Recent advances in the geotechnics of organic soils and peat - Geotechnics of Organic Soils and Peat - page 192

Figure 7.20 Polypropylene fibres: (a) SEM image ( after Kaniraj and Gayathri, 2003); (b) photograph
showing the discrete short PP fibre ( after Tang et al. , 2007).
(d) Dosage rates of 5, 15 and 25% of OPC along with 5 and 10% of silica fume
increase the soaked UCS values of undisturbed fibrous peat by a factor as high
as 10.
7.8.4 Polypropylene fibres (PPF)
Polypropylene (PP) is a versatile thermoplastic material which is produced by polymer-
izing monomer units of polypropylene molecules into very long polymer molecules or
chains in the presence of a catalyst under carefully controlled heat and pressure. It has
a good combination of properties, is cheaper than many other materials that belong
to the family of polyolefins and it can be manufactured using various techniques. In
general, polypropylene (Figure 7.20) is resistant to alcohols, organic acids, esters and
ketones. Its general use in the construction industry is to reinforce concrete to control
cracks as well as for increasing their load-bearing capacity and durability (Mullik et al. ,
2006). Some properties of polypropylene fibres are listed in Table 2.14. Polypropylene
fibres have also been used successfully as a non-chemical admixture to strengthen var-
ious types of soil, such as sands and clays, in conjunction with a binding agent such as
Portland cement and or lime (Kaniraj and Gayathri, 2003; Tang et al. , 2007).
Studies have also been carried out by several researchers (Gray and Ohashi, 1983;
Consoli et al. , 1998, 2002, 2009; Yetimoglu and Salbas 2003; Yetimoglu et al ., 2005;
Ranjan et al ., 1996; Park and Tan, 2005; Tang et al ., 2007; Chauhan et al ., 2008)
on the influence of fibre inclusion on the mechanical behaviour of cemented soil. In
general, reports in the literature show that the randomly distributed fibres can be
used to overcome the drawbacks of using cement alone, such as the high stiffness
and brittle behaviour of the stabilized soil. In a series of laboratory unconfined com-
pressive strength tests, the raw specimens attained a distinct axial failure stress at an