Enhanced mechanical and thermal performance of high-strength engineered geopolymer composites reinforced by hybrid polyethylene fibres and carbon nanotubes
Yuekai Xie
Abstract
Engineered geopolymer composite is a sustainable alternative to engineered cementitious composite due to its lower carbon footprint and comparable mechanical performance. This paper developed a high-strength engineered geopolymer composite reinforced with hybrid polyethylene fibres (2 % v/v) and multi-walled carbon nanotubes (0.1–0.4 % w/w with sizes from 5 to 100 nm) and evaluated its performance after thermal exposure. The results indicated the drying shrinkage of the engineered geopolymer composite decreased with increasing carbon nanotubes’ proportions and decreasing sizes, with a reduction of up to 25.1 %. The compressive strength (89.6–104.4 MPa), tensile strength (6.27–7.72 MPa), and strain capacity (8.46 %–10.25 %) were enhanced by the carbon nanotubes, particularly with finer sizes. After being exposed to the elevated temperatures, engineered geopolymer composite with the addition of the carbon nanotubes exhibited higher compressive strength, tensile strength, and strain capacity than the pure engineered geopolymer composite. The tensile strain with 0.2 % fine carbon nanotubes was maintained at 9.00 %, 66 % higher than the control group (5.42 %). The cost-effectiveness analysis also suggested that incorporating an appropriate quantity and dimension of carbon nanotubes provided economic benefits when exposed to the elevated temperatures. In addition to inducing filling and bridging effects, the carbon nanotubes also enhanced the formation of C-(A)-S-H gels. The enhanced intensity of the hump from X-ray diffraction, increased absorption band from Fourier-transform infrared spectroscopy, and higher mass loss between 50 and 600 °C in thermogravimetric analysis revealed the promoted gel formation due to the incorporation of the carbon nanotubes. In this study, the addition of 0.2 % fine carbon nanotubes (5–20 nm) was the optimum alternative to improve the mechanical and thermal performance, and achieve the cost-effectiveness of polyethylene fibre-reinforced engineered geopolymer composite. • Incorporating CNT in EGC mitigated 28-day drying shrinkage by up to 14.1 %. • Addition of fine CNT increased tensile strength and strain to 7.72 MPa and 10.25 %. • Incorporation of CNT enhanced geopolymerisation and gel formation of EGC. • EGC with 0.2 % CNT maintained tensile strain of 9.00 % after 140 °C exposure. • Strength retention ratio of 0.86 was achieved with 0.2 % fine CNTs after 600 °C.