No abstract

Lignin is the second most abundant natural polymer. Due to the high content of carbon and hydrogen (C-H, C-C, C=O), it can be used as a potential dispersant for cement matrix. The objective of this study is to extract lignin from date palm and study its effect in the form of black liquor (BL) on the rheological and physic-mechanical properties of the cements and concrete. The lignin in black liquor form represents approximately 30 wt% dry weight of date palm. It is a heteropolymer composed primarily of methoxylated phenylpropylene alcohol monomeric units interconnected by a variety of stable carbon-carbon and carbon-oxygen-carbon (ether and esters) linkages. The results found show the positive effect on the workability of cement and concrete and confirms its dispersion effect by improving compressive strength of concrete during the early and the later ages of hydration.

In this study, composite polymer-based materials, in which a significant proportion of polyester resin has been substituted by low cost and environmentally friendly clay-based raw materials, have been elaborated. The main objective is to improve mechanical properties keeping a reasonable electrical insulating behavior. A homogenized distribution of fillers within the matrix compatible with the processing parameters has been obtained up to a maximum added fraction of 20vol%. Mechanical characterizations performed with uniaxial traction tests and Charpy impact pendulum machine have shown that stress to rupture can be enhanced of about 25% and that fracture energy value has double for the best formulations. Dielectric constant decreases and loss factor slightly increases while electrical resistivity remains almost invariable. From a general point of view, composite materials with metakaolin fillers exhibit higher mechanical properties and a greater electrical insulating behavior. Microstructural observations revealed the presence of decohesive agglomerates of particles at the interface with the matrix. Finally, mechanical properties are more sensitive to the homogeneity of fillers dispersion in the matrix than electrical properties.

International audienceThis work aims to reveal the influence of thermal treatment on thermal conductivity of a clay-based raw material. The analysis of the effect of the porous network and solid skeleton on thermal conductivity has been performed by numerical simulation. Three steps were combined: (i) elaboration, (ii) characterisation, (iii) validation and comparison with experimental results. In filigree, the objective is to make an insulating material for the building field while decreasing energy of fabrication. After the step of elaboration, the porosity was evaluated experimentally by pycnometer and mercury intrusion porosimeter and numerically by means of micrographs observations. The effective thermal conductivity was evaluated using the laser flash technique and compared to results obtained by numerical simulation using ABAQUS software. The influence of the microstructure characteristics was highlighted by the numerical study which enables to overcome the limitation of the classical analytical models. As results, we observe that when the temperature of fabrication decreases of about 200 °C, the pore volume fraction is multiplied by six while the thermal conductivity decreases four times. The mechanical properties remain acceptable for a construction field. These tendencies were confirmed by both experimental and numerical approaches