Durability of reclaimed asphalt pavement–coal fly ash–carbide lime blends under severe environmental conditions

The sustainable use of industrial residue in enhancing the long-term performance of reclaimed asphalt pavement (RAP) has been proven to be effective under freeze–thaw and wet–dry conditions. This study focuses on coal fly ash (FA) and carbide lime (CL) as the enhancing agents. It evaluates how the durability and long-term performance of compacted RAP–FA–CL mixtures are impacted by dry unit weight and lime content. The tested mixture’s specimens were moulded in three layers through static compaction inside a cylindrical mould. Several single-level variables were used in the stabilisation process. Among these were: FA content of 25%, optimum water content of 9% (modified effort) and seven days of curing. Additionally, three target dry unit weights (17, 18 and 19 kN/m3 – the last of which was determined using the modified Proctor energy) and three percentages of lime content (3%, 5% and 7%) were used for a comparative analysis. The tested specimens’ accumulated loss of mass (after wetting–drying and freezing–thawing cycles) and splitting tensile strength were both evaluated as a function of the porosity/lime index. The experiments revealed that compacted RAP–coal FA–CL mixtures performed noticeably worse when subjected to freezing–thawing cycles than when subjected to wetting–drying cycles. These results indicate an increase in the breadth of the porosity/lime index, as it is shown to control the long-term performance of compacted RAP–coal FA–CL mixtures, in addition to controlling their mechanical response

Mechanical behavior of intact and remoulded calcareous silts

Calcareous siltsare encountered in many offshore areas where oil and gas exploitationsaretak-ing place (e.g., Arabian gulf, southeastof Brazil, south east and north west of Australia). Understanding be-haviorof calcareous silts remainschallenging as undisturbed siltsamples are difficult to obtain, and most studies rely on remouldedsiltsamples. The purpose of this paperis to characterizethe mechanical behaviorof intact and remouldedoffshore calcareous silts from two different water depths. The comparisons are done based on microstructure characterizationusing scanning electron microscopy (SEM) images supported by in-dex tests, one-dimensional compression tests and undrained monotonic triaxial tests. The results have shown that,except for the critical state friction angle, the behaviour of remoulded silts differs from that of intact silts, due to the change in microstructure, which appears to be more compact with less intact open shellparticles

Experimental assessment of sampling disturbance in calcareous silt

A small-scale physical modelling program using particle image velocimetry and digital image correlation techniques was designed to obtain a refined understanding of the disturbance experienced by calcareous silt during tube sampling. The influence of the sampler wall thickness (diameter-to-thickness ratio, B/t) and the tube penetration rate were evaluated by estimating displacement and strain fields around the tube sampler. The results indicate that sampling with a thin tube leads to a relatively narrow undisturbed zone located at the centre of the tube, with a width slightly smaller than the tube radius. Opposite to what is suggested for soft clays, tube sampling tends to densify the calcareous silt. This aspect has an important influence on the assessment of sample quality in calcareous silt for offshore and onshore projects