International Concrete Abstracts Portal

There is an increasing recognition of the necessity for designing structures capable of withstanding seismic activity. Two devastating earthquakes, measuring Mw 7.7 and 7.6 in magnitude, that struck Kahramanmaras in February 2023 highlighted the significance of high-quality materials, adherence to building codes, and products manufactured under established standards in structures that suffered damage. Various techniques are available for reinforcing existing buildings to enhance their earthquake resilience. These methods can be classified into several categories, including column jacketing, the addition of shear walls, wrapping of columns with fiber-reinforced polymer (FRP), and the reinforcement of structures with steel components. Research on the reinforcement of existing school buildings has been carried out using a shear wall-like approach involving a newly developed polyurethane brick material, which serves as an innovative building component. To validate the material properties, experimental studies including compression and three-point bending tests were conducted on polyurethane brick samples of varying densities in accordance with ASTM standards. The existing structural framework was evaluated against new performance benchmarks in conjunction with cost assessments. Subsequently, a comparative analysis was conducted between the newly developed polyurethane brick material and traditional reinforcement techniques, which included an assessment of its potential applications in the construction industry.

To address the issue of insufficient load-bearing capacity in brick columns over prolonged use, this paper proposes a novel reinforcement method utilizing thin-walled steel tubes and carbon fiber reinforced polymer (CFRP) sheets. Axial compression tests were performed on 27 specimens, comprising 8 types of reinforced brick columns and 1 unreinforced brick column, to assess the influence of CFRP layer count, steel tube wall thickness, and various reinforcement techniques on structural performance. The findings demonstrate that all reinforcement methods significantly enhanced both the axial load-bearing capacity and ductility compared to the unreinforced brick column. Notably, the composite reinforcement approach, integrating thin-walled steel tubes with CFRP, achieved greater improvements in both capacity and ductility than either reinforcement method applied independently. The axial load-bearing capacity of the reinforced columns increased with the addition of CFRP layers; however, beyond a certain number of layers, the capacity gain became marginal. In contrast, increases in the steel tube wall thickness resulted in more pronounced enhancements in axial load-bearing capacity. Based on these experimental results and established design codes, a formula is proposed for calculating the axial compressive bearing capacity of thin-walled steel tube-CFRP composite reinforced brick columns (TST-CFC).

Over the last two decades, the literature has focused on using glass fiber-reinforced polymer (GFRP) bars in compression members. Nonetheless, several aspects have yet to be explored. One such aspect is the lap splicing of GFRP reinforcement. Limited research has examined the splice strength of GFRP bars in concentric compression members. None has been performed on eccentrically loaded columns with lap-spliced bars. In the current study, nine full-scale GFRP reinforced concrete columns measuring 305 mm in diameter and 1600 mm in length with splices in both compression and tension were tested under moderate, high, and extreme eccentricity. The splice lengths used were 12, 24, and 36db for each eccentricity. In addition, five similar specimens from the literature were used for comparison: two had 24 and 36db splice lengths and were tested under concentric loading; the other three had continuous bars tested under different eccentricities. The comparison was in terms of load–displacement curves, load–splice strength curves, and contribution of splice components. The experimental results were compared to the provisions provided in ACI 440.11-22 and CSA S6-25. An interaction diagram based on the recommendations of CSA S806-12 was also drawn and compared to the interaction diagram of the experimental data. Test results indicate that the end-bearing was considerable and is a critical factor, especially at moderate eccentricity. Furthermore, the columns with spliced bars showed a higher peak load than columns with continuous bars, and splice length had a positive effect on splice strength and peak load. The analysis shows that the equation in ACI 440.11-22 and CSA S6-25 is significantly conservative. The results of this research will inform the development of new and accurate design equations for economic lap splices in subsequent phases of the study. They will also encourage design codes to consider end-bearing in compression splices.

Construction technology exerts a significant influence on the bearing behavior of pile foundations. Taking an airport expansion project as the engineering background in Lanzhou City, Gansu Province, China, a comparative analysis of the bearing behaviors of dry-bored piles and slurry wall-protected bored piles through static load tests and numerical simulations was conducted. The main conclusions are as follows: Both test piles exhibit a load-settlement curve of the steep-drop type. Compared with dry-bored piles, slurry wall-protected bored piles tend to accumulate sediment at the pile base, leading to increased settlement. In addition, a mud cake tends to form along the shaft of slurry wall-protected bored piles, which restrains the mobilization of shaft friction and further exacerbates settlement. Under identical load and pile length conditions, the end-bearing resistance, degree of shaft friction mobilization, and axial force in dry-bored piles are consistently lower than those in slurry wall-protected bored piles. Different construction technologies affect the load-transfer mechanism of pile foundations. During the drilling of slurry wall-protected bored piles, the surrounding soil is infiltrated by slurry, and a mud cake is formed on the pile shaft—this not only reduces the mobilization of shaft friction but also results in a slower decay of axial force along the pile. The presence of the mud cake increases the vertical displacement of the soil around the pile tip, and the magnitude of this displacement increases with the thickening of the mud cake. Moreover, the vertical displacement of the surrounding soil decreases as the elastic modulus of the mud cake increases.

Limestone calcined clay cement (LC3) has the potential to provide high clinker replacement in cement blends while providing excellent engineering properties and durability with low environmental impact, but such blends of clinker, limestone, and calcined clay are still in the industrial trial stage in the United States (US). In this study, it is proposed that sources of calcined clay (C), Type IL portland cement (IL), and additional limestone powder (L) can be blended into a “CC·I·L” cement to speed up the implementation of LC3-like systems in the US by combining already commercially available components during concrete mixing. In this investigation, regional CC·I·L blends were prepared using ASTM C595 Type IL cements and calcined clays, replacing 20% - 30% of the cement, from suppliers in the east, west, central, and mountain areas of the US, with additional ground limestone to reach a total limestone content of up to 15% by mass of the total cementitious system. To investigate the feasibility of this approach, fresh properties, early and late age performance, and durability of pastes and mortars made with the CC·I·L blends were examined and compared to ASTM C595 standard performance requirements and performance of regionally available Type IL cements. The results showed that 30% calcined clay and 15% limestone can be used to produce CC·I·L blends in each studied region to meet the ASTM C595 strength requirements. However, gypsum adjustment up to 5.0% was necessary to address undersulfation of CC·I·L blends in some of the regional blends. The results demonstrate the feasibility of using CC·I·L in the US without intergrinding, by taking into account key design factors such as the reactivity of calcined clays, sulfate balance, performance, durability, and possible environmental impact.