International Concrete Abstracts Portal

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.

In Japan, steel is mostly used to construct large-span buildings such as logistic terminals, office buildings, shopping malls, and medical facilities. However, in recent years with the fabrication cost of steel soaring, there is a concerted effort to reduce construction costs and at the same time increase productivity. Therefore, research investigations are being carried out and one of the methods involves using an innovative hybrid system where the columns are reinforced concrete and the beams are hybrid beams. In this study, concrete design strength, shear reinforcement ratio and length of RC section were altered to examine the structural performance of hybrid beams under flexural failure in a beam-column subassemblage. The results showed that ultimate flexural strength of a reinforced concrete section can be evaluated using an Architectural Institute of Japan abbreviated equation, and a coefficient of shear reinforcement of more than 2.5% will assure a plastic deformation capacity of more than 2%.