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Modifcation o bitumen

Bitumen has been used in the in the construction of exible pavement for a more

than a century in laying wearing course. There has been exponential increase in

trac volume, overloading of commercial vehicles and signicant variations in dailyand seasonal temperatures showing limitations in bituminous binder performance

and has led to early development of distress symptoms like cracking, rutting,

ravelling, shoving and potholing of the bituminous surfacing. Bitumen as visco

elastic materials plays a prominent role in determining many aspects of road

behavior !"amalinga et al, #$%&'. The wearing course should be exible enough at

low service temperature to prevent cracking and sti( enough at high service

temperature to prevent rutting. )lexible pavement that have been constructed

using conventional bitumen don*t perform as expected necessitating modication of 

bitumen to be carried out.

+onventional bitumen has been modied using polymer and chemical reaction.

nvestigations have revealed that properties of bitumen and bituminous mixes can

be improved to meet the growing re-uirements of pavement with incorporation of 

certain polymers as it o(ers a combination of performance related benets as it

improves the physical properties of the bitumen without changing the chemical

nature of it !"amalinga et al,  #$%&'. odied bitumen provides the diversied

properties needed to build better performing roads. Bitumen modied with polymer

has gained momentum due to its vast application in the eld of exible pavements

!/irey 01., #$$#'.

 The polymer usually inuences the bitumen by creating an interconnecting matrix

of the polymer through the bitumen. t is this matrix of long chain molecules of the

added polymer that modies the physical properties of the bitumen. These additives

increase the elasticity, decrease the brittle point and increase the softening point of 

the bitumen. This, in turn, will alter the properties of the mix in which such modied

bitumen is used and these mixes will exhibit greater sti(ness at higher temperature

and high exibility at low temperatures.

2sing of waste material to modify bitumen helps in solving serious environmental

problems and at the same time improve road performance. The main advantage ofusing polymer technology is to improve adhesion properties between the binder and

the aggregates and provide a higher strength to the modied bitumen or mixtures

!"amalinga et al, #$%&'.

3e may still be asking ourselves the big -uestion4 why do we need to improve the

properties of Bitumen5 ncreased trac loads and climate change is still a big

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challenge for researchers in the asphalt road industry. "esearches are trying to nd

a new addition to improve the properties of bitumen and to have a clear impact in

the performance of asphalt roads.

n improving the properties of bitumen, several types of modication have been

carried out. These include additive modication, polymer modication and chemical

reaction modication. nvestigations have revealed that properties of bitumen andbituminous mixes can be improved to meet the growing re-uirements of pavement

with incorporation of certain additives. )or many years, researchers and

development chemists have experimented with modied bitumen mainly for

industrial uses, adding asbestos, sulphur, magnesium, mineral bers and rubber

among other additives.

6unith et al !#$$7' used reclaimed 68 as asphalt modiers. They found that the

basic test properties indicated that the additional of 68 content to neat asphalt

reduces the penetration and ductility values, whereas increase in softening point

and specic gravity values were observed with the addition of 68 modier. / 68content of &9 by weight of asphalt is recommended for the improvement of the

performance of asphalt cement. / studies carried by 8meritus !#$$#', cement, lime

and chemicals like sulphur and manganese had been used to improve the viscosity

of bitumen enhancing adhesion between the bitumen and aggregate

:hirish et al !#$%;' carried out a study on utili' carried out a study on the performance evaluation of polymer

modied bitumen in exible pavement. The ob?ective of work was to investigate the

e(ect of plastic waste in exible pavement and suggest the optimum percentage of

bitumen that could be replaced by plastic waste for the improvement of roads. The

results obtained in the laboratory investigation indicated ma?or gain in strength with

substantial saving in cost. /nother experimental study was carried out by /shok et

al !#$%#' on performance of polymer modied bitumen for exible pavement.

8xperimental study was carried out on conventional bitumen and polymer modied

binder. The results indicated that rutting resistance, indirect tensile strength and

resilient modulus of the bituminous concrete mix with polymer modied bitumen

signicantly improved.

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 Tari- et al !#$%>' on his study on sustainability of bitumen with 68 as polymer,

concluded that polymer modied =/ shows better engineering properties than

simple bitumen mix and it has a higher sti(ness at high service temperature that

will result in reduced rutting as the blend has increased softening point. The

phenomenon indicated that the resistance of the binder to the e(ect of heat was

increased and it reduced its tendency to soften in hot weather. This is good in thesense that it improves the overall performance of =/ by increased rutting

resistance, durability, and load carrying capacity, improved resistance to

weathering e(ects, increased stability and improved binding properties of =/.

"upesh et al #$%& carried out study on economic construction of bituminous road by

the utili

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Sugar cane is one of Kenya*s most important cash crops. %urrently, most of the pulp, or 

+bagasse*, left after the cane*s uice is e'tracted goes to waste. -n this film, ohn /wero, an

engineer at the 0niversity of 1airobi, tals about his &h3 research on adding the ash left after 

 burning bagasse to cement. 1ot only does doing so recycle this readily available by4product, but

it also strengthens concrete.

 /wero*s &h3 was made possible through a scholarship with $/S51 (the $frican /aterials

Science and 5ngineering 1etwor#. $/S51 is part of 6-S5 (the 6egional -nitiative in Science

and 5ducation#, a programme designed to strengthen higher education in Sub4Saharan $frica.

/wero argues that without the access to other universities* equipment and the networing

opportunities with other $frican academics that the scholarship provided, it would have been

impossible to obtain his &h3 in Kenya.