Characterisation of Lightly Stabilised Granular Materials by Various Laboratory Testing Methods

Light cementitious stabilisation is a cost effective technique for improving the mechanical properties of granular base materials and is often used for constructing new as well as for rehabilitating and upgrading existing pavements. An extensive experimental investigation was undertaken to assess the behaviours and characterise the properties of two granular road base materials lightly stabilised with cement-flyash and slag-lime using various testing methods. The testing methods include flexural beam, indirect diametrical tensile (IDT), unconfined compression (UC) and accelerated model pavement (AMP). Two new/improved flexural beam testing setups (i.e., one for monotonic and the other for cyclic-load/dynamic testing) were developed to measure the net mid-span vertical deflection of the beam specimen from its neutral axis. The results indicated that the on-sample instrumentation proposed in this study is suitable for determining the flexural strength, breaking strain, static stiffness modulus (SSM), dynamic stiffness modulus (DSM) and fatigue life reliably and consistently. An improved IDT testing setup was also developed for directly calculating the Poissons ratio of lightly stabilised materials. Additionally, the IDT strength, SSM, DSM and fatigue life were also determined from the upgraded IDT testing setup. A nonlinear model based on modified Ramberg-Osgood expression was also proposed for predicting the nonlinear stress-strain behaviour of lightly stabilised materials obtained from UC testing. The test results indicated that the proposed nonlinear model can model the experimental stress-strain relationship with good accuracy. In addition, AMP testing was conducted by applying traffic-type sinusoidal loading on a model pavement consisting of a lightly stabilised base overlaying a compacted clay subgrade from which the stiffness moduli of each layer, permanent deformation accumulation and damage due to fatigue were determined. Finally, the mechanical properties obtained from different testing methods were compared and best-fit expressions among them were proposed, wherever appropriate. The average horizontal stiffness modulus of the lightly stabilised base layer obtained from AMP testing was very close to the SSM determined from the flexural beam testing. On the other hand, the fatigue life obtained from the flexural beam testing was found to be 23% of that from the IDT testing