International Concrete Abstracts Portal

A slag-based zero-cement concrete (ZC) was newly developed as an alternative, eco-friendly material to Portland cement concrete. To investigate the bond performance between ZC and steel reinforcing bars, lap splice tests were conducted for ZC beams. Fourteen beams (two cementitious normal concrete (NC) beams and twelve ZC beams) were tested at the ages of 6 days (45 MPa (6.53 ksi)) and 28 days (60 MPa (8.7 ksi)). For steel reinforcement, Grade 600 MPa (87.0 ksi) reinforcing bars were used. The test parameters included the concrete type, concrete strength (i.e., concrete age), reinforcing bar diameter, concrete cover thickness, ratio of actual lap splice length to required lap splice length, and use of stirrups. The test results showed that the performance of ZC beams was comparable to that of the counterpart NC beams in terms of moment–deflection relationship, damage mode, and reinforcing bar stress at the peak load. This result indicates that the bond performance of ZC was equivalent to that of NC with identical compressive strength. The bar development length specified in current design codes safely predicted the reinforcing bar stress of the ZC beams at failure: current design codes are applicable to the reinforcing bar development length design of ZC members.

Controlling deflections in reinforced concrete (RC) flexural members under service loads is a serviceability requirement prescribed by design codes, such as the ACI CODE-318. Serviceability requirements are challenged by productivity requirements, such as faster construction and longer span demands, among others. This paper summarizes a parametric analysis conducted to estimate long-term deflections of one-way RC slabs. The objective of this study is to assess the effect of geometrical, concrete, and construction parameters on the long-term deflections of one-way RC slabs. The effect of these parameters on immediate deflections is also analyzed. Results of this study show that increasing the slab thickness and the area of tension reinforcement proved to be the most effective strategies for reducing both immediate and long-term deflections of one-way RC slabs. Additionally, the results of the parametric study highlight the relative influence of each studied parameter in controlling deflections.

This study presents a comprehensive field investigation into the long-term behavior of unbonded post-tensioned (PT) concrete flat slabs using Smart Strands embedded with fiber Bragg grating (FBG) sensors. The monitoring program was conducted in a real-world building in Seoul, Korea, spanning over five and a half years and capturing continuous prestressing force and deflection measurements at multiple slab locations. Results revealed that approximately 5% of nominal strength of tendon prestress losses occurred within the first year, stabilizing thereafter, and that deflection patterns were significantly influenced by slab position and construction activities. Comparison with analytical models showed strong alignment, with ACI CODE-318-25 time-dependent coefficients accurately predicting long-term deflections after the early-age period. This study contributes valuable long-term data, validating design codes and guidelines and enhancing understanding of the time-dependent behavior of PT concrete structures.

To improve the ductility of fiber-reinforced polymer reinforced concrete structures, the hybrid reinforcement with glass fiber-reinforced polymer (GFRP) and stainless steel (SS) is selected in this paper. Nine seawater sea sand concrete beams were designed and tested. The effects of concrete strength, effective reinforcement ratio ρ₂, and reinforcement type in the tensile zone on the flexural behavior of the beams were analyzed. The test results show that with the same concrete strength and the same effective reinforcement ratio ρ₂, the ductility of hybrid reinforced beams is higher than GFRP reinforced beams; the comparison of mid-span deflection of the GFRP bars and hybrid reinforced beams are not only depend on the reinforcement type, but also depend on the total stiffness of reinforcement before SS bars yield in the tensile zone and whether the SS bars are yielding in the tensile zone. Meanwhile, theoretical analysis was conducted for cracking moment, ultimate flexural load-carrying capacity, and mid-span deflections. A new ultimate flexural load-carrying calculation equation was proposed, which predicted the experimental values in good agreement.

To promote the application of fiber-reinforced polymer (FRP) bars reinforced ultra-high-performance seawater sea-sand concrete (FRP-UHPSSC) structures in marine construction, four-point static bending tests were carried out on 16 FRP-UHPSSC beams with different reinforcement ratios, height of cross-section, and type of FRP bars to investigate the ultimate load-carrying capacity, the midspan deflection, and the failure modes of the beams. The experimental results show that all the test beams are brittle failures, and the failure mode of the beams is shear failure when the ratio of the actual reinforcement ratio to the balanced one is higher than 2.73. Increasing the reinforcement ratio and the beam section height both improve the bending moment at ultimate load and the flexural stiffness at the service limit state. The Steel-FRP composite bars (SFCB) reinforced UHPSSC beams have the maximal bending moment at ultimate load, and the basalt fiber reinforced polymer (BFRP) bar reinforced UHPSSC beams have the optimal ductility. The deviation of ultimate bending moment and midspan deflection obtained by the proposed calculation method is reduced from 7.5 to 2.8%, and from 15 to 3%, respectively, compared with current specifications for FRP-reinforced concrete structures.