Residual soil from the Passo Fundo region (Brazil), presents natural cementation, responsible for a peculiar behaviour that is clearly distinguishable from that of soils with other origins. Understanding this behaviour and the effects of the fabric, with an influence on the cementation bonding, is essential to characterise these materials. Therefore, the aim of the present study is the mechanical characterisation of this soil, mainly by analysis and testing of remoulded and undisturbed samples. The experimental programme included uniaxial compressive strength tests, oedometer tests, consolidated drained monotonic triaxial tests and consolidated undrained cyclic triaxial tests. Based on the data collected, a clear influence of interparticle bonding, provided by the natural cementation, was detected on the soil's intrinsic behaviour; the undisturbed material showed a higher stiffness modulus than the remoulded material, mainly due to the bond breakage to which the latter was submitted, losing its natural cementation. A uniaxial confining stress of 89.4 kPa was obtained for the undisturbed material, assumed to be its yield stress. This value was corroborated by the oedometric (87.5 kPa), isotropic (80 kPa) and triaxial compression (90 kPa). The natural cementation was influential in every type of loading and should be considered during the design process.
The use of industrial wastes such as coal fly ash (CFA) and carbide lime (CL) can enhance the long-term performance of recycled asphalt pavements under freeze–thaw conditions as well as reduce consumption of natural resources. Further improvement of the mechanical properties of such blends can be achieved by adding small quantities of sodium chloride (NaCl). Blends of recycled asphalt, CFA, CL and sodium chloride were therefore assessed in terms of their durability to freeze–thaw exposure. Additional splitting tensile tests were performed to evaluate strength improvements after adding sodium chloride. Specimens were moulded with three different dry unit weights and two different lime percentages, and cured for 7 d. The accumulated loss of mass was evaluated as a function of the porosity/lime index, which broadens the applicability of this index by demonstrating it, and influences not only strength but also long-term performance. The improvement in engineering properties provided by sodium chloride was found to be related to the formation of mineral phase thomsonite and to sodium chloride acting as a catalyser.
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