Some of the newly constructed highway pavements in the Kingdom of Saudi Arabia have shown premature failures with consequential negative impacts on both roadway safety and economy. A major type of these failures is permanent deformation (rutting). Fillers were suspected to be major contributors to rutting susceptibility. The effect of filler type and content on the rutting potential of asphalt concrete as well as other mixes properties was investigated. The wheel tracking test (LCPC) was employed to investigate susceptibility of these mixes to rutting. The mechanical properties of mixes were studied using tests such as resilient modulus, indirect tensile strength, Hveem stability and Marshall criteria. Results of this study indicate that partial replacement of limestone dust by hydrated lime or portland cement aggravates resistance of the mixes to rutting. Furthermore, an analytical model was developed for predicting rutting potential based on various mixes properties.
An improved model to predict the ultimate drying shrinkage of concrete is proposed. The model is derived from the theory of elasticity, composite theory, and microstructural considerations. The model includes the effects of the drying shrinkage of paste, the relative restraining volume of the aggregate and unhydrated cement, the elastic modulus, and Poisson's ratio of the shrinkage active phase (hydration products), the shrinkage restraining phase (aggregate and unhydrated cement) and the concrete. The model requires the ultimate drying shrinkage of a paste of the same wlc ratio as the concrete. It was found that the elastic modulus of concrete can be accurately predicted by using a model intermediate between the extreme boundaries described by Paul. The improved model proposed was tested on shrinkage data for thin mortar specimens at 50% relative humidity ( R H ) found in the literature for a wide range of aggregate content and curing times, and the results confirm the validity of the model.
The pore structure (i.e. surface area, pore size distribution and pore volume) of well-hydrated portland cement pastes of water-cement ratios 0.4, 0.6, and 0.75 were investigated by the nitrogen sorption and mercury intrusion porosimetry (MIP) techniques. The effect of solvent replacement by methanol on the pore structure was studied as well. It was concluded that the solvent replacement drying procedure preserves the original pore structure of hydrated cement because the calculated and measured bulk densities of the different water-cement ratio systems investigated were in excellent agreement. Capillary condensation analysis was used to estimate the volume of capillary pores smaller than 4 nm in pore diameter for the 0.6 and 0.75 water-cement ratio pastes. The 0.4 water-cement ratio paste has pores smaller than can be determined from capillary condensation analysis. The volume of pores smaller than 4 nm was estimated from volume-thickness (V-t) analysis. For the three systems investigated, the volume of pores greater than 4 nm was obtained by MIP. For solvent-replaced pastes that showed capillary condensation according to V-t analysis, excellent agreement was obtained between the nitrogen sorption and MIP techniques in the pore diameter range of 4 nm to 30 nm.
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