Molienda mecánica por alta energía de minerales mexicanos para producir concreto de alto desempeño (CAD)

Revista Ingeniería de Construcción RIC Vol 29 Nº3 2014 www.ricuc.cl ................................................................................................................................................................................................................................................................................... Molienda mecánica por alta energía de minerales mexicanos para producir concreto de alto desempeño (CAD) High energy milling (HEM) of Mexican minerals to produce high performance concrete (HPC) 1 María Fuentes *, Araceli Zúñiga**, Manuela Díaz**, Enrique Rocha***, Sebastián Díaz* * Instituto Politécnico Nacional, Centro de Investigación e Innovación Tecnológica. MÉXICO ** Instituto Politécnico Nacional, Departamento de Ingeniería Metalúrgica. MÉXICO *** Universidad Politécnica de Victoria, Tamaulipas. MÉXICO Fecha de Recepción: 27/03/2014 Fecha de Aceptación: 02/11/2014 PAG 256-269 Resumen Se caracterizaron química, física y mineralógicamente agregados minerales finos mexicanos, tales como: ceniza volante, microsílice, humo de sílice, escoria granulada de alto horno (EGAH) gruesa, fina y refinada para su dosificación con cemento Portland compuesto (CPC) en su estado normal y refinado por molienda de alta energía (HEM), con el objetivo de fabricar un concreto de alto desempeño (CAD), partiendo de subproductos industriales. Los materiales fueron acondicionados con tamaños menores a #200 mallas (75µm) y algunos con partículas del orden submicrométrico para analizar el aporte en la resistencia a la compresión dentro de las mezclas. Una vez caracterizada la materia prima se determinaron los parámetros experimentales para reducir los tamaños de partícula mediante HEM del cemento Portland compuesto y la escoria granulada de alto horno. Los productos de molienda, así como los demás materiales cementantes fueron caracterizados por: difracción de rayos X (DRX), microscopía electrónica de barrido (MEB) y absorción atómica. Se identificaron las fases presentes en dichos materiales, detectando una modificación en el porcentaje de las fases Alita C3S y Belita C2S favoreciendo la resistencia a la compresión, especialmente al moler el CPC durante 30 min por HEM. Los ensayos de resistencia a la compresión de las probetas del CAD obtenidas comprueban que la mayor resistencia a la compresión se alcanza usando humo de silice HS. Palabras claves: Molienda por alta energía (HEM), concreto de alto desempeño (CAD), cemento Portland compuesto (CPC) y agregados finos mexicanos Abstract In order to produce high performance concrete (HPC), fine Mexican mineral aggregates were characterized using chemical, physical and mineralogical procedures. Used materials included fly-ash, micro silica, silica fume, and coarse, fine and refined ground granulated blast furnace slag (GGBS), which were then dosed with Composite Portland Cement (CPC) in three forms: (1) commercially as-received, (2) as-screened and (3) after being high energy ball milled (HEM), i.e., as-milled. The materials were conditioned with less than 200 mesh (75µm) particles and with submicron particle sizes in order to analyze their contribution to the compressive strength of the paste. After characterizing the raw materials, the experimental parameters for reducing particle sizes by HEM - CPC and GGBS were determined. Milled products and other cementitious materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic absorption analyses. Different materials phases were identified, thus observing a change in the mass percentage of Alite C S and Belite C S, which promote the compressive strength of the specimens produced, provided that the CPC has been grounded by HEM for 30 min. Silica fume was proven to the best aggregate, which triggers the compressive strength of the specimens prepared. 3 2 Keywords: High energy milling (HEM), high performance concrete (HPC), composed Portland cement (CPC), and Mexican fine aggregates 1. Introduction High performance concretes (HPC) are composed of essentially the same materials as conventional concrete, with the significant difference of the proportions and conditioning of fine aggregates, and the use of special additives that are responsible for strength and durability. In turn, these characteristics may vary because they are based on the structural requirements of the masonry work, and they depend on environmental restrictions as well (Rivva, 2000). Among the fine aggregates used to produce HPC, the following were included: ground granulated blast furnace slag (GGBS), fly-ash (FA), micro silica (MS), silica fume (MF) and silica sand. 1 Autor de correspondencia / Corresponding author: Instituto Politécnico Nacional. Centro de Investigación e Innovación Tecnológica, Cerrada de CECATI S/N, 02250, México, D.F. Tel. 57296000, ext.68313 E-mail: Revista Ingeniería de Construcción Vol 29 Nº3 Diciembre de 2014 www.ricuc.cl 256 Revista Ingeniería de Construcción RIC Vol 29 Nº3 2014 www.ricuc.cl ................................................................................................................................................................................................................................................................................... These materials have latent cementitious properties which, together with their high chemical silica (SiO2) content and fineness, increase the concrete’s compressive strength (Martínez, 2011). The company of Altos Hornos de México S.A. de C.V. (AHMSA), located in Monclova, Coahuila, produces tons of granulated slag (GGBS) each month, which is considered as “waste” and represents 10wt% of the pig iron produced in the blast-furnace. When this slag is drastically cooled and granulated, it turns into a relevant industrial subproduct due to its intrinsic cementitious properties. Therefore, not only the cement industry is benefited by the recycling of this subproduct, but the ecological system itself (Pierre, 1998). Currently, GGBS is globally recognized as a total or partial replacement material for the OPC, given its cementitious properties and eco-friendly manufacturing (Escalante, 2002). Other national materials that are considered industrial subproducts due its high content of pozzolan properties are fly-ash, micro silica and silica fume. While fly-ash (FA) is generated from the coal gasification process in thermoelectric plants, micro silica (MS) and silica fume (SF) are obtained from the reduction of quartz (SiO2) by coal in electric arc furnaces, being fineness practically the only difference between them. Consequently, these materials are considered potential industrial subproducts, since their physical and chemical properties increase the compressive strength of concrete manufactured with composite Portland cement (OPC) (Lorenzo, 1993, Valdéz et al., 2007). The present study deals with the technological feasibility of Mexican subproducts recognized a (...truncated)