (GFRP-SWSSC) deep beams. Experimental and numerical programs were carried out on four-point shear tests of GFRP-SWSSC deep beams without stirrups. Seventy specimens were tested to investigate the effects of key parameters on shear responses, including concrete categories, seashell content, section heights, and GFRP bar diameter. The test results indicated that the cracking strength of GFRP-SWSSC deep beams was slightly higher than ordinary concrete deep beams. The increased section height of GFRP-SWSSC deep beams and the decreased shell content remarkably enhanced the stiffness and shear ultimate strength. The corresponding finite element model (FEM) of GFRP-SWSSC specimens was established and validated by comparison with test results. Further, three guidelines predictions for the shear strength of GFRP-SWSSC beams were too conservative. The new design formulae derived from modified tension-compression theory were put forward to evaluate the shear strength of GFRP-SWSSC deep beams, and the comparisons demonstrated that the proposed design formulae achieved sufficient accurate predictions for practical engineering. Based on research on shear performance, the hybrid GFRP-SWSSC structure is a feasible solution to resource shortages, which provides a promising application prospect in marine engineering.

Shear Behavior of Seawater–Sea Sand Concrete Beams Reinforced with BFRP Bars and Stirrups

Shear Behavior of Seawater–Sea Sand Concrete Beams Reinforced with BFRP Bars and Stirrups

Flexural Performance of Steel-Continuous-Fiber Composite Bar and Fiber-Reinforced Polymer Bar Hybrid-Reinforced Sustainable Sea-Sand Concrete Beams: Numerical and Theoretical Study

To investigate the flexural performance of steel-continuous-fiber composite bar (SFCB) and fiber-reinforced polymer (FRP) bar hybrid-reinforced sea-sand concrete (SSC) beams, a total of 21 SSC beams were numerically studied. The concrete damaged plasticity model (CDPM) and FRP brittle damage model were adopted, and the bond-slip behavior between the reinforcement and concrete was considered. Parametric studies were conducted to study the effects of the SSC strength, sectional steel ratio of the SFCB, core steel bar yield strength of the SFCB, out-wrapped FRP elastic modulus of the SFCB, and the ultimate tensile strength of the SFCB on the flexural performance of the beams. The results indicate that increasing the SSC strength and out-wrapped FRP modulus enhanced the bearing capacity and stiffness but reduced the ductility, shifting failure from concrete crushing to FRP bar fracture. A higher SFCB sectional steel ratio markedly improved the flexural stiffness, transforming the load–deflection curve. Elevated core steel bar yield strength maintained the cracking load and deflection while increasing the yield and ultimate loads. For SFCB fracture, higher ultimate tensile strength in the out-wrapped FRP enhanced the ultimate load and deflection, but not in concrete crushing failure. In addition, three failure modes were defined based on the proper assumption, with the proposed bearing capacity formulas aligning well with the FE results.

Flexural capacity and serviceability evaluation on seawater sea-sand concrete beams reinforced by BFRP bars and TRE composite in the dry-wet environment

To promote the durability and serviceability of offshore structures, the bearing capacity and serviceability of BFRP-reinforced seawater sea-sand concrete (SWSSC) beams with textile reinforced ECC (TRE) to retard deformation and cracking under chloride dry-wet cycles were investigated. A total of a BFRP-reinforced SWSSC beam and nine TRE composite beams were designed. The dry-wet cycles, thickness, fabrication method and shape of TRE composite layer as factors the on the bearing capacity, deflection and crack behavior, curvature and ductility of beams with TRE composite were analyzed. TRE composite layer still can visibly increase the cracking moment of BFRP-reinforced SWSSC beams even in the dry-wet conditions, but the improvement effect on the ultimate moment was noteless. The bearing moments of composite beams increased with the TRE thickness and the dry-wet cycles. The failure modes for composite beams with the same reinforced radio of FRP bars under dry-wet environment changed from failure in shear cross zone to failure in pure bending zone with the increase of the thickness of TRE composite layer. The development of deformation and cracks for beams with TRE composite was significantly distinct from that for BFRP-reinforced SWSSC beams, attributed to the bonding properties of the composite layer to concrete, which with the TRE composite subjected to service moments can be judged by the curvature of 0.00375/d, below the curvature of 0.005/d. The fine cracks in TRE composite beams developed sequentially throughout the pure bending of beams. The dry-wet environment can reduce the deflection by increasing the stiffness of beams. Under service moment, the neutral axis height of TRE composite beam was clearly superior to that of BFRP-reinforced SWSSC beam. The variation trend of ductility index on energy and deformation was different. And the ductility of TRE composite beams declined as the increasing dry-wet cycles, regardless of the energy or deformation.

Long-Term Behavior of FRP-Bar Reinforced Seawater Sea Sand Concrete Beams Under Load Sustaining and Environment Weathering

Long-Term Behavior of FRP-Bar Reinforced Seawater Sea Sand Concrete Beams Under Load Sustaining and Environment Weathering

Flexural behavior of seawater sea-sand concrete short beams reinforced with bamboo sheet

Bamboo reinforced concrete beams improved beam bearing capacity, but bamboo reinforcement's cross-sectional area affected its bond strength with concrete. Plain seawater sea-sand concrete beams are prone to cracking and poor flexural resistance. In order to solve these problems, this paper proposes bamboo sheet as a reinforcement material to improve the flexural behavior of plain seawater sea-sand concrete beams. Experimental results analyzed bamboo sheet reinforced seawater sea-sand concrete beam failure and ultimate bearing capacity. This test used 6 groups of 24 short beams: 5 groups of reinforced concrete and 1 group of contrast plain concrete, this test variable was reinforcement layers. The bamboo sheet reinforcement region was the entire beam bottom, which was strongly pasted to the beam bottom by resin glue. Bamboo sheet reinforcement increased beam deflection and flexural capacity, while the number of layers affected flexural behavior. When compared to plain seawater sea-sand concrete beam, the reinforcement effect was best when the number of bamboo sheet layers was 5, with the flexural capacity improvement degree being 81.88%. Finally, a theoretical calculation model for the bamboo sheet reinforced beam predicted its ultimate flexural capacity, with errors within 10%.

Flexural behavior and serviceability performance of SSC beams reinforced with hybrid GFRP-stainless steel bars

Using fiber-reinforced polymer (FRP) bars instead of steel bars to reinforce concrete structures has become an important method to solve the corrosion problems. FRP bars reinforced concrete (FRP-RC) beams suffer sudden failure owing to the brittleness of FRP bars. Therefore, it is suggested to add steel reinforcements in FRP-RC beams to improve the ductility. This study analyzes the flexural performance of seawater and sea sand concrete (SSC) beams reinforced with hybrid GFRP and stainless steel (SS) bars, in which GFRP bars are used as tension bars while SS bars are used as compression bars. The flexural performances of GFRP bars reinforced SSC beams and SS bars reinforced SSC beams were also studied for comparison. Based on the test results, the cracking moment, load-carrying capacity, deflection, and ductility of the SSC beams are discussed and compared with the guidance in current design codes. Results show that ACI 440.1R-15 and CSA S806-12 reasonably predict the cracking moment and bearing capacity, but both underestimate the deflection at the service load. Furthermore, the moment capacity calculation equation is proposed with good accuracy. The ratio between the reinforcement ratios of GFRP bars and SS bars is suggested to meet the ductility requirement.

Flexural behavior of BFRP reinforced seawater sea-sand concrete beams with the TRE shell under the coupled action of dry-wet cycles and load

In order to study the effect on the flexural behavior and durability of the textile reinforced engineered cementitious composites (TRE) shell for specimens under a dry-wet environment, the basalt fiber reinforced polymer (BFRP) reinforced seawater sea-sand concrete beams composited the TRE shell were subjected to the dry-wet cycles and the coupling of dry-wet cycles and the sustained load. The failure pattern, ultimate bearing capacity, deflection and crack width of composite beams under different dry-wet cycles, TRE shell shapes and sustained loadings were studied, and the ductility of beams with the TRE shell was further evaluated by energy and deformation. The experimental results showed that all composite beams with the U-shaped TRE shell suffered from the failure of concrete crushing. During the test, the interface of the TRE shell and concrete was debonded for all beams with the TRE shell, and the deformation of beams with TRE shell recovered after unloading. The ultimate bearing capacity of beams decreased slightly with the dry-wet cycles, while the deflection and crack width of the specimens hardly changed significantly. The ultimate bearing capacity of beams with the TRE shell decreased with the stress level of the sustained loading, whose stiffness increased and the cracks became sparse. Crack width decreased with the suatained load before the interface debonding, but the opposite phenomenon occurred after the interface debonding. From the ductility evaluation, the energy absorption index of beams with the U-shape TRE shell is higher than that of the BFRP reinforced seawater sea-sand concrete beam, indicating that TRE shells can effectively improve the energy dissipation capacity of beams.

Seawater sea-sand engineered cementitious composites contribution to shear performance of beams reinforced with BFRP bars

The combination of seawater sea-sand engineered cementitious composites (SS-ECC) and fiber reinforced plastic/polymer (FRP) bars to make structural beams is promising to mitigate the shortage of raw construction materials and improve shear performance. To better understand the shear behaviors of such kind of structural form, an experimental program was conducted to figure out the effects of longitudinal reinforcement ratio, shear span ratio and stirrup ratio. A total of eleven beams reinforced by basalt FRP (BFRP) bars were tested by four-point loading. The test results showed that the stiffness and ultimate shear capacity of SS-ECC beams without stirrups are higher than that of seawater sea-sand concrete (SSC) beams with a stirrup ratio of 0.67%. SS-ECC exhibits much lower compressive strength compared with ultra-high performance concrete (UHPC), but SS-ECC beam and UHPC beam have close ultimate shear capacity. The shear load contribution of fibers is above 70% in SS-ECC beams without stirrups, and it decreases significantly because of using BFRP stirrups. Furthermore, the modified deformation-based approach is proposed to characterize the ductility index of SS-ECC beams. Based on the calculation model of ultimate shear capacity in codes, the modified calculation model considering the shear load contribution of fibers is proposed and verified.

Flexural and compressive performance of BFRP-reinforced geopolymer sea-sand concrete beams and columns: Experimental and analytical investigation

The combination of geopolymer sea-sand concrete (GSSC) and basalt fiber reinforced polymer (BFRP) reinforcement has the potential to optimally exploit the advantages of both materials, resulting in superior structural durability and environmental friendliness. The resulting structure is called a BFRP-reinforced GSSC structure, which has broad application prospects in marine engineering construction. This paper presents a recent experimental and analytical investigation into the flexural and compressive performance of BFRP-reinforced GSSC structures to verify the expected benefits of such a material combination. In particular, a type of GSSC that uses MgO as an expansion agent to reduce concrete shrinkage was used in this study. The results of four-point bending tests on nine rectangular beams, where longitudinal reinforcement ratios and reinforcement types were key parameters, and monotonic axial compression tests on seven columns, where concrete types and transverse reinforcement ratios were key parameters, are reported in this paper. The test results initially confirmed the advantages of using GSSC in combination with BFRP reinforcement and showed that: (1) the ultimate carrying capacity of BFRP-reinforced GSSC beams and columns was higher than that of conventional steel-reinforced counterparts for the same reinforcement configurations; (2) the flexural and compressive capacity of BFRP-reinforced concrete beams and columns could be enhanced by an appropriate increase in reinforcement ratio and the addition of expansion agents. Finally, this paper presents design equations for the flexural and compressive capacity of BFRP-reinforced GSSC structures.

Seismic degradation behavior of steel-FRP composite bar reinforced concrete beams in marine environment based on experimental and numerical investigation

This study investigated the seismic behavior of seawater sea sand concrete (SWSSC, which is made of seawater, sea sand, ordinary aggregate and cement) beams reinforced with steel bars in a marine environment. To improve the durability of the specimens, different types of reinforcements, namely fiber reinforced polymer (FRP), steel-FRP composite bars (SFCBs), and macro basalt fibers, were introduced to replace steel bars owing to their superior durability and high strength. The failure mode, hysteretic response, energy dissipation capacity, and curvature of the pedestal were analyzed. Furthermore, a long-term performance prediction method based on finite element (FE) modeling was proposed. Results showed that the bond between the longitudinal reinforcements and SWSSC in steel and SFCB reinforced concrete (RC) beams degraded significantly after corrosion. Additionally, slips were observed during reciprocating loading. The total cumulative dissipated energy of the SFCB RC beam was approximately the same as that of the steel RC beam. Moreover, the corresponding value of SFCB and macro basalt fiber hybrid reinforced concrete specimen was almost twice that of the steel RC beam owing to a stable confinement of fibers on concrete. After corrosion, steel and SFCB RC beams exhibited a decrease in the lateral displacement at the top and a larger curvature at the pedestal, indicating that the rotation of the corroded specimens mainly occurred at the beam-column joint. The accuracy of the FE model was verified by comparing the obtained results with the experimental results. The prediction results revealed that the seismic performance of SFCB RC beams in the marine environment declined in the first three years and then stabilized gradually.which is made of seawater, sea sand, ordinary stone and cement.

Durability of GFRP bar-reinforced seawater–sea sand concrete beams: Coupled effects of sustained loading and exposure to a chloride environment

Seawater–sea sand concrete (SWSSC) structures reinforced with glass fibre-reinforced polymer (GFRP) bars can favour the eco-construction of marine infrastructure. This study aimed to investigate the coupling effects of sustained loading and exposure to a chloride environment on the durability of GFRP bar-reinforced SWSSC beams. Two types of specimens were designed and tested: (1) GFRP bars covered with SWSSC to simulate GFRP bars within the beams and (2) GFRP bar-reinforced SWSSC beams. An accelerated ageing environment imposed on the specimens by wet-dry cycles in saline solution containing 3.5 % NaCl. The relationship between the degradation of the GFRP bars and conditioned beams were investigated. The results showed that SWSSC exhibited a better cooperative performance with GFRP bars than with conventional bars, resulting in good durability of GFRP bar-reinforced SWSSC beams exposed to chloride environments. Although the coupling conditions had a negative impact on the prestress losses of the conditioned beams, the ultimate flexural strength of the conditioned beams with over-reinforcement did not decrease significantly due to their failure controlled by the concrete. In addition, a re-correction model adopting the deterioration of GFRP bars was presented to estimate the residual flexural strength of the conditioned beams exposed to the chloride environment. The results indicated that the strength deterioration of the GFRP bars by 36 % would trigger a 15 % degradation in the flexural strength of the conditioned beams.

Flexural performance of BFRP reinforced seawater sea-sand concrete beams with TRE SIP forms under a dry-wet environment

In order to improve the serviceability performance and durability of basalt fiber-reinforced polymer (BFRP) reinforced seawater sea-sand concrete (SWSSC) beams in the marine environment, a composite of stay-in-place (SIP) form of textile-reinforced ECC (TRE) and BFRP reinforced seawater sea-sand concrete (BFRP-SWSSC) was designed, to enhance bearing capacity and deformation suppression ability of this composite structure in the marine environment. A total of 10 specimens with an effective span of 1500 mm and section size of 150 mm × 250 mm were designed in this experiment, including one BFRP-SWSSC beam and the rest composed of TRE composite as SIP forms. The effects of different dry-wet cycles, thicknesses of TRE SIP forms, shape of TRE SIP forms and production methods of TRE SIP forms on the bending performance of composite beams were studied. The specimens displayed as the TRE thickness increased, the failure mode changed from bending shear failure to balanced or compression failure. Whereas the bearing capacity of the specimens was indistinctively affected by 90∼270 dry-wet cycles. The deflection deformation and crack width of the beams were effectively improved by TRE SIP forms. Meanwhile the stiffness of composite beams was effectively improved by the chlorine salt dry-wet environment. With the effective bonding between TRE and SWSSC, the deflection and crack width of the composite beams were within specification limits. The eminent ductility of the composite beams was shown by the chlorine salt dry-wet environment, the ductility index of the specimen decreased with the dry-wet cycles increased from 90 to 270. Based on the section analysis method, a calculation method was proposed for the disabled bearing capacity of BFRP-SWSSC beams with U-shape TRE SIP forms in a normal environment. On this basis, the environmental impact factor of the salt dry-wet environment was suggested, and the experimental value is in commendable agreement with the theoretical value.