Innovative and recycled materials Roads and highways Sustainability Composite stiffness Dynamic plate test
Drivers for sustainability have made it necessary for the construction industry to adapt
its traditional processes to become both more efficient and produce less waste.
Performance based design and specification in the UK for motorways and trunk roads
permits a very flexible approach to pavement design, material selection and
performance related testing aimed at utilising materials to their maximum potential.
However, it is clear that within the emerging philosophy of using materials that are ‘fit
for purpose’ there are many technical challenges for design and specification. There is a
need to develop suitable methods of evaluating materials prior to their being used on
site. This project was born out of this requirement, with a particular emphasis on coarse
granular materials due to their common role in capping construction and also their
unique difficulty for measurement under laboratory conditions due to their large range
of particle size.
A novel assessment test for coarse capping materials for roads that can be used to
indicate their likely short-term in situ performance, under controlled laboratory
conditions before construction on site, has been developed during this research
programme. Key findings relating to the behaviour of coarse capping materials, the use
of stiffness measuring devices and variables that influence the measurement of
composite stiffness are discussed in detail. The research highlights the necessity for
adequate drainage and protection of foundation materials against increase in water
content. When adopting a performance specification the timing of the pavement
assessment is critical, both on site and in the laboratory. The performance measured on
site should perhaps only be considered as a ‘snapshot’ relating to the stress state in the
material at the time of testing.
A dissertation thesis submitted in partial fulfilment of the requirements for the award of the degree Doctor of Engineering (EngD), at Loughborough University.