Thermal and mechanical properties of hemp fabric-reinforced nanoclay-cement nano-composites

The influence of nanoclay on thermal and mechanical properties of hemp fabric-reinforced cement composite is presented in this paper. Results indicate that these properties are improved as a result of nanoclay addition. An optimum replacement of ordinary Portland cement with 1 wt% nanoclay is observed through improved thermal stability, reduced porosity and water absorption as well as increased density, flexural strength, fracture toughness and impact strength of hemp fabric-reinforced nanocomposite. The microstructural analyses indicate that the nanoclay behaves not only as a filler to improve the microstructure but also as an activator to promote the pozzolanic reaction and thus improve the adhesion between hemp fabric and nanomatrix

Porosity and permeability of Mortars Exposed to elevated Temperatures

Abstract: It is demonstrated that the key parameters that affect the performance of plain mortars are volume instability, phase transformation, porosity, and permeability. Experimental results point at the major role of porosity, microstructure, and mechanical properties. Three thermal zones are identified, low (up to about 300°C), intermediate (about 300 to 600°C), and high (> 600°C). It is shown that in the low thermal zone, the mechanical properties are about the same or better than those at room temperature. The intermediate thermal zone is characterized by a moderate decline of mechanical properties, whereas a rapid decline is registered in the high thermal zone. An experimental investigation was conducted to evaluate the performances of mortar incorporating silica fume (FS) and exposed to temperatures up to 900°C. Mechanical tests (strength), porosity tests (mercury and helium) and helium permeability tests are undertaken. At a heating temperature of 900°C, the compressive strength as well as the tension strength by flexion of not heated materials increase with the diminution of the water/cement ratio (E/C) and with the addition of silica fume. Furthermore, the strength evolution versus the materials age depends on the mode of cure and its duration. On the other hand, in the case of heated materials, a regression of resistance is observed and it is far more important for the formulation containing the silica fume. The replacement of cement by silica fume fall the porosity of not heated mortars of a considerable manner, but the total specific surface of pores varies little. This porosity increases linearly with the temperature elevation. Around 900°C permeability to the helium is quasi identical to these of ordinary mortars and with silica fume