Physico-Mechanical Characteristics of Earth Bricks Stabilized with Cement and Padouk Sawdust Residues

The objective of this work is to improve the physical and mechanical properties of stabilized earth blocks (BTC) used in construction in the Ndé department of Cameroon. To achieve this, two stabilizers, cement and sawdust, were used at varying percentages of 0%, 4%, 6%, and 8%. Physical characterization tests, including natural water content, specific weight, jar test, Protor, and Atterberg limits, were conducted. Additionally, mechanical tests, such as compression and three-point bending, were performed. The results show that as the amount of stabilizer increases, the density of BTC decreases. The samples with 8% sawdust have the highest density, while those without stabilizers have the lowest. Porosity decreases as sawdust and cement content increases, with smaller values observed in samples with 8% sawdust or cement. Our tests indicate that blocks stabilized with cement have slightly higher compressive strength than those stabilized with sawdust. However, the water absorption rate increases with higher sawdust content.

Effects of temperature and age on physico-mechanical properties of cemented gravel sand backfills

Cemented backfill used in deep mines would inevitably be exposed to the ambient temperature of 20−60℃in the next few decades.In this paper,two types of cemented gravel sand backfills,cemented rod-mill sand backfill(CRB)and cemented gobi sand backfill(CGB),were prepared and cured at various temperatures(20,40,60℃)and ages(3,7,28 d),and the effects of temperature and age on the physico-mechanical properties of CRB and CGB were investigated based on laboratory tests.Results show that:1)the effects of temperature and age on the physico-mechanical properties of backfills mainly depend on the amount of hydration products and the refinement of cementation structures.The temperature has a more significant effect on thermal expansibility and ultrasonic performance at early ages.2)The facilitating effect of temperature and age on the compressive strength of CGB is higher than that on CRB.With the increase of temperature,the compressive failure modes changed from X-conjugate shear failure to tensile failure,and the integrity of specimens was significantly improved.3)Similarly,the shear performance of CGB is generally better than that of CRB.The temperature has a weaker effect on shear strength than age,but the shear deformation and shear plane morphology are closely related to temperature.

Physico-mechanical properties of granite after cyclic thermal shock

Understanding rock mechanical behaviors after thermal shock is critically important for practical engineering application.In this context,physico-mechanical properties of Beishan granite,Gansu Province,China after cyclic thermal shock were studied using digital image correlation(DIC),acoustic emission(AE)monitoring,and microscopic observation.The results show that the peak strength and elastic modulus decreased gradually with increase in thermal shock cycle.However,the above two parameters showed no further changes after 10 thermal shock cycles.The loading stress ratio(i.e.the ratio of the current loading stress level to the peak stress in this state)corresponding to the occurrence of the uneven principal strain field and the local strain concentration zone on the surface of the granite specimen decreased with increase in thermal shock cycle.Three transformation forms of the standard deviation curves of the surface principal strain were found.For granite with fewer thermal shock cycles(e.g.no more than 2 cycles),the standard deviation curves exhibited approximately exponential growth in exponential form.With increase in thermal shock cycle,the S-shaped curve was dominant.After 10 thermal shock cycles,an approximate ladder-shaped curve was observed.It is displayed that AE activity was mainly concentrated around the peak strength zone of the granite specimen when the rock samples underwent fewer thermal shock cycles.With increase in thermal shock cycle,AE activity could occur at low loading stress levels.Microscopic observation further confirmed these scenarios,which showed that more microcracks were induced with increase in thermal shock cycle.The number of induced microcracks at the edge location of the granite specimen was significantly larger than that at the interior location.Finally,a continuum damage model was proposed to describe the damage evolution of the granite specimen after cyclic thermal shock during loading.

Experimental study on the physico-mechanical properties of Tamusu mudstone — A potential host rock for high-level radioactive waste in Inner Mongolia of China

Tamusu mudstone, located in Bayin Gobi Basin in Inner Mongolia of China, has been selected as a potential host rock for high-level radioactive waste(HLW) disposal in China. A series of tests has been carried out, including X-ray diffraction(XRD) tests, scanning electron microscopy(SEM) tests, disintegration tests, permeability tests and triaxial compression tests, to estimate the physico-mechanical properties of Tamusu mudstone in this work. The mineral composition of Tamusu mudstone was analyzed and it was considered as a stable rock due to its low disintegration rate, i.e. approximately 0.11%after several wet/dry cycles. Based on the results of permeability test, it was found that Tamusu mudstone has a low permeability, with the magnitude of about 10—20m^(2). The low permeability makes the mudstone well prevent nuclide migration and diffusion, and might be influenced by temperature.The triaxial tests show that Tamusu mudstone is a stiff mudstone with high compressive strength, which means that the excavation disturbed zone would be smaller compared to other types of mudstone due to construction and operation of HLW repositories. Finally, the properties of Tamusu mudstone were compared with those of Opalinus clay, Callovo-Oxfordian(COx) argillite, and Boom clay to further discuss the possibility of using Tamusu mudstone as a potential nuclear waste disposal medium.

A new method to test rock abrasiveness based on physico-mechanical and structural properties of rocks

A new method to test rock abrasiveness is proposed based upon the dependence of rock abrasiveness on their structural and physico-mechanical properties. The article describes the procedure of presentation of properties that govern rock abrasiveness on a canonical scale by dimensionless components, and the integrated estimation of the properties by a generalized index. The obtained results are compared with the known classifications of rock abrasiveness.

Relationship between Physico-Mechanical Properties, Compacting Pressure and Mixing Proportion of Briquettes Produced from Maize Cobs and Sawdust

This study examined the relationship between selected physico-mechanical properties, compacting pressure and mixing proportion of briquettes produced from combination of maize cob particles and sawdust of low, medium and high density timber species. Particle sizes of maize cobs and sawdust used for the study were ≤1 mm. The two materials were combined at mixing percentages of 90:10, 70:30 and 50:50 (Sawdust:maize cobs). Briquettes were produced at room temperature (28°C) using compacting pressures 20, 30, 40 and 50 MPa. The results suggested that combining maize cob particles with sawdust of low, medium and high density wood species could significantly enhance the relaxed density, compressive strength in cleft and impact resistance index of briquettes produced from agricultural biomass residue like maize cobs. The results further indicated that the physical and mechanical characteristics of briquettes produced from combinations of sawdust of low density species and maize cobs were exceptionally higher than that produced from combinations of maize cob particles, and medium density and high density timber species. The R2 values for the regression model between the independent variables (mixing percentage and compacting pressure) and relaxed density, compressive strength in cleft and impact resistance index of briquettes produced from combinations of maize cob particles and sawdust of low density species (Ceiba pentandra) were 0.966, 0.932 and 0.710 respectively. This study provides a hope for briquetting maize cobs at room temperature using a low compacting pressure.

Physico-Mechanical Properties of Bio-Based Bricks

The aim of this work is to improve the high performance of mud bricks. The latter was reinforced with rice straws as stabiliser leading to an improvement of the physico-mechanical properties. Thus, the physical characteristics of the clay such as natural water content, density, atterberg limit, plasticity limit (Wp) and plasticity index (Ip) were determined. Their values are respectively 8.39%, 2025.73 Kg/m3, 47.66%, 29.75% and 17.91%. The clay used is a low plastic organic silt. The normal proctocol provided an optimum dry density (ɣOP) of 1.28 Kg/m3 at an optimum moisture content of 12.42%. The actual density of the straw is 464 Kg/m3, its absorption rate reached 206% in 5 mins and stabilised at 385% at 480 mins of immersion. The maximum bending and compression strengths are respectively 1.52 and 0.164 MPa. The mud brick absorption coefficients obtained are between 4.875 at 0% straw and 20.573% at 3% straw.

Physico-mechanical characterization of polyurethane foam dressings containing natural polyols

Advanced wound dressings are replaced traditional dressings in order to provide appropriate environment for healing and also to promote cell migration[1].The key characteristics of wound dressings are non-toxic,highly absorbed,air permeable,biocompatible and have good mechanical properties[2].Due to providing moist environment and also protecting maceration at the wound edge area,foam dressings are used in various clinical applications[3].They are mostly prepared from polyurethane between polyols and isocyanate polymerization.

Physico-mechanical performance of debris-flow deposits with particular reference to characterization and recognition of debris flow-related sediments

To characterize and recognize the debris flow-related deposits,the physico-mechanical performance of four deposits from the Dongyuege(DYG),Shawa(SW),Jiangjia Gully(JJG),and Gengdi(GD)debris flows in southwest China is investigated through laboratory analyses and tests.The four debris-flow materials can all be remolded into coherent,homogeneous cylinders with high densification and strength–porosity of 25%-36%,mean pore-throat radius of 0.46-5.89μm,median pore-throat radius of 0.43-4.28μm,P-wave velocity of 800-1200 m/s,modulus of elasticity of 28-103 MPa,unconfined compressive strength(UCS)of 220-760 kPa,and cohesion of 65-281 kPa.Based on the comparison in slurryability and formability among debris-flow deposits,granular flow deposits,fluvial deposits,residual lateritic clay and loess,whether a sediment can be cast into competent cylinders for physico-mechanical tests can be regarded as a diagnostic evidence of old debris-flow deposits.The discrepancy in physico-mechanical properties among the four debris-flow deposits suggests that the combination of foregoing physico-mechanical parameters can characterize assembling characteristics of debris flow-related sediments including grain size distribution,mineralogy,and accidental detritus.Four deposited sediments above can be surprisingly classified as hard soil-soft rocks according to UCS,and the hard soil-soft rock behaviors can advance the further understanding of debris flows.

The Relationship between Microtexture Types and Indices of Physico-Mechanical Properties of Loess in China

The paper deals mainly with the relationship between the microtexture types and the indices of physicomechanical properties of loess. The results of study demonstrate that the study of microtextures of loess is of importance in the prediction and preliminary evaluation of engineering geological properties of loess in a region.

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.

Chemically Modified Sugarcane Bagasse for Innovative Bio-Composites. Part One: Production and Physico-Mechanical Properties

Sugarcane bagasse is an agro-waste that could replace timber resources for the production of bio-composites.Composite boards such as particleboard offer an issue for the use and recycling of poor quality timber,and these engineered products can overcome some solid wood limitations such as heterogeneity and dimension.Bagasse offers an alternative to wood chips for particleboard production but present some disadvantages as well,such as poor physico-mechanical properties.To address these issues,bagassefibers were treated with an innovative natural resin formulated with tannin and furfural.Impregnated particles with different concentrations of resin(5%,10%,and 15%m/m)were exposed to temperatures of 40℃,60℃,80℃,and 100℃ for resin curing.Various types of tannin-based adhesives,including tannin formaldehyde,tannin/formaldehyde-furfural,and tannin hex-amine,were utilized for bonding the treated bagasse particles.The resultant panels were assessed for their physical and mechanical properties and compared to those produced using Melamine-Urea-Formaldehyde(MUF)adhe-sive.The density of the panels varied from 650 to 730 kg/m^(3) depending on the resin concentration.The values for both modulus of elasticity and modulus of rupture increased as the resin concentration increased.The internal bonding values exhibited an increase with resin concentration up to a critical point,after which a decreasing trend was observed.The water absorption and thickness swelling were significantly reduced with an increase in resin concentration.However,the panels produced using MUF adhesive yielded the most favorable physico-mechanical properties.Additionally,the panels made with tannin-based adhesives met the minimum requirements specified in the standard EN 312(specifications for uncoated resin-bonded particleboards)for application in dry condi-tions.The analysis of formaldehyde emissions indicated that panels produced with tannin-based adhesives exhib-ited significantly lower emissions compared to those made with MUF.The tannin/furfural resin showed great potential for improving the quality of bagasse particleboard using tannin-based adhesives.

Thermal expansion behavior,phase transitions and some physico-mechanical characteristics of fired doped rice husk silica refractory

This paper presents the findings on thermal expansion behavior of slaked lime doped rice husk silica(RHS)refractory monitored between 25℃and 1500℃.It also reports the phase transition analysis within the temperature range of 850-1450℃.A sudden expansion of 0.7%noticed at 220℃is due to the transformation ofα-cristobalite toβ-cristobalite.The highest expansion(0.85%)reached within the temperature range of 650-850℃,remains almost constant for the investigated temperature range,and is not high enough to cause macro cracks in the refractory.The phase transition order is similar to those reported for quartzite refractory after 600℃,though the crystallization temperature is lowered due to the presence of the dopant.Modulus of rupture,apparent porosity,bulk density,refractoriness and reheat change are reported and their results meet with the standards qualifying them for use in coke ovens.

Experimental Testing of Cellular Construction Materials Containing Flax Particles

The feasibility of a sustainable non-autoclaved cellular concrete,based on flax vegetable co-products,for the production of usable specimen in the lightweight construction field,has been investigated experimentally.The produced specimen,containing various volume ratios of flax particles with respect to preformulatd Tradical PF70 lime binder of 0,1,and 2,were lightened by creating a porous structure in the matrix through the addition of 0.3%wt.Aluminium powder(able to react with calcium hydroxide from the binder and result in microscopic air-bubbles).Fresh and hardened specimen properties,including hydration,fresh density,porosity,hardened density,compressive and flexural strengths,toughness energy,and dry thermal conductivity at different temperatures,were assessed for varying flax-to-binder ratios.Results have shown that the addition of Aluminum powder leads to restrain the setting time delay of binder-based lime.Moreover,the hardened material displays a significant decrease in specimen density,thereby resulting in a compressive strength level compatible with that required in the cellular construction materials sector.Results also highlighted the ability of added flax to induce a change in the specimen from brittle to ductile behavior.Moreover,a high degree of thermal insulation can be achieved,which makes the cellular specimen based on flax particle suitable as insulated-bearing walls material.

Experimental studies on the pore structure and mechanical properties of anhydrite rock under freeze-thaw cycles

To study the deterioration mechanisms of anhydrite rock under the freeze-thaw weathering process,the physico-mechanical characteristics and microstructure evolutions of anhydrite samples were determined by a series of laboratory tests.Then,a descriptive-behavioral model was used to measure the integrity loss in anhydrite samples caused by cyclic freeze-thaw.Finally,the freeze-thaw damage mechanisms of anhydrite rock were revealed from the macro and micro aspects.The results show that the pore size of the anhydrite rock is mainly concentrated in the range of 0.001-10μm.As the number of freeze-thaw cycles increases,there is a growth in the proportion of macropores and mesopores.However,the proportion of micropores shows a declining trend.The relations of the uniaxial compressive strength,triaxial compressive strength,cohesion,and elastic modulus versus freeze-thaw cycles can be fitted by a decreasing exponential function,while the internal friction angle is basically unchanged with freezethaw cycles.With the increase of confining pressure,the disintegration rates of the compressive strength and the elastic modulus decrease,and the corresponding half-life values increase,which reveals that the increase of confining pressures could inhibit freeze-thaw damage to rocks.Moreover,it has been proven that the water chemical softening mechanism plays an essential role in the freeze-thaw damage to anhydrite rock.Furtherly,it is concluded that the freeze-thaw weathering process significantly influences the macroscopic and microscopic damages of anhydrite rock.

Correlations between ultrasonic pulse wave velocities and rock properties of quartz-mica schist

Physico-mechanical properties are critically important parameters for rocks. This study aims to examine some of the rock properties of quartz-mica schist（QMS） rocks in a cost-effective manner by establishing correlations between non-destructive and destructive tests. Using simple regression analysis, good correlations were obtained between the pulse wave velocities and the properties of QMS rocks. The results were further improved by using multiple regression analysis as compared to those obtained by the simple linear regression analysis. The results were also compared to the ones obtained by other empirical equations available. The general equations encompassing all types of rocks did not give reliable results of rock properties and showed large relative errors, ranging from 23% to 1146%. It is suggested that empirical correlations must be investigated separately for different types of rocks. The general empirical equations should not be used for the design and planning purposes before they are verified at least on one rock sample from the project site, as they may contain large unacceptable errors.

Physical and mechanical characteristics of composite briquette from coal and pretreated wood fines

Melina wood torrefied at 260℃ for 60 min was agglomerated with lean grade coal fines into composite briquettes using pitch as binder.Torrefied biomass(3%-20%)and coal fines(80%-97%)were blended together to produce the composite briquettes under a hydraulic press(28 MPa).The briquettes were cured at 300℃.Density,water resistance,drop to fracture,impact resistance,and cold crushing strength were evaluated for the composite briquettes.The proximate,ultimate,and calorific value analyses were carried out according to different ASTM standards.Microstructural studies were carried out using scanning electron microscope and electron probe microanalyzer equipped with energy dispersive x-ray.Fourier Transform Infrared Spectrophotometer(FTIR)was used to obtain the functional groups in the raw materials and briquettes.The density of the composite briquettes ranged from 0.92 to 1.31 g/cm^(3) after curing.Briquettes with<10%torrefied biomass has good water resistance index(>95%).The highest cold crushing strength of 4 MPa was obtained for briquettes produced from 97%coal fines and 3%torrefied biomass.The highest drop to fracture(54 times/2 m)and impact resistance index(1350)were obtained for the sample produced from 97%coal and 3%torrefied biomass.The fixed and elemental carbons of the briquettes showed a mild improvement compared to the raw coal.The peaks from FTIR spectra for the briquettes shows the presence of aromatic C=C bonds and phenolic OH group.The composite briquettes with up to 20%torrefied biomass can all be useful as fuel for various applications.

The Reinforcing Effect of Graphene on the Mechanical Properties of Carbon-Epoxy Composites

Graphene nanoplatelets (GNPs) are novel nanofillers holding attractive characteristics, including vigorous compatibility with majority polymers, outstanding mechanical, thermal, and electrical properties. In this study, the outstanding GNPs filler was reinforced to the epoxy matrix and carbon fabric/epoxy hybrid composite slabs to enrich their mechanical properties. Graphene nanoplatelets of 0.5, 1, 1.5 and 2 weight percentages were integrated into the epoxy and the physico-mechanical (microstructure, density, tensile, flexural and impact strength) properties were investigated. Furthermore, the mechanical properties of unfilled and 1 wt% GNPs filled carbon fabric/epoxy hybrid composite slabs were investigated. Subsequently, noteworthy improvement in the mechanical properties was conquered for the carbon fabric/epoxy hybrid composites.

STUDIES ON PHYSICAL AND MECHANICAL PROPERTIES OF DAHURIAN LARCH-WOOD OF TWO WOOD COLOURS

Dahurian larch growing in Daxing’an Mountains can be divided into two types according to the wood colour: one is red, the other is white. Based on the national standard of the "Testing methods for physical &mechanical properties of wood", the parameters of wood colour and physico-mechanical properties of the above two different woods were tested and analyzed.The result showed that the colour rational phenetic parameters, physico-mechanical properties and work abilities of thc two woods were quite different, combincd with the other morphological characteristics, they belong to intraspccific two different types of Dahurian larch. The white wood is superior to the red one as a valuable timber tree. Because the cocfficients of shrinkage, hardness and colour of both are different, they were mixed working in the past, inevitably there have been various defects in working. In order to overcome these defects, we propose that the departments of wood production, salesmen and consumers should use them differently according to their individual character.

Chitosan/Nanocrystalline Cellulose Biocomposites Based on Date Palm (Phoenix Dactylifera L.) Sheath Fibers

In this study,nanocrystalline celluloses were used to enhance physical,mechanical and water vapor barrier properties of chitosan films for potential food packaging applications.Two different mineral acids(sulfuric and phosphoric)were used to extract nanocrystalline cellulose from date palm sheath fibers.The influence of cellulose I and cellulose II on the properties of the isolated nanocrystalline celluloses(e.g.,yield,energy and length of intra-and intermolecular hydrogen bonds,and degree of substitution)were studied too.The characteristics of chitosan biocomposite film with phosphorylated nanocrystalline cellulose were compared to those with sulfated nanocrystalline cellulose.Results showed that besides cellulose polymorphism,the ionic ester groups on the surface of nanocrystalline cellulose is one of the factors influencing the physical,chemical,mechanical,and water vapor barrier properties in chitosan/nanocrystalline cellulose biocomposites.