Concrete sandwich wall panels (CSWPs) have been constructed since the early 1900s using various wythe connectors, panel geometries, and construction methods to create a structurally and thermally efficient system. Initially, thermal bridging hindered thermal efficiency due to the concrete connections and steel bars used to transfer interface forces between the concrete wythes. This issue was mitigated with the advent of polymer connectors, now widely used in the precast and tilt-up industries. As a result, CSWPs now offer buildings an efficient envelope, aiding in energy savings and reducing the need for additional construction materials and therefore contributing to the construction industry’s sustainability goals. This paper examines the current state of the practice in CSWP construction, focusing on CSWP’s construction methods, sustainability, material selection, and design processes. This manuscript delves into the history of CSWPs and showcases projects ranging from housing to industrial applications. Moreover, the materials and hardware popularly used in their construction are reviewed from the practicing engineer and researcher’s point of view and other aspects, such as environmental, architectural, and structural design, are presented. The most popular construction methods and approaches when precasting these panels on- or off-site and their associated challenges are also presented. Lastly, current deficiencies in CSWP design and construction are outlined and future directions for research and practice are suggested to advance this field further.

This paper presents an iterative sandwich beam theory (ISBT) and a simplified version suitable for the design termed simplified sandwich beam theory (SSBT) used to predict the elastic mechanics of partially composite insulated concrete sandwich wall panels (SWPs) under flexural, axial, and thermal loads. These solution methods expand upon closed-form solutions to create a more general analysis technique. Design and analysis of SWPs are handled largely outside of codified documents and are almost exclusively designed such that they will remain within the elastic range. The presented ISBT and SSBT methods have been used in the United States precast industry since 2017 and are implemented in widely available software, LECWall, as of 2020, for predicting elastic deflections and stresses. In this paper, the ISBT and SSBT solution methods are validated with experimental data from the literature and using finite-element analysis. For the ISBT cracking moment and deflection, the measured-to-predicted ratio were 0.99 and 1.0 with coefficients of variation (COVs) of 0.10 and 0.11, respectively. For the SSBT cracking moment and deflection, the measured-to-predicted ratio was 0.99 and 0.99 with COVs of 0.21 and 0.19, respectively. For thermal loading, the ISBT and SSBT deflection m easured-to-predicted ratios were 0.95 and 0.90, respectively. The model was then used to investigate the behavior of sandwich wall panels under varying load combinations and with various section and material properties to demonstrate the robustness of the presented methods.

Cracking in concrete structures is a ubiquitous problem and affects the serviceability of such structures. In many cases, it is imperative to properly measure and monitor a crack’s size to identify locations for repair and rehabilitation. This paper describes two field studies that used digital image processing to measure the width of cracks in concrete structures. The first field study compared crack measurements from digital image processing, a handheld microscope, and a crack gauge card. In the second field study, digital image processing was used to measure end region cracks in precast pretensioned concrete girders. Guidance is provided for engineers who wish to use digital image processing in field studies. Conditions where digital image processing may lead to errors are identified, and limitations of the methods are discussed. In general, the studies demonstrate that image processing methods can efficiently measure the size of cracks in concrete structures in field settings and that image-based measurements are comparable to microscope measurements.

Welded-wire reinforcement (WWR) is widely used as the main reinforcement in bridge decks and vertical shear reinforcement in concrete bridge girders. Previous studies on concrete members reinforced with WWR have indicated that the reduced ductility of the cold-drawn wires leads to lower member ductility and rupture of shear reinforcing steel at failure. Additionally, the influence of the heat-affected zones created at the electric-resistance welds raises concerns regarding the mechanical behavior at the welded connections. To evaluate the fracture behavior of WWR meshes, an experimental program was developed involving tensile and Charpy V-notch (CVN) specimens sampled from straight bars and welded intersections. Due to size constraints, both full and subsized CVN specimens were tested, and a variety of size correction methods were trialed for degree of accuracy in comparing the two sizes of specimens tested. Tensile tests showed that the cross-welds decreased ultimate strain by an average of 10% without significantly altering yield stress, ultimate strength, or elongation at fracture. CVN tests indicated that the cross-weld tended to increase impact toughness by up to $30\mathrm{J}$ ($22\mathrm{ft}\text{-}\mathrm{lbf}$ ) as the longitudinal and transverse bars became closer in size. Experimental values are evaluated using statistical methods and compared to specification minimums in American and European standards.

Three-dimensional (3D) concrete printing has emerged as a promising technology for revolutionizing construction practices, offering unparalleled flexibility and efficiency in building complex structures. However, the successful implementation of 3D concrete printing relies heavily on the development of appropriate mixture designs tailored to the unique requirements of additive manufacturing. This paper presents a comprehensive review of mixture properties critical for successful 3D concrete printing, including pumpability, extrudability, and constructability, and summarizes published concrete mixtures tailored for optimal 3D printing performance. Key aspects of the mixture designs include water-cement ratio, fly ash, silica fume, superplasticizers and viscosity-modifying agents, and fibrous additions. This paper serves as a valuable resource for researchers, engineers, and practitioners involved in 3D concrete printing, fostering continued innovation and refinement in mixture design methodologies to advance the adoption of this transformative construction technology.