Question: $4$

Bitumen Emulsion vs Foamed Bitumen Technology

$[20$marks$]$

Using the relevant sources of literature, publications, and carry out a critical comparison of foamed

bitumen versus emulsion technology as used in pavement construction. Some of the factors to be

included in the analysis includes:

Binder characterisation and contents typically used,

Suitable aggregate types and gradings,

Active filler $($type$,$ percentage and its role$)$

Moisture considerations $($mixing$,$ placement, compaction etc$)$

Curing rates

Engineering properties $($UCS$,$ ITS, shear parameters etc$)$

Performance indicators, failure mechanisms

Comment on similarities and differences between bitumen emulsion and foamed bitumen, including

references.

Question: $5$

The Binder

$[20$marks$]$

a$)$ With bitumen emulsions the settlement process $($the bitumen phase or part of it moves

towards the bottom of the emulsion container during storage$)$ is a known phenomenon.

How can one reduce the settlement sensitivity of an emulsion????? $($at least Stokes law must

be used in the explanation$).$

b$)$ Bitumen can be characterised with a Bitumen Test Data Chart, BTDC$,$ Why would an asphalt

producer and a contractor be interested in the BTDC plot for bitumen $($what information

would they extract?$)$ how can one easily compare temp susceptibility of two types of

bitumen on the BTDC$?$ Demonstrate by schematic BTDC graphs

c$)$ A certain bitumen has the following test results Penetration $(25$C$)90,$ Softening

$($Tr&b$)=48$C$,$ Viscocity @$60$C$=102$Pa$.$s$,$ Viscosity @ $135C=0\mathrm{.}28Pa.$s$,$ plot the results in the

BTDC$?$ What do you expect to be the grade of this bitumen? What is PI for the bitumen?

d$)$ Name five different approaches to asphalt mix design and give example on each which are

appropriate to be used in Rwanda and Why?

END