Dosagem micromecânica de compósitos cimentícios reforçados com fibras de juta

Abstract

In this work the micromechanical theorical model developed by LEUNG et al. (1991) is used for the dosage of Strain Hardening Cementitious Composites (SHCC) reinforced with jute fiber. To let the composites dosage, it was considered the changes of the matrix fracture energy, the physical and mechanical properties of the fiber and fiber-matrix bonding. The variation of the fracture matrix energy was carried out with the utilization of three maximum sand particle sizes related to 50% of passing material , with diameters of 175, 300 and 410µm. The jute fiber properties and the bonding with the cement matrix was evaluated with the application of an alkaline surface treatment based in a saturated solution of Ca(OH)2. The critical fiber length of treated fiber was adjusted to 20mm and the fiber volume needed to obtain the strain hardening behavior for every matrix was determined using the micromechanical model. Experimental and theoretical results indicated that the cementitious matrix with maximum particle size of 300 and 410µm have the major potential for the developing of multiple cracking in direct tension, considering reinforce with fiber volumes between 3-4%. For the model validation, it was performed direct tension and flexural tests. The results obtained indicated that values of matrix first crack strength of 1,5 and 2MPa are needed to obtain strain hardening behavior with treated fiber volume of 3% and 4%, respectively.