International Concrete Abstracts Portal

The Modulus of elasticity of concrete is typically estimated using numerical models that consider factors such as the compressive strength of the concrete, aggregate properties, unit weight of concrete, and water-cement ratio. The most used equation depends on the relationship between the compressive strength of the concrete and its Modulus of elasticity. However, this simplified formula may provide an inaccurate estimate of the Modulus of elasticity of concrete containing different types of aggregates under varying loading conditions. More sophisticated models can be used to accurately estimate the Modulus of elasticity for specific applications, such as expressions involving the unit weight of concrete. This study presents a probabilistic update to the expressions used for estimating the Modulus of elasticity of concrete based on an extensive database of over 2600 experimental tests from 20 different studies. Bayesian Inference was used to update the currently proposed models, allowing for the determination of the expressions representing the trends of the current database along with their associated uncertainties. The updated expressions were formulated considering either the compressive strength of concrete or both the compressive strength and the unit weight as input parameters. Expressions for estimating the Modulus of elasticity, considering the aggregate's origin, were also updated. This comprehensive approach enhances the accuracy and reliability of predicting the Modulus of elasticity, providing valuable insights and tools for concrete structures' design and structural reliability analysis.

Researchers have concentrated on the durability characteristics of textile-reinforced cementitious composites with quartz and silica sand. To make it easily available for construction, this study explores the durability characteristics of cementitious composites (CC) with the available manufactured sand before applying it to textile reinforcement. It is more important to study the durability characteristics as the main aim of its application is to construct thin structures without coarse aggregate. Thus, the durability and microstructural characteristics of basalt fiber-reinforced fine-grained cementitious composites incorporated with ground granulated blast-furnace slag (GGBS) as a partial substitution of cement (BFRFGC) are studied. The CC were exposed to different exposure conditions such as acidic environment, alkaline environment, and elevated temperature. Then its visual appearance, change in weight, and strength are studied per the code provisions at several exposure ages. In addition, microstructural studies were also performed at different exposure conditions and were compared with the specimens before exposure. The BFRFGC showed 61.93 and 27.58% lower strength and weight change than controlled fine-grained cementitious composites (CFGC) under extreme conditions (i.e., exposure to sulphuric acid). Also, the results from microstructural studies reveal that basalt fiber (BF) and BFRFGC are resistant to all these conditions. Subsequently, BFRFGC has superior resistance under various exposure conditions and excellent durability characteristics.

With a well-thought-out packing theory for sand, fine aggregates, cement, a water-cement ratio lower than 0.2, and steel fibers, ultra-high-performance concrete (UHPC) achieves remarkable mechanical properties. Despite UHPC’s superior mechanical properties compared to conventional concrete, its use remains limited, especially in structural applications, due to factors such as high cost, lack of design standards and guidelines, and inadequate correlation between material properties and structural behavior. By compiling and synthesizing the behavior of 70 structural- or full-scale axial UHPC columns, this research provides a new set of generalized design and detailing guidelines for axial UHPC columns. The study first uses the assembled database to assess and revisit the current ACI 318 axial strength design factors for applicability for UHPC. Next, the behavior trends are carefully analyzed to provide detailed recommendations for proper transverse reinforcement (ρt volume), spacing-to-longitudinal reinforcing bar diameter ratio (s/db, where s represents the centerline-to-centerline spacing between transverse reinforcement), and UHPC steel fiber ratio for best use of confinement.

Fiber-reinforced polymer (FRP) reinforcements have been used in versatile forms in recent construction practices to enhance durability performance and, consequently, to attain longevity of concrete structures. The shear strength of FRP-reinforced concrete (FRP-RC) beams holds significant importance in structural design. However, inherent analytical uncertainty exists concerning shear in concrete members due to the distinctive material characteristics of FRP bars compared to conventional steel reinforcements, such as their low axial stiffness and bond properties. This study aims to identify the shear-resistance mechanisms developed under combined actions between concrete and FRP reinforcements. To this end, the dual-potential capacity model (DPCM) was extended to FRP-RC beam members subjected to shear and flexure, and an attempt was also made to derive a simplified method. To validate the proposed approaches, a total of 437 shear test results from RC members incorporating FRP bars were used. Findings indicate that the proposed methods can provide an acceptable level of analytical accuracy. In addition, a significant shift in the shear failure mode of FRP-RC members with no stirrups was observed from the compression zone to the cracked tension zone as the FRP reinforcement ratios increased. Conversely, when FRP stirrups were added, the shear failure mode was mostly dominated by the compression zone.

An experimental investigation was conducted to evaluate the shear-friction capacity of cylindrical pocket connections without reinforcement crossing the interface, which is a common connection detail between precast concrete substructure elements. Current Code expressions for shear-friction capacity include components for cohesion or aggregate interlock and contribution from steel crossing the interface or a clamping force. These expressions were primarily derived and calibrated based on pushoff tests with reinforcement crossing the shear plane, which do not represent the behavior of the shear plane in a cylindrical pocket connection. Thirty-four large-scale specimens were built and tested to investigate the shear friction of the cylindrical pocket connection without reinforcing steel crossing the shear plane. This experimental study showed that current Code expressions provided conservative estimates for this connection. A revised proposed theory is presented that more accurately predicts the shear-friction capacity of this connection without interface steel.