The development of fibre reinforced geopolymer cladding systems with integral foamed insulation

Abstract

This research aimed to develop the next generation of building cladding, which can reduce the environmental impact civil engineers have on our planet, create the unique, architectural styles of the future, and provide increased safety to people in buildings, while eliminating fire tragedies like Grenfell tower.

Global warming is the most pressing issue currently faced by society. Carbon dioxide levels are the highest in human history and without major changes by 2100, temperatures are predicted to rise by up to 60 C. There is no longer any real scientific debate, 97% of researchers confirm this, yet we so far governments and industry have failed to enact the changes required to meet climate change targets such as achieving net zero by 2050 (Skidmore, 2023). Full decarbonisation of the construction industry by 2050 will require widespread rapid change, which will need to be implemented by 2030. One vital area to change is how buildings are constructed. Buildings account for around 40% of the energy used and a third of the greenhouse gases emitted worldwide, with their component materials making up a further 10% (World Green Building Council , 2019). The EU recognise the scale of change required to achieve net zero and plan to invest £84 billion through Horizon Europe by 2027 to address these challenges and aim to make all new builds require no energy from the grid by 2030 (European Commission, 2020). Lightweight, non-structural cladding can create energy efficient buildings. However, achieving high levels of insulation, fire safety and surface finish whilst using minimal amounts of energy, time and money whilst emitting minimal greenhouse gases is becoming increasingly challenging. Materials commonly used for building cladding include Glass reinforced concrete, sheet glass walling and aluminium plastic composites, which were unfortunately set alight on Grenfell tower. While these all excel in providing an aesthetically pleasing and low maintenance finish, they have high embodied energy and CO2 ; whereby they use cavities and separate flammable insulation materials for their thermal protection. This is no longer acceptable from environmental and safety prospectives; hence new material solutions must be developed.

Geopolymers are considered to be serious contenders as stronger alternatives to Portland cement-based concretes and mortars. They have similar mechanic strength properties and are equally fire-proof, but are formed from recycled waste and have significantly smaller carbon footprints. Geopolymers with fibre reinforcement and chemical foaming additives can produce a fireproof high strength material for cladding applications, with huge design flexibility. Furthermore, geopolymer mixtures can be tailored such that their mechanical and thermal performances exceed existing standard materials, with added benefits such as being lightweight (due to reduced thickness) and no cavities for fire to spread.

This research developed novel mix design methods suitable for a wide range of geopolymer mix designs and source materials, including MK, GGBS, SF and IS precursors with potassium silicate activation. Optimised empirical equations accurately predicted strength, flowability and carbon embodiment, which informed a user-friendly contour-based mix design procedure. Fibre composites created with 2% volume of 13μm, concrete-sized, basalt fibres in a GGBS/MK mortar achieved 84% the MOR of a GRC control and concrete. Specific sizing was proven effective and necessary for basalt fibres in high performance geopolymer composites. Industrial surfactant-based geopolymer foam insulation was created with density > 607 kg/m 3 and TC >0.0933 W/mk. This thereby presents a new range of novel, ‘greener’ cladding materials that comply with UK building regulation U-values. Furthermore, a carbon embodiment of 0.228 kgCO2 /kg was achieved, which represented a 62% reduction compared with the average GRC studied.

Date of Award	Aug 2023
Original language	English
Sponsors	Department for Employment and Learning, Northern Ireland
Supervisor	Phillip Millar (Supervisor), Alistair McIlhagger (Supervisor) & Bryan Magee (Supervisor)