Fibers in Bituminous Mixtures - A Review 11-14

8/13/2019 Fibers in Bituminous Mixtures - A Review 11-14

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Effectiveness of Fibers in Stabilizing and Reinforcing Bituminous Mixtures: A review

Juzer Naushad Moosajee, 14070 Page 11

properties (SEM). Lignin was found to have a rough surfaced, porous structure with non-uniform size,

which would explain its high water absorption (28.14%). Asbestos fiber also has non-uniform size, but a

smoother surface, and absorbed less water (23.12%) by mass of fiber. The three plastic fibers had

smooth surfaces, uniform sizes with antenna-like features at the ends that could improve spatial

networking within the asphalt matrix. Asphalt-fiber blends were tested for absorption, adhesion.

Unsurpisingly, the lignin-asphalt blend had the least asphalt drop and separation, equating to highest

absorption. Asbestos blend was found to be least stable of the five blends. A DSR setup of 25mm

diameter plates was used to test the rheological properties of Asphalt-fiber blends at 82C and 10 rad/s.

Results clearly show improvement in rheological properties and rutting resistance due to the fibers, with

lignin the most effective, increasing the Shear Modulus (G*) by 497% and the G*/sin ratio by 540%.

They concluded that all fibers were effective in the basic requirement of limiting draindown, in addition

to improving other desirable properties.

Basalt fiber was developed by Moscow Research Institute in 1953-1954. In 1985, the Ukraine Fiber

laboratory became the first industrial producer of basalt fiber with a high-tech production furnace

operated at ~1450C. The fiber is drawn from wire bushing made of platinum and rhodium alloy. Basalt

fiber is claimed to have natural compatibility with asphalt, superior mechanical and stable chemical

properties. Its high temperature production makes it resistant to heat and fire. (Morova, 2013), (Liu, et

al., 2012)

Wang, Wang, Gu, & Zhou (2013) studied the effect of basalt fiber on asphalt binder and mastic at low

temperatures. The basalt fiber reinforced specimen, when tested under direct tension showed improved

tensile resistance with 0.3% fibre content. The fibre increased the stiffness of the asphalt binder and the

mastic specimen. A new fatigue test procedure, that applies direct cyclic loading was used to test the

fatigue resistance of the fibre reinforced specimen. The results showed improved fatigue life of both the

binder and the mastic. The above results were further supported by finite element simulation and X-ray

tomography scan, that showed that under unidirectional tensile and cyclic tensile loading the fiber

reduced the stress concentration on the critical areas and diminished fatigue damage due to cyclic

loading. However, use of basalt fibre in surface courses is not recommended by Morova (2013) since it

can cause accelerated wear and tear to tyres.


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2.7 Alternate Stabilizers in SMA Mixtures:

The use of fibers as stabilizer in SMA and PA mixtures has been well documented; however some

researchers have found success in using non-fibrous materials for stabilizing SMA/PA mixtures.

Asphalt Rubber:Bitumen modified with appropriate quantity of crumb rubber has been found to be

effective in stabilizing asphalt mixes in addition to other desirable properties. Lyons & Putman (2013)

showed that CRM 12% binder was equally effective as cellulose fibers in limiting draindown in PAmixtures. CRM binders were found to reduce abrasion loss in PA mixtures by almost 60% when

compared to neat (unmodified) binders. It even performed better than SBS without cellulose fibers.

Mohamed (2010) showed that bituminous mixtures made with crumb-rubber modified binder

performed better against long term aging than unmodified bitumen.

Hassan et al. (2005) studied OGFC mixtures containing cellulose fibers, SBR Polymer and fiber-SBR blend.

PG 60/70 asphalt binder was used in the control mix. The fiber, SBR, and fiber-SBR mixes all met the

draindown requirements. The SBR polymer and fiber-SBR mixes successfully limited unaged abrasion to

20% at 6% AC and higher, as required by NCAT specifications. However only the 6.5% fiber-SBR mix

succesfully limited aged abrasion to a maximum of 30% (NCAT specifications). The fiber-SBR mixture was

also found incur less damage due to moisture, as shown by its higher TSR ratio compared the control

mixture. This is mainly attributed to the SBR, since cellulose fiber mixture did not exhibit any change in

moisture susceptibility.

Polyethylene: Al-Hadidy & Yi-qiu (2009) studied LDPE as bitumen modifier for use in SMA mixtures.

LDPE that has undegone pyrolysis and mechanical grinding was blended with 50/60 penetration grade

asphalt cement using wet process. They tested four different LDPE-asphalt blends were (2%, 4%, 6%,

and 8%) and conculded that LDPE improved the ductility, temperature susceptibility and durability of

the binder. The 6% blend when used in SMA mixtures gave the highest Marshall Stability, flow, ITS and


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TSR values. The 6% blend also increased the Rupture and Stiffness Modulus which contributes to lesser

strain in the SMA mixtures. They concluded that using LDPE-asphalt blend in asphalt mixture can reduce

required thickness of both base layer and surface (SMA) by 25% and 34% respectively.

2.8 Sisal Fiber

Sisal Fiber is extracted from leaves of Agave Sisalana, a plant native to tropical and sub-tropical

Americas. It is also widely grown in tropical regions of Africa, East Asia, and the Indies. Worldwide sisal

fiber production stands at 300000 tons/yr, with Brazil producing more than a third (120000tons/yr).

Tanzania, Kenya, China and Mexico are the other leading producers (UN FAO, 2013). Sisal fiber is mainly

used in manufacture of rope and twine for the marine, construction and agriculture industry. It is also

used in production of high grade paper, upholstery, carpets and related products.

Sisal fiber is mainly composed of varying amounts of cellulose, lignin, hemi-cellulose and pentosan,

depending on the age and source of fiber and method of measurements. Standard fiber length ranges

from 1-1.5m, and its diameter its in the range of 100-300 m. Table 1 gives a brief insight into chemical

compositions of sisal fiber as reported by different sources.

Table 1: Chemical Properties of Sisal Fiber

Study

Content

Wilson

(1971)

Rowell

(1992)

Chand & Hashmi

(1993)

Joseph et al.

(1996)

Textile Fashion Industry

(2012)

Cellulose (%) 78 43-56 49.62-60.95 85-88 71.5

Lignin (%) 8 7-9 3.75-4.4 5.9

Hemi-cellulose (%) 10 18.5

Pentosan (%) 21-24

Chand, et al. (1986) found that cellulose content and spiral angle of the microfibrils contributed to its

strength and stiffness. Gordon and Jeronidimis (1980) proved that the highest impact toughness of fiber-

composites is at an optimal microfibrillar angle in the range of 15-20, which makes sisal fiber (21)

excellent for use in composites. A comparison of properties of sisal fiber with oil palm fiber as compiled


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by Shinoj, et al. (2011) indicates that sisal fiber exhibits equal, if not better, properties than oil palm

fiber.

Sisal fiber-rubber matrices have been extensively studied for improving properties of rubber (Prasantha,

et al., 1997), (Kumar & Thomas, 1995), (Varughese, et al., 1994), (Maya Jacob, 2004), (Bakare, et al.,2010). 6mm fiber length was found to be optimal. A high fiber-volume fraction, and proper orientation

significantly improved rubbers resistance to aging (Varughese, et al., 1994). Li et al. conducted an

extensive review of developments in sisal fiber and its composites in 2000. He discovered that sisal fiber

was effective as a reinforcement in a variety of other matrices including polymers (polyethylene,

polystyrene, PVC), gypsum, cement and resin.

Conclusion

A thourough review of use of fibers in bituminous mixtures has been presented. From Europes use of

wood pulp cellulose fibers in SMA Mixtures, to BoniFibers used in surface courses in Lansing, Michigan

and Malaysian studies investigating rheology of COPF-asphalt blends. Fibers have been found to

improve: a) Rheological and ageing properties of asphalt cements and b) Mechanical and Volumetric

properties of flexible asphalt mixtures. The properties of sisal fiber and the potential it has shown as

reinforcement in a variety of matrices make it a prime candidate for use in asphalt mixtures. As a

sustainable, locally sourced product in Tanzania, its use in SMA mixtures can be easily implemented with

the right information and guidelines, to the benefit of the whole country. In order to develop these

guidelines, an in depth study of Tanzanian sisal fiber-asphalt blends and mixtures shall be conducted.

Compatibility of sisal fiber with asphalt-rubber blend shall also be examined during this study.

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Fibers in Bituminous Mixtures - A Review 11-14