Silvio Delvasto Arjona

Refuerzo secundario de pastas de cemento portland ultrafino con nanofibras agregadas de poli (alcohol vinílico)

En este articulo se presentan resultados de una investigacion sobre la validacion de nanofibras agregadas de PVA obtenidas por sol-gel electrohilado, para reducir la retraccion y las fisuras por fraguado de pastas de cemento portland ultrafino. La metodologia aplicada consistio en variar la longitud de las nanofibras agregadas de PVA en 6 y 12 mm. Este procedimiento permitio evaluar el desempeno de estas nanofibras y compararlas con el de la misma matriz cementicia reforzada con fibras comerciales de polipropileno (PP). Las tecnicas de caracterizacion aplicadas sobre las pastas fibrorreforzadas fueron granulometria laser del cemento, ensayos a la compresion, a la flexion e impacto y observacion de falla a traves de microscopia electronica de barrido (SEM). Igualmente se observo la retraccion y el fisuracion a edades tempranas. Los resultados mostraron que las pastas de cemento con fibras agregadas de PVA presentaron resultados mejorados comparados con las pastas de cemento que contenian fibras de PP. Este tipo de material compuesto podria ser utilizado en la elaboracion de tuneles, lechadas en la reparacion de edificaciones, y en general, en aplicaciones que requieran la inyeccion o relleno debido a las caracteristicas fluidas de este tipo de cementos.

Materiales compuestos ligeros basados en yeso con refuerzo de fibra de cascarilla de arroz y poliestireno

Gypsum matrix composites were made with rice husk and polystyrene particles in order to obtain lightweight materials. The composites were mechanically characterized, and morphologically analyzed by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). Gypsum and rice husk interfacial transition zone were studied by means of pull-out testing and microstructural analysis. The results showed that the polystyrene allows obtaining lightweight composites with low mechanical properties, which may be considered for non-structural applications. Rice husk fibers reinforcements significantly increased the mechanical properties of the gypsum matrix that due to the good adhesion and the amount of reinforcement used in a major way affecting the toughness.

Caracterización física y mecánica de agregados reciclados obtenidos a partir de escombros de la construcción

The saturation of disposal sites of solid wastes is a major problem faced by Latin America countries, including Colombia, which can be attributable to their inefficient use and the lack of adequate policies on how to manage, for example, construction and demolition debris. In the city of Cali, Colombia, for example, approximately 2,480 m 3 of debris are produced per day, of which only 40% is recycled. An alternative is to reuse this debris to manufacture prefabricated materials. This study accordingly transformed a specific, representative sample of construction and demolition debris into different-sized aggregates to characterize their physical and mechanical properties; evaluate their potential use in conventional concretes; and determine the viability of their use in the production of building materials.

Concreto autocompactante con altos contenidos de subproductos de la combustión de carbón

The self-compacting concrete (SCC) has been considered as a great achievement in concrete technology due to its great advantages like self-compactability. In order to have self-compactability fresh concrete should demonstrate high fluidity, segregation resistance and good cohesion. Having the purpose of evaluate these properties, it was used a byproduct of coal combustion fly ash (CV) and grilled slag (E), also several self-compacting concrete mixes were prepared by replacing the cement in 35% and 50 % in each one of these additions. Their properties were evaluated in fresh and hardened state. The fresh properties were evaluated using the slump flow, V-funnel and box in L. While in hardened state mechanical properties were evaluated (compressive strength, indirect tensile and flexural) and permeability (capillary suction, absorption, porosity and chlorides resistance). All SCC showed good properties in fresh state and developed after 28 days curing, compressive resistance in the range of 34 and 48 MPa. The results show that the use of coal combustion sub-products can be incorporated in the production of SCC.

Evaluación de las propiedades mecánicas de paneles de ferrocemento con agregado fino reciclado

This paper describes the obtention of panels of ferrocement with the incorporation of recycled fine aggregate (SFR) from the grinding of concrete rubble We used a reference mortar that met the minimum resistance to the understanding required for this application (25 Mpa at 28 days) and maximum settlement of 6 cm. This study shows the effect on the compressive strength of this reference mortar, of the incorporation of AFR at levels of 25,50,75 and 100%. Then, based upon optimal results panels of ferrocement were drawn using rods of steel, hexagonal mesh and mesh shale shaker (ZAG). The results revealed the possibility of completely replace natural sand by AFR in the manufacture of ferrocement panels with resistance to Flex up to 31.16 MPa and mortars with up to 7.3% higher compressive strength compared to those based on a 100% natural sand.

Comportamiento en estados fresco y endurecido de un concreto autocompactante, adicionado con escoria de carbón, y elaborado con agregado grueso de concreto reciclado

The steady growth of remodeling, demolition, and in general the construction activity in the populous cities generate large volumes of waste from demolished concrete, which now have become a serious problem of environmental pollution. Furthermore, given the global need to increase efficiency in the consumption of materials and energy, it is imperative to study the recycling of the materials, especially as in the case of concrete, which today, is the material most produced per year in the world, and one of the greatest contributors to a negative impact on the environment. In this sense, this research evaluates the effect of partial and total replacement of natural aggregates by recycled aggregates obtained from the crushing of construction waste and demolition on the behavior in fresh and hardened state of a self-compacting concrete. The results showed that the incorporation of these recycled aggregates did not significantly affect the behavior of the fresh blends, but instead does have an influence on the behavior of the hardened concrete causing a decrease of the compressive strength between 15% and 29 % depending on the percentage of natural aggregate that was replaced by the recycled one (25, 50, 75 and 100 %). In addition, it was observed a slight increase in the amount of permeable pores depending on the amount of natural aggregate that was replaced by the one recycled.