Sea-sand Concrete Beams Research Articles

Flexural study of concrete beams with basalt fibre polymer bars

Basalt fibre polymer bars are used to replace steel bar as the reinforcement in non-desalinated sea-sand concrete structures. Experimental and computational studies were carried out for the concrete beams. Flexural performance tests were performed on ten basalt fibre bar-reinforced sea-sand concrete beams with two strength grades and four reinforcement ratios by using the four-point bending method. The testing assessed the compression properties of the sea-sand concrete material and the flexural properties of the sea-sand concrete beams. The beam's cracking load, ultimate bearing capacity, basalt fibre polymer bar strain, crack width, failure mode, load–deflection curve and other properties were measured in the tests. The effects of the concrete strength and reinforcement ratio on the beam's bearing capacity were investigated. Formulas were developed to calculate the bearing capacity, deflection deformation and crack width of the basalt fibre bar-reinforced sea-sand concrete beam. Guidelines for designing basalt fibre bar-reinforced sea-sand concrete beams were also developed.

Fatigue behaviour of sea sand concrete beams reinforced with basalt fibre-reinforced polymer bars

As the most commonly used structural component in recent decades, the durability of reinforced concrete (RC) is always a concern owing to the corrosion of steel in harsh service environments. Using fibre-reinforced polymer (FRP) bars with sea sand concrete avoids the corrosion problem, solves the shortage of natural river sand, and is in line with the sustainable use of resources. In the present study, fatigue tests were conducted on two sizes of basalt FRP (BFRP)-reinforced sea sand concrete beams. The minimum load was set as zero, the maximum loads as 0.5, 0.6, and 0.7 of its ultimate capacity (Fu), and four-point bending with a frequency of 10 Hz was used. The experimental programme consists of two BFRP-reinforced concrete beams as control and four BFRP-reinforced concrete beams for the fatigue test, and a traditional RC beam was used for comparison. The load-deflection relationship showed a bilinear relationship for BFRP-reinforced concrete beams. The slope of the curves showed a rapid growth during the first stage and a relatively slow growth after concrete cracking as the cycles increased. This phenomenon can be attributed to the decreased stiffness of the concrete beam, and it was confirmed through the theoretical calculation of the interface damage. Fatigue life prediction was performed on the BFRP-reinforced sea sand concrete beam, and a fatigue limit 0.55Fu was proposed as a threshold for the applied load level.

Bond and Flexural Behavior of Sea Sand Concrete Members Reinforced with Hybrid Steel-Composite Bars Presubjected to Wet–Dry Cycles

In this paper, accelerated tests are conducted on the bond performance of steel fiber–reinforced polymer composite bars (SFCBs) with sea sand concrete and the flexural performance of SFCB-reinforced sea sand concrete beams after conditioning in a simulated seawater wet–dry cycling environment for 30, 60, and 90 days. The beams are coupled with a sustained load during conditioning. The steel bar pullout specimens and steel bar–reinforced sea sand concrete beams are conditioned in the same environment for comparison. Overall, 24 direct pullout specimens and eight beams are tested. The test results indicate that the maximum bond stresses of the SFCBs improve after wet–dry cycling, whereas the average bond stresses at 0.05, 0.10, and 0.25 mm of free-end slippage decrease slightly. Both the maximum bond stresses and the average bond stresses at 0.05, 0.10, and 0.25 mm of free-end slippage of the steel bars decrease. No significant changes occur in the characteristic loads of the steel bar beams during the aging period, whereas the characteristic loads of the SFCB beams decrease. Residual deflections after unloading increase the flexural stiffness and energy ductility of all the conditioned beams. The crack widths of the steel bar beams significantly increase after conditioning, but these increases are not obvious for the SFCB beams.