A re-visit of aggregate properties of granitic rock in Hong Kong

Abstract

Hong Kong's buildings and infrastructures rely heavily on concrete, where locally sourced granitic aggregates historically played a significant role. This dissertation critically re-evaluates the suitability of Hong Kong's granitic rocks as concrete aggregates through the comparison with the technical requirements under Construction Standard CS3: 2013. With the completion of surface quarrying at Hong Kong's last active quarry----Lam Tei in 2023, it is necessary to reassess the local aggregate properties to provide strategic support for the development of underground and new quarries. With time of data ranges from 2013 to 2023, this research benchmarks aggregate performance against both the landmark previous study on the aggregates suitability in Hong Kong (Irfan 1994) and the requirements in Construction Standard CS3:2013. Comprehensive analyses of geometric, physical, and chemical properties reveal significant advancements. Modern aggregates exhibit superior mechanical strength, evidenced by Ten Percent Fines Values consistently exceeding 170 kN and markedly reduced Aggregate Impact Values, reaching lows of 8.3%. Enhanced particle geometry, reflected in substantially lower Flakiness and Elongation Indices, alongside strict adherence to updated gradation specifications, confirms improved workability potential. Durability assessments demonstrate exceptional chloride resistance (consistently <0.02%) and soundness (>94%), though Alkali-Silica Reactivity requires careful monitoring. The exclusion of abundant local volcanic rocks is systematically justified by their high reactivity and problematic porosity, which compromise concrete integrity. This study validates the enduring suitability of Hong Kong granitic aggregates under contemporary standards. It advocates for strategic revitalization of local supply through pioneering underground quarrying at Lam Tei and targeted development of dormant surface sites. These measures are crucial for enhancing supply resilience, reducing carbon-intensive imports, and securing sustainable construction materials for Hong Kong's future infrastructure needs.