International Concrete Abstracts Portal

The increased use of alternative deicers to rock salt and introduction of anti-icing prior to winter events using concentrated brines has, in some cases, been associated with deterioration of concrete, especially at joints in pavements. While many commercial products are being used, most either are sodium, calcium, or magnesium chlorides, or mixtures of chlorides. In this study, the effects of different concentrations of calcium and magnesium chlorides on concrete are compared to that of sodium chloride. This study, completed in 2009, found that highly concentrated calcium and magnesium chloride brines caused damage to concrete exposed to low-temperature and freezing temperature cycles by formation of expansive oxychlorides. These results were confirmed by subsequent extensive research performed by others. This paper focusses on concrete performance when exposed to the different forms of chlorides.

To overcome the time- and resource-intensive electrochemical assessments used to evaluate the pitting corrosion resistance of stainless steel (SS) rebar alloys, a non-destructive assessment tool such as the Pitting Resistance Equivalent Number (PREN) index is important for decision-making involving building resilient engineering structures. By addressing the limitations of the existing PREN index, initially designed for SS alloys in hightemperature acidic or neutral environments, this study sought to develop a PREN index tailored for highly alkaline ambient-temperature concrete environments through a combination of electrochemical experimental analysis and machine learning modelling. This integrated approach and newly developed PREN index account for variations in SS alloying composition, concrete alkalinity, and environmental exposure conditions, addressing the growing demand for non-destructive, time- and cost-effective, and reliable alternatives for assessing SS rebar corrosion performance. Developed PREN will aid design of new and selection of existing SS alloys for reinforced concrete structures across diverse localities and applications. Two major formulas were reported, one for electrochemical parameters and the other for PREN related to these electrochemical parameters, each establishing their relationship with major SS alloying elements (i.e., Cr, Ni, Mo, Mn), concrete type (i.e. pH of testing solution), and concentration of deleterious species in exposure environment (i.e. chloride, sulphate). This study marks an initial step toward developing a non-destructive corrosion-performance assessment tool for civil engineering applications.

The electrical properties of concrete are being increasingly used to assess concrete resistance to fluid transport. Electrical measurements are strongly dependent on sample conditioning, which includes the degree of saturation. This paper presents an analytical approach for interpreting electrical measurements in partially saturated concrete. Previous approaches have used a power law to describe the influence of saturation. This paper proposes a saturation function that accounts for the contributions of the entrained air voids, the capillary pores, and the gel pores (the GCA function). The proposed approach is demonstrated for high performance, internally cured concrete mixtures tested between the ages of 30 d and 120 d. The power function had a greater measured uncertainty than the GCA function, which performed better at both high and low degrees of saturation. The resistivity of specimens submersed in simulated pore solution was measured as was the resistivity of sealed specimens. The sealed specimens have a degree of saturation that is similar to those at the nick point (matrix saturation), with an offset consistently only due to the self-desiccation of the binder.

Due to the low lateral stiffness of slabs supported on columns alone reinforced concrete flat plates are typically combined with other structural elements, such as shearwalls. In these structures, the slab-column connections are designed to carry gravity loads only, and the shearwalls, which also carry gravity loads, are required to resist the lateral forces. Therefore, the slab-wall connections (SWCs) are essential for the adequate performance of both the gravity and lateral force resisting systems. However, the majority of punching shear research and design provisions have been focused on slab-column connections, even though punching failures around slab-wall connections have been observed experimentally. Empirical testing of slab-wall connections is difficult due to the required specimen size. This paper investigates the punching shear behaviour of interior slab-wall connections subjected to concentric vertical loading, and combined concentric vertical loading and uniaxial unbalanced moment using a plasticity-based nonlinear finite element model (FEM) in Abaqus. The FEM, developed to study the impact of column aspect ratio on punching shear, was calibrated considering seven isolated slab-column specimens. The analysis of isolated slab-wall connections demonstrates that punching failures can occur before one-way shear failures, although the connection capacity is much higher than the expected loads in most structures. Punching shear design methods for interior slab-wall connections subjected to gravity load only, developed from finite element analysis results, are developed and presented in the paper.

Ultra-high-performance concrete (UHPC) is an advanced cementitious composite material with extraordinary mechanical and durability properties. This article discusses the construction of a short-span bridge using UHPC as well as the cost considerations associated with building an entire bridge with UHPC and reflects on lessons learned from the process.