Mechanical properties, durability and environmental assessment of low-carbon cementitious composite with natural fibrous wollastonite

Abstract

Cementitious composite is one of the most widely used construction materials around the world, but cement production is accompanied by energy waste and CO2 emission. Wollastonite, a natural fibrous silicate mineral, can be a potential supplementary cementing materials (SCMs) for cementitious composite owing to its similar calcium silicate system, and it has an eco-friendly and convenient production process. Furthermore, its unique fibrous structure can possibly act as reinforcement for the cement matrix. In view of this, this study aimed to investigate the effects of different sizes (the median diameter of 3 μm, 6 μm, 9 μm and 12 μm) and contents (0%, 5%, 10%, 15% and 20% by mass) of wollastonite combined with 5% silica fume on the mechanical strength, durability and microstructure of cementitious composite by compressive test, flexural test, shear test, rapid chloride migration test, sulfate corrosion test, X-ray diffraction(XRD), scanning electron microscope (SEM) and fourier transform infrared spectrometer (FTIR). The results showed that the strength and durability of samples increased and then decreased as wollastonite content increased. An addition of 10% wollastonite into the cement matrix increased compressive strength, flexural strength and shear strength by 6.22%, 29.3% and 18.4%, respectively. However, an addition of 5% wollastonite was found to be more beneficial for improving resistance to chloride and sulfate corrosion. Additionally, samples prepared with 3 μm wollastonite performed better, which can be attributed to the fact that the small size of wollastonite contributed to both the filling effect and the skeletal support and bridging effect of microfibers. The CO2 emissions of cementitious composites decreased as the wollastonite percentage increased. The findings confirm that natural wollastonite as SCMs for cementitious composite has performance enhancement and environmental benefits, however, it is recommended that the wollastonite content should not exceed 15%.