Wool-Reinforced Cement Based Composites

Abstract

In this paper, an overview of the latest research activities in the field of cement-based composites incorporating sheep wool reinforcement is presented. First, the characteristics of this type of natural fibre are described. Then, the current use of sheep wool fibres in cement-based composites is discussed. The research problems regarding the properties of cement matrix composites reinforced with sheep wool are divided into four groups: thermal and acoustic properties, mechanical behavior, durability issues, and microstructure aspects. The latter two groups are analysed separately, because both durability and microstructure are of particular importance for future applications of wool reinforcement. Finally, the main directions of future researches are presented.

Keywords: durability; mechanical properties; microstructure; natural fibres; sheep wool fibres.

Figure 1

Schematic diagram of wool fibre structure [37] (2020, https://www.hdwool.com/blog/the-structure-of-wool).

Figure 2

SEM image of (a) sheep’s wool fibre showing its surface scales [30] (CC BY 4.0, 2020, Sustainability), and (b) man-made synthetic smooth glass fibre [38] (BY-NC-ND 3.0, 2017, E-Polymers).

Figure 3

Effect of relative humidity on stress–strain curves of wool at room temperature [41] (RightsLink, License numer 4875281426526, 2008, Physical properties of textile fibres, 4th ed.).

Figure 4

Sheep wool used in cement based composites.

Figure 5

The microstructure of the mortar samples made with high-alkali cement and wool fibres addition cured at 20 °C: (a) 3 days and (b) 27 days, scale bar = 100 µm.

Figure 6

Thin section photograph of the microstructure of sheep wool reinforced mortar cured in water for 27 days in 20 °C, plane polarized light with gypsum plate, areas with visible wool fibre cross sections are marked, 1—air-voids, 2—fine aggregates, scale bar = 0.5 mm.

Figure 7

SE image of the sheep wool fibre—interface—cement matrix, scale bar = 20 µm.