High-Workability Concrete Mixtures for Bored Pile Construction

Abstract

The article investigates the characteristics of high-workability concrete mixtures designed for use in CFA (Continuous Flight Auger) pile technology, which involves continuous concrete placement through a hollow auger under pressure. The subsequent stage includes inserting the reinforcement cage into the freshly placed concrete. This technology is widely applied in construction under complex engineering-geological conditions, in mountainous areas, and within densely built urban environments, where low noise levels, the absence of vibrations, and stability of concreting parameters are essential. The high requirements for homogeneity and rheological stability of the concrete mixture necessitate careful selection of modifying admixtures capable of maintaining workability and preventing segregation throughout the entire technological cycle. The study presents an analysis of the influence of modern superplasticizers from different manufacturers on water demand, workability, slump retention, and compressive strength of concrete. It has been established that the use of such modifiers enables the production of stable high-workability mixtures suitable for pressure-fed placement and positively affects the cement hydration process, ensuring a more uniform strength development. Special attention is given to the ability of admixtures to preserve the required consistency for a duration sufficient for transportation and concreting under challenging conditions. Experimental results confirm that properly selected superplasticizers allow for optimizing the water-cement ratio, improving rheological properties, and forming concrete with enhanced physical and mechanical characteristics at the design age. The obtained results can be applied in developing concrete mix designs for CFA technology and are valuable for engineering practice related to pile foundation construction in demanding modern construction environments.