Mechanical behavior of cement-based materials reinforced
with sisal fibers
H. Jr Savastano Æ A. Turner Æ C. Mercer Æ
W. O. Soboyejo
Received: 15 November 2002 / Accepted: 28 October 2003 / Published online: 16 September 2006
Ó
Springer Science+Business Media, LLC 2006
Abstract Fiber-reinforced cement composites were pro-
duced in Brazil using blast furnace slag cement reinforced
with pulped fibers of sisal originated from agricultural
by-products. Thin pads were produced by slurring the raw
materials in water, followed by de-watering and pressing
stages. Studies of mechanical behavior included observa-
tions of stable crack growth behavior under monotonic
loading (resistance-curve behavior), followed by scanning
electron microscopy (SEM) analysis of the fracture surfaces.
Reinforcement with cellulose fibers resulted in improved
fracture toughness, even after 9 months in laboratory envi-
ronment. Microscopic analysis indicated a considerable
incidence of crack bridging and fiber pull-out in the com-
posite. The shielding contributions from crack bridging
are estimated using a fracture mechanics model, before
comparing with the measured resistance-curve behavior.
Introduction
In recent years, there have been considerable efforts to
develop natural fiber-reinforced cementitious composites
for affordable infrastructure [1]. Such composites are typ-
ically reinforced with natural fibers obtained from agri-
cultural wastes, such as bamboo fibers [2], sisal fibers [3],
sugar cane fibers [4], or fibers extracted from eucalyptus
trees [5] or banana pseudo-stem [6]. In most cases, these
fibers have little or almost no current economic value [7].
Their use as reinforcements in infrastructural components,
such as roof tiles [7], can, therefore, be achieved at rela-
tively low cost. Furthermore, natural fiber-reinforced
composites (NFRC) are attractive due to the overall
reductions in CO
2
emissions [8], and reduced amounts of
energy needed to process natural fiber-reinforced slag-
based composites, compared to those of conventional
synthetic fiber-cement. They may also be used to replace
environmentally hazardous materials, such as asbestos,
which are currently used as roof sheet materials in several
developing countries [9].
However, the long-term durability of NFRC in potential
roof tile applications may be limited by their permeability
and resistance to crack growth [10]. These are not prop-
erties that can be optimized by the design for improved
strength. Instead, a more balanced approach is needed for
the optimization of strength, fracture toughness/resistance-
curve behavior, fatigue resistance and permeability.
This paper presents the results of a combined experi-
mental and theoretical study of fracture toughness/resis-
tance-curve behavior in a cementitious composite
reinforced with sisal fibers. Following a review of related
prior work, a brief description of the material processing
and microstructure is presented. The resistance-curve
behavior of the composite is then described along with the
observations of crack/microstructure interactions that con-
trol the measured toughening. Subsequently, fracture
mechanics models are used to estimate the resistance-curve
behavior and the steady-state toughening. The implications
H. Jr Savastano
Rural Construction Group, Faculty of Animal Science and Food
Engineering, University of Sa
˜
o Paulo, C.P. 23, 13635-900
Pirassununga, SP, Brazil
A. Turner Æ C. Mercer Æ W. O. Soboyejo (&)
Princeton Materials Institute and The Department of Mechanical
and Aerospace Engineering, Princeton University,
D404 E.-Quad., Olden Street, Princeton, NJ 08544, USA
e-mail: soboyejo@princeton.edu
J Mater Sci (2006) 41:6938–6948
DOI 10.1007/s10853-006-0218-1
123