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This paper proposes a new model for predicting the axial capacity and behavior of Fiber Reinforced Polymer-reinforced concrete (FRP-RC) columns using a promising variant of Genetic Expression Programming (GEP). Current design codes, such as the ACI 440.1R-15 and the Canadian Code CSA S806, disregard the compressive contribution of FRP bars when used in compression members. The behavior of concentrically short FRP-RC columns has been widely investigated in the past few years; however, limited research has been dedicated to investigating the effect of load eccentricity and the slenderness ratio of FRP-RC columns. In addition, the methodologies adopted for including the effect of column slenderness remain a subject of debate, as no solid conclusions are withdrawn in this regard. In this paper, the experimental results of FRP-RC columns are gathered from the literature and used to formulate two GEP models to predict the axial capacity based on load eccentricity. The experimental data includes columns reinforced with different FRP types and subjected to concentric and eccentric axial compressive loads. In addition, the database comprises short and slender columns. The proposed GEP models are functions of concrete compressive strength, longitudinal reinforcing bars ratio, FRP bars elastic modulus, eccentricity level, and column dimensions. For the aim of comparison, a preliminary evaluation of previously suggested empirical equations/models for estimating the axial capacity of FRP-RC columns was carried out over the collected database. The proposed models showed superior accuracy in axial capacity prediction with coefficients of determination R2 equals to 0.978 and R2 equal to 0.992 for eccentric and concentric axial load, respectively. The proposed models were found to give reliable estimates of the axial capacity of columns reinforced with FRP longitudinal bars. Finally, a parametric study to evaluate the effect of each variable on the proposed models was conducted.

This article is aimed at investigating the long‐term performance of three original hydrophobic materials, namely, sodium acetate, fluoropolymer, and silicone resin. Their performance was compared with traditional silane when applied to fully dry concrete, fully saturated concrete, and concrete with 2 and 4% moisture content. A recently developed freeze–thaw process, which is based on temperature and humidity variations, was employed in this study to assess the durability of applied materials. The outcomes of the adopted freeze–thaw system were compared with the results obtained from running a conventional freeze–thaw test. Mass change, water absorption, and microcracks development of treated concrete were investigated and compared with untreated concrete after completing 6 months of freeze–thaw cycles. Results confirmed the high affinity of the proposed materials to moisture at application time compared with silane. Additionally, it was demonstrated that moisture content has a critical impact on the bonding between applied materials and concrete, hence their efficacy in enhancing the durability of concrete.

The Shear Tester with Normal Stress (STNS) is developed in this study for measuring the fundamental shear properties of asphalt mixes at a low cost. The device can shear an asphalt concrete specimen subjected to controlled normal stress of 113 kPa (16.35 Psi). A total of 72 test specimens of three asphalt mixes, produced at different daily times, were tested for the Frequency Shear Test at Normal Stress (FSNS) and Repeated Shear Test at Normal Stress (RSNS). The FSNS test was used to measure the dynamic shear modulus |G*| and shear phase angle (δ), whereas the RSNS test was conducted to measure the permanent shear deformation for asphalt mixes. The results showed that the average values of the measured |G*| and (δ) have generally the same trends over the shear load frequencies for all mixes. All sample groups have average permanent shear deformations of less than 1.1 mm at 5000 repeated shear loads. The shear phase angle had comparable variabilities to that of the dynamic shear modulus at high shear load frequencies. The measured permanent shear deformations had variabilities of less than 17% for all mixes.