The effect of fillers specific area on the fluidity and mechanical resistance of cementitious pastes

• Grant number: 16/03110-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: June 01, 2016
• End date: May 31, 2017
• Field of knowledge: Engineering - Civil Engineering - Construction Industry
• Principal Investigator: Bruno Luís Daminelli
• Grantee: Felipe Vergili Sgarbosa
• Host Institution: Instituto de Arquitetura e Urbanismo de São Carlos (IAU). Universidade de São Paulo (USP). São Carlos , SP, Brazil

Abstract

The use of concrete in construction, which is the most consumed material in the world after water, is widespread. The great demand, which is expected to grow more than 2 times in the next 30 years, combined with the high impact of cement production (1 ton of clinker generates approximately 1 ton of CO2), has increased the discussion about the chain, it' changes and developments in recent times in order to reduce the large environmental impact for which it is responsible. Among the available options, the current mitigation strategies - optimization and ovens, use of new fuels and clinker replacement by blast furnace slag and fly ash - are not sufficient for major changes in the panorama, so that the use of new additions that have reduced impact of production and higher availability, as inert fillers, have been the most important subject of discussions. However, in practice the use of fillers in cementitious matrices has brought great technical difficulties, because the variability of these materials causes widely variations of water consumption among different mixtures. Often this means that these materials are not used in usual dosages. Thus, a better understanding of the characteristics of fillers that determine the water content in mixtures with cement is fundamental to the advancement of the chain. And among these characteristics, the surface area seems to vitality important, because it is where the water and dispersant (if present) are adsorbed during the plastic stage of mixtures. The objective of this study is to evaluate the influence of the surface area of 6 different fillers on the rheology (behavior in a fluid state) and compressive strength of pastes composed by cement filler. The method is based on measurement of granulometry and surface area (by BET technique) of fillers and cement, and cement-filler pastes mixtures on 2 different proportions for each filler used, and two percentages of water. The rheological behavior will be measured by mini-cone trunk (measuring the yield stress) and Marsh funnel (measures the viscosity). The pastes will then be molded and tested in compression test, to also check the influence of the area of materials on resistance. However, in practice the use of fillers in cementitious matrices has brought great technical difficulties, because the variability of these materials causes the water consumption varies widely between different mixtures. Often this means that these materials are not used in possibles dosages.. Thus, a better understanding of the characteristics of fillers that determine the water content in mixtures with cement is fundamental to the advancement of the chain. And among these characteristics, the surface area seems to vitality important, because it is where the water and dispersant (if present) are adsorbed during the stage of plastic mixtures. The objective of this study is to evaluate the influence of the surface area of 6 different fillers on the rheology (behavior in a fluid state) and compressive strength of pastes composed by cement filler. The method is based on measurement of granulometry and surface area (by BET technique) of fillers and cement, and cement-filler pastes mixtures on 2 different proportions for each filler used, and two percentages of water. They will be measured by the rheological behavior of mini-cone trunk (measuring the yield stress) and Marsh funnel (measures the viscosity). The pastes will then be molded and tested in test compression, to also check the influence of the area of materials on resistance. (AU)