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| Author(s): |
Markus Samuel Rebmann
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Escola Politécnica (EP/BC) |
| Defense date: | 2016-10-06 |
| Examining board members: |
Rafael Giuliano Pileggi;
Sérgio Cirelli Angulo;
Paulo Cesar Correia Gomes;
Marcelo Henrique Farias de Medeiros;
Luiz Roberto Prudêncio Júnior
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| Advisor: | Rafael Giuliano Pileggi |
| Abstract | |
The use of concretes with low Portland cement content is justified by technical reasons (lower hydration heat, shrinkage and cracking) and sustainability (lower energy and raw materials consumptions, CO2 emissions and demand for transport). Variability in raw materials, environmental conditions and production process result in variability of various concrete properties in the fresh and hardened states. The feasibility of applying low cement concretes in large production scale depends on the sensitivity that these concretes show, given the existing variability. Concretes with adequate robustness, that is, sufficiently tolerant to variations are desirable. This research evaluated the robustness of concretes with low cement consumption, with focus on deviations in proportioning and particle size and morphological variability of the aggregates. Applying particle packing and dispersion concepts, rheological control, use of limestone fillers and appropriate of material choice a concrete with effective low binder consumption (3.66 kg/m3/MPa) was developed. The obtained results indicate that among the considered scenarios, the particle size changes are the most impactful, especially due to the presence of fine dust in the crushed aggregates. Morphological changes, especially in the size fraction that most impacts the packing (dominant fraction), are also relevant. Weighing deviations provided the smallest impact among the three evaluated scenarios. These findings, however, are specific to the analyzed concrete and the considered variability scenarios. For this reason, this research aimed to explain more generally the influence of several variables. The distance between the particles (IPS and MPT), the specific area of the granular material and the solids concentrations are some of the parameters that explain the rheological behavior. Based on the experimental process and the analysis of the applied results, a methodology was proposed for robustness evaluation and a numerical index for the quantitative evaluation of the robustness. Some additional tools to confer robust mechanisms to the concrete production process were proposed: a computer system for forecasting concrete properties, based on fundamental characterization of the constituents, use of a mobile rheometer as a quality control instrument and mixer instrumentation as change detection mechanism during the mixing process. (AU) | |
| FAPESP's process: | 12/21134-2 - Robustness of concrete with low Portland cement content: proportioning deviations and variability in particle size and morphology of the aggregates |
| Grantee: | Markus Samuel Rebmann |
| Support Opportunities: | Scholarships in Brazil - Doctorate |