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Balanites aegyptiaca est une espèce caractéristique et emblématique des zones sèches d’Afrique et d’Asie. Elle revêt une grande importance socio-économique dans toute sa zone naturelle de répartition du fait de ses multiples usages. Toutefois, les propriétés technologiques de son bois sont mal connues, d’où des utilisations parfois inappropriées mais qui pourraient être élargies. Afin de mieux adapter ses applications à ses caractéristiques, nous avons déterminé les indicateurs de stabilité physique (masse volumique, infradensité, retrait radial total, retrait tangentiel total, retrait volumique total et point de saturation des fibres) et les indicateurs de comportement mécanique (module d’élasticité longitudinal, contrainte de rupture en flexion et compression) de ce bois. Quatre-vingt-treize éprouvettes prélevées dans 13 arbres provenant des zones sahélienne et soudanienne tchadiennes, et de la zone sahélienne sénégalaise ont été testées. Les résultats obtenus montrent que, pour les trois provenances, le bois de B. aegyptiaca est mi-lourd (797 kg/m3) avec une stabilité dimensionnelle moyenne : l’anisotropie de retrait est supérieure à 2 (2,2), le retrait radial total et le retrait tangentiel total sont moyens, respectivement égaux à 4 % et 8,5 %. Ses caractéristiques mécaniques sont moyennes (contraintes de rupture en compression et flexion statique respectivement égales à 49,4 MPa et 104,5 MPa) à faible (module d’élasticité longitudinal de 10 473 MPa). Une comparaison des résultats obtenus en fonction des zones de prélèvement a mis en évidence des tendances variables selon les caractéristiques étudiées. Ces variations entre les trois provenances restent cependant limitées. Les résultats de l’étude montrent que le bois de B. aegyptiaca pourrait être utilisé de façon appropriée sous forme de matériau pour une plus large gamme d’emplois, sous réserve de la mise en place d’une gestion adaptée permettant sa restauration par plantation.

Faidherbia albida is a typical emblematic species of African dryland areas. In Chad, it is used for many purposes, but very little is known about the technological properties of its wood, which sometimes leads to inappropriate uses. This work consisted to study the physical and mechanical properties of this wood, collected in the Sahelian and Sudanian chadian zone. As well as the impact study of the sampling areas of these properties. The result obtained shows that, the density, infradensity; modulus of elasticity, compression strength were significantly higher in the Sahelian zone than in the Sudanian zone, i.e. 508 and 409 kg·m−3; 5555 and 23.7 MPa, compared to 444 and 359 kg·m−3; 4150 and 19.6 MPa. The total tangential shrinkage, total volumetric shrinkage, fibre saturation point; static bending strength were significantly lower in wood from the Sahelian zone compared to the Sudanian zone, i.e. 4.6%, 7.7%, 23.7%; 42.5 MPa, compared to 6.6%, 9.5%, 28.9%; 52.6 MPa. The total radial shrinkage values obtained were not significantly different between the two provenances (mean: 3.1%).

In this study, carbonized peanut shells, cashew shells and millet stalks were used as raw materials to produce coal briquettes. Clay and arabic gum were applied as binders during briquetting by use of manual press. Physicochemical and mechanical tests of the obtained briquettes were conducted. The results show that the lower heating values of coal briquettes remain higher to that of wood; however, their ash contents are very high compared to wood. Combustion of coal briquettes samples show also that coal briquettes of peanut shells, cashew shells, and millet stalks ignite respectively at 312, 202.5 and 150.5°C. Bulk densities of these briquettes are respectively 543, 765 and 579 kg/m3. Briquette made with arabic gum presents mechanical compressive strength above 1 MPa. Key words: Coal briquettes, binders, heating value, bulk density, compressive strength.

Flax fibers are commonly used to reinforce mechanical properties of polymer-matrix composites, but can also enhance antioxidative properties of polyethylene matrix: lignin, which is one of the components of plant fibers has the advantage of containing phenols, molecules well known for their antioxidant properties. In this study, its oxidative stabilization effect on unstabilized polyethylene matrix has been demonstrated. It has then been shown by thermal analysis, that the Oxidation Induction Time of the polyethylene matrix increases from 0 to 25 min when the flax fiber content is raised from 0 to 54%, and that the flax fibers cause a slight increase in the degradation temperature of the polyethylene matrix. During thermooxidative ageing, this study has highlighted that the flax fibers also improve the oxidative stability of the polyethylene by inhibiting the oxidation mechanisms of the polyethylene matrix.

Natural materials are a focus for development of low carbon products for a variety of applications. To utilise these materials, processing is required to meet acceptable industry standards. Laminated bamboo is a commercial product that is currently being explored for structural applications, however there is a gap in knowledge about the effects of commercial processing on the chemical composition. The present study utilised interdisciplinary methods of analysis to investigate the effects of processing on the composition of bamboo. Two common commercial processing methods were investigated: bleaching (chemical treatment) and caramelisation (hygrothermal treatment). The study indicated that the bleaching process results in a more pronounced degradation of the lignin in comparison to the caramelised bamboo. This augments previous research, which has shown that the processing method (strip size) and treatment may affect the mechanical properties of the material in the form of overall strength, failure modes and crack propagation. The study provides additional understanding of the effects of processing on the properties of bamboo.

45e Congrès de la Société de Biomécanique, Metz, France, 26-/10/2020 - 28/10/2020; Bones are the third most affected organs by metastasis (Du et al. 2010). The qualitative effect of cancer types on metastatic bone has been largely described. Bone metastases weaken bones (Coleman 1997) by creating lytic, blastic or mixt (i.e. lytic and blastic) lesions. The prediction of fracture risk is clinically assessed by evaluating several parameters such as the size and location of the lesion or the Mirels' score. However, it seems these predictions overestimate the risk of fracture and are not specific enough to produce a reliable prediction (Van Der Linden et al. 2004). A quantification of the effect of the different cancer types on mechanical properties of the bone should improve clinical evaluation of the fracture risk. As a first step, the goal of our study was to develop a better assessment of the bone fracture risk by evaluating the mechanical properties of mice tibia affected by three different human cancer cell lines.

This research aimed to develop biofilms based on starch isolated from chachafruto (Erythrina edulis) grown in Colombia. The physicochemical, functional, and morphometric properties of chachafruto starch were characterized. Edible biofilms were developed using chachafruto starch, glycerol, oil, and Tween 80. The films were characterized in terms of their physical, mechanical and barrier properties. The data showed a high starch yield of 28.59% with high purity (95.92%) and 0.21% phosphorous and 14.14% amylose content. Chachafruto starch granules had a bimodal distribution of circular and oval shapes; longitudinal sizes varied from 25.86 to 119.82 μm, and transverse sizes ranged from 40.14 to 45.86 μm. The gelatinization pasting temperature (PT), peak viscosity (PV) and final viscosity (cool paste viscosity, CPV) of starch were 74.7°C, 2602 cP and 3171 cP, respectively. The addition of oil (0.1, 0.2 and 0.3%) and Tween 80 (0.4%) increased the moisture content of the starch and decreased the water vapor permeability (WVP) of the film. Additionally, the oil significantly reduced the tensile strength and elongation at break but had no effect on the percent elongation. The data showed that chachafruto seeds are a potential new and unconventional source of starch that shows feasibility for applications in starch-based edible films.

A number of studies have shown the ability of the vibration resonant method (VRM) to measure the modulus of elasticity (MOE) and the damping ratio ( $$\xi$$ ) of calibrated wooden samples of various dimensions. This method based on free transverse vibrations was also studied to assess the decay extent in small stakes. Nevertheless, a need for investigations was identified in order to apply the method to decayed logs. Both decay and geometrical singularities brought heterogeneity not taken into account by the VRM. The aim of this study was to examine the effects of fungal decay on these two mechanical properties of small-diameter silver fir logs using the VRM. Fifty-five small-diameter logs were monitored over a decay process taking place in a greenhouse located near Grenoble (France). The MOE and $$\xi$$ were measured in intact and decayed states. The results showed the reliability of the measurements of both properties. $$\xi$$ was found to be independent of moisture content for wood above the fibre saturation point. The results validated the loss in MOE and the gain in $$\xi$$ due to fungal activity. Thus, indicators based on the MOE and $$\xi$$ were proposed and compared to quantify the decay extent. Indicators calculated from the first mode of vibration appeared to be relevant for that purpose. Future work is needed to validate indicators on structural size logs and to compare this quantitative assessment to those obtained by the standard EN 152 that currently serves as a benchmark.

Cork is a natural raw materials used in numerous traditional and innovative applications among which the most famous are cork stoppers, insulation boards, and wall and floor covering. Cork exhibits a relatively homogeneous honeycomb structure composed of polyhedron cells filled with gas, which gives its specific properties such as elasticity or hydrophobic behavior. Mechanical properties of cork have been studied from a long time. However, in many industrial applications cork is increasingly used as granulate (>200 μm) or powder (

Wind damage is an important driver of forest structure and dynamics, but it is poorly understood in natural broadleaf forests. This paper presents a new approach in the study of wind damage: combining terrestrial laser scanning (TLS) data and finite element analysis. Recent advances in tree reconstruction from TLS data allowed us to accurately represent the 3D geometry of a tree in a mechanical simulation, without the need for arduous manual mapping or simplifying assumptions about tree shape. We used this simulation to predict the mechanical strains produced on the trunks of 21 trees in Wytham Woods, UK, and validated it using strain data measured on these same trees. For a subset of five trees near the anemometer, the model predicted a five-minute time-series of strain with a mean cross-correlation coefficient of 0.71, when forced by the locally measured wind speed data. Additionally, the maximum strain associated with a 5 ms−1 or 15 ms-1 wind speed was well predicted by the model (N = 17, R2 = 0.81 and R2 = 0.79, respectively). We also predicted the critical wind speed at which the trees will break from both the field data and models and find a good overall agreement (N = 17, R2 = 0.40). Finally, the model predicted the correct trend in the fundamental frequencies of the trees (N = 20, R2 = 0.38) although there was a systematic underprediction, possibly due to the simplified treatment of material properties in the model. The current approach relies on local wind data, so must be combined with wind flow modelling to be applicable at the landscape-scale or over complex terrain. This approach is applicable at the plot level and could also be applied to open-grown trees, such as in cities or parks. publishedVersion

Background and Aims Root anchorage function is crucial for tree survival as most trees are exposed to recurrent wind throughout their lifespan. Trees exhibit a large variability of root system architecture (RSA) due genetic and environmental factors. This study aims to understand the links between RSA and tree stability. Methods A 3D biomechanical model was used to simulate tree overturning. To capture the variability of sinker RSA, fourteen virtual root patterns were created from an ensemble average of measured Pinus pinaster root systems. Root virtual patterns and tree-pulling simulations were verified against experimental data. Results The model predicts realistic tree anchorage strength, root stress, and failure patterns. Only a few root components contribute significantly to anchorage strength. The taproot contributes the most to anchorage rigidity, representing 61 % of the anchorage strength. The windward roots failure drives ultimate anchorage failure, representing 25 % of the anchorage strength. Simulations show that root secondary thickening induces higher anchorage rigidity and increases anchorage strength by 58 %. Conclusions This innovative approach appears promising for describing tree stability and its acclimation to external constraints.

Whatever in pulp or biocomposite sectors, the elements called fines coming from plant fibres have generally a length lesser than 200 μm. Their mechanical impact has long been debated in short plant fibre thermoplastic composites. Are they solely a filling agent or on the contrary, have they a potential of reinforcement in such composites depending on their numbers, their length and aspect ratio? This work proposes an original experimental approach to explore the mechanical role of fine flax particles. Based on controlled milling of an initially homogeneous flax fibre batch that provides a population of fines (99% under 200 μm, average Lw of 147 μm), we devised a set of composites made of an increasing content of flax fines (0, 3.1, 5.6, 12.3, 20.4, 34.6 and 40.2%-vol) mixed with poly(propylene) (PP) and maleic anhydrid grafted PP (PP-PPgMA). Reference composites reinforced with chalk and also with cut flax fibre (Lw of 2000 μm) were also manufactured and studied. Results demonstrate that, despite a low aspect ratio (5 ± 0.2 for 20.4%-vol), fines can act more than as just a simple filler, a slight modulus reinforcement is depicted but only beyond a high threshold of about 20%-vol (+29% compared to raw PP for 20.4%-vol). In addition to PP, we then investigated the mechanical influence of the flax fines in two representative matrix thermoplastic families Poly(amide)-11 (PA11) and poly(butylene-succinate) (PBS). We highlighted an increase of the Young’s modulus of PA11 and PBS fines composites (+41% and +115, respectively for 20.4%-vol), whereas strengths were lower compared to the respective neat polymers, exhibiting the possible negative role of fines on composite mechanical properties.

This experimental study aims to determine the effect of relative humidity on concrete expansion due to delayed ettringite formation (DEF), which still remains imperfectly known. Test methods were designed to trigger reaction in concrete specimens and determine how ambient RH affects expansion of the specimens. Saturated salts solutions were used to achieve distinct ambient RH conditions within containers. Also, chemical analysis was performed to determine and quantify the fractions of alkalis leaching out of the pore solutions of concretes. Results showed that the critical ambient RH value that corresponds to significant suppression of DEF could be greatly dependent on the alkalis fractions leached out. Finally, the consequences of swelling due to DEF on the concrete properties are assessed. After swelling, both of gas permeability and porosity was increased significantly and dynamic modulus was reduced by about 45%.

International audience; In the European Union, timber is used in structural applications and must be graded with a Conformité Européene (CE) mark. To achieve standard, machine strength grading is used. A common technology for these machines is based on using the vibrational response of each wood board to estimate the timber modulus of elasticity and modulus of rupture. The first Eigen frequency is usually used to predict these mechanical properties. However, in heterogeneous wood species such as oak, this parameter is less correlated with mechanical properties. The current study proposes two new methods based on an extended exploitation of the vibrational response that predicts oak wood mechanical properties. The first method was based on the mechanical parameters deduced from several Eigen frequencies that were chosen with regards to a stepwise regression. The second method was based on the full vibrational spectrum and used a partial least squares method. The first method slightly improved the prediction of the modulus of elasticity compared with the first Eigen frequency in edgewise transversal vibration. Both methods significantly improved the prediction of the modulus of rupture.

The urban solid waste problem has been one of the biggest environmental challenges these days. In this context, developing biocomposites with improved performance by using various sources and wastes has been intensified in the last decades for economic and environmental points of view. In this study, physical behavior, fungal decay and termite attack tests were conducted in laboratory conditions to investigate the performance of composites developed from TetraPak and textile wastes. All the results were compared to standard wood products. The water swelling properties strongly decreased in the manufactured TetraPak composites when compared with the conventional particleboard panels. The fungal decay resistance tests revealed that the stand alone TetraPak based composites were not completely resistant to wood-decaying fungi. A significant amelioration in the decay durability was observed for the manufactured TetraPak composites compared to the standard wood samples. Durability classes were determined according to the criteria given in the European standard (CEN/TS15083-1). Interestingly, the data indicated that the increment of the wool waste proportion in the produced boards lead to a significant enhancement counter the test fungi. The results of termite screening test showed further considerable resistance for whole TetraPak based composites against termites when compared to traditional wood samples. Such panels could be an available alternative without any additives for wood based composite structures and it can be used in a wide range of applications.

Key message Lambro, Brenta, Taro, Alcinde and Soligo are new poplar cultivars suitable for laminated veneer lumber (LVL) for structural purposes. While Lena, Koster, Dvina, Mella and Trichobel must be used with careful veneer material selection to obtain high value of mechanical properties. Context In France, the veneer processing industry uses only a very small number of different poplar cultivars. Aims This paper set out to investigate the potential of laminated veneer lumber made from 14 new cultivars for structural purposes, with a focus on juvenility and veneer thickness effects. Methods The mechanical properties of laminated veneer lumber panels made from each cultivar (114 samples per cultivar) were characterized by measuring their density, modulus of elasticity and modulus of rupture. Results A tight correlation was found between destructive and non-destructivemodulus of elasticity tests (R2=0.90, 1,808 samples). Five cultivars had suitable mechanical properties for structural applications (‘Lambro’, ‘Brenta’, ‘Taro’, ‘Alcinde’ and ‘Soligo’). Five cultivars needed to be used with careful sample selection (‘Lena’, ‘Koster’, ‘Dvina’, ‘Mella’ and ‘Trichobel’), and the final four (‘I214’, ‘A4A’, ‘Triplo’ and ‘Polargo’) could not be recommended for structural purposes. Conclusion The advantage of using veneers of mature wood compare to juvenile wood for laminated veneer lumber (LVL) production was due to an improvement of modulus of elasticity and modulus of rupture in the range of 15 to 20 %. The use of thick veneers (5.25 mm compared to 3 mm) did not appear to be detrimental to laminated veneer lumber mechanical performance. This research was carried out at the Laboratoire Bourgogne des Matériaux et des Procédés (LaBoMaP), Ecole Nationale Superieure d’Arts et Metiérs (ENSAM), Cluny, Bourgogne, France. We wish to thank our partners FCBA and CNPF IDF for their active collaboration on this large research programme. We also wish to thank our partners and funders of the Xylomat Technical Platform from the Xylomat Scientific Network funded by ANR-10-EQPX-16 XYLOFOREST.

Novel fibers containing different ratios of PVA and d-limonene were fabricated using electrospinning for antibacterial active packaging applications. The PVA/d-limonene fibers were thoroughly characterized using a scanning electron microscope, fourier-transform infrared spectrometry, thermal gravimetry, differential scanning calorimetry, tensile tests, and oxygen permeability tests. The results of these analyses showed that the highest tensile strength and elongation at break values of 3.87 &plusmn, 0.25 MPa and 55.62 &plusmn, 2.93%, respectively, were achieved for a PVA/d-limonene ratio of 7:3 (v/v) and an ultrasonication time of 15 min during processing. This material also showed the lowest oxygen permeation and the best degradability and bacteriostatic properties of all samples.

6 pages; International audience; The production of natural fibers is not sufficient to accommodate the textile needs of the growing world population. Therefore, textile research is exploring alternative natural resources to produce fibers. Though typically known for its nutritional use, the sugarcane can also be used for textile production because of its high fiber content.The aim of our study was to extract fibers from sugarcane and to analyze their mechanical behavior. Cane particles were treated with an alkaline solution in order to get cellulosic fibers. Physical and mechanical characterizations were carried out on these fibers: linear density, fineness, tensile properties, and bending rigidity. Their microstructure was analyzed to better understand their behavior. The results showed a strong influence of extraction parameters on the characteristics of fibers. Depending on these parameters, fibers fineness ranged from 8 to 80 tex, length ranged from 19 to 62 mm, and tenacity ranged from 7 and 25 cN/tex.

The influence of the addition of polymer in mortars is investigated with special emphasis on the microstructure and mechanical properties of hardened materials. The presence of polymer in the mortars causes an increase of both the setting time of the cement and the porosity in hardened materials. The observation of these composites by scanning electron microscopy shows the formation of a continuous film of polymer within the matrix for a polymer/cement ratio of 10%. Therefore, the presence of polymer provides a structure where bicontinuous phases of polymer and cement hydrates are intertwined. This leads to a better resistance to acid attack and improves the adhesion between the cement paste and aggregates in mortars. The mechanical properties of composite mortars decrease with the addition of polymer due to the increase of porosity. L’influence de l’addition de polymere dans un mortier est caracterisee en s’interessant particulierement a la microstructure et aux proprietes mecaniques des materiaux durcis...

This paper aims at providing the first shear mechanical properties of spleen tissue. Rheometric tests on porcine splenic tissues were performed in the linear and nonlinear regime, revealing a weak frequency dependence of the dynamic moduli in linear regime and a distinct strainhardening effect in nonlinear regime. These behaviours are typical of soft tissues such as kidney and liver, with however a less pronounced strainhardening for the spleen. An analytical model based on power laws is then proposed to describe the general shear viscoelastic behaviour of the spleen. Soft tissues Mechanical properties Test conditions

The feasibility and industrial potential of using bio-flours from tropical crop residues, in particular starch containing bio-flours, for the manufacture of bio-composites was investigated. Polypropylene (PP) and poly(butylene succinate) (PBS) were compounded with bio-flours from pineapple skin (P) and from non-destarched (CS) and destarched (C) cassava root by twin-screw extrusion. In CS composites, two levels of starch granules melting were achieved by adjusting the extrusion temperature, enabling control of morphological and mechanical properties. The use of bio-flours reduced tensile strength by 26-48% and impact strength by 14-40% when the proportion of bio-flour was increased to 40% w/w, while flexural strength initially increased upon addition of bio-flours, before decreasing at higher loads. The use of compatibilizers, in particular maleic anhydride-polypropylene (MAPP) in PP composites with 30% bio-flour resulted in tensile strength similar to non-compatibilized composites with 10% bio-flour (34-35?MPa). MAPP also increased flexural strength to higher levels than pure PP, resulting in a stronger, but less flexible material.

International audience; The aim of this study was to establish the relationship between the stiffness of scantlings, approaching structural size materials, and small specimens of 6-year-old Eucalyptus urophylla 9 grandis wood using a resonance technique. The correlation between the elastic modulus (E) of the scantlings in longitudinal vibration and small specimens in flexural vibration was r = 75 when comparing the scantling values with the averaged values of the specimens per scantling. However, when the E of each single specimen was compared with its respective scantling, the coefficient of correlation decreased to r = 0.64 in the longitudinal tests and r = 0.61 in the flexural tests. A roughly linear correlation (r = 0.59) between specific modulus and loss tangent was obtained for the small specimens of Eucalyptus. In short, the resonance technique rapidly provided a large, accurate data set of mechanical wood properties as required for high-throughput phenotyping in recent genetic studies.

The effects of the ambient fluid on granular flow dynamics are poorly understood and commonly ignored in analyses. In this article, we characterize and quantify these effects by combining theoretical and experimental analyses. Starting with the mixture theory, we derive a set of two-phase continuum equations for studying a compressible granular flow composed of homogenous solid particles and a Newtonian ambient fluid. The role of the ambient fluid is then investigated by studying the collapse and spreading of two-dimensional granular columns in air or water, for different solid particle sizes and column aspect (height to length) ratios, in which the front speed is used to describe the flow. The combined analysis of experimental measurements and numerical solutions shows that the dynamics of the solid phase cannot be explained if the hydrodynamic fluid pressure and the drag interactions are not included in the analysis. For instance, hydrodynamic fluid pressure can hold the reduced weight of the solids, thus inducing a transition from dense-compacted to dense-suspended granular flows, whereas drag forces counteract the solids movement, especially within the near-wall viscous layer. We conclude that in order to obtain a realistic representation of gravitational granular flow dynamics, the ambient fluid cannot be neglected.

Dans ce travail une approche expérimentale est utilisée pour la modélisation de la propagation des ondes acoustiques dans le bois vert (Douglas). Le bois est supposé un matériau orthotrope et la vitesse de propagation des ondes acoustiques dans la section transverse est déduite des équations de mouvement pour une déformation plane. L'expérimentation est réalisée en deux étapes sous des conditions d'encastrement, le temps de propagation est mesuré sur des rondelles échantillon et sur des petits barreaux extrait des rondelles. Les propriétés mécaniques et physiques sont déterminées en vibration libre. Les résultats montrent une différence significative entre les vitesses de propagation obtenues sur les rondelles échantillons et celles des ondes guidées dans les barreaux. L'anisotropie du bois vert dans le plan transverse est discutée et la simulation de la forme des ondes est présentée. Un bon accord est observé entre les résultats expérimentaux et simulés.

The mechanical properties and microstructure of 15-5PH martensitic stainless steel were investigated after solution treatment, quenching and tempering. Aging at 350 and 400°C leads to a marked drop of the impact strength, an increase in the ductile to brittle transition temperature and an increase of both yield strength and hardness. Evolution of these mechanical properties during aging can be linearly correlated to allow aging in service to be determined via hardness measurements. During long term aging at intermediate temperatures, below 400°C, the martensite matrix of the 15-5PH suffers spinodal decomposition into chromium enriched and iron enriched domains. This specific embrittlement is reversible by an appropriate heat treatment performed on the aged alloy. However, this regeneration treatment is only effective if the interconnected network formed during aging has not reached its decomposition limit.

In many countries there is a trend to recycle wastes obtained during pavement maintenance or reconstruction, and to forbid the landfill of these products. Thus, in some circumstances it can be tempting to use reclaimed asphalt pavement (RAP) in new hydraulic concrete mixtures. This paper presents experimental data and modelling about the effect of RAP incorporation on cement concrete mechanical properties (compressive strength, tensile strengths and E-modulus). All these properties tend to decrease with the rate of RAP dosage, and with temperature. Then attempts are made to adapt LCPC mix-design models to these innovative concretes. Two alternative hypotheses are evaluated. In the first one, RAP aggregate is viewed as composite particles playing the role of an homogenous aggregate having lower bond, strength and E-modulus as compared to normal aggregate. In the second one, the bitumen phase is assumed to be finely dispersed within the cement paste, acting as a supplementary dosage of water (or air). According to the simulations, the second hypothesis is the best one. This finding extends the scope of application of modern mix-design methods, and will help in using RAP in cement concrete, for the technical, economical and environmental benefit of the road community.

Fifteen wheat doughs with various compositions have been selected and baked in order to obtain products with densities in the range of commercial bread values (0.25–0.35 g/cm3). A quick sensory profiling technique (Flash Profile), based on the combination of free choice profiling and a comparative evaluation of the whole product set was used. The sensory jury had to focus on the sensory perception of crumb texture (tactile and visual). The treatment of collected data by Generalized Procustes Analysis shows that products were perceived differently by the panel. The main differences concern the uniformity and the size of gas cells but also mechanical properties of corresponding crumb for which attributes like hardness, springiness and crumbliness were used. Instrumental characterization was performed using uniaxial compression (Young's modulus) and image analysis based on texture granulometry (fineness and homogeneity of cell distribution). A Multiple Factor Analysis allowed assessing the correlations between the sensory attributes and the instrumental measurements. Density and Young's modulus are positively correlated with the sensory elasticity. The instrumental and sensory measurements of the size and of the homogeneity of the cells distribution are correlated.

Carbonatation of hydrated lime compacts produces shrinkage and changes in mechanical properties comparable with those found in similarly treated compacts of bottle-hydrated cement and samples of hardened Portland cement paste. From experimental results obtained with the simpler lime system a mechanism for carbonatation shrinkage is proposed that postulates a through-solution reaction and induced cycles of wetting and drying. Experiments on compacts of bottle-hydrated cement show that carbonatation of the ‘combined lime’ is at least as rapid and extensive as the carbonatation of the ‘free lime,’ and that contrary to current opinion the former reaction results in even greater carbonatation shrinkage. The mechanism for carbonatation shrinkage of this system is considered to be connected with dehydration and polymerisation of the hydrous silica product of carbonatation.

This study involves the special case of lime compacts which are considered to serve as models for the system of lime in hydrated Portland cement paste. The ageing of lime was studied by measuring length changes of powdered samples under various steady-state and alternating conditions of humidity. As an explanation for the unique behaviour of lime compacts, a primary mechanism is proposed based on the theory that recrystallisation occurs at least at areas of particle contact when lime compacts are exposed to humidities above a certain value. Furthermore, this recrystallised product is more accommodating than the parent material, and hence it can be consolidated by forces due to menisci or changes in surface free-energy. This action is manifested by irreversible shrinkage on storage at intermediate humidities, by drying after storage or by alternating between two levels of humidity.

A sequential examination of strength development in terms of microhardness was studied during paste hydration of C[3]S in the presence of 2 and 5% CaCl[2] and at w/s ratios of 0.3 or 0.5. An attempt has been made to relate strength with microstructural features studied by means of Scanning Electron Microscopy. Generally, at earlier periods it was found that the 2% addition of CaCl[2] gave the strongest material; the effect was most pronounced in the 6-month sample of the series with 0.3 w/s. The high strength for the sample prepared at a w/s ratio of 0.3 may be related to a high CaO/SiO[2] C-S-H phase, low porosity, and possibly a hydrated calcium hydroxy chloride complex. The pore size distribution was also measured. In general, the higher the porosity the lower the strengths but the relationship was not perfectly linear even on the semi-logarithmic plot.

Wood heat treatment is an attractive alternative to improve decay resistance of wood species with low natural durability. However, this improvement of durability is realized at the expense of the mechanical resistance. Decay resistance and mechanical properties are strongly correlated to thermal degradation of wood cells wall components. Mass loss resulting from this degradation is a good indicator of treatment intensity and final treated wood properties. However, the introduction of a fast and accurate system for measuring this mass loss on an industrial scale is very difficult. Nowadays, many studies are conducted on the determination of control parameters which could be correlated with the treatment conditions and final heat treated wood quality such as decay resistance. The aim of this study is to investigate the relations between kinetics of temperature used during thermal treatment process representing heat treatment intensity, mass losses due to thermal degradation and conferred properties to heat treated wood. It might appear that relative area of treatment temperature curves is a good indicator of treatment intensity. Heat treatment with different treatment conditions (temperature-time) have been performed under vacuum, on four wood species (one hardwood and three softwoods) in order to obtain thermal degradation mass loses of 8, 10 and 12%. For each experiment, relative areas corresponding to temperature kinetics, mass loss, decay resistance and mechanical properties have been determined. Results highlight the statement that the temperature curves’ area constitutes a good indicator in the prediction of needed treatment intensity, to obtain required wood durability and mechanical properties such as bending resistance and Brinell hardness. LERMaB is supported by the French National Research Agency through the Laboratory of Excellence ARBRE (ANR-12- LABXARBRE-01), the authors gratefully acknowledge this aid

Third Coastal and Maritime Mediterranean Conference, FERRARA, ITALIE, 25-/11/2015 - 27/11/2015; Chemical stabilization is one of techniques which can improve mechanical and hydraulic properties of dredged sediments. This paper presents an experimental study focused on different techniques of stabilization of dredged sediment from La Baule-Le Pouliguen (France). Dredged sediments are stabilized with lime, Portland cement and fly ash. Three mixes were produced and submitted to uniaxial compression strength (UCS), indirect tensile strength (ITS) and shear tests at different curing ages. In addition, suction and mercury porosimetry tests are performed to highlight the effect of binders on the microstructure of treated sediment. Results indicated sediment treated with lime plus cement and fly ash, is promising, despite the time necessary to obtain the threshold of UCS (1MPa); unfortunately, ITS reference value (0.25 MPa) was not obtained. But this mixture presented good performance of shear strength parameters, exhibiting higher increases in cohesion (c) and friction angle (f) compared to the others mixes. In terms of porosimetry and suction results, it was observed that each type of binder acts differently, changing initial unimodal to bimodal porous distribution curves, and reducing suction in treated sediment due to macroporous occurrence and water retention for chemical reaction.

A finite element model was developed to study the influence of aerial architecture on the structural dynamics of trees. The model combines a complete description of the axes of the aerial architecture of the plant with numerical techniques suitable for dynamic nonlinear analyses. Trees were modeled on the basis of morphological measurements that were previously made on three 4-year-old Pinus pinaster Ait. saplings originating from even-aged stands. Calculated and measured oscillations were compared to evaluate model behavior. The computations allowed the characteristics of the fundamental mode of vibration to be estimated with satisfactory accuracy. Inclusion of a topological description of the aerial system in a mechanical model provided insight into the effect of tree architecture on tree dynamic behavior. Simplifications of the branching pattern in the model led to overestimations of the natural swaying frequency of saplings by 10 to 20%. Inadequate values of stem and root anchorage stiffness resulted in errors of 10 to 20%. Modeling results indicated that aerodynamic drag of needles is responsible for 80% of the damping in the studied trees. Additionally, damping of stem movement is reduced by one half when branch oscillations are not considered. It appears that the efficiency of the dissipative mechanisms depends directly on crown topology.

The arrangement of a plant's roots in the soil determines the ability of the plant to resist uprooting. We have investigated the influence of root morphology on anchorage using simple patterns of root systems and numerical simulation. The form and mechanical properties of roots were derived from results found in the literature. Major parameters determining soil characteristics, root patterns and strength were varied so that their influence could be evaluated. The design of the experimental method we used generated an optimal number of configurations of different root systems, the tensile resistances of which were calculated by two-dimensional finite element analysis. We could quantify the influence of specific parameters, e.g. branching angle, number of lateral roots and soil cohesion, as well as global parameters such as total contact area, basal diameter and volume of the whole root system. We found that the number of roots and the diameter of roots were major components affecting the resistance to uprooting. The combination of topology and biomass explained 70% of the variation of tensile resistance.

Summary This study develops a high performance grading process based on the analysis of acoustic vibrations in the audible frequency range. The unique feature of the method is that the spectrum is directly applied to obtain predictive variables for estimating the modulus of elasticity and modulus of rupture. A partial least squares regression was used. This powerful method represents a compromise between principal component regression and multi-linear regression. Partial least squares regression screens for factors which account for the variance in the predictor variables and achieves the best correlation between factors and predicted variable. The method is based on projections, similar to principle components regression, whereby a set of correlated variables is compressed into a smaller set of uncorrelated factors.

International audience; This paper is the second part of a comprehensive approach that allows the elastic and shrinkage properties of oak to be determined from the properties of the anatomical tissues and the spatial distribution of those tissues, obtained by a high resolution digital X-ray imaging device. The computation of the macroscopic properties employs a 2-D numerical tool, called MorphoPore, that utilises periodic homogenisation over the representative volume. The paper starts with the derivation of the mechanical formulation and analyses the effect of mesh refinement on the overall solution quality. Thereafter, a first example is presented that depicts the effect of fibre proportion and fibre zone shape on the macroscopic properties using a virtual anatomical pattern and a second example uses finite element meshes built from actual patterns coming from two positions of the same tree, just before and just after thinning the forest stand. The approach presented in this research allows the increase of rigidity and shrinkage coefficients due to the increase of the annual ring width to be quantified. Finally, two localisation problems are proposed in which the micro-stress fields are computed from the macroscopic loading. The first case assumes that no macroscopic stress field exists (free shrinkage configuration), whereas the second assumes that the macroscopic displacement is constrained along one direction (drying configuration).; Utilisation de l'imagerie X pour la prédiction du bois de chêne : représentation, homogénéisation et localisation. Partie II : Calcul des propriétés macroscopiques et des champs de micro-contraintes. Cet article est la deuxième partie d'une approche complète qui permet de prédire les propriétés élastiques et de retrait du chêne à partir des propriétés des tissus qui le composent et de leur distribution spatiale décrite par un système d'imagerie X de haute résolution spatiale. Le calcul des propriétés macroscopique est effectué par homogénéisation de milieux périodiques sur un volume élémentaire représentatif à partir d'un code numérique 2-D, appelé MorphoPore. Ce papier commence par la présentation de la formulation mécanique. Viennent ensuite quelques considérations sur l'effet du raffinement du maillage numérique. À l'aide de plans ligneux virtuels, le premier exemple d'application montre l'effet de la proportion des fibres et de la forme de zone de fibres sur les propriétés macroscopiques. Le deuxième exemple utilise deux plans ligneux réels, provenant du même arbre. La seconde zone produite juste après éclaircie, a un accroissement annuel très important. Notre approche permet de quantifier l'augmentation des rigidités et des coefficients de retrait. Enfin, deux exemples de localisation sont proposés. Cette démarche permet le calcul des champs de micro-contraintes à partir du chargement macroscopique de la structure. Le premier cas considère l'absence de contrainte macroscopique (retrait libre) tandis que le deuxième considère que le déplacement est bloqué selon une direction (zone externe d'une planche durant le séchage).

The design of meshes for the treatment of incisional hernias could benefit from better knowledge of the mechanical response of the abdominal wall and how this response is affected by the implant. The aim of this study was to characterize the mechanical behaviour of the human abdominal wall. Abdominal walls were tested ex vivo in three states: intact, after creation of a defect simulating an incisional hernia, and after reparation with a mesh implanted intraperitonally. For each state, the abdominal wall was subjected to air pressure loading. Local strain fields were determined using digital image correlation techniques. The strain fields on the internal and external surfaces of the abdominal wall exhibited different patterns. The strain patterns on the internal surface appeared to be related to the underlying anatomy of the abdominal wall. Higher strains were observed along the linea alba than along the perpendicular direction. Under pressure loading, the created incision increased the strain of the abdominal wall compared to the intact state in 5 cases of a total 6. In addition, the mesh repair decreased the strains of the abdominal wall compared to the incised state in 4 cases of 6. These results suggest that the intraperitoneal mesh restores at least partially the mechanical behaviour of the wall and provides quantification of the effects on the strains in various regions.

As the proportion of sapwood (SW) transformed into heartwood (HW) is irregular both radially and longitudinally in trunks of Maritime pine (#Pinus pinaster# Ait.), it has been suggested that HW formation is a developmental process, regulated internally within the tree. In trees where stem growth is eccentric due to stem lean or wind action, the number of annual growth rings of SW transformed into HW is greater on the compressed side of the tree. To determine the contribution to bending stiffness, if any, of this prematurely formed HW, four point bending tests were carried out on fresh HW and SW samples taken from the same growth ring, or neighbouring growth rings, at different cross-sectional positions at a height of 2 m from six 52-year-old Maritime pines. The mean (± s.e.) modulus of elasticity (E) was 7.6 ± 0.3 GPa (longitudinal direction) for all samples. No significant differences in E were found between HW and SW; thus HW does not play a significant mechanical role in bending stiffness. To test a second hypothesis that early HW formation on the compressed side of trees may maintain a constant, optimal volume of SW around the tree, the Pipe Model Theory was applied to 12 52-year-old leaning Maritime pines (angle of lean varied from 0-22°). The surface area (S) of the SW was determined at different heights up the trunk and correlated with crown surface area (S crown). Regressions between Ssw and S crown were highly significant, thereby supporting the theory that HW formation and extension is controlled internally in Maritime pine. HW formation in Maritime pine then serves to maintain an optimal proportion of functional SW which is an important criterion for survival in a species often subjected to severe drought for long periods.

Epoxidised liquid natural rubber (ELNR) constitutes a new family of polymers chemically derived from natural rubber. It is a highly viscous rubber of low molar mass generally used as plasticiser or processing aid, especially during processing of natural rubber and styrene/butadiene rubber stocks. The effect of incorporating this polymer rather than a standard plasticiser in a nitrile/butadiene rubber based mix has been investigated. The retention in mechanical properties following air and oil aging of the vulcanisates was also studied. Satisfactory processability of compounded stocks, mechanical properties, and aging resistance was maintained following incorporation of ELNR into nitrile/butadiene rubber formulations even at the lowest plasticiser concentrations. The improvement in aging behaviour was more pronounced when 25 mol-% ELNR was used at concentrations above 15 pphr (parts per hundred of rubber).

From the K-L model proposed by Lewellen [LEW 77], an analytical expression of turbulence macroscale L was established. This expression, obtained with the hypothesis of a zero horizontal pressure gradient can be used for inertial or Couette flow. This formulation is better than the classical linear expression and in good agreement with numerical computations. We obtain a new solution for the velocity profile which can be compared with the logarithmic profile.

Trauma is a leading cause of death for young people in developed countries, becoming a public health issue. After the spleen and liver, the digestive tract is the third most frequently affected organ during blunt abdominal trauma. Gastrointestinal injuries are responsible for significant morbidity and mortality, due to the difficulty in diagnosing such intestinal lesions and the resulting delay in treatment. Mechanical behaviour of the colon has only been studied under quasi-static loads.This study involves the experimental characterisation of the mechanical behaviour of the colon using tensile tests, to determine the mechanical response under different loads.

Une structure en béton doit assurer des fonctions structurales qui vont au delà de la simple résistance. Dans ce cadre, la fissuration du béton armé joue un rôle primordial sur la durabilité, l’étanchéité et même la sûreté des structures. La structure poreuse du béton rend naturellement possible la pénétration au cours du temps d’espèces délétères. En outre, sous l’effet des chargements mécaniques et des conditions environnementales au sens large, le béton se fissure. Les fissures constituent, elles aussi, des voies préférentielles pour la pénétration de fluides ou d’agents agressifs et ajoutent de manière significative leur contribution à la dégradation des performances structurelles. Dans la thèse une stratégie de modélisation macroscopique probabiliste du couplage entre fissuration et transferts de fluides dans les structures en béton est présentée. Le béton est modélisé comme un milieu poreux saturé d’eau tandis que la fissuration (mécanique) est modélisée au travers d’une approche numérique probabiliste tenant compte de l’hétérogénéité naturelle du matériau et des effets d’échelle qu’elle induit. L’hypothèse physique de base du modèle de fissuration est que chaque élément fini peut être considéré comme représentatif d’un volume de matière hétérogène dont le comportement est géré par son degré d’hétérogénéité, défini comme le rapport entre le volume élémentaire et un volume représentatif de l’hétérogénéité du matériau. Dans la formulation développée, les propriétés mécaniques du matériau sont considérées comme des variables aléatoires (non corrélés) distribuées dans les éléments du maillage selon des distributions statistiques validées expérimentalement. Une approche par analyse inverse permet d’accéder aux paramètres de fonctions de distribution qui, selon les hypothèses du modèle, varient en fonction de la dimension des éléments finis. Le couplage fissuration-transfert est traité de manière faible, sous l’hypothèse d’absence d’interaction entre les deux processus (à savoir que la fissuration de l’élément fini, d’origine mécanique, induit une variation locale de sa perméabilité). L’utilisation d’une loi de Poiseuille modifiée et adaptée expérimentalement selon un protocole développé dans le cadre de la thèse permet de mettre en relation une telle variation avec l’ouverture de fissure et de prendre en compte, de manière macroscopique, les principales causes d’écart entre l’écoulement idéalisé, représenté par la loi de Poiseuille (loi cubique), et l’écoulement dans des fissures réelles. Une approche de type Monte-Carlo permet de valider les résultats des simulations mécaniques et hydriques. Les capacités de la stratégie de modélisation proposée en termes de prédiction des débits d’eau en milieu fissuré sont explorées au travers de la simulation d’essais de perméabilité sous charge sur des éprouvettes cylindriques soumises à du fendage. Ces essais sont utilisés dans le cadre du protocole expérimental. Une première validation à l’échelle d’un élément structurel multifissuré est présentée. Elle consiste en la simulation d’un essai (récemment proposé dans la littérature) développé pour l’étude de l’impact de la fissuration sur les propriétés de transfert de tirants en béton armé. Concrete durability is strongly affected by the flow of fluids, gas and pollutants in its porous matrix. The presence of cracks weakens the resistance of concrete porous matrix and constitutes preferential flow paths for aggressive components. In the thesis, a probabilistic numerical modeling strategy for modeling fluids transfers in cracked concrete structures is presented. The concrete is modeled in the framework of water saturated porous media. Its (mechanical) cracking is modeled by means of a macroscopic probabilistic approach, explicitly taking into account material heterogeneity as well as size effects. The main assumption of the model, developed in the frame of the the Finite Element Method, is to consider a finite element volume as a volume of heterogeneous material and to assume that physical mechanisms influencing the cracking processes remain the same whatever the scale of observation. At the scale of the finite element, mechanical properties are then functions of its own volume. To describe the heterogeneity of the material, these mechanical properties are considered as uncorrelated random variables distributed over the finite element mesh. Characteristics of statistical distribution laws are directly depending on the degree of heterogeneity of the finite element (the ratio between its volume and the volume of the coarsest aggregate) and of the quality of the cement paste. An inverse analysis approach allows to find their parameters as functions of the elementary volume. A weak coupling between cracking and fluid transfers is considered, under the assumption of no interaction between the two processes (i.e. the mechanically produced cracking of a finite element induces a local variation of its permeability tensor). An experimentally adapted Poiseuille (cubic) law, based on an original experimental protocol, allows to relate this permeability variation to the crack aperture and to macroscopically take into account the influence of crack roughness, aperture variation and tortuosity. A Monte-Carlo like approach is used in order to statistically validate mechanical and hydraulic simulations. The coupling strategy is validated in two phases, both at the scale of a laboratory specimen and at the scale of a multi-cracked structural element.

The proprietary materials used to repair concrete structures are often polymer-modified hydraulic binders. The influence of the presence of polymer on the properties of these composites has been studied, but few works have focused on the evolution of these properties when the material is applied on a structure exposed to an environment that can be aggressive to concrete. In this paper, the properties of polymer-modified mortars made in the laboratory are reported and compared to those obtained on similar commercial products but whose precise composition is unknown. Thus, the influence of the type and quantity of polymer on the consistency, the setting time, the microstructure, the porosity and the mechanical properties of the mortars are analyzed. Special attention is given to the study of the influence of the curing conditions on the final properties of the hardened material.

Numerical models of the human body require realistic mechanical properties of the muscles as input, but, generally, such data are available only for animals’ muscles. As a consequence, the aim of this study was to identify the hyper-elastic behavior of the human sternocleidomastoideus muscle in tension using different constitutive laws. Ten sternocleidomastoideus muscles were tested in vitro. The hyper-elastic behavior was modeled with an exponential law and a hyper-elastic constitutive law studied analytically. The latter was also studied with an inverse approach using a subject-specific, finite-element model of each muscle. The three approaches were compared statistically. From these laws and methods, the shear modulus μ (4 to 98 kPa) and the curvature parameter α (17 to 52) were identified. Both the analytical and finite-element approaches gave parameters of the same order of magnitude. The parameters of the exponential and hyper-elastic laws were linked thanks to simple linear equations. Our results evidence that the hyper-elastic tension behavior of human sternocleidomastoideus muscle can be described using a simple model (exponential) considering basic geometric features (initial length and cross-sectional area).

An edible wheat gluten film was developed and effects of gluten concentration, ethanol concentration (ET) and pH of the film-forming solution on various film properties were evaluated using Response Surface Methodology. pH and ethanol concentration had strong interactive effects on film opacity, water solubility and water vapor permeability. A simultaneous variation of ethanol concentration and pH between 32.5% ET, pH 4 and 45% ET, pH 2 resulted in homogeneous and transparent film with relatively low water solubility. The lowest water vapor permeability would be expected with 20% ethanol concentration and pH 6. Mechanical properties were mainly affected by gluten concentration and pH. The most resistant film was obtained at high gluten concentration (12.5%) and pH 5.

International audience; Gravitropism is necessary for plants to control the orientation of their axes while they grow in height. In woody plants, stem re-orientations are costly because they are achieved through diameter growth. The functional diversity of gravitropism was studied to check if the mechanisms involved and their efficiency may contribute to the differentiation of height growth strategies between forest tree species at the seedling stage. Seedlings of eight tropical species were grown tilted in a greenhouse, and their up-righting movement and diameter growth were measured during three months. Morphological, anatomical and biomechanical traits were measured at the end of the survey. Curvature analysis was used to analyse the up-righting response along the stems. Variations in stem curvature depend on diameter growth, size effects, the increase in self-weight, and the efficiency of the gravitropic reaction. A biomechanical model was used to separate these contributions. Results showed that (1) gravitropic movements were based on a common mechanism associated to similar dynamic patterns, (2) clear differences in efficiency (defined as the change in curvature achieved during an elementary diameter increment for a given stem diameter) existed between species, (3) the equilibrium angle of the stem and the anatomical characters associated to the efficiency of the reaction also differed between species, (4) the differences in gravitropic reaction were related to the light requirements: heliophilic species, compared to more shade-tolerant species, had a larger efficiency and an equilibrium angle closer to vertical. This suggests that traits determining the gravitropic reaction are related to the strategy of light interception and may contribute to the differentiation of ecological strategies promoting the maintenance of biodiversity in tropical rain forests.

Fourier transform infrared spectroscopy has been used to investigate the conformational changes of glycinin, a major storage protein of soybean seeds, upon film-forming. The results show that the secondary structure of glycinin is mainly composed of a β -sheet (48%) and unordered (49%) structures. The amide I band of glycinin in film-forming conditions, i.e. in alkaline media and in the presence of plasticizing agent, reveals the conversion of 18% of the secondary structure of the protein from the β -sheet (6%) and random coil (12%) to the α -helical conformation due to the helicogenic effect of the ethylene glycol used as the plasticizing agent. Conformational changes also occur upon the film-forming process leading to the formation of intermolecular hydrogen-bonded β -sheet structures. Results obtained from other plant families indicate that, whatever the origin and conformation of protein, formation of films leads to the appearance of intermolecular hydrogen-bonded β -sheet structures, suggesting that this type of structure might be essential for the network formation in films. Thus, it is hypothesized that, in the film state, intermolecular hydrogen bonding between segments of β -sheet may act as junction zones in the film network. This study reveals for the first time that there is a close relationship between the conformation of proteins and the mechanical properties of films.

Several hydrated portland cement systems have been studied at DBR in a wide range of porosities. These systems include room-temperature hydrated paste, autoclaved paste, autoclaved with addition of sulfur and silica, hot-pressed samples and compacts of synthetic 14A tobermorite. Measurements included compressive strength, Young's modulus, product density, porosity and helium inflow, by which the various systems were characterized. It was concluded that, at a given porosity, an optimum proportion of higher density crystalline material and poorly aligned and ill-crystallized material yields the best strength but the quantity of poorly-crystallized material required decreases with porosity.

Modulus of elasticity and microhardness measurements were made on compacts of four sulfur preparations having different crystallinities morphologies and a wide range of porosities. Compacts amde from Crystex — a high polymeric sulfur — had mechanical properties inferior to those of other preparations studied. Annealing compacts resulted in a large increase in microhardness. Measurements of modulus of elasticity and microhardness of sulfur compacts reinforced with poly (ethylene terephthalate) fibers were made for a wide range of porosities.

Compressive strength, modulus of elasticity, and microhardness measurements were made on a variety of autoclaved cement-silica preparations covering a wide range of porosity. A spectrum of linear log mechanical property — porosity functions was observed. Analysis demonstrated that the slopes of these functions were dependent on the preparation silica content and density of the hydrated product. The slopes of the lines for each mechanical property bore a constant ratio with slopes calculated from the corresponding lines of the other two mechanical properties. This resulted in expressions interrelating mechanical properties which were independent of porosity and valid for all preparations studied. Compressive strength and microhardness for preparations studied were shown to be directly related.