Assessing Mechanical Properties of Free-Fall Self-Compacting Concrete and its Application in Concrete-Filled Steel Tube Columns

The application of Self-Compacting Concrete (SCC) in the construction industry has been adopted over the years and its quality over normal concrete has been influential. The high-rise construction demands emphasize the necessity of concrete pumping technology due to limited working space. Concrete made from manufactured sand was produced and the variation of free fall height based on the experiment of SCC was studied. This study assesses both the mechanical properties of SCC cast after free fall from various heights and its applications in the CFST columns. The study specifically focuses on a varied height of free fall at 6m, 6.5m, 7m, 7.5m, and 8m. The workability performance of this SCC, batched from manufactured sand has been evaluated, and slump extension between 500-600 mm was obtained. The concrete cubes and prism specimens were tested for compressive and splitting, therefore the associate strength was obtained. Testing both normal and SCC reveals unfavourable effects in strength reduction with an increase in free fall height. At the final height of 8m, an observed decrease in strength of about 15%-20% using SCC was observed. At 6.5m, there is a 3% decrease in strength, and the reduction in cube-splitting strength ranges from 7% to 11% with SCC from natural sand. When the free fall height is 7m, the cubic compressive strength is reduced by about 4.3-5.4%, and its cube-splitting strength at a height of 7m decreases by approximately 7–11%. Despite the gradual decrease noted in this study, the application of SCC obtained at 7m in CFST has demonstrated reliable results in terms of combined strength, suggesting its use in columns not exceeding the same height.