International Concrete Abstracts Portal

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.

This paper describes the experimental testing of a reinforced concrete tessellated shear wall. The wall specimen was tested as part of a National Science Foundation-funded research project designed to demonstrate the concept of tessellated structural-architectural (TeSA) systems. TeSA systems are constructed of topologically interlocking tiles arranged in tessellations, or repeating geometric patterns. As such, these systems are designed with easy repair and reuse in mind. The specimen discussed in this paper is a TeSA shear wall constructed from individually precast I-shaped tiles. This paper presents the results of reverse cyclic loading of the specimen, including load-displacement behavior, crack propagation, and energy dissipation. A simplified analytical model for predicting the wall’s flexural capacity is also discussed.

Mixed recycled aggregate (MRA) is considered a sustainable construction material, and its use in precast concrete is currently banned due to its poor engineering performance. This paper aims to evaluate the feasibility of partial replacement of natural coarse aggregate with MRA in self-consolidating concrete (SCC) for manufacturing architectural precast concrete sandwich wall panels. To this end, five MRAs from recycling plants were characterized, out of which two were selected to develop SCC. SCC mixtures with three replacement levels and three water compensation degrees were produced, and their physical, mechanical, durability, and aesthetic properties were examined. The results showed that the incorporation of MRA dominated the mechanical properties of SCC, while the water compensation degree primarily affected the flowability and carbonation resistance. The presence of MRA had no considerable effect on the aesthetic characteristics. Up to 10% MRA in weight of total aggregates could be used in precast SCC.

Reinforced concrete (RC) shear walls are used as a part of the lateral load-resisting system of the majority of the high-rise buildings all over the world. Due to architectural or mechanical reasons, openings may be required to be provided in these walls. These openings affect the behavior of RC shear walls and their lateral load-carrying capacity; however, these openings are unavoidable. Accordingly, strengthening these walls using fiber-reinforced polymers (FRPs) is one of the effective methods to increase their shear capacity. In this research work, the effect of openings on the behavior of RC squat shear walls has been investigated using finite element (FE) software (ANSYS) under lateral cyclic loading conditions. Also, this study aims to figure out the enhancement in the lateral load-carrying capacity of these walls when being strengthened by carbon FRP (CFRP) sheets with a specific strengthening scheme. It has been found that both the size and the location of the opening significantly affect the wall’s lateral load-carrying capacity. To avoid the severe effect of the near-edge-positions of the opening, it is recommended to locate the opening at the wall’s center. On the other hand, the opening size has the largest effect of any other factor. Finally, the used CFRP strengthening system around the opening has proven its reliability in enhancing the nonlinear performance of RC shear walls with opening and increasing the shear capacities of these walls. It has been found that the enhancement in the shear capacities depends mainly on the location of the constructed opening.

Three-dimensional (3D) printing, also known as additive manufacturing, is a revolutionary technique, which recently has gained a growing interest in the field of civil engineering and the construction industry. Despite being in its infancy, 3D concrete printing is believed to reshape the future of the construction industry because it has the potential to significantly reduce both the cost and time of construction. For example, savings between 35 and 60% of the overall cost of construction can be achieved by using this technique due to the possibility of relinquishing the formwork. Moreover, this innovation would free up the architectural gesture by offering a wider possibility of shapes. However, key challenges should be addressed to make this technique commercially viable. The effect of mixture composition on the rheological properties of the printed concrete/mortar is vital and should be thoroughly investigated. This paper investigates the effect of using red mud, nanoclay, and natural fibers on the fresh and rheological properties of 3D-printed mortar. The rheological properties were evaluated using the penetrometer test, flow table test, and cylindrical slump test. The estimated yield stress values were then calculated based on the cylindrical slump test. Further, relationships between the tested parameters were established. The main findings of this study indicate that the use of an optimum dosage of a nanoclay was beneficial to attain the required cohesion, stability, and constructability of the printed mortar. The use of natural fibers reduced pulp flow by improving cohesion with a denser fiber network and reducing the cracks. With respect to red mud, it may be appropriate for printable mortar, but more testing is still required to optimize its use in a printable mixture. A printability box to define the suitability of mixtures for 3D printing was also established for these mixtures.