International Concrete Abstracts Portal

This research aims to prepare porous ceramsite with low thermal conductivity. The porous ceramsite was also used as fine aggregate to substitute the river sand in pumice concrete. Its impact on improving the thermal insulation performance of pumice concrete was thoroughly investigated. The experimental method included high-temperature calcination, transient planar heat source analysis, as well as the use of X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Mercury-Intrusion Porosimetry (MIP) techniques. The investigation revealed that the best calcination parameters were a preheating temperature of 400°C, a preheating duration of 25 minutes, a calcination temperature of 125°C, and a calcination duration of 25 minutes. Under these conditions, the crushing index of the porous ceramsite was determined to be 29.1%, with a thermal conductivity of 0.138 W/(m·K). It is worth noting that an increase in calcination temperature promotes the hole content in ceramsite, leading to a 52.19% increase in macropore volume and a corresponding decrease in thermal conductivity. Furthermore, as the replacement rate of ceramic aggregate increases, the thermal conductivity of pumice concrete gradually decreases, with values ranging from 18% to 34.8%. This reduction occurs because the replacement elevates the volume of coarse capillary pores and non-capillary pores in pumice concrete, increasing by 13.9 to 91.3% and 63.1 to 128.5%, respectively. Additionally, a prediction model for the thermal conductivity of pumice concrete has been established using the Mori-Tanaka homogenization method. The model's verification accuracy falls within an error range of 5%, demonstrating its effectiveness in accurately predicting the thermal conductivity of pumice concrete.

A twin-screw extruder was employed to melt-blend polylactic acid (PLA), bamboo fibers (BF), aluminum diethyl pyrophosphate (ADP), melamine cyanurate (MCA), and polyethylene glycol (PEG). In the PLA/BF/PEG ternary composite, increasing PEG dosage reduced mechanical properties. Conversely, in the PLA/BF/ADP/MCA/PEG multicomposite, higher PEG content enhanced mechanical performance. Compared with PLA/BF composites, the addition of ADP, MCA, and PEG increased the melt flow index by over 15-fold, with MCA-containing composites showing a 24-fold improvement. Both PEG-containing and non-PEG PLA/BF/ADP/MC composites achieved UL94 V-0 flame retardancy ratings, with oxygen barriers ranging between 24 and 26 vol%. Importantly, while maintaining the UL94 V-0 rating, the introduction of PEG improved mechanical properties through more uniform dispersion of bamboo fibers.

This study presents a machine learning–driven framework for the sustainable design of ultra-high-performance concrete (UHPC) mixtures with a focus on maximizing flexural strength while minimizing material cost and embodied CO₂ emissions. A curated dataset of 333 UHPC mixtures was developed, incorporating 13 input features including binder composition, steel fiber dosage, and curing parameters. A Bayesian Neural Network (BNN) was trained to predict flexural strength with high accuracy (R² = 0.936, RMSE = 1.37 MPa, MAE = 1.09 MPa), supported by residual analysis confirming minimal prediction bias and robust generalization. SHAP analysis was used to interpret model predictions and identify key drivers of flexural behavior—namely, curing time, steel fiber dosage, and silica fume content. The BNN was coupled with the NSGA-III algorithm to perform multi-objective optimization and generate Pareto-optimal UHPC mixtures. A utility-based scoring method was introduced to select designs aligned with different project priorities—enabling the identification of fiber-rich, high-strength mixtures as well as low-emission, cost-efficient alternatives. The framework supports field-level implementation and is well-suited for integration with sustainability rating systems such as LEED or Envision. It provides a transparent, generalizable, and industry-ready tool for intelligent UHPC mixture optimization, advancing data-driven design practices for green infrastructure applications.

The influence of axial compression is not incorporated into the design provisions for concrete breakout or pryout strength of anchors under shear. This study experimentally evaluated the shear capacities of anchors subjected to axial compression on a base plate using ten large-scale specimens. The test variables included axial compression N, edge distances from the anchor shaft in the direction of applied shear, edge distances perpendicular to the applied shear, and the compressive strength of concrete. The results showed little difference in crack initiation and propagation with varying axial compression. However, axial compression significantly improved the concrete breakout strength of anchors in shear. The applied axial compression reached up to 2.5 times the mean concrete breakout strength V_cbgo, as determined by the Concrete Capacity Design (CCD) method, and the average increase in shear strength was approximately 0.6 times the applied compression. In addition, axial compression suppressed concrete pryout failure by preventing the uplift of base plates. Based on the lowest N/V_cbgo ratio used in the tests, if axial compression of at least 0.5V_cbgo is applied to a base plate, pryout failure need not be considered.

Research presented in this paper is part of a program investigating the durability of fiber-reinforced polymer reinforcement after exposure to a marine environment or elevated temperatures. This paper presents the results of an experimental study on the tensile behavior of basalt fiber-reinforced polymer (BFRP) bars after exposure to elevated temperatures under different heating protocols. Under the steady-state heating protocol, specimens were exposed to elevated temperatures up to 250°C (482°F) first and then subjected to monotonically increasing load until failure. In other testing protocols, specimens were exposed to a specific sustained stress level first, keeping deformation or load constant, and then heated until failure. Under these conditions, specimen stress levels varied from 39 to 91%. Results showed that different testing protocols yielded different results, and the criticality shifted between protocols depending on the stress level. Lastly, a direct comparison is made between BFRP and glass fiber-reinforced polymer (GFRP) bars tested under identical conditions. The direct comparison showed that thermal degradation of BFRP at higher stress levels was comparable with that of GFRP bars, whereas GFRP bars exhibited superior performance at lower stress levels.