International Concrete Abstracts Portal

Built in 1964, the John Coffee Memorial Bridge is a two-lane, 38-span, plate-girder bridge with a concrete deck that provides a direct route for travelers from Tennessee to Mississippi. Because of its scale, inspection is challenging. A recent evaluation was conducted to select appropriate restoration methods, using robotic tools that enabled nondestructive evaluations (NDEs) without the need for traffic control. This article describes these tools and summarizes the evaluation.

With the reduced availability of traditional supplementary cementing materials (SCMs), a need arises for alternatives. This study presents an investigation into the reactivity of powders derived from reactive siliceous aggregates, some of which demonstrated pozzolanic potential by reducing concrete expansion associated with alkali-silica reaction (ASR). A dissolution test was conducted to quantify the amounts of soluble silica and alumina available for pozzolanic reaction. The aggregate powders were immersed in an alkaline solution designed to simulate the alkalinity of concrete pore fluid and tested at four different temperatures to evaluate the effect of temperature on the dissolution behavior. These tests were performed in parallel with ASR expansion testing to determine whether dissolution data could serve as a rapid indicator of pozzolanic potential, reducing the need for long-term monitoring. The results indicated that dissolution kinetics varied significantly with temperature, raising concerns about the use of high-temperature methods to evaluate pozzolanic activity. Aggregate powders containing calcium exhibited notable physical changes, suggesting reactions involving both silica and calcium in the solution. A strong inverse relationship was observed between dissolved silica and aluminum concentrations; all solutions exhibited either high aluminum and low silica, or high silica and low aluminum, but never elevated levels of both simultaneously. Finally, the powders were analyzed using X-ray diffraction (XRD) to assess mineralogical changes following alkaline exposure. Cryptocrystalline quartz, muscovite, and kaolinite phases were altered during the dissolution test, whereas other phases, including crystalline quartz, did not.

Long-term testing of the cement is essential to evaluate the well integrity of oil, gas, geothermal, hydrogen storage, or carbon capture and sequestration (CCS). While most studies on cement testing focus on short-term curing, typically 28 days, this paper presents the mechanical and thermal testing results of neat Class G cement that has been cured for more than 300 and 750 days, respectively. Moreover, to analyze the effect of the curing days on the cement carbonation, two samples of Class G were used; the first sample was cured for 2,246 Days (6.15 Years), and the second was cured for 7 days before exposure to a CO₂ environment. The samples were placed in CO₂-saturated fresh water for 1,115 Days (3.05 years). After the exposure time, compressive strength, porosity, and phenolphthalein tests were performed. The long-cured sample showed less carbonation front and retained compressive strength, while the 7-day sample showed a deeper carbonation front, temporary and localized compressive strength, and higher porosity. The result of this study highlights the importance of long-term testing for a better understanding of cement behavior in a CO₂ environment.

An innovative automated experimental system is proposed for precise evaluation of cement dispersant performance. The system enables comprehensive rheological measurements of 230 mL mortar samples without human intervention, overcoming limitations of traditional manual testing methods. Our automated experiment platform incorporates a continuous-processing approach with precise control over sample preparation, including automated water and dispersant dosing via peristaltic pumps, programmed mixing sequences, and systematic rheological measurements through a specialized vane rotor system. The experimental sequence consists of dry mixing, water incorporation, final high-speed mixing, and rheological measurements at controlled rotational speeds, all executed automatically with consistent timing and conditions. This approach reduces the labor-intensive nature of conventional testing while enabling the collection of substantially more data points for comprehensive analysis. The system allows for finer increments in dispersant dosage evaluation and eliminates variations associated with manual handling, thereby providing more reliable and reproducible results. Combined with data science techniques including principal component analysis and observation-informed learning, this automated framework establishes a new paradigm for cement-based materials characterization and quality assessment, suitable for both research and industrial applications in concrete technology.

This article discusses the development and benefits of CEM II/C-M type low-carbon cements, highlighting their future role in reducing CO₂ emissions within the cement industry. It outlines key production strategies, including the use of quality improvers to enhance early strength and overall cement performance. Comprehensive laboratory testing assessed the durability of CEM II/C-M cements, revealing low shrinkage and robust resistance to water ingress and aggressive chemical agents such as chlorides. Additionally, these cements demonstrated adequate freeze-thaw and carbonation resistance, with performance comparable to standard cements. These findings underscore the potential of CEM II/C-M cements to meet the demands of sustainable construction while maintaining high performance standards. The article also showcases examples of industrial production and the application of these cements in concrete.