Pilot-scale trials were laid to investigate the properties of roller-compacted lean concrete roadbases in which pulverised fuel ash was included as a partial replacement for some of the cement. A conventional lean concrete and a cement-rich concrete were included in the trials for comparison. Structural performance was assessed by measuring strain and deflection under a moving wheel and elastic modulus by surface wave propagation. Beam specimens cast in moulds and cut from the trial area were used to determine stress-strain relationships, flexural strength and elastic modulus. The measured transient deflections and strains in the ash-modified lean concrete pavements were similar to those in the conventional lean concrete; the values of elastic modulus were also similar. Results from the beams showed that in general the ash-modified mixes have a lower early life strength and a higher long term strength than conventional lean concrete. An analytical study suggested that both ash-modified lean concrete with a low early life strength and conventional lean concrete may suffer from microcracking when trafficked by construction vehicles at 7 days old but visible cracking should not occur. The overall structural behaviour of the pilot-scale trials was sufficiently encouraging to recommend a full-scale trial of ash-modified lean concrete. (A)

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