Read Journal 1261 Volume 58 No 1 – Are estimate of catchment response time inconsistent as used in current flood hydrology practice in South Africa?

Ultra-thin continuously reinforced concrete pavement (UTCRCP) is an innovative pavement type that has the potential to fulfil South Africa’s pavement repair strategy requirements. Premature failure in UTCRCP is linked to the formation of cracks that allow water ingress into supporting layers. Environmental conditions, as well as concrete properties, determine the concrete cracking tendency. Concrete properties are a function of the mixture proportions, and unlike environmental conditions, mixture proportions are controllable. The effect of mixture proportions on the properties of high-strength concrete (HSC) used in UTCRCP should be investigated.

The objective of this research was to study the influence of paste content on the properties of HSC used in UTCRCP. Two sets of concrete were tested. The paste content of the first
set was varied from 23% to 37% by mass, using multivariable analysis in conjunction with superplasticiser (SP) dosage. The paste content of the second set was varied from 25% to 60% by mass, only varying SP dosage to control the workability.

The multivariable analysis revealed that, within the parameter range tested, paste content influenced early-age properties, but not long-term properties. Through variation of the paste content over a wider range during the second set it was found that paste content does influence both the early-age and long-term properties of HSC. From the results it could be seen that increasing the paste content of HSC generally has a detrimental effect. The paste content of HSC used in UTCRCP should be minimised, while maintaining a reasonable workability.