Virginia Rubio

Debris flows in a weathered granitic massif: Sierra de Gredos, Spain

Abstract Sierra de Gredos is composed of Hercynian granitic rock, the parent material for a weathering mantle, which extends throughout the range except in the areas that were eroded by glaciers during the late Pleistocene. Recent debris flows have formed on the steep slopes covered by the weathering mantle, causing considerable destruction. This study analyzes the impact of the mantles structure and chemical composition on the formation and evolution of debris flows. The results show that the weathering mantle, despite its incipient state, is very thick in certain areas and that debris flows always originate here forming head scarps and channels that funnel the slope wash. This action leads to gullying, which quickly destroys the debris flow deposits and channels. Debris flows are influential in developing the drainage system in Sierra de Gredos, and the research suggests that debris flows occurring in other weathered granitic mountain ranges may have a similar impact.

Random ionic mobility on blended cements exposed to aggressive environments.

It is known that the partial replacement of cement by pozzolanic admixtures generally leads to modifications in the diffusion rates of harmful ions. Recent research has centred on obtaining new pozzolanic materials from industrial waste and industrial by-products and on the way that such products can influence the performance of blended cements. This paper reports the behaviour of cements blended with calcined paper sludge (CPS) admixtures under exposure to two different field conditions: sea water and cyclic changes in temperature and humidity. Cement mortars were prepared with 0% and 10% paper sludge calcined at 700 degrees C. The penetration of ions within the microstructure of cement matrices was studied using X-ray diffraction (XRD) and scanning electron microscopy equipped with an energy dispersive X-ray analyser (SEM/EDX) analytical techniques. The results show that ionic mobility varies substantially according to the type of exposure and the presence of the calcined paper sludge. The incorporation of 10% CPS is shown to assist the retention and diffusion of the ions.

Forced Aging and Ionic Mobility of Ternary Cements Exposed to Aggressive Saline Marine Environments and Cryoclastic Processes

The most common supplementary cementitious materials used in concrete, in addition to Portland cement, are fly ash and silica fume; metakaolin, produced by controlled thermal treatment of kaolin, is also used in cementitious composites on account of its pozzolanic properties. This study forms part of an extensive research into the degradation of uncommercialized pozzolanic ternary Portland cement (TPC) exposed to different saline marine environments and cryoclastic processes. In marine environments, CSH gels from ordinary Portland cement fill the gaps between the grains and cover the surfaces. However, the porosity of ternary Portland cement is notably higher and permits the retention of ions. Cracking as a consequence of cryoclastic processes is found in the CSH gels and ettringite of ordinary Portland cement in continental climates. However, when ternary Portland cement is studied under similar conditions, the cracks are partially sealed by the gels without further rupturing due to the aforementioned processes.