International Concrete Abstracts Portal

The paper presents a comparative study on the seismic behavior of circular columns reinforced with glass fiber-reinforced polymer (GFRP) and steel. The study specifically investigates the influence of replacing steel bars with GFRP bars on columns’ seismic response. All the studies summarized in this article were conducted at the University of Toronto. Results from the tests of 24 columns (all having 356 mm diameter and tested in a similar manner) from three different studies are closely analyzed to compare their responses. Based on the experimental results, it is found that replacing steel spirals with GFRP spirals did not result in substantial variation in the seismic performance of columns. Both types demonstrated similar ductility parameters and drift ratios when similar amounts of spirals were used at comparable pitches. Likewise, columns with steel longitudinal reinforcement and GFRP longitudinal reinforcement achieved similar displacement ductility, energy dissipation, and drift ratio.

The reduction in shear capacity when using recycled coarse aggregate (RCA) made from crushed concrete is evaluated in terms of tensile cracking and fracture-surface characteristics. An experimental investigation into the fracture and flexure-shear behaviors of recycled aggregate concrete (RAC) is presented. Replacing natural aggregate in concrete proportioned for 30 MPa (4350 psi) compressive strength with RCA results in lower compressive and tensile strengths. The tensile fracture-surface characteristics vary between RAC and natural aggregate concrete (NAC). While the surface area created in the tensile fracture of RAC is larger than that of NAC, the fracture surface profile in RAC has a smaller roughness than NAC. In the flexure-shear response of reinforced concrete beams, the dilatancy determined from the slip and crack opening displacements measured across the shear crack is smaller in RAC than in NAC. The failure in the reinforced beam is due to the frictional stress transfer loss across the primary shear crack. There is a larger decrease in the shear capacity with the use of RAC than indicated by the reduction in compressive strength. The reduced shear capacity of reinforced RAC is due to the combined influences of reduced tensile strength and crack surface roughness. The design provisions require calibration for crack surface roughness when using RAC in structural applications.

This study focuses on enhancing the durability of two-component grouting materials by incorporating ground granulated blast furnace slag (GGBFS) and replacing cement with industrial waste to reduce environmental pollution. A ternary cementitious system was developed using 30% GGBFS and 10% carbide slag (CS) as partial cement replacements. The research investigates the effects of different water-bentonite ratios, water-binder ratios, and AB component volume ratios on the physical and mechanical properties of the grout, including density, fluidity, bleeding rate, setting time, and strength performance. The microstructural evolution and hydration products were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), and thermogravimetric analysis (TGA). The findings provide insights for optimizing the mix design of grouting materials in shield tunneling applications, with a focus on improving performance and sustainability.

As global demand for concrete has been forecasted to keep rising, one of the approaches towards more sustainable constructions is the adoption of mix designs replacing conventional ones. The current study contains a comparison between concrete mixes that constitutes only Ordinary Portland Cement (OPC) and mixes incorporating 25% OPC with a 75% replacement by supplementary cementitious materials (SCM). The major experimental hypothesis circles around investigating whether it is effective to use thermal treatment under moderately elevated temperatures to enhance the physical and mechanical properties of concrete. Comparisons were performed using mechanical tests such as: compressive strength, tensile strength, flexural strength, and through several non-destructive physical experiments as well as microstructural investigation using SEM and EDS. In conclusion, the experimental results have shown a mostly positive influence observing significant enhancements after thermal treatment. However, treated concrete mixes that constitute only OPC seem to excel in overall performance compared to those incorporating SCM.

To evaluate the calculation accuracy of traditional yield displacement models and to describe the probabilistic characteristics of yield displacement, a probabilistic model for yield displacement of reinforced concrete (RC) columns with flexural failure was developed based on the Bayesian theory and the Markov Chain Monte Carlo (MCMC) method. The analytical expression for the yield displacement of RC columns was established by applying the plane-section assumption and cross-section analysis first. Then, the probabilistic model for yield displacement of RC columns with flexural failure was developed by replacing the empirical coefficients in the analytical expression with probabilistic coefficients. Moreover, the posterior information of the probabilistic coefficients was determined based on the prior information from experimental data and the MCMC method. Finally, the calculation accuracy of deterministic models for yield displacement was evaluated based on the experimental data, probability density functions, and confidence intervals. Analysis results demonstrate that the proposed probabilistic model provides an alternative approach to evaluate the calculation accuracy of deterministic models for yield displacement of RC columns with flexural failure. Priestley's model, JTD's model, and Cui's model tend to underestimate the yield displacement of RC columns, while Fardis's model and Billah's model often overestimate the yield displacement of RC columns.