Civil Engineering

In light of the unsustainable provision of river sand in Hong Kong and the limitations of existing river sand substitutes, Hong Kong urgently needs to discover new river sand substitutes to meet the growing demand for concrete. Hence, this project aims to investigate the feasibility of using “CDT sand” in completely decomposed tuff (CDT) as river sand substitute for concrete production.

With the introduction of 3D printing technology, a new era of the construction industry can finally be formed! Traditionally, buildings are constructed by using wooden formwork as a mold to hold the concrete. However, engineers started researching ways to implement 3D printing technology into the construction industry, which would help reduce the waste of wood and shorten the construction time. So far, little research on 3D-printable Ultra-high Performance Concrete (UHPC) is done, and our project is to help with the research. We are designing some concrete mixes that are 3D-printable. We check their fresh state properties like workability and printability, as well as their hardened state properties such as compressive strength. We have successfully printed some models, and we are looking forward to promoting 3D-printable UHPC for the construction industry to use.

During the COVID-19 pandemic, the use of disinfectants has surged in order to contain the spread of the virus. Many disinfectants will be sent to wastewater treatment plants after use for treatment before discharging back to the environment. Nevertheless, studies have shown that large amounts of disinfectants can inhibit biological reactions during the wastewater treatment process. The activated sludge process, which counts on microorganisms to break down complex organic matters in wastewater, is particularly susceptible to disinfectants. Hence, this study aims to investigate the inhibitory effects of two common active ingredients of disinfectants, namely QACs and sodium hypochlorite, on the activated sludge process. It is hoped that the study will be able to recommend an active ingredient of disinfectant that has the required efficacy and the least impact on the wastewater treatment system.

Hong Kong is facing an increasing demand of reclamation land use. However, we are facing an unstable supply and increasing price of the tradition backfilling material – sand. Therefore, we need to investigate an alternative. Ash-strengthed marine deposit can be a solution. Marine deposit can gain strength after mixing with cement, coal ash and water. This material can also reuse contaminated marine deposit. Therefore, the feasibility of using ash-strengthened marine soil is going to be investigated.