Potencialidade do uso da cinza da folha da bananeira como substituição parcial do cimento Portland em concretos

Abstract

The use of alternative materials in the composition of concretes has been the object of research that investigates the possibility of improvements in the physical, mechanical and durability properties of this composite, also encouraging the incorporation of mineral additions of natural origin and / or substitutions in relation to the constituent materials. . In this perspective, this research aims to study the use of banana leaf ash (CFB) as partial binder replacement in Portland cement concretes. CFB was characterized by specific mass, Blaine fineness, organic matter content, pozzolanic activity by the modified Chapelle method and electrical conductivity. Mineralogical, chemical, thermogravimetric and microstructural analyzes were also performed. Regarding aggregates and cement, the tests performed were related to physical properties. The concretes were produced considering a trait 1: 1.89: 2.45: 0.5 (cement: sand: gravel: water), dosed by the ABCP method, with variations of the contents from 0 to 15% of mass replacement. CFB. After dosing, the concretes were subjected to technological tests: slump test, specific mass, compressive strength (7, 28 and 49 days), water absorption, voids index, specific mass in the hardened state and microstructure evaluation. Scanning Electron Microscopy (SEM). Analyzing the properties of the concrete in the fresh state, it was found that the incorporation of the residue decreased the consistency and increased the specific mass, with a tipping point of 10% for these tests. Regarding the physical indices, the substitution by CFB presented lower water absorption and lower voids index. The concretes had increased compressive strengths with increasing age and increasing substitution content, up to 10%, with decreasing values for the 15% content, behavior also observed for the specific mass. Therefore, it was found that the technical feasibility of partial replacement of cement by CFB, under the conditions addressed, is favorable for the 10% content, given the improvements in physical and mechanical properties.