Deterioration Of Bond Strength Research Articles

The effect of pore characteristics on the bonding properties of steam-cured concrete and GFRP bars

Steam cured concrete prefabricated components has the advantages of short construction period, less environmental pollution, convenient construction and low cost, and is widely used in high-speed railway projects. However, the changes of later strength, capillary water absorption and pore distribution led to the reduction of durability of steam-curing concrete and accelerated the damage speed of GFRP bars and bond performance between concrete and GFRP bars. In this study, the method of steam curing is adopted to simulate the damage of components caused by actual steam curing environment. The influence of pore characteristics on the bonding properties of steam cured concrete and GFRP steel bar is analyzed from both micro and macro perspectives. Analysis method combining pore characteristics with bonding strength. The test results showed that the hydration products of concrete were unaffected, but the density of the hydration products changed due to the steam curing. The porosity of the steam-cured concrete was much higher than that of the standard-cured concrete. The number of gel pores smaller than 20 nm accounted for 12.27% of the total number of pores on average, which was about twice the proportion of the gel pores of this size in the standard-cured concrete. The proportion of harmful voids with pore size of 50–200 nm and greater than 200 nm is higher than that of standard curing concrete. The bond strength of the steam-cured concrete and GFRP bars was 30% lower than that of the standard-cured concrete. With the change of the thickness of the concrete cover and the diameter of GFRP bars, the bond strength changed significantly. Based on the analysis of the test data, a predictive model of the bond strength deterioration for the steam-cured concrete and GFRP bars was established. The model fully accounted for influence factors such as the porosity, diameter, anchor length, and concrete strength.

Bond performance of steel rebar in alkali-activated slag-based concrete after exposure to elevated temperature

Bond strength deterioration between reinforcing bars and surrounding concrete is critical to structural performance loss during a fire. However, available studies on the bond behavior between alkali-activated concrete and reinforcing bars at elevated temperatures are insufficient. This study conducted pull-out tests on alkali-activated slag-based concrete (AAC) specimens with three concrete strength grades (C30, C50, and C70) and rebar diameters (14, 18, and 22 mm) at ambient temperature and after exposure to 200, 400, 600, and 800 ℃. The experimental and analytical results showed that AAC pull-out specimen using normal-strength concrete was more prone to splitting failure than Portland cement concrete (PCC) specimens and required greater lateral confinement. The absolute and relative values of residual bond strength for AAC and PCC specimens after high-temperature exposure were similar, which corresponds to their similar thermal degradation of concrete strength. After exposure to 200 ℃, 400 ℃, 600 ℃ and 800 ℃, their rebar bond strength declined rapidly to about 80%, 50%, 15%, and less than 10% of their respective bond strength at ambient condition, respectively. Compared with the counterpart PCC specimens, AAC specimens exhibited greater peak slip and relatively smaller bond stiffness after exposure to elevated temperature due to smaller elastic modulus of AAC. Further, the concrete strength and concrete cover-to-rebar diameter ratio have a significant effect on the failure mode and residual bond strength of AAC pull-out specimens. To evaluate the residual bond property of reinforced AAC after exposure to elevated temperature, an empirical model of bond strength versus temperature and a simplified bond-slip constitutive equation were proposed.

Bond deterioration of corroded reinforcements in SFRC: Experiments and 3D laser scanning

The bond deterioration behavior of reinforcements in steel fiber-reinforced concrete (SFRC) subjected to chloride-induced corrosion has not yet been fully elucidated. This study investigates the corrosion characterization, resistivity, corrosion-induced cracking, and associated effects on the bond performance of reinforcing bars in SFRC with milled-cut steel fibers (M fibers), referred to as MCSFRC. Pull-out tests were performed following galvanostatic corrosion, with the M fiber, concrete cover, and corrosion level being the main variables. A closer look at the bar corrosion was conducted using 3D laser scanning technology, which allowed for estimating the spatial-domain corrosion pattern and bond index degradation that characterize the rib-concrete interaction. The results indicated that, with the increase in corrosion levels, the bond index decreased exponentially as a result of pits propagating from the rib root to the rib peak. The bond strength of the MCSFRC specimens deteriorated less than that of the control counterparts and hook-end fiber-reinforced specimens in the literature. It is further revealed that the crack opening and bond index reduction are the bond deterioration mechanisms under corrosion, reducing the contact area between the bar and concrete through the ribs. On that basis, a mechanics-based model for bond strength deterioration was developed. The proposed model considered the two aforementioned effects, as well as the fiber reinforcement effect on crack suppression, showing good agreement with the experimental results.

Influence of Filler Type and Rheological Properties of Asphalt Mastic on the Asphalt Mastic-Aggregate Interaction.

The asphalt mastic-aggregate interaction plays an important role in the overall properties of asphalt mixtures and their durability in service in flexible pavements. This paper aims to study the influence of the physico-chemical features of fillers and the rheological properties of asphalt mastics on the bonding behavior between asphalt and aggregate, and the interfacial deterioration mechanism when subjected to static water immersion and pressured water immersion. It was found that the filler type (limestone powder, basalt powder, and granite powder) had a certain influence on the complex modulus of asphalt mastics, and its pore volume and specific surface area had significant effects on the phase angles and permeability of asphalt mastics. The effect of water pressure can accelerate the deterioration of bond strength of the asphalt mastic-aggregate interface in the short term, indicating that the dynamic water pressure generated by the driving load promotes the water damage process in asphalt pavements. In comparison, the residual bond strength ratio of the granite-asphalt mastic aggregate was the highest, while its bond strength was lower than that of the interface between limestone-asphalt mastics and limestone aggregate. This demonstrated that a low asphalt mastic complex modulus and a high phase angle are helpful in improving the durability of asphalt mixtures subjected to static and pressured water immersion conditions.

Convolution-based ensemble learning algorithms to estimate the bond strength of the corroded reinforced concrete

Reinforced concrete bond strength deterioration is one of the most serious problems in the construction industry. It is one of the most common factors impacting structural deterioration and the major cause of premature decadence of reinforced concrete structures. Therefore, developing an accurate model with the lowest variance and high reliability for the bond strength of corroded reinforced concrete is very important. The current work evaluates the efficiency of convolution-based ensemble learning algorithms. To address these issues, convolution-based ensemble learning models are developed using a database collected from the previous experimental studies of relative bond strength for corroded reinforced concrete. Seven parameters are considered as inputs, including bar diameter, the ratio of concrete cover to bar diameter, the ratio of the bar diameter to embedment length, transverse reinforcement ratio, yielding strength, concrete compressive strength and the corrosion level. Results indicate that the convolution-based integrated stacking model produces excellent predictions with the coefficient of determination, a-20 index, and mean square error values of 0.84, 0.75, and 0.022. Since machine learning based models are commonly black-box models, the Shapley Additive Explanations (SHAP) method is used to explicitly relate the predicted output to the inputs. Based on SHAP, the corrosion level, concrete compressive strength, transverse reinforcement ratio, and the concrete cover to bar diameter ratio are ranked among the most influential parameters on the bond strength of the corroded reinforced concrete.

Impact of Corrosion on the Bond Strength between Concrete and Rebar: A Systematic Review.

Corrosion of the reinforcement affects more than the cross-sectional area of the rebar. The volume of steel also increases due to expansive corrosion products, leading to the cracking, delamination, and spalling of concrete. As a result, the bond capacity between concrete and rebar is affected. Researchers have extensively examined the impact of corrosion on the bond strength between concrete and rebar to propose empirical, theoretical, or numerical predictive models. Therefore, research programs on this topic have increased rapidly in recent years. This article presents a systematic literature review to explore experimental methods, outcomes, and trends on this topic. The Web of Science search collected 84 relevant research articles through a rigorous selection. Key factors that affect bond strength degradation, including concrete cover, concrete strength, and stirrups, have been documented. However, a general model is still unavailable due to discrepancies caused by differences in testing methods to evaluate the effect of corrosion on bond strength. Furthermore, researchers attempted to clarify the degradation mechanism of bond strength affected by corrosion. As a result, new alternatives have been proposed to build a practical model to assess the bond strength deterioration of corroded structures.

Influence of sulfate crystallization on bond-slip behavior between deformed rebar and concrete subjected to combined actions of dry-wet cycle and freeze-thaw cycle

The bond-slip behavior of deformed rebar with medium embedded length and surrounding concrete without stirrup under sulfate salt, dry-wet cycle and freeze–thaw cycle was investigated in this study. Physical crystallization of sulfate was produced by using a 3:1 drying/wetting time ratio in erosion specimens. Different concentrations of sodium sulfate solution (CSSS), different drying and wetting cycles (DWC), and different freeze–thaw cycles (FTC) were considered as environmental variables in central pull-out tests. The bond characteristics of post-yielding rebar and surrounding concrete under combined environmental factors were obtained. Scanning electron microscope and x-ray diffraction analysis were conducted to identify reaction products. The experimental results showed that CSSS and DWC had both beneficial and adverse effects on the bond strength.1% CSSS and 25 DWC were the turning points of increasing and decreasing of bond strength. The expansion force caused by Na2SO4 physical crystals improved the bond strength in the initial stage, but impaired it after the crack of pore wall of concrete in the later stage. After superimposed FTC, the bond strength was greatly reduced. Sulfate crystallization significantly accelerated the deterioration of bond strength under freeze–thaw cycles. The prediction models of the bond strength between deformed rebar and surrounding concrete after yielding in terms of single and multiple environmental factors had been established. The models can be used to predict the bond strength of post-yielding rebar and surrounding concrete in complex environments of sulfate, dry-wet cycle and freeze–thaw cycle.

Application Modes Affect Two Universal Adhesive Systems' Nanoleakage Expression and Shear Bond Strength.

Objectives The aim of this study was to evaluate the shear bond strength and the nanoleakage expression of CLEARFIL Universal Bond Quick and Tetric N-Bond adhesive systems bonded to dentin. Materials and Methods 100 freshly extracted human premolar teeth were utilized. The teeth were sectioned to expose dentin. All dentin specimens were assigned into 4 experimental groups; 2 groups had Universal Bond Quick (Universalself group) and Tetric N-Bond (Tetricself group) applied in the self-etch mode, while 2 groups had Universal Bond Quick (Universaltotal group) and Tetric N-Bond (Tetrictotal group) applied in the total-etch mode. n = 15 for shear bond strength and n = 10 for nanoleakage experiment. One-way ANOVA and Kruskal-Wallis test were utilized to analyze the shear bond strength test and the nanoleakage expression, respectively. Results The highest significant bond strength value was recorded by the Tetricself specimens (p < 0.05) when compared to the remaining three groups. There were no statistically significant differences between the shear bond strength values recorded in the Tetrictotal, Universalself, and Universaltotal groups (p < 0.05). Both bonding systems applied in the self-etch mode (Universalself, Tetricself) had no silver nitrate deposits in the hybrid layer and the hybrid layer-adhesive interface (p < 0.001); however, both bonding systems applied in the total-etch mode (Universaltotal, Tetrictotal) had silver nitrate deposits in the hybrid layer, the hybrid layer-adhesive interface, and the bonding layer (p < 0.001). Conclusion Applying the Universal Bond Quick and Tetric N-Bond in the self-etch mode exhibited better results in terms of nanoleakage expression. Universal Bond Quick showed the stability of the shear bond strength to dentin when applied using the total-etch or self-etch modes. Tetric N-Bond showed significant deterioration in bond strength when applied in the total-etch mode and exhibited the highest bond strength when applied in the self-etch mode.

Bond deterioration effects on corroded RC bridge pier in seismic zone

AbstractThe effects of corrosion focusing on the consequences of bond strength deterioration for a reinforced concrete bridge pier in a seismic affected area are examined in this research. A bond degradation model based on the local bond stress‐slip model presented in FIB Model Code 2010 is chosen. A motorway overpass object of a previous study, which considered the rebars cross‐section reduction effect only, has been selected to assess the seismic capacity of the corroded pier in the time domain when bond degradation due to corrosion is also taken into account. The modification of strength capacity and ductility of the structural element is analyzed and the effect of corrosion during the whole service life of the structure is obtained. It is concluded that the effect of bond degradation is more critical for the safety of the pier than the effect of rebars cross‐section loss.

Short- and Long-Term Dentin Bond Strength of Bioactive Glass-Modified Dental Adhesives.

This study investigated the short- and long-term effects of dental adhesives doped with nano-sized bioactive glass 45S5 (BAG) on the resin–dentin interfacial bond strength. Two etch-and-rinse adhesives (Adper Scotchbond Multi-Purpose (ASB) and Solobond Plus (SB)) and one self-etch adhesive (Clearfil SE Bond (CF)) were doped with different concentrations of BAG (5, 10, and 20 wt%). The unmodified (0 wt% BAG) commercial adhesives served as control groups. Dentin of 120 molars (n = 10 per group) was treated with the different adhesives, followed by buildups with a conventional composite restorative material. From each tooth, 14 sticks were prepared for micro-tensile bond strength (µTBS) testing. The sticks were stored in simulated body fluid at 37 °C and tested after 24 h or six months for µTBS and failure mode. Data were analyzed using Kruskal–Wallis tests in combination with post-hoc Conover-tests and Wilcoxon signed-rank tests at a level of significance of α = 0.05. After 24 h and six months, both etch-and-rinse adhesives with a low BAG content (up to 10 wt% for ASB and 5 wt% for SB) showed similar µTBSs as their respective control groups (0 wt% BAG). CF showed a significant decrease in µTBS even after addition of 5 wt% BAG. At a high concentration of added BAG (20 wt%), all three adhesives showed a significant decrease in µTBS compared to the unmodified controls. The CF control group showed significantly lower µTBS after 6 months of storage than after 24 h. In contrast, the µTBS of all CF groups modified with BAG was unaffected by aging. In conclusion, the tested etch-and-rinse adhesives can be modified with up to 5 wt% (SB), or 10 wt% (ASB) of BAG without reducing their short- and long-term dentin bond strength. Moreover, the addition of nano-sized BAG may prevent long-term bond strength deterioration of a self-etch adhesive.

Bond strength degradation in concrete cracked by expansion agent filled pipes

AbstractIn this study, the bond behavior of corroded reinforced concrete was investigated by conducting pull‐out tests on concrete specimens with variable induced crack widths and different splitting modes. To simulate cracks due to corrosion and focus on their effect on bond strength degradation, a novel method using expansion agent filled pipes is proposed. With the increase of the crack width over elapsed time from filling the aluminum pipe with an expansion agent, a target crack width was obtained. The results confirm that the type of splitting greatly influences the reduction in bond strength with deterioration of bond strength more severe in “Side‐split” than in “Single‐split.” Furthermore, using the surface crack width as a variable, empirical formulas to predict bond strength degradation due to corrosion of rebar are proposed. These prediction models give a good correlation when compared to the available literature.

Development of discrete meso-scale bond model for corrosion damage at steel-concrete interface based on tests with/without concrete damage

Rebar corrosion can lead to significant deterioration in bond strength between steel and concrete. However, since confinement is lost as the concrete cracks, the changes in frictional bonding and mechanical bonding resulting from corrosion remain unclear and there is a need for an efficient tool that can evaluate the bond performance of corroded concrete structures. In this study, an innovative pull-out test is used to study changes in bonding in reinforced concrete after rebar corrosion, then a discrete meso-scale model based on the Rigid Body Spring Model (RBSM) is developed to simulate the observed bond behavior. To isolate the effects of concrete cracking, after an initial pull-out test, the corroded rebars are obtained and used as the reinforcement in newly cast sound specimens that are subject to a further pull-out test. A corrosion acceleration method is used to obtain corroded rebars. Different types of reinforcement (round rebars and deformed rebars) are studied. The results are used to study changes in frictional bonding and mechanical bonding at different degrees of corrosion. It is found that, without concrete cracking, the frictional bond in specimens with both round and deformed rebars significantly increases with the amount of corrosion, while total bond strength of specimens with deformed bar is almost unchanged because mechanical bonding is weakened. In the presence of concrete cracking, for specimens reinforced with a corroded round rebar, bond capacity increases initially (up to 3% corrosion) and then falls as corrosion increases, while bonding in those with a corroded deformed rebar shows a consistent decrease. In the RBSM-based simulations, the effect of corrosion is modeled by adjusting springs at the corroded interface. Constitutive models of shear and normal springs are developed to simulate corrosion and reflect the changes on frictional and mechanical bonding. Simulated results for load-displacement relationship, pull-out capacity and crack pattern are in good agreement with the experimental results. The numerical simulation is used to visualize internal stress development and strain distribution along the rebar as the degree of corrosion increases, a result that cannot be obtained by experimental methods. The results demonstrate that RBSM is a useful tool for evaluating the mechanical performance of corroded reinforced concrete structures.

State-of-the-art review on the bond properties of corroded reinforcing steel bar

Abstract This review summarizes the latest research progress in regard to the bond behavior of corroded reinforcing steel bar. The literature survey indicates that the previous studies mainly focus on the deterioration of bond strength. The primary factors influencing bond strength, including main bar corrosion, concrete cover, concrete type, stirrups, stirrup corrosion, and corrosion rate, have been well recognized. However, the existing models for bond strength are mostly developed based on specific test results and are not generalized. The corrosion-induced surface crack width is an ideal parameter for the evaluation of bond strength, but models in this respect are still scarce. As for the bond-slip behavior, literature studies reveal that the bond-slip mechanism is hardly affected by corrosion. Currently, discrepancies exist regarding the corrosion influence on the key parameters that shape the bond-slip curves. Preliminary comparisons of the existing bond-slip models show that reliable and generalized models remain to be developed based on larger database. Studies on the bond behavior of corroded steel bar under cyclic loading are quite few. The limited test results indicate that the repeated loading without changing sign shows no apparent influence on bond strength, whereas the cyclic reversed loading exacerbates the corrosion-induced bond deterioration. Knowledge gaps and research areas where further investigations are required are outlined.

Micro-mechanics based numerical simulation of NaCl brine induced mechanical strength deterioration of sedimentary host-rock formations

Artificial fracture stimulation in low-grade sedimentary ore deposits is one method to improve mineral extraction efficiency of In-Situ Leaching (ISL) process. Low to moderate saline environments are found in most sedimentary ore deposits that deteriorate intact rock strength over time. It is important to recognize the host rock strength properties prior to artificial fracture stimulation. Therefore, to identify the effect of salinity on the mechanical properties of brine-saturated sandstone, a series of uniaxial compressive strength (UCS) tests and Brazilian tensile strength tests were performed on specimens saturated with water, and with varying NaCl brine concentrations (5.0%, 7.5%,10% and 12.5%). Scanning electron microscopy and inductively coupled plasma mass spectrometry (ICP-MS) tests reveal that increasing salinity deteriorate the mechanical integrity of sandstone by accelerated clay mineral dissolution. Consequently, 12.5% saturation fluid salinity resulted in a 40% reduction in UCS, 22% reduction in Young's modulus and 33% reduction in tensile strength. The strength deterioration observed in the experimental study was then successfully simulated using Particle Flow Code 3D (PFC3D) in consideration of the bond strength deterioration mechanism for sandstone. The calibrated model was used to accurately replicate the damage mechanism of sandstone under the influence of brine saturation. The model forms an accurate intact rock assembly for numerical modelling of saline sedimentary host-rock formations.

Dentin Bond Strength of Experimental Composites Containing Bioactive Glass: Changes During Aging for up to 1 Year.

To investigate dentin bond strength of experimental composites based on a bis-GMA/TEG-DMA composite filled with a varying amount (0 to 40 wt%) of bioactive glass 45S5 (BG) at a total filler content of 70 wt%. Specimens for shear bond strength testing (diameter = 3.12 mm, height = 3 mm) were bonded to human dentin using a two-step self-etch adhesive and subjected to aging in water at 37°C for 1 week, 1 month, 3 months, 6 months, and 1 year. A total of 600 specimens were prepared (6 materials × 5 aging times × 20 specimens per experimental group). Bond strength was tested by loading specimens in a universal testing machine at a constant crosshead speed of 0.5 mm/min until fracture. Reliability analysis was performed using Weibull statistics. Experimental composites with a low BG content (up to 5 wt%) showed dentin bond strength and reliability comparable to those of the commercial reference composite. A further increase in the BG amount diminished both bond strength and reliability. The bond strength decline was linearly dependent on the amount of BG when observed within each aging time. One-year aging in water caused no deterioration of bond strength, but diminished bond reliability. The reliability after 1-year aging was similar among all composites, including the commercial reference composite. The variation in BG amount diminished the bond strength and reliability in a dose-dependent manner.

Assessment of bond strength in CFRP retrofitted beams under marine environment

Carbon fibre reinforced polymer (CFRP) sheet has gained its popularity to retrofit civil structures which is bonded externally, typically on the soffit of a beam. In this study, the bond between carbon fibre reinforced polymer (CFRP) and concrete is improved by modifying the property of commercial epoxy and compared against normal epoxy. The deterioration in bond strength was produced by placing the beam into salt water under wet dry cycles. Also, a model is proposed to determine the bond strength from flexural test and compared against the available bond strength models which are typically obtained from pull out test. This proposed model shows promising results in terms of predicting the bond strength from flexural test. In addition, a strength reduction factor is introduced to incorporate the effect of wet dry cycles to predict the long term behaviour. It is found that the modified epoxy enhance the ductile property and bond strength.

Surface hydrogenation regulated wrinkling and torque capability of hydrogenated graphene annulus under circular shearing.

Wrinkles as intrinsic topological feature have been expected to affect the electrical and mechanical properties of atomically thin graphene. Molecular dynamics simulations are adopted to investigate the wrinkling characteristics in hydrogenated graphene annulus under circular shearing at the inner edge. The amplitude of wrinkles induced by in-plane rotation around the inner edge is sensitive to hydrogenation, and increases quadratically with hydrogen coverage. The effect of hydrogenation on mechanical properties is investigated by calculating the torque capability of annular graphene with varying hydrogen coverage and inner radius. Hydrogenation-enhanced wrinkles cause the aggregation of carbon atoms towards the inner edge and contribute to the critical torque strength of annulus. Based on detailed stress distribution contours, a shear-to-tension conversion mechanism is proposed for the contribution of wrinkles on torque capacity. As a result, the graphane annulus anomalously has similar torque capacity to pristine graphene annulus. The competition between hydrogenation caused bond strength deterioration and wrinkling induced local stress state conversion leads to a U-shaped evolution of torque strength relative to the increase of hydrogen coverage from 0 to 100%. Such hydrogenation tailored topological and mechanical characteristics provides an innovative mean to develop novel graphene-based devices.

Analytical Model for Residual Bond Strength of Corroded Reinforcement in Concrete Structures

Bond strength deterioration in corrosion-damaged reinforced concrete structures significantly affects serviceability and load-carrying capacity in their remaining service life. This paper presents a new analytical model for predicting the cracking development in the surrounding concrete and the residual bond strength of rebar in concrete structures due to reinforcement corrosion. The proposed analytical method adopts the thick-walled cylinder model for the cover concrete and considers the realistic properties of the corrosion-induced cracked concrete such as anisotropic behavior, residual tensile strength, and reduced tensile stiffness. As corrosion progresses, three phases for bond strength evolution associated with concrete cracking development are defined and the corresponding corrosion levels in each phase are determined. By using the constructed new governing equation, the crack width growth in the concrete cover and the radial bursting pressure at the bond interface are evaluated. The ultimate bond strength is then estimated from the contributions of adhesion, confinement, and corrosion pressure as a function of corrosion level. Finally, the effectiveness of the proposed analytical model is demonstrated by comparing the predicted results with experimental data available, and the results show that the proposed model is useful for predicting the bond strength evolution of the corroded rebar in concrete structures.

자동차 전장품용 무연솔더 접합부의 시리즈 시험 유효성

Abstract Due to environmental regulations (RoHS, WEEE and ELV) of the European Union, electronics and auto-motive electronics have to eliminate toxic substance from electronic devices and system. Specifically, reli-ability issue of lead-free solder joint have an increasing demand for the car electronics caused by ELV banning. The authors prepared engine control unit and cabin electronics soldered with Sn-3.0Ag-0.5Cu (SAC305). To compare with the degradation characteristics of solder joint strength, thermal cycling test (TC), power-thermal cycling test (PTC) and series tests were conducted. Series tests were conducted for TC and PTC combined stress test using the same sample in sequence and continuously. TC test was per-formed at -40~125 ℃ and soak time 10 min for 1000 cycles. PTC test was applied by pulse power and full function conditions during 100 cycles. Combined stress test was tested in accordance with automotive company standard. Solder joint degradation was observed by optical microscopy and environment scanning electron microscopy (ESEM). In addition, to compare with deterioration of bond strength of quad flat pack-age (QFP) and chip components, we have measured lead pull and shear strength. Based on the series test results, consequently, we have validated of series test method for lifetime and reliability of Pb-free solder joint in automotive electronics.Key Words : Pb-free solder, Solder joint, Series reliability, Automotive electronics, DegradationISSN 1225-6153Online ISSN 2287-8955

Effect of hot temperature on pull-off strength of FRP bonded concrete

In recent years, thin fiber reinforced polymer (FRP) composite sheets have been successfully used in strengthening deficient concrete structures. Although the short term performance of these FRP sheets has been satisfactory, their long term durability performance remains yet to be confirmed. The bond strength between FRP and its concrete substrate is one of the critical design factors due to the composite action requirement. In this paper, the effects of hot temperature (100 and 180°C) on the deterioration of bond strength and the changes in failure modes are presented and discussed. Three possible failure modes are considered in this study: cohesive in the concrete substrate, mixed, and adhesive at the interface. Therefore, the true bond strength between concrete and FRP can only be measured when the failure mode is adhesive. Under the control conditions at room temperature, the true adhesive strength exceeds 6MPa, which is adequate for most engineering applications. A combination of high temperature and low humidity is the most detrimental to bond strength.