No abstract

e influence of two lightweight aggregates (LWA) on concrete and the effects of cement substitution for nanosilica (NS) on the interfacial transition zone (ITZ) and cementitious matrix of concrete in resistance to attacks by magnesium sulfate (MgSO 4 ) are researched in this work. e aggregates evaluated were perlite, which is a lightweight aggregate of open porous structure, and expanded clay (aliven) with closed porous structure. e variables included in the study were replacement percentage of coarse aggregates by lightweight coarse aggregates (0 and 100% by volume) and replacement percentage of cement by nanosilica (0 and 10% by weight). In the dosage of the mixtures, water/cementitious-material ratio constant of 0.35 was used. e LWA were characterized by XRD, XRF, and SEM techniques. Compressive strength, water absorption, and volume change in magnesium sulfate solution (according to ASTM C1012 for a period of 15 weeks) of lightweight concretes were evaluated. It was found that the nanosilica had effect on refinement in the pore system; however, the main incidence on the compressive strength and durability of lightweight concrete (LWC) was defined by the characteristics of lightweight aggregate used in its preparation.

Fly and Bottom ash a coal combustion residue of thermal power plants has been regarded as a problematic residue all over the world. This study presents the results of testing for resilient modulus and permanent deformation to evaluate the mechanical properties of a soil stabilized with fly or bottom ashes, with and without lime addition. The soil tested is a regional sandy soil, which is not suitable for use in pavement works. The addition of fly ash with lime improved their mechanical properties, these being dependent on the ash content, moisture and number of load cycles. However in the mixtures only with ashes, the improvement was lower than the mixtures with ashes and lime. It was performed a paving project to assess their competitiveness as a base material for pavements. The results of this project showed that the soil stabilized with ashes is competitive for low volume traffic roads, with the advantages of minimizing the environmental problems caused by coal ash disposal.