International Concrete Abstracts Portal

Crack densities obtained from on-site surveys of 74 bridge deck placements containing concrete mixtures with paste contents between 22.8% and 29.4% are evaluated. Twenty of the placements were constructed with a crack-reducing technology (shrinkage-reducing admixtures, internal curing, or fiber reinforcement) and 54 without; three of the decks with fiber reinforcement and nine of the decks without crack-reducing technologies involved poor construction practices. The results indicate that using a concrete mixture with a low paste content is the most effective way to reduce bridge deck cracking. Bridge decks with paste contents exceeding 27.3% had a significantly higher crack density than decks with lower paste contents. Crack-reducing technologies can play a role in reducing cracking in bridge decks, but they must be used in conjunction with a low paste content concrete and good construction practices to achieve minimal cracking in a deck. Failure to follow proper procedures to consolidate, finish, or cure concrete will result in bridge decks that exhibit increased cracking, even when low paste contents are used.

The production of Ordinary Portland Cement (OPC) is a major contributor to carbon emissions. One immediate and viable solution is the use of optimized concrete mixtures that employ a decreased quantity of cement and increased dosage of high-range water-reducing (HRWR) admixtures. This study investigates five different concrete mixtures with varying w/c (0.37 to 0.42) and reduced cement contents. The mixtures with “low cement + high dosage HRWR admixture” content had over 30% increase in mechanical strength and presented 40% lower water absorption, and 68 to 97% higher formation factor, indicating enhanced durability. The optimized concrete mixtures with reduced cement and lower w/c have a service life increase of up to 117% and a life-cycle cost reduction of 29%. The application of “low cement + high dosage HRWR admixture” mixtures can improve the sustainability of concrete mixtures by reducing cement and water contents and increasing the service life of concrete in severe environments.

This study investigates the impact of under-sulfated cement combined with high-calcium fly ash and lignosulfonate-based admixtures in ready mixed concrete, leading to rapid stiffening and delayed setting. Using an on-board slump-monitoring system (SMS) installed on a ready mixed concrete truck, significant increases in water demand were recorded to maintain target slumps, with mixtures showing minimal slump response to water additions. Laboratory tests, including isothermal calorimetry and mortar trials, confirmed the under-sulfated cement’s inadequate sulfate levels as the cause. Optimal sulfate addition was determined through calorimetry, and adjustments with gypsum effectively remedied rapid stiffening and delayed setting. This research demonstrates that an SMS can detect undesirable combinations of cement, fly ash, and admixtures in concrete, allowing real-time corrections. It underscores the importance of optimized sulfate levels in cement, particularly when using high-calcium fly ash combined with some high-range water reducers, to achieve desired concrete performance under varying field conditions.

Engineered cementitious composites (ECC) represent a significantinnovation in construction materials due to their exceptionalflexibility, tensile strength, and durability, surpassing traditionalconcrete. This review systematically examines the composition,mechanical behavior, and real-world applications of ECC, with afocus on how fiber reinforcement, mineral additives, and micromechanical design improve its structural performances. The present study reports on the effects of various factors, including different types of mineral admixtures, aggregate sizes, fiber hybridization, and specimen dimensions. Key topics include ECC’s strain hardening properties, its sustainability, and its capacity to resist crack development, making it ideal for high-performance infrastructure projects. Additionally, the review discusses recentadvancements in ECC technology such as hybrid fiber reinforcementand the material’s growing use in seismic structures. The paper also addresses the primary obstacles, including high initial costs and the absence of standardized specifications, while proposing future research paths aimed at optimizing ECC’s efficiency and economic viability.

This study investigates the impact of air-entraining admixtures (AEAs) on mortar performance, focusing on fresh-state and hardened-state properties critical to durability and engineering applications. Ten distinct mortar mixtures were analyzed, following guidelines established by the European Federation of National Associations Representing Producers and Applicators of Specialist Building Products for Concrete (EFNARC). AEAs were introduced at varying proportions (0.01 to 0.5% of cement weight) to evaluate their effects on intrinsic properties (density, void ratio, and water absorption), rheological parameters (plastic viscosity and yield stress), and mechanical characteristics (compressive strength, ultrasonic velocity, and modulus of elasticity). Regression models were developed and yielded high predictive accuracy, with R2 values exceeding 0.98. Notably, ultrasonic velocity and modulus of elasticity demonstrated strong correlations with intrinsic properties across all curing ages. Similarly, compressive strength showed significant associations with rheological parameters, highlighting the influence of air content and flow behavior on structural performance. These findings offer precise quantitative models for predicting mortar behavior and optimizing formulations for enhanced performance.