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.

Cast-in-drilled-hole (CIDH) piles are often constructed to depths that are inaccessible, and internal vibration is not performed over the length of the pile. Because of this, the likelihood of voids occurring increases. Many state highway agencies use inspection pipes to detect if voids are present along the length of the pile. High reinforcement densities and concrete void detection inspection pipes can congest CIDH piles. Although concrete void detection and reinforcement spacing are critical to ensuring adequate CIDH pile structural performance, eliminating concrete voids can also ensure expected performance. This research will assess the influence of coarse aggregate (CA) type and mixture proportions on concrete workability for CIDH pile applications. Results indicate that identifying an optimal paste volume-to-aggregate void ratio (PV/AV) can be used to proportion flowing concrete (FC) mixtures with adequate slump flow and stability. Concrete containing rounded CA achieved higher slump flow values than concrete with crushed CA at the same paste volume. However, increasing PV/AV also decreased stability. Stability was increased by increasing the FA-to-CA ratio (FA/CA).

A pilot-scale field investigation was conducted through which: 1) a refined ultra-high-performance concrete (UHPC) mixture was prepared in a ready mixed concrete plant; 2) a large reinforced UHPC block was constructed through placement, consolidation, and finishing of UHPC; and 3) a commonly available concrete curing (insulating) blanket was applied for field thermal curing of the UHPC block using the exothermic heat of hydration of the cementitious binder in UHPC. Monitoring of the reinforced UHPC block temperature over time confirmed the development of a reasonably uniform temperature and a viable temperature time history, which suited thermal curing of UHPC without any heat input. In-place nondestructive inspection of the reinforced UHPC structure pointed at timely setting and strength development, leading to achievement of ultra-high-performance status. Specimens were cored from the large reinforced concrete block and subjected to laboratory testing. The experimental results indicated that the field thermal curing was more effective than the laboratory thermal curing considered in the project, and that the pilot-scale production of the UHPC mixture produced compressive strengths approaching 170 MPa (24.7 ksi).