Journal of Materials in Civil Engineering

In many concrete structural applications, such as concrete pavements, joints or cracks are relied upon to transfer load between adjacent slabs in order to better distribute the stresses in the material. This study has developed a new method to characterize the shear transfer ability of preexisting concrete cracks and joints. The measured concrete surface roughness and fracture energy $\left(G_F\right)$ were related to a concrete mixtures ability to transfer shear load across a preexisting cracked surface. The wedge splitting test (WST) was used to obtain the concrete’s fracture energy. A modified method for determining $G_F$ based on WST is presented. A novel laser profilometer was implemented for quantifying the three-dimensional cracked concrete surface characteristics. The fracture energy was found to characterize both the physical and mechanical properties of the concrete crack face better than previously used surface parameters. In addition, the surface roughness of the concrete crack was related to the fracture energy at the time of cracking, whereas its ability to transfer shear load or shear stiffness was more related to the fracture energy at $28\text{-}\text{day}$ age.

In the present paper, an analytical model is proposed that is able to determine the flexural response of supported beams under four-point bending tests. Cases of normal strength reinforced concrete beams with longitudinal bars in the presence of reinforcing hooked steel fibers and transverse stirrups are considered. A simplified analytical model is presented that is able to calculate the load-deflection curves and the maximum and ultimate deflections occurring in the case of shear or flexure failures. In the case of shear failure, the maximum shear strength of the beams is evaluated by using a recent analytical expression proposed by the author able to account for the shear-to-moment interaction, which covers a large range of shear span-to-depth ratios. This expression is based on the evaluation of shear strength contribution due to beam and arch actions including their interaction with the fibers. In the case of flexural failure, the hypothesis of perfect bond of steel bars and concrete and limiting the range of shear-to-depth ratios to between two and four was considered to determine the ultimate moment. No tension stiffening and size effects were considered. A nonlinear finite element analysis program (ATENA) was utilized to verify the simplified model. The program was utilized by assigning the constitutive laws in compression and in tension for fibrous concrete available in the literature. Finally, on the basis of test data obtained by the author and of that available in the literature, a comparison was made to show the ability of the simplified proposed model to also predict the flexural response of beams when shear failure is attained.

In this study, the shear transfer behavior of reinforced concrete across a crack is investigated both analytically and experimentally by conducting tests on 19 precracked push-off specimens. The major parameters considered are the compressive strength of concrete and reinforcement parameter through the shear plane. Test results indicate that the behavior of a crack (in terms of stress-displacement relations) during shear transfer is characterized by four significant events. The mechanisms involved in each of these events are described. It has been shown that an independent increase either in concrete strength or reinforcement parameter stiffens the initial (after taking off the slack created by the precrack) straight portion of the curve, raises the linear response to a higher load level and increases the ultimate strength and the corresponding deformation, but the slope of the branch where frictional slip occurs remains relatively unchanged. A large pool of test data on reinforced concrete has been collated from the available literature. These, together with the test data generated in this study, have been analyzed and modeled embracing concrete strength up to about $110\mathrm{MPa}$ for predicting the ultimate shear transfer strength across a crack. A comparison of theoretical predictions with available test results shows good agreement.

This study presents experimental procedures conducted to characterize the bond between concrete and fiber reinforced polymeric laminates. The experimental characterization was aimed at obtaining the softening of the concrete-epoxy interface (CEI) formed during the installation of these laminates. In particular, splitting tensile and three-point bending tests were used to determine the tensile strength $\left(f_t\right)$ , the size-effect fracture energy $\left(G_f\right)$ , and the cohesive fracture energy $\left(G_F\right)$ of two concrete-epoxy interfaces. The sensitivity of these properties to the type of epoxy, specimen geometry, and surface conditions was also investigated experimentally. From this study, it was found that the tensile strength $\left(f_t\right)$ and the cohesive fracture energy $\left(G_F\right)$ of plain concrete and the two concrete-epoxy interfaces under consideration are similar in magnitude. Conversely, the size-effect fracture energies $\left(G_f\right)$ of plain concrete and a CEI are up to 64% different. Experimental results indicate that the condition of the concrete surface is the principal factor affecting the size-effect fracture energy $\left(G_f\right)$ of a concrete-epoxy interface. Results also indicate that the size-effect fracture energy $\left(G_f\right)$ can be used to characterize and compare concrete-epoxy interfaces.

Ordinary portland cement (OPC) has been traditionally used in the construction of concrete silos in Ireland. However, the aggressive nature of the effluent produced by silage leads to severe degradation of the concrete. GGBS is a common addition to PC composites. It has been demonstrated that GGBS improves the general performance of PC concrete, decreasing chloride diffusion and chloride ion permeability, reducing creep and drying shrinkage, increasing sulfate resistance, enhancing ultimate compressive strength, and reducing heat of hydration and bleeding. It has also been suggested that GGBS may increase concrete durability in the aggressive environment of silos. In order to investigate this theory, a simulation study was carried out by immersing samples of mortars incorporating increasing amounts of GGBS in a silage effluent solution and a magnesium sulfate solution. Over the course of an experiment consisting of three, $28\text{-}\text{day}$ cycles of immersion in the silage effluent, the sample performance was evaluated by testing permeability, porosity, water absorption, capillary suction, compressive strength, and mass loss. According to the results obtained, the OPC samples suffered the highest rise in permeability and porosity, and the greatest loss in both mass and compressive strength. In addition, the durability of the mortars, when subjected to both salt crystallization and silage effluent cycles, increased with increasing amounts of GGBS. The significant rise in capillary suction, water absorption, and permeability over the course of the experiment indicates that the damage induced by the effluent is not as superficial as previously reported. Loss in mass and increase in permeability were found to be the most reliable indicators of corrosion, as they gave the most dramatic and uniform results.

This technical note presents the behavior of dam and sieved concretes in uniaxial tension and compression together with the effects of curing age on large size specimens of $450\mathrm{mm}\times 450\mathrm{mm}\times 900\mathrm{mm}$ (prism shape) and $450\mathrm{mm}\times 450\mathrm{mm}\times 450\mathrm{mm}$ (cube shape) and small size specimens of $150\mathrm{mm}\times 150\mathrm{mm}\times 350\mathrm{mm}$ and $150\mathrm{mm}\times 150\mathrm{mm}\times 150\mathrm{mm}$ , respectively. The complete stress–strain curves both in tension and compression were acquired through a systematic experimental program. The specimen ages varied from 7 to 180 days. Models with hyperbolic form are proposed to estimate the tensile and compressive strengths, the elastic modulus, and the fracture parameters of the concretes with effects of specimen ages. On top of that, the maximum crack width, fracture energy, and brittleness of dam concretes were also obtained based on the stress–deformation curves. It was found that the strengths, modulus of elasticity, and fracture energy increase with specimen age, and that the specimen size and maximum aggregate diameter significantly affect the fracture energy, peak strain, and crack width of concretes in uniaxial tension.

This paper presents the laboratory investigations carried out to determine the various engineering properties such as physical properties of asphalt cement and (polymer modified asphalt binder) PMAB with (styrene-butadiene-styrene triblock copolymer) SBS, Marshall properties using modified Marshall method, static indirect tensile strength at different temperatures, tensile strength ratio, and resilient modulus ratio for asphalt concrete (AC) and polymer modified asphalt concrete mixes (PMAC) with SBS. The temperature susceptibility of PMAB-SBS is lower than asphalt cement. Marshall stability and flow values of PMAC mix are higher when compared to AC mix at optimum binder content. The static indirect tensile strength values for PMAC mixes were higher when compared to AC mixes at different temperatures. Moisture susceptibility of PMAC mixes is low when compared to AC mixes.