Protecting Our Coasts with Durable and Environmentally-Sustainable Geopolymer Concrete
Coastal protection structures are necessary for protecting our coastlines and coastal infrastructure from erosion but they themselves are in danger of eroding away. Thus, we turn towards environmentally-friendly geopolymer concrete as an alternative. Geopolymer concrete utilizes industrial waste materials such as slag and fuel ash to create a denser and more durable concrete. By incorporating such technology into our coastal protection structures, we can create stronger and longer-lasting protection that is also better for the environment.
Coastal protection structures such as breakwaters are built to protect coastlines from extreme beach erosion but are prone to damage and weathering process due to changes in wave climates. Breakwaters and seawalls are normally armoured with quarried rocks or concrete-made units, and as such they need to be highly dense and durable due to being constantly attacked by waves, (see Figure 1).
Concrete is a complex material of construction that enables the high compressive strength of natural stone to be used in any configuration. However, in term of tension, concrete can be no stronger than the bond between the cured cement and the surfaces of the aggregate. Concrete is therefore frequently reinforced, usually with steel rebar and is then termed as reinforced concrete. The steel rebar within the reinforced concrete will support most of the tensile stresses and leave the immediately surrounding concrete comparatively free of tensile stress. However, the steel rebar tends to have a corrosion problem. This is because steel rebar is made largely from steel or iron, which is an unstable material in nature when it is exposed to corrosive agents such as salt, carbonation, and even air, see Figure 2. Surface deterioration of exposed materials such as steel and concrete are major problem in construction, especially in or near sea water environment because of the loss of cover and ensuing reinforcement corrosion that affect the integrity of the structure.
Indeed, findings from the 2015 National Erosion Study stated that the coastal erosion process poses a significant threat to existing structures, populations, and ecosystems, with about 30 Category 1 sites in Peninsular Malaysia alone (see Figure 6). States like Terengganu have adopted Tetrapod-type armour units in their coastal protection structure (see Figure 5). Unfortunately, a large portion of the units had to be replaced with quarried rocks due to the failure issue and lack of supply from the foreign manufacturer.
Due to this concern, Universiti Malaya’s Water Engineering and Spatial Environmental Governance (WESERGE) studied various alternatives, one of which being geopolymer concrete. Geopolymer concrete possess environmentally-friendly qualities and have been used as an alternative to conventional cement concrete for the last decades. It is denser, more durable, low corrosion rate and has a lower carbon footprint compared to conventional cement concrete, properties that make it a promising material to be used in the construction of coastal protection structures.
Geopolymer concrete gains their strength and durability from being made out of industrial waste materials such as fly ash (a residue from coal combustion), ground granulated blast furnace slag (a non-ferrous waste-product from steelmaking), silica fume, palm oil fuel ash and rice husk ash, most of which (especially blast furnace slag) are quite dense and very durable.
Both fly ash and blast furnace slag are of special interest to Malaysia as both waste-products are very abundant as a result of the country’s steelmaking industry and extensive coal-burning activities (see Figure 3). Thus, combining these two materials to create a geopolymer concrete will not only provide a stronger, environmentally cheaper and more durable alternative to conventional cement concrete but will also solve the alarming issue of landfill capacity in the country.
This project aims to develop a robust and sustainable high-density geopolymer concrete mix armour unit made from waste material, as an alternative to conventional cement concrete and other building materials in the construction of coastal protection structures in Malaysia. This geopolymer concrete will be produced under ambient temperatures, with good workability and setting time based on real application in Malaysia.
The project is divided into 4 milestones: 1) Enhancement of the formulation of geopolymer mix; 2) Completion of model testing and engineering properties; 3) Product development of armour unit using new geopolymer mix and; 4) Final evaluation of the model of the armour unit. The first milestone (see Figure 7) focuses on the characterization of raw materials within the geopolymer mix, creating a new formulation in the process. Following the completion of this first milestone by the end of February 2022, the mix will be prepared and tested at the Department of Civil Engineering’s Concrete Laboratory at UM (see Figure 8).
The relationship between stability and damage level of the armour units will be determined using the physical wave flume test in the final milestone of the project (see Figure 4). Such approach is important to render the entire concrete cement-free product that made of sustainable materials with optimised engineering properties against wave actions.
By using this geopolymer concrete, not only will we create stronger and longer-lasting coastal protection structures, but by recycling local industrial waste products, we will reduce the amount that ends up at our landfills and create an environmentally cheaper, in-house product.
This project will address the Environment and Biodiversity element in the 10-10 MySTIE framework by MOSTI, in line with the national science, technology, and innovation plan 2021-2030 outlined in the RMK-12. The project outputs are also expected to fulfil the Quintuple Helix innovation model, meeting the innovation and commercialization criteria in Technology Readiness Levels (TRLs).
Figure 1: Existing armour units by international counterparts.
Figure 2: Chloride attack corrosion on steel rebar in a coastal structure (Farhana et al., 2013).
Figure 3: Steel slag aggregates waste from Mega Steel, Selangor, Malaysia.
Figure 4: Example of past project using quarried rocks and armour units in 2D flume (left panel) and 3D flume (right panel) at NAHRIM, Seri Kembangan.
Status of project
Approved funding by MOSTI under the Technology Development Fund (TED01) 2021.