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This study investigates the durability of fly ash-based geopolymer pastes (FA-GP). Thermal behavior was evaluated by heating the FA-GP pastes at 1000 °C for 2 h (FA-GP-1000 °C). Acid resistance was studied by immersing specimens in a 5% sulfuric acid solution for a period of 4 months (FA-GP-H2SO4). Physicochemical, microstructural and mechanical changes after heat and acid exposure were studied using several analysis methods such as Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM) and compressive strength. The results showed that the visual appearance of fly ash-based geopolymer samples was well preserved after high temperature exposure, and kept about 37% of its initial compressive strength value. SEM micrographs of acid exposed samples showed very porous structure with some micro-cracks, inducing a decrease of the residual compressive strength of about 33.33 %.

The effect of the substitution by 5%, 15%, 30% and 45% of cement in mortars by milled kaolinite has been studied. Milled Kaolinite clay is obtained by using planetary ball mill. The influence on the mechanical performance and on the pozzolanic reactions are discussed. For both CEM I and CEM II formulations, after only 7 days of curing, the compression strength of mortars with 5% of milled kaolinite is comparable to the one of reference mortars for milling times of 3 h and above. For CEM I mortar, the results of the compressive strength show that 15% of kaolinite milled for 9 h allows the best compressive gain for 28 curing days and 90 curing days with 18.5% and 25.6%, respectively. For CEM II mortar, 15% of kaolinite milled for 9 h exhibits the best values of compressive gain for 28 curing days and 90 curing days with 9.8% and 9.7% respectively.

Mechanical performance of modified mortar using hemp fibres is studied following various processing conditions. Hemp fibres combined with carbon nanotubes (CNT) are introduced in mortar and their effect is studied as function of curing time. The cement phase is replaced by different percentages of dry or wet hemp fibres ranging from 1.1 wt% up to 3.1 wt% whereas carbon nanotubes are dispersed in the aqueous solution. Our experimental results show that compressive and flexural strengths of wet fibres modified mortar are higher than those for dry hemp-mortar material. The achieved optimal percentage of wet hemp fibres is 2.1 wt% allowing a flexural strength higher than that of reference mortar. The addition of an optimal CNT concentration (0.01 wt%) combined with wet hemp has a reinforcing effect which turns to be related to an improvement of compressive and flexural strengths by 10% and 24%, respectively, in comparison with reference condition.

The consideration of planetary ball mill processing is attempted to obtain modified fly ashes powders that are used as substitutes in a cement paste. Ball milling conditions are related to structural modifications of processed powders. These modifications are retrieved from X-ray diffraction, infrared spectroscopy, powder granulometry, and scanning electron microscopy. As an industrial application, the milled fly ashes are substituted to two different cements to show possible effect on compressive strength of cement pastes. Structural analysis of milled fly ashes show loss of crystallinity of the magnetite phase, nanosizing trend of quartz and mullite phases with some straining that takes place after only 1 h of milling. The drop of particle size of the milled fly ashes is also evidenced but with tendency to agglomeration and particle shape modification from spherical to irregular forms.Mechanical performance results related to modified cement pastes indicate successful substitution of cements by milled fly ashes up to 50%. Substitution results in levels of compressive strength as large as 70 MPa for particular combination of milling time, fly ash content and curing time. Keywords: Ball milling, Fly ash substitution, Structural analysis, Compressive strength, Cement paste

Date palm residues capabilities in civil engineering are evaluated by combining numerical and experimental approaches. Date palm spikelet originated from Elghers variety is added to mortar as a raw material or after chemical modification. Evaluation of reinforcement effect is performed using mechanical testing. Finite element modelling is considered to predict the interfacial behaviour and mechanical performance under various structural and mechanical hypotheses. Experimental results show limited effect of untreated spikelet on mortar performance for volume reinforcement of 1%. Larger contents result in severe degradation of mechanical performance compared to reference mortar. The addition of carbon nanotubes improves slightly the performance. Chemical treatment using both NaOH and CaO results in reinforced effect of spikelet. Numerical predictions show limited load transfer across the matrix/untreated spikelet interface and large interface stiffness for those formulations including small spikelet, CNT and chemical treatment.

This paper is dedicated to the optimization of magnetic properties of iron based magnetic materials with regard to milling and coating process conditions using artificial neural network methodology. Fe–20 wt.% Ni and Fe–6.5 wt.% Si, alloys were obtained using two high-energy ball milling technologies, namely a planetary ball mill P4 vario ball mill from Fritsch and planetary ball mill from Retch. Further processing of Fe–Si powder allowed the spraying of the feedstock material using high-velocity oxy-fuel (HVOF) process to obtain a relatively dense coating. Input parameters were the disc Ω and vial ω speed rotations for the milling technique, and spray distance and oxygen flow rate in the case of coating process. Two main magnetic parameters are optimized namely the saturation magnetization and the coercivity. Predicted results depict clearly coupled effects of input parameters to vary magnetic parameters. In particular, the increase of saturation magnetization is correlated to the increase of the product Ωω (shock power) and the product of spray parameters. Largest coercivity values are correlated to the increase of the ratio Ω/ω (shock mode process) and the increase of the product of spray parameters.

In this work, we investigate the effect of hemp fibre and shive addition on modified mortars microstructure and mechanical performance. The mortar formulation is adjusted with different percentages and lengths of either hemp fibres or shives. Workability of fresh modified mortars is carried out using two main techniques including maniabilimeter and flow table experiments. Microstructural effects are revealed using X-ray μ-tomography where the pore content and 3D spatial arrangement and content of hemp are all investigated. Mechanical performance is derived from bending and compression testing at different curing times. Results show the potential of using natural fibres as substitutes leading, in this study, to improvement of mechanical strength but deterioration of stiffness. Superior mechanical performance with compression full strengths as large as 66 MPa is achieved using high-energy ball milling process of fly ashes that are added to unmodified mortar. Results show also that optimal formulations need to involve both hemp fillers and milled fly ashes. These formulations reveal superior mechanical performance compared to all tested conditions after only 7 curing days. Keywords: Hemp fibres, Hemp shives, Modified mortar, Milled fly ashes, Mechanical performance, X-ray μ-tomography

The so called “vario mill” (P4 Fritsch) planetary ball mill has been used to prepare nanocrystalline Fe-10 wt% Ni and Fe-20 wt% Ni alloys from powder mixtures. For both studied alloys, a disordered body cubic centered (BCC) solid solution has been formed after 36 h of milling. The higher the shock power, the larger the lattice parameter of the investigated systems. It has been found that in friction mode process (FMP), the lower the crystallite size, the lower the lattice strain of the prepared alloy. In shock mode process (SMP), the lower the crystallite size, the higher the lattice strain. FMP has been found to induce a soft magnetic behavior for Fe-10% Ni and F-20% Ni alloys. The highest values of coercivity have been found in materials prepared by SMP.

Version Number : 1.0; In this article, we present an identification procedure that allows the determination of the viscoelasticity behavior of different grades of pure bitumen (bitumen 35/50 and bitumen 10/20). The procedure required in the first stage a mechanical response based on macroindentation experiments with a cylindrical indenter. A finite element simulation was performed in the second stage to compute the mechanical response corresponding to a viscoelasticity model described by three mechanical parameters. The comparison between the experimental and numerical responses showed a perfect matching. In addition, the identification procedure helped to discriminate between different bitumens characterized by different asphaltene and maltene contents. Finally, the developed procedure could be used as an efficient tool to characterize the mechanical behavior of the viscoelastic materials, thanks to the quantified relationship between the viscoleastic parameters and the force-penetration response. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3440-3450, 2013

International audience; Physical properties of pure bitumen 35/50 and polymer-modified bitumen 13/40 are studied using needle penetration test and differential scanning calorimetry (DSC). In particular, the mechanical response under indentation conditions is achieved as a function of different loads and temperatures. Our results show that lower temperature susceptibility is associated to larger loads but its change is rather small for the tested bitumens. A pure bitumen 35/50 exhibits a single glass transition temperature for different heating rate whereas modified bitumen 13/40 presents two T-g for different heating rate.

International audience; The mechanical properties and microstructure of modified mortar and concrete using Carbon NanoTubes (CNT) are experimentally studied at 7, 14, 28 and 90 curing days. Part of the formulation, CNT are dispersed in a liquid solution. Different concentrations ranging from 0.01% to 0.06% and 0.003% up to 0.01% are used for mortar and concrete, respectively. Mechanical testing of the modified materials reveals that maximum compressive strength is obtained for CNT concentrations close to 0.01%wt and 0.003%wt for mortar and concrete, respectively. The microstructural characterisation of the modified materials suggests that CNT act as bridges between pores and cracks leading to a reduction in porosity and in turn an increase of compressive strength.

International audience; Binary 50Ni–50Ti mixture was prepared by mechanical alloying from elemental powders. After 48 h of milling, the nanocrystalline B2-NiTi powder was produced. Then, this as-milled powder was deposited by cold spraying in order to produce a target which can be used to create thin films by magnetron sputtering technique. The objective is to improve the electrical characterizations of the NiTi/SiO2/Si M.O.S structures. Themorphology evolution of the powder particles, the phase identification and the alloying evolution process as function of milling time were studied using scanning electron microscopy, X-ray diffraction and transmission electron microscopy. In addition, the target was also characterized using X-ray diffraction, Scanning electron microscopy, and microhardness measurements. The milling of powders leads to the formation of disorderednanocrystalline B2-NiTi with a crystallite size of about 12 nm and a microstrain of level 2.10%, after 48 h of milling. The microstructure, the composition and grain size of the milled powders for 24 h and 48 h characterized by TEM are heterogeneous. The as-deposited intermetallic NiTi can be retained in the coating with a lattice parameter of 0.3 nm, crystallite size of 14 nm, microstrain and high microhardness of 2% and 694Hv0.25, respectively.

An artificial neural network (ANN) methodology was applied to relate the powder-milling process parameters to the magnetic properties of Fe–10%Ni and Fe–20%Ni alloy materials. An optimization procedure based on ANN training and testing steps has been developed to predict magnetic properties over a large range of process parameters. A good agreement was found between experimental and predicted results with an average standard deviation between experimental and predicted values less than 6%. The following features have been anticipated: (i) the higher disc rotation speed and the lower the vial rotation speed, the higher the coercivity; (ii) the lower the disc rotation speed and the higher the vial rotation speed, the lower the coercivity.