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The performance of cemented pavement materials under heavy axle loading
In order to distinguish essays and pre-prints from academic theses, we have a separate category. These are often much longer text based documents than a paper.
posted on 25.06.2020, 02:16by Yeo, Richard Eng Yat
In this thesis, improved approaches to the laboratory characterisation of
cemented materials are developed and verified enabling a more informed
understanding of the load-carrying capacity of cemented materials used in road
The increasing use of high productivity road freight vehicles and the application
of mechanistic-empirical pavement analysis has led to the need for improved
knowledge of the performance of pavement materials. In Australia, standard
methods are not available for the elastic characterisation of cemented materials.
As a result, presumptive values or correlations with parameters such as
unconfined compressive strength (UCS) are used. In this study pavement
design methods, failure mechanisms and approaches to cemented materials
characterisation are investigated. Theoretical modelling and prediction of crack
growth in cemented materials under repetitive loading is reviewed. The use of
initial modulus and the reduction in modulus under repetitive loading is
proposed as a pragmatic indicator of fatigue crack growth. Improved laboratory
protocols for the characterisation of strength, breaking strain, modulus and
fatigue are developed using a four-point bending, dynamic flexural beam test.
The protocols were applied to two typical cemented materials, a hornfels with
3% cement and a siltstone with 4% cement at a range of curing ages. Breaking
strain was identified as an indicator of initial micro-cracking. A stress controlled
fatigue test was used to establish relationships between initial strain (S) and
fatigue life (N) (load cycles to half initial modulus).
The verification of the improved laboratory protocols involved a comparison of
the labboratory test results with the results of full-scale accelerated pavement
testing (APT). For the siltstone, the laboratory and field performance results
aligned well. Differences between the laboratory and field materials properties
resulted in a lesser alignment of the performance results for the hornfels. The
relative performance ranking between the two cemented materials from the improved laboratory protocols matched that from the APT. The ranking from
the traditional UCS did not align with the APT results.
Further verification was sought using the Australian long term pavement
performance study and anecdotal evidence of cemented materials performance
to enable consideration of combined environmental and traffic effects over an
In the final stage of the study, the applicability of the improved laboratory
protocols to a wide range of cemented materials was confirmed and a limited
study into the extent of initial micro-cracking and the fatigue load-damage
exponent was undertaken for two cemented materials.
It was concluded that the four-point bending flexural beam test developed and
verified in the study provided a significantly improved method of assessing the
performance of cemented materials compared to the UCS test. The improved
laboratory protocols were found to be suitable for testing a wide range of
cemented materials. It was also found that, where consistent micro-cracking
was present, the load-damage exponent was not dependent on the extent of