Search Results (5)

This study explores the use of volcanic glass powder (VG) derived from Shirasu volcanic deposits as a substitute for silica fume (SF) in producing high-strength precast concrete piles with a compressive strength of 123 MPa. Initially, mortar specimens with varying VG replacement ratios and curing temperatures were prepared to assess their compressive strength. After identifying the optimal mix ratios and curing conditions for high-strength mortars, concrete specimens incorporating VG were produced. Subsequent testing revealed that a VG replacement ratio of 20% by cement volume and a curing temperature of 70 °C were optimal for achieving the target compressive strength. Although the Young’s modulus of VG-incorporated concrete was slightly lower than that of pure cement and SF concrete, its performance remained satisfactory. These findings suggest that VG is a viable alternative to SF in high-strength concrete applications, providing a sustainable method to enhance concrete properties using locally available volcanic deposits. Full article

The impacts of concrete on global warming through its use in structures such as buildings and infrastructure must be identified and better understood, as concrete is known to have a very high global warming potential (GWP). However, in contrast with ordinary on-site constructed reinforced concrete, GWPs of off-site factory-made prefabricated concrete products such as precast concrete (PC) and concrete piles that are widely used in construction are rarely evaluated, owing to the complicated manufacturing processes that make the determination of greenhouse gas emission difficult. In this study, the embodied life cycle GWPs were derived for PC and pretensioned spun high-strength concrete (PHC) piles to enable precise assessment of the global warming impact of concrete structures and the concrete industry of Korea. The determined embodied GWPs of PC and PHC piles were 1.77 × 10⁻¹ kg CO₂ eq/kg and 1.87 × 10⁻¹ kg CO₂ eq/kg, respectively. As a result, both prefabricated concrete products were determined to have high GWP due to input materials, such as cement rebars, while the GWP contributions of the off-site prefabrication processes were low. Moreover, the embodied GWPs of both prefabricated concrete products were significantly higher than those of ordinary reinforced concrete, and the impact of both products on global warming was found to be approximately 4% of the impact of the Korean concrete industry. This indicates that it is necessary to consider the impacts of the PHC pile and PC industries when assessing the impacts of greenhouse gas occurring in the concrete industry at the national level. It is expected that these findings will be widely used to obtain a more accurate assessment of the impact of concrete structures and industry on global warming. Full article

Controlling the river regime in the lower wandering reaches of the Yellow River Basin is important for ecological protection and high-quality development. This study reviews the development of pile groynes suitable for wandering rivers. As a widely used form of reinforced concrete pile, pile groynes, including round and sheet piles, have been built in alluvial rivers in large numbers for many years. Currently, research focuses on improving the stability and erosion resistance of these piles. Here, three types of groynes are discussed according to the construction technology: cast-in situ bored pile, vibratory-driven pile, and jetted precast concrete pile. Detailed discussions are provided regarding their respective applicability, improvement processes and characteristics. In contrast to the other two methods, jetting minimizes the damage to the structure and strength of the concrete pile and is characterized as fast-tracking, cost-effective, and environmentally friendly. Enhancing the safety and practicality of concrete piles can be effectively achieved through improvements in construction techniques, modified construction materials, and multi-structure combination pile designs. Furthermore, in the current context of pursuing a resource-saving and environmentally friendly society, energy conservation and emissions reduction have become focal points in engineering technology development, while still maintaining a strong emphasis on construction quality. Full article

Prestressed, precast concrete piles using High-Strength Steel Strands (PPCPs using HSSS) are a new type of precast pile. Compared with prestressed high-strength concrete (PHC) piles, the adoption of ultra-high-strength concrete and HSSS not only improves the load-bearing capacity, but also enhances the ductility of precast piles. The engineering application of PPCPs using HSSS requires not only a high bearing capacity of the pile segments, but also reliable splicing to ensure cooperation between pile segments. Based on the characteristics of strand anchorage plates, this paper proposes a new combination splice using the clamp ring and welding (Combination Splice). The theoretical analysis and design method of this Combination Splice is introduced. This research gives a thorough investigation into the flexural performance of PPCPs using HSSS with the Combination Splice. The flexural tests of PPCPs using HSSS with the Combination Splice were firstly conducted on eight full-scale pile specimens with three different pile diameters and four different steel reinforcement ratios. The flexural performances are evaluated in terms of crack resistance, flexural capacities, crack distribution, as well as strain development. The results indicate that the Combination Splice remain safe and intact when the piles reach the ultimate bending capacity. The ultimate bending moment of tested specimens with the Combination Splice is, on average, 10% larger than that of specimens using a theoretical formula. In light of the experimental data, a finite element analysis (FEA) model has been created to simulate the flexural performance of the piles with the Combination Splice. The FEA results show that the load–displacement curves and crack distribution regions are in good agreement with the experimental findings, which verifies the reliability and accuracy of the FEA model. The parameter analysis investigates the effects of the assembly gap and clamp ring corrosion on the flexural performance of PPCPs using HSSS. The results show that assembly gaps have a greater influence on the flexural capacity and deformation, while the influence of the clamp ring corrosion is negligible, indicating that the Combination Splice has certain advantages in terms of durability. Full article

Investigation on the long-term thermal response of precast high-strength concrete (PHC) energy pile is relatively rare. This paper combines field experiments and numerical simulations to investigate the long-term thermal properties of a PHC energy pile in a layered foundation. The major findings obtained from the experimental and numerical studies are as follows: First, the thermophysical ground properties gradually produce an influence on the long-term temperature variation. For the soil layers with relatively higher thermal conductivity, the ground temperature near to the energy pile presents a slowly increasing trend, and the ground temperature response at a longer distance from the center of the PHC pile appears to be delayed. Second, the short- and long-term thermal performance of the PHC energy pile can be enhanced by increasing the thermal conductivity of backfill soil. When the thermal conductivities of backfill soil in the PHC pile increase from 1 to 4 W/(m K), the heat exchange amounts of energy pile can be enhanced by approximately 30%, 79%, 105%, and 122% at 1 day and 20%, 47%, 59%, and 66% at 90 days compared with the backfill water used in the site. However, the influence of specific heat capacity of the backfill soil in the PHC pile on the short-term or long-term thermal response can be ignored. Furthermore, the variation of the initial ground temperature is also an important factor to affect the short-and-long-term heat transfer capacity and ground temperature variation. Finally, the thermal conductivity of the ground has a significant effect on the long-term thermal response compared with the short-term condition, and the heat exchange rates rise by about 5% and 9% at 1 day and 21% and 37% at 90 days as the thermal conductivities of the ground increase by 0.5 and 1 W/(m K), respectively. Full article