International Concrete Abstracts Portal

The pressure of urbanization and the increasing concerns about climate change are pushing the construction industry to find new solutions for infrastructure development with low environmental impact. Additive construction offers several benefits, including the possibility of creating complex shapes without formwork, reducing labor, and utilizing locally available materials, thus resulting in an optimization of the construction process and less CO2 emission. The performance of 3-D printing systems at both the material and structural level has been extensively studied in recent years. Yet, results remain scattered and challenging to homogenize given the diversity of adopted materials, printing scale and process, and testing protocols. This study introduces a framework for experimentally and numerically evaluating the performance of 3D-printed cementitious materials and systems. Printed mortar samples were constructed and tested under different loading conditions, and their performance was compared to that of traditional cast mortar. The constitutive response and damage patterns of the tested specimens were recorded and analyzed. Concurrently, detailed finite element models were developed explicitly simulating the orthotropic contact properties at the interface between the printed layers. This had a twofold objective: (1) allow an in-depth mechanics-based interpretation of the experimental results, and (2) calibrate the numerical model for subsequent utilization in sensitivity analyses. Preliminary results suggest that ordinary finite element models can be adopted for the analysis of additively constructed structural systems after calibration of subsets of the layers’ interface properties depending on the loading plane, thus relieving the need to employ heavily sophisticated models.

This study investigates the bonding behavior of large-diameter steel bars (D43 and D57) embedded in concrete using pull-out tests coupled with acoustic emission (AE) monitoring. These large bars, commonly used in nuclear containment structures from the 1970s, were compared with conventional steel bars (D19 and D32) across three concrete strength levels. All tests were performed under displacement-controlled loading using an MTS testing machine. Results indicate that ACI 408R provisions remain valid for large-diameter reinforcing bars. The test results showed that when specimens reached ultimate bond stress, the D57 bar developed only 12 to 16% of its yield strength, whereas the D19 bar reached at least 70%. AE monitoring effectively captured the debonding process, and cumulative AE hit counts correlated with the strain energy released at each loading stage, offering insight into bond failure mechanisms.

This study investigates the structural performance improvement when bond beams are included in stack bond walls. Nine 4.0 m x 2.4 m x 0.20 m masonry walls were tested under out-of-plane and axial loads. The walls were constructed in three configurations: running bond, stack bond without bond beams, and stack bond with bond beams, following TMS 402/602 standard. Results show similar failure patterns and crack formation between running bond and stack bond walls, but stack bond walls with bond beams exhibited distinct behavior. Stack bond walls with bond beams showed slightly higher out-of-plane flexural capacity compared to running bond walls, with a difference ranging from 4 to 5%. These findings provide valuable insights for evaluating the structural performance of concrete masonry walls with different bonding patterns. This study suggests a potential revision to the Canadian (CSA S304) masonry design standard, potentially lifting restrictions on stack bond masonry wall construction.

Accelerated carbonation treatment is recognized as an effective method for enhancing recycled aggregates (RA), but its potential in structural concrete, particularly with respect to seismic performance, remains underexplored. To address this gap, this study is the first to integrate mesoscale modeling with structural finite element analysis (FEA) to systematically investigate the seismic behavior of carbonated recycled aggregate concrete (CRAC) shear walls under dynamic loading. At the material scale, uniaxial compression tests on CRAC cylindrical specimens with varying replacement ratios were conducted to evaluate their stress–strain behavior and mechanical properties. A mesoscale model of CRAC was developed using a random aggregate placement method, and FEA was employed to extend the analysis of replacement ratios. At the structural scale, a CRAC shear wall FEA model was established, incorporating the material-level stress–strain relationships into cyclic lateral loading simulations. Parametric analysis revealed that increasing both the axial load ratio and the replacement ratio significantly reduced the seismic performance of CRAC shear walls, with a maximum reduction of 21.7%. Based on these findings, recommended ranges for RA replacement ratios and axial load ratios are proposed, providing practical guidance for the structural application of CRAC.

In this study, the behavior of diaphragm-to-wall connections with collector reinforcement and construction joints was investigated. Four slab-to-wall connection specimens were tested under cyclic loading. Diaphragm connection details, such as shear friction reinforcement (i.e., slab dowel bars anchored by 90-degree hooks within the wall) and the use of spandrel beams as collectors, were considered as test variables. When fabricating the specimens, concrete was consecutively cast for the wall and slab, and construction joints were placed on the sides of the wall and spandrel beams. The tests showed that the diaphragm connections exhibited the typical ductile behavior characterized by the robust initial stiffness and subsequent post-yield plastic behavior. Before concrete failure on the front of the wall, the load transfer from the diaphragm to the wall was governed by a nodal zone action; then, the subsequent connection behavior was dominated by shear friction as sliding failure occurred on the side of the wall along the slab construction joints. The diaphragm-to-wall connection strengths were evaluated using the strut-and-tie model and shear friction theory. The calculated strengths were in good agreement with the test strengths. Based on the investigation results, design considerations of the diaphragm-to-wall connection were proposed.