Summary

A review of relevant properties of Keuper Marl indicates that much of the Marl is likely to be suitable for cement stabilization, exceptions being marls which are either too plastic or contain deleterious proportions of sulphates.

The results of static, rapid and repeated compression tests carried out on a 'typical' marl stabilized with cement are reported. The stiffness of the material as measured by the modulus of deformation is shown to be a function of cement content, moulding moisture content, rate of strain and stress history. Repeated load tests showed that when the intensity of stress applied was 65 per cent of the initial compressive strength, fatigue failure was imminent after 104 applications of load. Of particular significance was the fact that the modulus of resilient deformation was independent of the number of load cycles applied and sensibly constant over a range of stress intensities. Values of Poisson's ratio were of the low order of 0·04 to 0·20 and increased rapidly as samples approached failure.

The marl containing 10 per cent cement had a 7-day compressive strength of the order of 300 lb/sq in and would therefore fail to comply with the Ministry of Transport's proposed new specifications requiring 400 lb/sq in. It is concluded that although the stabilized marl may not be acceptable for road base construction, it should serve satisfactorily for sub-bases.

Two construction problems previously encountered when stabilizing Keuper Marl, are discussed and suggestions made for overcoming them.

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