This paper presents the test results of an experimental study to investigate the effect of elevated temperatures on the bond properties of glass fiber-reinforced polymer bars in concrete. For this purpose, a total of 39 pullout specimens with glass fiber-reinforced polymer bars were cast for bond strength tests. In addition to the laboratory temperature, specimens were exposed to heating regimes of 100, 200, 300 and 350℃ for a period of 1, 2 or 3 h. The test results are presented in terms of bond strength, bond–slip relationship, and mode of failure. All specimens failed by shearing of the concrete corbels surrounding the bars and almost no damage was seen in the glass fiber-reinforced polymer bars. The results showed that the bond strength decreased as the temperature or exposure period increased. Reductions of about 20% of the original bond strength were recorded after exposure to 100 and 200℃ for 3 h. Significant reductions of about 50% in the bond strength were recorded after exposure to 350℃ for periods of 2 and 3 h. A modification to the ACI (American Concrete Institute) and CEB-FIP (Comité Euro-International du Béton-Fédération Internationale de la Précontrainte) equations was developed to consider the effect of elevated temperatures and it showed good agreement with test results.

Recycled expanded polystyrene (EPS) beads were used as a partial replacement for concrete mix components to develop lightweight concrete mixes with good thermal insulation properties. The replacement ratios were 50, 55, and 60% of the total mix volume. Workability, compressive, flexural, splitting tensile strengths, and thermal conductivities were evaluated. Two casting methods were investigated (with and without compaction). The results showed that using the recycled EPS beads significantly reduced the density, thermal conductivities, and mechanical properties of the mixes. Compared to the control mix, the decrease in the density ranged between 37% and 46% for the compacted samples and between 52% and 60% for the un-compacted samples. The thermal conductivities decreased by about 63% to 74% for the compacted samples and by about 78% to 85% for the un-compacted samples, which makes them efficient in thermal insulation applications. The decrease in the compressive strength ranged from 87% to 94% for the compacted samples and from 97% to 98% for the un-compacted samples. The test results revealed that the compacted samples with 50% and 55% of EPS achieved compressive strengths of 7.2 and 5.1 MPa, respectively. This makes them suitable for environmentally friendly non-structural applications with good thermal insulation properties.

Near surface mounted fiber reinforced polymer reinforcement has become very popular method in strengthening of reinforced concrete structures. The major problem that accompanied the near surface mounted technique is the bond between fiber-reinforced polymers and concrete that corresponds to the stress transfer from concrete into fiber-reinforced polymers. This article presents the test results of pullout tests of near surface mounted glass fiber reinforced polymer bars to investigate the effect of different parameters on the bond performance of this strengthening technique. The test parameters include: adhesive type, groove size, bonded length, environmental condition, and concrete strength. A total of 40 near surface mounted–fiber-reinforced polymer bars, installed in C-shaped concrete blocks, were constructed and tested to failure. Five types of cement and epoxy-based adhesives were used. Two groove sizes and three bonded lengths were also investigated. Normal and high strength concrete were also used. In addition, the effect of two harsh environmental conditions on the performance of the strengthening system was also investigated. The results are presented in terms of pullout loads, free end slip, and mode of failure.

Fatigue life has to be considered in the design of many concrete structures at various stress levels and stress ratios. Many flexural fatigue test results of plain normal-weight concrete are available in the literature and almost every set of test results provides different fatigue equations. It is necessary, though, to have a common fatigue equation to predict the design fatigue life of concrete structures under flexural load with reasonable accuracy. Therefore, a database of flexural fatigue test results was created for concrete with strengths ranging from 25 to 65 MPa; this database was used to derive new fatigue equations (Wöhler fatigue equation and S-N power relationship) for predicting the flexural fatigue life of normal-weight concrete. The concept of equivalent fatigue life was introduced to obtain a fatigue equation using the same stress ratio. A probabilistic analysis was also carried out to develop flexural fatigue equations that incorporate failure probabilities.

Due to their high strength, corrosion resistance, and durability, fiber reinforced polymers (FRP) are very attractive for civil engineering applications. One of these applications is the strengthening of concrete columns with FRP sheets. The performance of this strengthening technique at elevated temperature is still questionable and needs more investigations. This research investigates the effects of exposure to high temperatures on the compressive strength of concrete cylinders wrapped with glass and carbon FRP sheets. Test specimens consisted of 30 unwrapped and 60 wrapped concrete cylinders. All specimens were exposed to temperatures of 100, 200, and 300°C for periods of 1, 2, and 3 hours. The compressive strengths of the unwrapped concrete cylinders were compared with their counterparts of the wrapped cylinders. For the unwrapped cylinders, test results showed that the elevated temperatures considered in this study had almost no effect on their compressive strength; however, the wrapped specimens were significantly affected, especially those wrapped with GFRP sheets. The compressive strength of the wrapped specimens decreased as the exposure period and the temperature level increased. After three hours of exposure to 300°C, a maximum compressive strength loss of about 25.3% and 37.9%, respectively, was recorded in the wrapped CFRP and GFRP specimens.