International Concrete Abstracts Portal

As global demand for concrete has been forecasted to keep rising, one of the approaches towards more sustainable constructions is the adoption of mix designs replacing conventional ones. The current study contains a comparison between concrete mixes that constitutes only Ordinary Portland Cement (OPC) and mixes incorporating 25% OPC with a 75% replacement by supplementary cementitious materials (SCM). The major experimental hypothesis circles around investigating whether it is effective to use thermal treatment under moderately elevated temperatures to enhance the physical and mechanical properties of concrete. Comparisons were performed using mechanical tests such as: compressive strength, tensile strength, flexural strength, and through several non-destructive physical experiments as well as microstructural investigation using SEM and EDS. In conclusion, the experimental results have shown a mostly positive influence observing significant enhancements after thermal treatment. However, treated concrete mixes that constitute only OPC seem to excel in overall performance compared to those incorporating SCM.

The term “mass concrete” characterizes a specific concrete condition that typically requires unique considerations to mitigate extreme temperature effects on a structure. Mass concrete has historically been defined by the physical dimensions of a massive concrete element with the intent of identifying when differential temperatures may induce early-onset cracking, leading to reduced service life. More recently, in addition to differential temperature considerations, extreme upper temperature limits have been imposed by the American Concrete Institute to prevent long-term concrete degradation. Studies dating back to 2007 show shafts as small as 48 in. (1.2 m) in diameter can exceed both differential and peak temperature limits; in 2020, augered cast-in-place piles as small as 30 in. (0.76 m) in diameter exceeded one or both limits. This suggests the term “mass concrete” is misleading when considering today’s high-early-strength or high-performance mix designs. This study applies numerical modeling coupled with field measurements to investigate the effects of concrete mix design, drilled shaft diameter, and environmental conditions on heat energy production and temperature. Further, the outcome of this study focuses on developing criteria that combine the effects of both size and cementitious material content to determine whether unsafe temperature conditions may arise for a given drilled shaft design.

Additive construction augments the laborious construction of structural concrete; however, its implementation remains mostly limited to building envelopes. Culvert construction benefits from alternative methods due to the high demand for transportation infrastructure. In this study, extrusion-based 3-D concrete printing (3DCP) is developed for the first time for culvert construction. Large-scale unreinforced concrete pipes were printed, and the early-stage (e.g., buildability), mechanical, and durability properties of two commercially available 3DCP materials were determined. Additionally, the specimens were tested structurally and exceeded the expected structural performance (by about an average of 32%) under the three-edge bearing test. However, the desired durability was not met due to the porosity of the specimens. The mix design with microfibers exhibited marginally higher compressive and tensile strength, but did not meet durability criteria similar to non-fiber material. Results indicated the 3DCP feasibility for pipe culvert construction and mapped further direction for widespread implementation and addressing concrete pipe durability issues.

Engineered cementitious composite (ECC), a prominent innovation in the realm of concrete materials in recent years, contains a substantial amount of cement in its composition, thereby resulting in a significant environmental impact. To enhance the environmental sustainability of ECC, it is plausible to substitute a large portion of cement in the composition with fly ash, a by-product of coal-fired power plants. Recent years have seen increased research in ECC containing high-volume fly ash (HVFA) binder and its wider application in construction practices. In this particular context, it becomes imperative to review the role of HVFA binder in ECC. This review first examines the effects of incorporating HVFA binder in ECC on the fiber dispersion and fiber-matrix interface behavior. Additionally, mechanical properties, including compressive strength, tensile behavior, and cracking behavior under loading, as well as durability performances of HVFA-based ECC under various exposure conditions, are explored. Last, this review summarizes the research needs pertaining to HVFA-based ECC, proving valuable guidance for future endeavors in this field.

This study investigated the flexural behavior and seismic connection performance of precast lightweight aggregate concrete shear walls (PLCWs) using the relative emulation evaluation procedure specified in the Architectural Institute of Japan (AIJ). Six PLCW specimens connected through a bolting technique were prepared and tested under constant axial and cyclic lateral loads. In addition, three companion shear walls connected through the most commonly used spliced sleeve technique for precast concrete members were prepared to confirm the effectiveness of the bolting technique for the seismic connection performance. The main parameters were the concrete type (all-lightweight aggregate (ALWAC), sand-lightweight aggregate (SLWAC), and normal-weight concrete (NWC), the compressive strength of the concrete, and the connection technique. The test results showed that none of the specimens connected through the conventional spliced sleeve technique reached the allowable design drift ratio specified by the AIJ, indicating that the spliced sleeve is an unfavorable technique for obtaining a seismic connection performance of PLCWs equivalent to that of cast-in-place reinforced concrete shear walls. However, the specimens made of ALWAC or NWC and connected through the bolting technique not only reached the allowable design drift ratio specified by the AIJ but also satisfied the requirements of the seismic connection performance (lateral loads and allowable error at yield displacement) within the allowable design drift ratio. Consequently, the displacement ductility ratio of the specimens connected through the bolting technique was 1.52 times higher than that of the specimens connected through the conventional spliced sleeve technique, respectively. This difference was more prominent in the specimens made of ALWAC than in those made of SLWAC or NWC. Thus, the use of the bolting technique as a wall-to-base connection in shear walls can effectively achieve a seismic connection performance equivalent to that of cast-in-place shear walls while maintaining the medium ductility grades.