Thermal and mechanical properties of hardened cement paste reinforced with Posidonia-Oceanica natural fibers

This paper focuses on thermal and mechanical properties of a hardened cement paste reinforced with Posidonia-Oceanica fibers. Fibers volume fractions are varied from 0% to 20%. Thermophysical and mechanical properties are measured. Simplified models are developed to predict thermal conductivity, tensile and compressive stresses and fracture toughness variation as a function of fibers volume fraction and geometrical characteristics of samples. Results showed that the addition of Posidonia-Oceanica fibers improved the material insulating properties. In fact, a decrease of about 22% (from 0.0718 W.m(-1).K-1 to 0.559 W.m(-1).K-1) of thermal conductivity was found with adding 20% of fibers compared to control cement paste. Concerning mechanical properties, flexural and compressive strengths increased for fiber volume fractions in the range of 5 to 10% and then decreased for higher fiber volume fractions. It was shown through a simplified model and MEB observations that agglomeration of fibers for high volume fraction is behind this phenomenon. Moreover, a noticeable increase of toughness was observed with increasing fibers amount: for instance, an increase of about 65% (from 0.245 MPa.m(1/2) to 0.404 MPa.m(1/2)) was observed with the introduction of 20% of fibers in the composite. Simplified analytical models are also developed to predict thermal conductivity, tensile and compressive strengths and fracture toughness. These models are validated with experimental data. (C) 2020 Elsevier Ltd. All rights reserved.