Adjustments in the mixture formulations for the production of fiber cement by the extrusion process.

Author(s)

Yatsen Jepthe Maldonado Soto

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Escola Politécnica (EP/BC)
• Defense date: 2010-12-21

Examining board members

Holmer Savastano Júnior; Mounir Khalil El Debs; Philippe Jean Paul Gleize; Rafael Giuliano Pileggi; Romildo Dias Toledo Filho

• Advisor: Holmer Savastano Júnior

Abstract

This work intends to contribute in the development of the extrusion process for the production of cementitious composites, through methodology that makes it possible to obtain formulas using high resistance Portland cement, silica fume, limestone, eucalyptus pulp, polypropylene fibers and admixtures. With this intention, the raw materials were characterized as a support for the discussions. The effects of the different components of the formula on the rheological behavior of the mixture were evaluated using an extrusion rheometer. The physical and mechanical properties of the composites elaborated with the combinations of limestone, silica fume and cement were modeled statistically with the purpose of estimating the behavior of the matrix. The water demand of the cementitious systems was determined experimentally and used in the matrixes extrusion. After the Matrix Selection, their mechanical and physical properties were modeled statistically, with different pulp eucalyptus and polypropylene fibers quantities. The formulas with the expected characteristics were evaluated to the accelerated aging for 200 wet-drying cycles. Finally the reproducibility was analyzed using the Weibull module for the selected formulas. The rheological studies verified that the polypropylene fibers demonstrate the largest increase in the values of the rheological parameters when compared with the effects of the limestone, silica fume or eucalyptus pulp, inducing larger extrusion pressures. The increment of the rheological modifier hydroxypropyl methylcellulose decreases the module of rupture in the cementitious composite, and simultaneously during the process it promotes the increment of the extrusion pressure. The statistical models used to reinforce the matrix modeling were of large complexity and with smaller coefficient determination when compared to matrixes used for modeling. The fiber cement market price is approximately 64% smaller than the raw materials and admixtures used in extruded fiber cement in this study. (AU)

• FAPESP's process: 05/04035-7 - Adjustments in the mixture formulations for the production of fiber cement by the extrusion process
• Grantee: Yatsen Jepthe Maldonado Soto
• Support Opportunities: Scholarships in Brazil - Doctorate