The extent of rubber-bitumen interaction in crumb rubber modified (CRM) binders depends on the contact time of rubber-bitumen as well as the temperature and mixing energy. However, this can vary depending on the composition of the base binders as well as the characteristics of the rubber particles (composition, method of grinding, and size). The present study aims to determine the influence of the composition of the base binders and the type of rubber on the properties of the crumb-rubber modified (CRM) binders and the performance of the asphalt mixtures produced with them. To carry out this project, two different base binders were chosen with the same penetration grade but different naphthenic-aromatic content (56.7 versus 46.0%). Additionally, different types of ambient ground rubber powder were evaluated: two different sources (70% of truck tyres +30% of passenger car tyres and 100% of truck tyres) and two different maximum particle sizes (0.8 and 1.25 mm). According to the main results of this study, higher naphthenic-aromatic content of the base binder results in greater modification of the CRM binders. Likewise, asphalt mixtures made with CRM binders from base binder with higher naphthenic-aromatic content appear to offer better performance in terms of water resistance and fatigue life.
The aim was to measure the behaviour of various mortars employed in livestock media in central Spain and to analyse the aggressiveness of pig slurry to cement blended with flyash mortars. To achieve this, mortar specimens were immersed in ponds storing pig slurry. Mortar specimens, of 40 x 40 x 150 mm, were made from four types of cement commonly used and recommended for rural áreas. The types were a sulphate-resistant Portland cement and three cements blended in different proportions with fly ash and limestone fiUer. After 3, 5, 12, 24, 35, 48 and 50 months of exposure, three or four specimens of each cement type were removed from the pond and washed with water. Their compressive strength and microstructure (X-ray diffraction, mercury intrusión pore-symmetry, thermal analysis and scanning electrón microscopy) were then measured. Sulphate-resistant Portland cement (SR-PC), found to be more susceptible to degradation due to its greater proportion of macro-pores and increased total porosity, was found not to be suitable for use with livestock. After 50 months of immersion in the pig slurry médium, CEM II-A (40.3%) mortar retained the greatest compressive strength. Mortars with less than 20% replacement of cement by fly ash were found to be the most durable, with the most suitable mechanical behaviour.
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