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Author(s)

Leonardo Fagundes Rosemback Miranda

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Escola Politécnica (EP/BC)
• Defense date: 2005-11-28

Examining board members

Silvia Maria de Souza Selmo; Vahan Agopyan; Elton Bauer; Jefferson Benedicto Libardi Liborio; Tarcisio de Paula Pinto

• Advisor: Silvia Maria de Souza Selmo

Abstract

Although the vast volume of construction and demolition waste has stimulated its recycling, the process in national recycling plants is primary and the recycled aggregates have been employed only in pavement works and earthworks, thus limiting the expansion of recycling, its use by the market and its commercial valorization. Hence it is necessary to develop recycling processes of CDW for new applications. Considering the tradition of the use of mortars in Brazilian civil construction, developing the production of these mixtures from recycled sand, with guaranteed quality, may be a viable alternative. Therefore this thesis aims at developing a mortar production methodology for wall and ceiling rendering with recycled sand from recycling plants, guaranteeing homogeneity and good performance, continuing the research of MIRANDA (2000). A five-step experimental program was designed in order to evaluate the variability in recycled sand and mortars produced in a plant in Socorro/SP and to test the following variables: control of grain size distribution, control of the nature and content of material finer than < 75 µm by washing, visual classification of CDW and the formation of homogenization piles. The mix proportions of mortars were defined according to MIRANDA (2000) and to dosage parameters proposed in SELMO (1989) and were set at 1:8 (cement, unwashed recycled sand) or 1:1:8 (cement, lime, washed recycled sand) in mass. Aggregates and mortars werecharacterized by usual methods. Statistical process control tools were employed in the analysis of results. Renderings on concrete block and ceramic brick substrates were also produced, and their performance was verified regarding fissures and bond tensile strength. ) As a conclusion it was verified that the control of grain size distribution of recycled sand and visual classification of CDW were not sufficient to reduce the variability of mortars. Nevertheless, the control of the content of fines < 75 µm through washing in a 0.15 mm sieve or through the use of spiral classifier, with the replacement of fines with lime, as proposed by MIRANDA (2000), provided a significant reduction in the variation of mortar properties, which was increasingly reduced with the use of the technique of homogenization pile, in pilot equipment designed by the author. However, this was also insufficient to obtain a process under statistical control by usual industrial standards (3\'SIGMA\'). In spite of this, and given the fact that there is no national or international document with the data and field experiment collected here, the thesis is concluded with a complete proposal of mortar production in recycling plants, including the recycling process, the procedure to form lots for quality control of the washed recycled sand and the mortars, by means of simplified methods selected on the basis of the correlations observed in this work between aggregate and mortar properties. (AU)