Coralline materials are usually considered to be of poor quality due to variation in coral type, degree of recrystallisation, level of self-cementation and amount of contamination with plastic fines. The existence after 40 years however, of pavements and concrete structures constructed by the Americans during World War II, belies this commonly held belief. This thesis describes a field study, a testing programme and a numerical modelling exercise which have been carried out to develop a better understanding of the success of coral-derived materials in engineering works.
The documented information concerning the uses of coral-derived materials was found to be mainly of an historical or anecdotal nature. The initial phase of the work constituted a literature review and study of current construction practice throughout the South Pacific.
To enable the systematic evaluation of the properties and uses of coral-derived materials a field evaluation and sampling procedure was developed. A number of coralline materials, with varying quality, from Papua New Guinea and Australia, were selected to represent the full range of coralline materials available.
Engineering aggregate tests, for particulate evaluation, were carried out on the selected materials. The performance of compacted coralline mass was studied using triaxial compression, unconfined compression and CBR tests. Trial mixes of Portland cement concrete and asphaltic concrete were used to determine the functionability of coral-derived materials in those areas.
The propensity of the materials for self-cementation was investigated by ageing CBR, triaxial specimens and specially prepared mini-specimens. Curing was carried out for up to 150 days.
The strength parameters derived during the initial studies were utilised in computer simulation trials to evaluate the behaviour of compacted coralline materials. Modelling of the CBR test and a coralline pavement (subjected to a standard axle) were carried out.
Permeability studies were undertaken on compacted base material and cemented surface crust material to determine susceptibility to water ingress.
It was concluded that the low shear strength properties of coralline particulates preclude the use of the material as a high strength aggregate in concretes. The most effective use of the materials is in a compacted state in pavement base and sub-base construction where high compacted strength and stiffness characteristics are best utilised.
The self-cementation phenomena allowed the development of increased strength and stiffness within the pavement mass. The cementation within the surface crust was found to be dependent upon the grinding action at the pavement surface.
Permeability data indicated that coralline pavements were susceptible to water infiltration. The presence of a cemented surface crust greatly reduced vertical infitration and aided in the reduction of scouring.
The parametric studies carried out demonstrated that the high compacted strength and increased cohesion and stiffness due to self-cementation allows coral-derived materials to function as excellent pavement bases and sub-bases. The increased stiffness and cohesion resulted in reduced transient and permanent deflections throughout the pavement profile.
It was concluded that the widespread use of coral-derived materials is justified with particular emphasis on use in road and airfield pavements.