As obras disponibilizadas nesta Biblioteca Digital foram publicadas sob expressa autorização dos respectivos autores, em conformidade com a Lei 9610/98.
A consulta aos textos, permitida por seus respectivos autores, é livre, bem como a impressão de trechos ou de um exemplar completo exclusivamente para uso próprio. Não são permitidas a impressão e a reprodução de obras completas com qualquer outra finalidade que não o uso próprio de quem imprime.
A reprodução de pequenos trechos, na forma de citações em trabalhos de terceiros que não o próprio autor do texto consultado,é permitida, na medida justificada para a compreeensão da citação e mediante a informação, junto à citação, do nome do autor do texto original, bem como da fonte da pesquisa.
A violação de direitos autorais é passível de sanções civis e penais.
This thesis studies both the short-term and long- term
behaviour of sisal and coconut fibre reinforced mortar
composites.The experimental work involved extensive
laboratory testing to determine the physical and mechanical
properties of the fibre reinforcement and to study the
influence of fibre type, volume fraction, fibre length,
fibre arrangement and matrix composition on the
mechanical properties of the composite.Studies were also
made to determine the influence of fibre reinforcement in
controlling free and restrained shrinkage during the early
age of mortar mixes. Cracking due to restraint and the
phenomenon of crack self-healing were also investigated.
The mode of failure and the properties of the resistance to
fibre-matrix interfacial bonding were determined using the
single fibre pull-out test.The long-term properties of the
sisal and coconut fibre reinforced-mortar composites
were assessed throughout creep, shrinkage and durability
tests. The influence of the addition of sisal and coconut
fibres, of various volume fraction and lengths, on the
creep of a mortar matrix was determined using sealed and
unsealed specimens subjected to a pressure of 14.4 MPa over
a period of 210-350 days. Recovery strains were recorded
for a period of 56-180 days.The influence of fibre types,
volume fraction, fibre lengths, cure types, mix proportions
and replacement of OPC by slag and silica fume on the
dimensional stability of mortar matrices was determined
using drying shrinkage tests for a period of 320 days.
The durability of sisal and coconut fibres exposed to
alkaline solutions of calcium and sodium hydroxide and
stored in tap water was measured as strength loss over a
period of 420 days. The durability of fibre-reinforced
mortars after 320 to 360 days, stored under water, exposed
to cycles of wetting and drying as well as to the natural
weather,was assessed from results of flexural tests and
from observations of the photomicrographs obtained using
backscattered imaging and secondary electron imaging.
Dotting maps of chemical elements were obtained in order to
verify possible migration of cement products from the
matrix to the lumen and voids within of the fibres.
Treatments to enhance the durability performance of the
composites were studied,including: (a) modifications to the
matrix through the replacement of Portland cement
by undensified silica fume and by blast-furnace slag; (b)
carbonation of the cementitious matrix and (c) immersion of
the fibres in slurry silica fume prior to being
incorporated into the Portland cement matrix.