International Concrete Abstracts Portal

This study uses neutron radiography (NR) and visual inspection to quantify water penetration in concrete samples exposed to water pressure on one face. It provides experimental data regarding the impact of mixture proportions on the hydraulic permeability of concrete. Specifically, it illustrates the influence of water-cement ratio (w/c), curing duration, entrained air content, and coarse aggregate (CA) size and volume on water transport. In addition, this paper quantifies the impact of permeability-reducing admixtures (PRAs) on water transport in concrete. It was observed that decreasing the w/c and/or increasing the curing duration reduced the fluid transport. Liquid and powder PRAs efficiently reduced fluid transport in concrete without impacting the compressive strength. The liquid PRA showed more consistent results, likely due to better dispersion than the powder PRA. Fluid ingress in concrete samples appears to increase with entrained air content due to a lower degree of saturation (DOS) at the start of the test. Increasing the CA volume fraction or decreasing the CA size will increase the fluid transport in concrete due to an increase in the connectivity of the interfacial transition zone. The influence of entrained air content, curing duration, CA volume fraction, and CA size was less noticeable on mixtures with PRAs due to the higher density and low permeability of these samples compared to control samples.

The improvement of durability and service life of reinforced concrete structures in the marine environment with the incorporation of corrosion inhibitors has attracted significant attention in recent years. The present study aims to evaluate the performance of a commercially available organic corrosion inhibitor in protecting the steel reinforcement of concrete structures in marine conditions. The study was performed on a control mixture and a test mixture with water-cement ratios (w/c) of 0.4 and 0.6, providing aggressive laboratory and field environments following the recommendation of international standards for corrosion inhibitors assessments. Corrosion monitoring methods and visual inspection of reinforcing bars confirmed the effectiveness of migrating corrosion inhibitor in mitigating chloride-induced corrosion. The migratory properties of the corrosion inhibitor and its ability to densify the matrix microstructure were confirmed through scanning electron microscopy and X-ray photoelectron spectroscopy analyses.

This paper reports the splitting tensile strength of concrete corroded by saline soil. The wet-dry cycle erosion test and splitting tensile test were performed on concrete cubic specimens with six different erosion inspection periods and a solution with the same concentration as the saline soil. The variation of chlorine and sulfate with erosion depth for different erosion inspection periods of corroded concrete, as well as the powder on the concrete within the erosion depth, were analyzed via X-ray diffraction (XRD). Combined with the parallel bar system, corroded concrete specimens were divided into corrosion and non-corrosion parts. Considering the corrosive effect of saline soil on the concrete specimen, the splitting tensile strength model of the corroded concrete in the saline soil area was established and compared with experimental values. The results show that the calculated values of the splitting tensile strength model established herein agreed with experimental values. The splitting tensile strength of concrete gradually decreased with the increasing erosion depth, and the erosion depth gradually deepened with the increasing wet-dry cycle time. This is because CaCO3, ettringite, gypsum, and Friedel’s salts were produced by reacting with concrete in the range of erosion, which resulted in the decrease of splitting tensile strength of concrete.

Fly ash concrete mixtures were tested for the chemical and physical sulfate attack. Concrete mixtures consisting of ratios of fly ashes, Type I cement, silica fume, and ultra-fine fly ash (UFFA) were tested. Four exposure conditions were simulated by subjecting the concrete specimens to: 1) immersion in 5% Na2SO4 solution; 2) wet-dry cycling in 5% Na2SO4 solution at 23°C (73°F, wet) and 38°C (100°F, dry); 3) immersion in saturated CaSO4 solution; and 4) wet-dry cycling in saturated CaSO4 solution at 23°C (73°F, wet) and 38°C (100°F, dry). Control specimens were stored in water at ambient temperature. Performance of the concrete mixtures was studied through visual inspection and by monitoring the changes in mass, length, and dynamic modulus of elasticity over time. It was found that improved sulfate resistance can be provided to the fly ash concrete by controlling water-cement ratio (w/c) and blending with Class F fly ash, UFFA, and silica fume.

An investigation was carried out on basalt fiber-reinforced concrete (BFRC) produced using various dosages of basalt fibers. The concrete mixture was designed with a target strength of 35 MPa (5075 psi), which is a typical strength for floor slabs and similar applications in which fiber reinforcement is often used. The concrete was tested for slump and air content in the fresh condition and for compressive strength, splitting tensile strength, flexural strength, and toughness in the hardened condition. Using these tests, the behavior of the BFRC was investigated and compared to fiber-reinforced concretes produced using similar dosages of polypropylene polyethylene synthetic fibers and crimped steel fibers. The basalt fibers were found to generally increase tensile and flexural strength (modulus of rupture), but were found to have very little effect on compressive strength and post-cracking behavior, and inspection found that the fibers had ruptured upon macrocracking.