Quantitative Analysis of Micro-porosity of Eco-material by Using SEM Technique

Microstructure of the eco-material combining vegetation recovery with slope protection is important for determining plant-growing properties.Several techniques for analyzing the eco-material microstructure are presented,including the freeze-cut-drying method of preparing samples for scanning electronic microscopy (SEM),the SEM image processing technique and quantifying analysis method of the SEM images,and etc.The aggregates and pores in SEM images are identified using the different mathematics operators,and their effects are compared.The areas of aggregates and pores are obtained using the operator of morphology,and the influences of different thresholds in image segmentation are also discussed.The results show that the method,in which the variation of non-maximum grey-level gradient is limited,improves the effect of edge detections due to a weak distinction existing at the edge between the aggregates and pores in image.The determination of the threshold should combine the image characteristic with filling operation,so as to assure the precision of the image analysis,in which the contact-segmentation is the simplest and most effective method.The results also show that the pore areas in eco-materials are generally larger than those in the correlative soils,and their increment is large as soil fabric being fine.These differences are related to admixture of expansive perlitic.The operator of morphology provides a new method for the image analysis of other porous material microstructure such as soils and concretes.

Powder Mixing Simulation Using Random Walk Model in Eco-material Preparation

The eco-material composition is not well-distributed in preparation. The eco-material samples were taken for computer image analysis, and its particle numbers and appearance parameters were measured. Based on the mechanism of connective mixing and diffusion, the particles distribution was simulated by a computer using the random walk with Levy flight. The results show that the eco-material microstructure simulated by a computer has an idealized porous structure. The particles distribution has a cluster characteristic that changes with the different size and number of particles in Levy flight trajectory. Each cluster consists of a collection of clusters and shows a structure of self-similar cluster,hence presents a well-defined fractal property. The results obtained from SEM observation are in good agreement with the numerical simulations, and show that the convective mixing presents in the Levy flight walk.

Thermal Conductivity of Compressed Earth Bricks Strengthening by Shea Butter Wastes with Cement

Currently, in a context of sustainable development, the economic and environmental challenges incite, to valorize local materials such as clays and agro-industrial waste. It is in this approach that a new category of compressed earth bricks (BTC) stabilized with shea meal (TK) and cement was proposed. The purpose of this paper is to investigate the effect of shea meal rate on the thermal conductivity properties of cement stabilized earth bricks. A lateritic clay (Lat) mainly composed of kaolinite (38.44%), quartz (24.94%), goethite (12.28%), hematite (4.44%) and illite (19.9%) was used to make bricks. Different mix designs made up of lateritic clay and 5% cement were studied. The shea meal is added as a partial lateritic clay replacement in different proportions. The thermal conductivity was determined by hot disk method and correlated to both porosity and density of elaborated materials. The results obtained show that the thermal conductivity and density of bricks decrease respectively from 0.72 W·m-1·K-1 to 0.52 W·m-1·K-1 and from 2.77 g·cm-3 to 2.52 g·cm-3. The presence of shea meal within the material generates pore formation, which may partly explain the improvement of the thermal insulation properties. A positive correlation was noted between density and thermal conductivity of these materials.

Effect of Substitution of Cement by Mineral Powders on the Physico-mechanical Properties and Microstructure of Sand Concretes

The approach that contributes to the development of eco-materials in construction is the use of mineral powders,which can improve mechani­cal properties and reduce cement consumption.This article aims to study the effect of substitution by mass of cement with mineral powders on the physicomechanical properties and microstructure of sand concretes.The used mineral powders are A:the limestone,B:the natural pozzolan,C:the hydraulic lime,D:(1/3 limestone+1/3 natural pozzolan+1/3 hydraulic lime),and E:(1/2 natural pozzolan+1/2 hydraulic lime).The studied percentages are 5%,10%and 15%,in both separated and combined states.The studied properties are workability,compressive strength,the elastic­ity modulus in compression,shrinkage and microstructure analysis.The objective is to target the optimal percentage of the substitution of cement with mineral powders,which ensures the best compromise between the main properties of the studied sand concretes.The obtained results show that the optimal percentage is in favor of the substitution of cement by 10%D(1/3 limestone,1/3 natural pozzolan and 1/3 hydraulic lime).Even the 15%of mineral powder D,presented similar performances compared to the sand concrete(without mineral powders).Finally,in the context of the development of eco-materials,it should be noted that the 10%D and 15%D(1/3 limestone,1/3 natural pozzolan and 1/3 hydraulic lime)contribute to decrease the use of cement and consequently to reduce of CO2 emissions.

Freeze–thaw resistance of eco–material stabilized loess

In the Loess Plateau in Northern China,repeated freeze–thaw(FT)cycles deteriorate the strength and structure of loess as a foundation soil,resulting in the instability or failure of supporting structure.Lignosulfonate is an eco–material,utilized as an effective and nontraditional stabilizer to improve the engineering properties of metastable soils.A series of laboratory tests,including unconfined compression tests,cyclic loading–unloading tests and scanning electron microscopy,on calcium lignosulfonate(CL)-and sodium lignosulfonate(SL)-stabilized loess were performed to investigate the stabilization effect,deterioration mechanisms of the FT cycles,and the resistance to FT cycles.Two traditional stabilizers,quicklime(QL)and sodium silicate(SS),were selected,and the engineering properties of QL-and SS-stabilized loess were compared with those of CL-and SLstabilized loess.The results showed that the strength values of CL-and SL-stabilized loess specimens decreased by 34.2%and 50%respectively,after 20 FT cycles,whereas those of the traditionally SS-and QL-stabilized specimens decreased by 85.3%and 82.87%,respectively.The elastic moduli of SL-and QL-stabilized loess specimens decreased by 22.1%and 92.0%,respectively.The mean energy dissipations of nontraditionally treated specimens also decreased significantly less than those of traditionally treated specimens.Overall,the results showed CL and SL had better stabilization effects on engineering properties of loess than QL and SS,and their stabilized loess specimens exhibited stronger resistance to FT cycles.The study findings demonstrated the significant potential of lignosulfonate for extensive application in cold loess areas.

Characterization of Two Clay Raw Materials from Côte d’Ivoire with a View to Enhancing Them in Eco-Construction

This study was carried out with a view to appreciate the value of clay, raw materials in eco-construction. To achieve this, we sampled two clay raw materials denoted Aga and Bak and then characterized. The results obtained from geotechnical and mineralogical tests have shown that the clay samples Aga and Bak are fine soils moderately plastic class A soils consisting essentially of quartz with 73.13% and 74.56% respectively for Aga and Bak and clay minerals (kaolinite and illite) with 12.73% kaolinite and 8.55% illite for Aga against 8.31% kaolinite and 13.72% for Bak. Moreover, these samples do not contain swelling clays and contain a sufficient quantity of iron oxides which allows them to be valued in ceramics, in particular in compressed earth bricks (CEB).

Cork and Sustainability:Discussing the Sustainable Use of the Material from a Design Perspective

There is the challenge to use materials in a more sustainable way.Even though cork has an interesting eco-profile as a material,other aspects contributing to an enhanced sustainable use of the resource are discussed:addressing the life-span of products,materials substitution,and the trend of materials development identified.