Structural repair and strengthening have long been dynamic and challenging activities in construction work. One of the most commonly used methods for such repairs is the application of fiber-reinforced polymer (FRP) sheets to strengthen RC or even steel structure members. A major issue of concern in flexural strengthening of RC beams with FRP laminates is the debonding of the concrete substrate, which leads to premature failure of the structural member thus strengthened. One reason for this premature rupture may be the lack of proper preparation of the concrete surface in contact with the FRP sheet. Surface preparation is typically associated with such constraints as adverse environmental impacts, economic losses due to stoppage of activities, repair costs, or even inaccessibility of the member(s) to be strengthened. This study aims to investigate surface preparation for application of FRP sheets in an attempt to develop substitute methods for conventional surface preparation methods. The experimental spe...

A major cause underlying the collapse of reinforced concrete (RC) moment-resisting frames observed in past earthquakes is the shear failure of nonseismically detailed exterior beam–column joints. A number of studies have investigated the external application of fiber-reinforced polymer (FRP) composites for the seismic rehabilitation of these members. However, the main challenge facing this technique is the premature debonding of FRP composites off the concrete substrate posed. The grooving method (GM), as an alternative to the conventional externally bonded reinforcement (EBR) technique, has yielded promising results in postponing, or in some cases eliminating altogether, the undesirable debonding failure mode in the flexural/shear strengthening of beams. The present experimental study was conducted to investigate the effects of GM in the seismic behavior of exterior RC beam–column deficient joints strengthened with carbon-FRP (CFRP) sheets taking advantage of the special technique of externally b...

In recent years, the grooving method in the form of “externally bonded reinforcement on groove” (EBROG) has been introduced as an alternative method of the conventional externally bonded reinforcement (EBR) for strengthening concrete structures using fiber-reinforced polymer (FRP) materials. This paper is a first attempt to develop an FRP-concrete bond strength model based on nonlinear regression on the experimental results. The agreement of the model to the data is verified using different statistical tools and analysis of variance. One hundred and fifty-four single lap-shear tests are conducted on 136 specimens made through the EBROG method and 18 specimens through the EBR method. The design of experiments techniques in the form of response surface methodology and I-optimality criteria are used to design and optimize the test layouts. The effects of groove dimensions, concrete compressive strength, and FRP sheet width and stiffness on the EBROG bond strength and its efficiency are investigated and compared with those on similar EBR specimens. Although debonding failure is observed to occur in all of the specimens, the results obtained confirm the superiority of the EBROG over the EBR specimens, as evidenced by an average enhancement of 31% achieved in bond strength and the postponed debonding. A bond strength model for the EBROG method was proposed by modifying the well-known Chen and Teng model, originally used for EBR.

Concrete is one of the most widely used materials in building structures; hence, improving its durability is important. Corrosive agents affecting concrete durability find their way into concrete through surface cracks and pores. However, concrete can be made resistant to such destructive agents if calcite sediments are allowed to form in the concrete by certain types of bacteria. This study investigated the effects of certain bacterial agents on the electrical resistance, chloride penetrability, and steel corrosion of concrete specimens. The water absorption and compressive strength of the specimens were evaluated. For this purpose, concrete specimens were made using two different bacteria (S. pasteurii and B. subtilis) and two different mixture proportions. The specimens were cured for 28 or 91 consecutive days in two types of media (a solution of urea–calcium chloride and a solution of urea–calcium lactate). Results showed that the water absorption and chloride penetrability of the specimens decreased but their compressive strength and electrical resistance increased when bacteria, especially S. pasteurii, was used in the concrete. Moreover, the reinforcement provided enhanced resistance against corrosion in concrete specimens containing S. pasteurii and subsequently cured in the urea–calcium lactate medium.

Application of carbon fiber-reinforced polymer (CFRP) composites has been promoted successfully for strengthening or repairing concrete structural members. However, if a column member is strengthened with longitudinal FRP sheets in which fibers are laid parallel to the column axis, the FRP composite will soon buckle under compression to ultimately debond off the concrete surface. It is the objective of the current research to investigate the effect of the recently developed grooving method (GM) on cylindrical specimens strengthened with FRP sheets under compressive loading, and to determine whether GM postpones the buckling of FRP sheets and their debonding off the concrete substrate. For the purposes of this study, 35 cylindrical reinforced concrete specimens, 150 mm in diameter and 500 mm in height, were tested under compressive loading with eccentricities of zero, 30, 60, and 90 mm. The specimens were additionally subjected to the four-point flexural bending test to represent infinity eccentric...