Creep of pre-cracked sisal fiber reinforced cement based composites: Fid-Bau Portal

Creep of pre-cracked sisal fiber reinforced cement based composites

Barbosa da Silva Junior, Iranildo / Maria Silva de Souza, Lourdes / de Andrade Silva, Flávio

Highlights • Composites reinforced with saturated sisal fibers resulted in a denser interface with smaller crack width. • The fiber–matrix interface plays a major role during creep tests in pre-cracked specimens. • During creep tests composites reinforced with saturated sisal fibers showed lower crack widths. • Composites reinforced with natural humidity fibers presented higher first crack strength but larger crack widths in static and long term tests.

Abstract In the present paper, the creep behavior of sisal fiber cement based composites was investigated. The composites were manufactured using a matrix with low calcium hydroxide content, obtained by partially replacing the cement by fly ash and metakaolin. Two types of composites were developed, each with three layers of long and unidirectional sisal fibers, varying the condition of the fibers in saturated with water and with natural humidity. The mechanical behavior was evaluated through direct tension and four-point flexural tests. The composites reinforced with saturated fibers showed higher strain capacity in tension due to the properties of the fiber–matrix interface and lower ultimate bending strength. Cracking mechanisms were studied through photographs obtained during the tests, as well as analyzes by a stereoscopic microscope. All composites presented strain/deflection hardening behavior with the formation of multiple cracks. Tensile and flexural creep tests were performed on pre-cracked composites in order to study time-dependent responses. The evolution of cracks was monitored throughout the creep test with a stereoscopic microscope. The composites showed a reduction in strength and strain capacity after the creep tensile and flexural test, which resulted in a decrease in toughness of 36.9% and 48.5% for the composites with saturated fibers and natural humidity, respectively. In addition, for the flexural creep test, the composites with saturated fibers showed a decrease in toughness of 48.2% while the composite with natural humidity had a decrease of 35.3% for the load equivalent to 50% of their strength.