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Modern concrete construction depends on the application of water reducers and superplasticizers. Without their use, many placements would not be possible, and a significantly greater environmental impact would be realized. Their development in the United States in the early 1930’s is an example of innovation, recognition of potential new applications, competition, and, ultimately, cooperation. In this presentation the author, undoubtedly the last person alive who both knew individuals involved in this early development and participated in later development himself, will review how this very important technology was birthed.

BCSA cement is a rapid setting, rapid hardening cement that has been used extensively in pavement repair applications. Concrete made with this cement has also been shown to have excellent structural performance in terms of flexural strength and shear strength. Due to its rapid strength development and low shrinkage, it makes an ideal structural repair material, especially for important infrastructure that cannot be taken out of service for long periods of time. This presentation will detail the mix design development of a self-consolidating concrete (SCC) repair mixture made with BCSA cement. The process of developing this mixture and the properties of the rapid setting SCC will be described. Special considerations required in proportioning SCC with BCSA cement will be explained. Since the desired application of the mixtures is structural repair, descriptions of structural tests of damaged members repaired with BCSA cement SCC will be described and some preliminary results will be shared.

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One of the outstanding questions regarding use of alternative cements in concrete infrastructure systems is the corrosion potential of these systems. This study investigated a variety of commercially available alternative concrete systems, including two calcium sulfoaluminate-based systems, tracking changes in conductivity, microcell current, chloride infiltration, and initiation and propagation of corrosion through cracked and uncracked concrete and mortar specimens to provide a comparison of corrosion-related behavior between ACM and OPC systems.

Alternative cementitious materials (ACMs) such as calcium sulfoaluminate cement (CSA) have the potential to be successfully used in a variety of new structural applications. However, there is a significant concern about their ability to resist carbonation, which can result in accelerating the ingress of chloride and the corrosion of the steel reinforcement. In the same vein, the presence of cracks could drastically reduce the chloride threshold for the corrosion initiation of steel hence exacerbating the corrosion of steel reinforcement. In this study, the susceptibility to corrosion due to chloride ingress was accessed on several concrete mixtures produced with four different CSA based systems and one ordinary portland cement (OPC). Six samples were fabricated from each mix per ASTM G109 and subjected to three different pre-conditions prior to chloride exposuer: 1) two samples out of the six samples had cracks of a depth of 10 mm and width of 0.04 mm introduced in them during casting using a plastic shim inserted at the top of the mold; 2) another two out of the six were exposed to accelerated carbonation at 4% CO2 concentration and 57% RH for 28 days; and 3) the remaining two samples of the six were left without cracks or exposure to accelerated carbonation. The six samples for each mix were ponded with 3% NaCl (30g/liter of de-ionized water) for 2 weeks after which they were allowed to dry for another 2 weeks before the process is repeated. Microcell corrosion monitoring was conducted with Gamry testing equipment and software using the linear polarization resistance (LPR) technique. Whereas, microcell corrosion monitoring was done using a volunteer.

The serious CO2 footprint pertaining to the production of Portland cement has necessitated the development of alternative cementing materials with lower CO2 emission (Mo et al. (2015)). Calcium sulfoaluminate (CSA) cement represents an ecofriendly alternative to Portland cement owing to less CaCO3 input than Portland cement and hence has been drawing attention as a potential replacement of Portland cement (Chen and Juenger (2021)). Meanwhile, the characterization of cementitious materials exposed to weathering carbonation is of critical importance since most of these materials are typically jeopardized by the ambient atmosphere (Han et al. (2013)). In addition, the carbonation behavior of cementitious materials is a significant issue in relation to the concrete durability given that the carbonic reaction induces neutralization of the matrix and depassivation of reinforcing steel (Puertas et al (2005)). In particular, the carbonation-induced microstructural evolution of the reaction products in CSA cements is known to be significantly different from that in Portland cement (Seo et al. (2021)). In this regard, earlier works on the characterization of CSA cements exposed to accelerated weathering carbonation conditions will be summarized and presented.