Making concrete a sustainable building material
By Dr. Lee Yeong Huei
Concrete has been a building material since ancient times. It is the second-most-used substance in the world after water, and is the most widely used building material due to its strength and durability. It can easily withstand normal and shear stresses without getting affected.
Concrete is a composite material composed of cement, aggregate and water, and occasionally admixtures, that hardens over time. When cement and water are mixed, a chemical reaction called the hydration process generates a binding material (CSH gels) to bond the aggregates.
Eventually, after the hydration and hardening processes, a strong concrete matrix is formed and ready to serve in load transfer in a building form. However, theoretically and practically, concrete can be used for both structural and non-structural purposes.
Many means can be used to reduce the carbon footprint of the construction industry and this includes the use of sustainable concrete. In this modern age, sustainable or green concrete is applied to protect our natural resources from depletion.
Concrete can be classified as ‘sustainable’ or ‘green’ when its carbon footprint is lower than conventional concrete. To achieve this, the current trend is to replace portions of the concrete matrix with sustainable substitute materials.
These substitute materials are often referred to as replacements. They can be cement replacements, coarse aggregate replacements, fine aggregate replacements, or even the application of seawater.
Of all these replacements, cement replacements are the most significant contributor to carbon footprint reduction. As cement production produces higher carbon dioxide emissions, a replacement to even a small portion of cement can result in significant carbon dioxide reduction.
The usage of industrial wastes as replacements can also contribute to the sustainability of concrete. These supplementary cementitious materials (SCM) are effective substitutions as they do not compromise the strength of the concrete, yet maintain the sustainable feature. Silica fume, rice husk ash, palm oil fuel ash and ground granular blast furnace slag are common SCMs currently used in the construction industry.
Current research in the field of sustainable concrete revolves around partial or full cement replacement. Concrete without cement (full cement replacement) is known as geopolymer concrete. Most of the SCMs are industrial by-products disposed of in landfills. Hence, better waste management in the construction industry should be investigated and applied to achieve greater sustainability.
Artificial aggregates and industrial wastes are often used to replace aggregate in the concrete matrix, including the SCMs mentioned earlier. Other examples of artificial aggregates are recycled bricks, recycled concrete, siliconmaganese slag, expanded clay, and expanded slate.
Substantial research has been conducted on sustainable or green concrete, yet its application is limited in the Malaysian construction industry. The industry seems to lack confidence in its usage in building applications due to limited identified success cases.
Sustainable concrete should therefore be actively promoted in building material applications and efforts made to encourage its wider implementation in Malaysia. After all, there are massive sources of wastes from the palm oil, metal smelting, power generation and other industries that could potentially be applied in the concrete matrix to enhance its sustainable features. Let’s build together a sustainable construction community through sustainable concrete implementation!
Dr. Lee Yeong Huei is a senior lecturer in the Department of Civil and Construction Engineering and Head of the Structures and Materials Research Cluster at Curtin Malaysia’s Faculty of Engineering and Science. He is actively involved in various research activities in the fields of numerical analysis, structural analysis, concrete materials, interlocking blocks, fire engineering, sustainable construction and engineering education. Sustainable concrete is one of his research focus areas. In addition, he has jointly published more than 50 journals, conference papers and book chapters related to his research. Dr. Lee can be contacted by email to firstname.lastname@example.org.