Dr ASOKAN PAPPU and MOHAMED OSMANI explore the potential of GRP waste as an additive in rubber and concrete composites for construction activities.
Fibre reinforced plastics (FRP) have been used in various applications such as construction, aerospace, automobile, locomotive industry, electrical, commercial and consumer products. Mostly in FRP, the use of glass fibre is more pronounced. While the utilisation of Glass Reinforced Plastic (GRP) products in the construction industry is witnessed more in developed countries like Europe and North America, developing counties like India have not yet capitalised on its use. It is important to note that vast quantities of GRP waste have been land filled universally with limited recovery initiatives. Due to lack of recycling endeavours, disposal of such hazardous wastes becomes a major environmental threat as it is mostly disposed to landfills.
In order to effectively utilise GRP wastes, Loughborough University in UK has conducted a comprehensive laboratory experimental programme for characterisation of pulverised GRP waste powder and fibres and their recycling potential in architectural cladding panels, concrete and rubber composites. This research programme was performed as part of a project entitled 'Built Environment Action on Waste Awareness and Resource Efficiency (BEAWARE)', which was jointly funded by the UK Government and 14 industrial partners.
The extensive university research on concrete, cement and rubber composites showed that GRP waste can be used as a partial replacement for fine aggregate as well as an admixture in cement concrete. Further, the presence of polymer and short glass fibre content in GRP waste significantly contributes as a binder and reinforcing medium to improve the quality of concrete products. Not only has GRP powder ample scope for use in several applications in the construction sector but its inclusion has significant benefits on rubber properties. The inclusion of GRP waste increases the hardness and reduces the elongation, tensile strength and tearing energy. Further, modulus of elasticity results in enhancing the stiffening effect and carrying capacity of rubber. The improved acoustic properties of the GRP waste filled rubber composite also makes it suitable for building acoustic applications.
Furthermore, findings revealed that GRP waste can be potentially recycled to attain high performance polymer and concrete composites with appropriate casting techniques and hybrid polymeric and geo-polymeric binder system. The outcome of this study showed a viable technological option to help GRP waste management in a wider range of multidisciplinary applications leading to cross-sector and pan-industry waste recycling.
GRP waste in concrete has the potential to create pre-cast paving slabs, roof tiles, pre-cast concrete wall elements, lightweight concrete, high performance concrete, high strength concrete, concrete paving blocks and architectural cladding panels.
GRP waste powder can be an alternative filler for manufacturing rubber composites, which can be used as carpet underlay, bearing pads, bridge and concrete expansion joints and insulation pads in the construction industry. Further, hybrid and high performance polymer composites can also be fabricated using GRP waste powder and fibre.
Economic and environmental benefits
High on GRP
YAHYA YUSIF AL-BALUSHI and KRUPAVARAM NALLI highlight the features of GRP.
GRP as a construction material is the most common type of composite used in the engineering industry at present. It has a wide range of properties and features that make it applicable in very adverse environment and sophisticated structures. This is due to the fact that it contains two different materials which are fibres (ceramics) and plastic (polymer) and some additives. They are designed and processed to meet specific functional performance criteria. The fibre reinforcements' - amount, type, location, and orientation - will provide the required mechanical strength. Resin selection will provide the physical and chemical properties.
The operating life of GRP is in the range of 50-60 years. However, most of the international standard and specifications limit the product design life to 20 years as service life. The high strength to light weight ratio of this material offers distinct features especially in architectural projects. It can be stronger than steel. From the corrosion point of view, unlike metals, GRP is immune to all types of corrosion and can withstand a very harsh environment.
It is also a good solution to overcome the drawbacks of steel materials where the corrosive and aggressive fluid is an issue. Accordingly, the maintenance required is low compared to the steel material as there is no rust or paint involved. The flexibility to manufacture complex shapes, sizes and contours for GRP makes it one of the most favourable materials of construction. GRP can be moulded to various forms like tees, bends, flanges, and other complex shapes to suit site construction profiles. The flexibility, cost effectiveness of its composite material and almost nil maintenance makes it an extremely affordable solution. The nil maintenance in case of GRP makes it more attractive with respect to lifecycle operation.
There are a few challenges faced by using GRP as a construction material. Firstly, the temperature limitation depends primarily on the type of resin used and the nature of service. There is no specific benchmark for the limited temperature as it has to qualify for the specific application and usage. Also, cyclic loading, low modulus of elasticity, and fire resistance are all drawbacks, which can be avoided through proper customised design and manufacture.
There has certainly been a great development in the usage of GRP pipes in various industries, especially in the Gulf's oil and gas industry. There the GRP products, which act as a good replacement for solid steel metals, have been recommended for many equipment and flowing pipes in the upstream facilities. This includes multiphase flow lines, exported gas and oil pipeline, manifolds, vessels and tanks, etc. In most applications, these materials are constructed underground as they are vulnerable to mechanical damage by any external means. Also, GRP has shown an excellent performance in water services where a clean service is required.
This material is relatively a new entrant in the Indian sub-continent due to the limited availability of manufacturers and skilled manpower during construction and installation phases. However, few metro municipal corporations dealing with water and sewage application are using GRP to a limited extent. Some of the private sectors, chemical and other industries like fertilisers and chemicals use it for effluent treatment plants. However, it is acknowledged that in the coming years, GRP will be a potential construction material in the country.
About the authors:
Dr Asokan Pappu is Principal Scientist at the Council of Scientific & Industrial Research-Advanced Materials and Processes Research Institute, Bhopal.
Mohamed Osmani is a Senior Lecturer in Architecture and Sustainable Construction at Loughborough University, UK.
Yahya Yusif AL-Balushi is Material and Corrosion Engineer at Tebodin and Partner LLC.
Krupavaram Nalli is Material and Corrosion Engineer at Tebodin and Partner LLC.