Higher Compressive Strength Values Research Articles

Effect of Water Glass on Compressive Strength of Aluminosilicate-Based Geopolymer

The inorganic binders, fly ash and meta kaolin were used to prepare geopolymer. Water glass was added to the recycled inorganic binders to improve compressive strength of geopolymers. The ratio of the solid materials (inorganic binder and alkali activators) and liquid materials (distilled water, water glass) for the polymerization was optimized as 3:1. Compressive strength of the geopolymers increased because water glass improved the extent of polymerization of the inorganic binder and resulted in dense microstructure. It was found that geopolymers using fly ash showed the higher value of compressive strength, compared with meta kaolin- based geopolymers.

Injectability of brushite-forming Mg-substituted and Sr-substituted α-TCP bone cements

The influence of magnesium- and strontium-substitutions on injectability and mechanical performance of brushite-forming alpha-TCP cements has been evaluated in the present work. The effects of Mg- and Sr-substitutions on crystalline phase composition and lattice parameters were determined through quantitative X-ray phase analysis and structural Rietveld refinement of the starting calcium phosphate powders and of the hardened cements. A noticeable dependence of injectability on the liquid-to-powder ratio (LPR), smooth plots of extrusion force versus syringe plunger displacement and the absence of filter pressing effects were observed. For LPR values up to 0.36 ml g(-1), the percentage of injectability was always higher and lower for Mg-containing cements and for Sr-containing cements, respectively, while all the pastes could be fully injected for LPR > 0.36 ml g(-1). The hardened cements exhibited relatively high wet compressive strength values (~17-25 MPa) being the Sr- and Mg-containing cements the strongest and the weakest, respectively, holding an interesting promise for uses in trauma surgery such as for filling bone defects and in minimally invasive techniques such as percutaneous vertebroplasty to fill lesions and strengthen the osteoporotic bone.

Effect of S2Cl2 Addition on the Sulfate Attack of Hydrated Portland Cement

Abstract In this study the resistivity effect of laboratory-produced S2Cl2 as an additive in Portland cement PC 32.5 which was hydrated at the water/cement ratio of 0.5 and room temperature against sulfate attack in the curing solution of 0.35M sodium sulfate was investigated. Hydrated cement products were determined by using X Ray Diffraction (XRD) and Thermogravimetry—Differential Thermal Analyses (TG-DTA) techniques. The additive substance, S2Cl2 in Portland cement, was used 5 and 10 percent by weight. The highest compressive strength value was found as 36.7 MPa in case of hydrated cement PC 32.5, samples containing 5% S2Cl2 (additive) after curing time of 28%21 days.

EFFECT OF CEMENT CONTENT AND CEMENT TYPE ON THE RESISTANCE OF CONCRETE AGAINST CHEMICAL ATTACK

Mortar and concrete are two important construction materials widely used in both domestic and industrial constructions all over the world. A durable concrete is able to withstand the attacks of destructive processes of chemical, physical or mechanical origin, acting externally or arising internally. Chemical salt attack is caused by ingressing salts into cementitious materials, and the reactions with cement hydrates resulting in either the deterioration of the matrix or loss of corrosion protection of the steel reinforcement. The chemical resistances of the materials against deleterious reactions determine the performance of the materials. Cement type and mix proportions are keys to the resistance of concrete against chemical attack. In this paper, the resistance of concrete against sulfate and chloride attack was investigated in the laboratory by storing different specimens of concrete cubes in a solution of calcium chloride with concentration 5%, or solution of magnesium sulphate with concentration 5% or in solution of magnesium sulphate with concentration 5% + sodium chloride with concentration 5% at different ages (7, 28, 59, 90 and 180 days). Compressive strength is determined for specimens submerged in the previous chemical solutions. The chemical resistance of concrete is expressed by the percentage of compressive strength losses for those specimens exposed to the chemical attack compared with those similar ones submerged in fresh water. Both specimens were kept in the condition of laboratory temperature. It is of importance to mention that, only external attack was implemented in this research because it is the more common type and typically occurs where water containing dissolved chloride and sulphate penetrate the concrete. It can be concluded that, the highest values of compressive strength were obtained from concrete mix cured in water (control mix) meanwhile, the lowest values were resulted from mixes cured in a solution of magnesium sulphate with concentration 5%+sodium chloride with concentration 5%.

Fabrication and characterization of bioactive glass (45S5)/titania biocomposites

Bioactive glass (BG) (45S5) has been used successfully as bone-filling material in orthopedic and dental surgery but its lean mechanical strength limits its applications in load-bearing positions. Approaches to strengthen these materials decreased their bioactivity. In order to realize the optimal matching between mechanical and bioactivity properties, bioactive glass (45S5) was reinforced by introducing titania (TiO 2) in anatase form and treated at 1000 °C to form new bioactive glass/titania biocomposites. The prepared biocomposites were assessed by XRD, FT-IR, mechanical properties and SEM. The results verified that the increase of titania percentage to BG powder enhanced gradually the mechanical data of the prepared biocomposites. SEM and FT-IRRS confirmed the presence of a rich bone-like apatite layer post-immersion on the composite surface. It has been found that the new BG/titania biocomposite materials especially those containing high content of titania have high bioactivity properties and compressive strength values comparable to cortical bone. Therefore, these biocomposite materials are promising for medical applications such as bone substitutes especially in load-bearing sites.

Use of Chemically Stabilized Soil as Cushion Material below Light Weight Structures Founded on Expansive Soils

Among the several remedial techniques suggested to combat the damages caused by expansive soils, the use of sand cushion and cohesive nonswelling (CNS) soil cushion were widely accepted, especially for light weight structures such as floorings, pavements, and canal linings, which cover large areas. CNS cushion is preferred to sand cushion in view of the sceptical performance of sand cushion at several work sites. However, various investigators have reported the nonavailability of suitable CNS materials at many project sites and in such circumstances, it is also suggested to prepare the artificial CNS materials by mixing suitable admixtures to the native clay. The present work deals with the modification of black cotton soil using Ca Cl2 and rice-husk-ash (RHA), which resulted in two favorable combinations of soil +0.5% Ca Cl2 +8% RHA and soil +1% Ca Cl2 +6% RHA with nonswelling properties, while retaining high unconfined compressive strength values. The mix of soil +0.5% Ca Cl2 +8% RHA was taken for furth...

Production of Briquettes from the Golden Horn Sediments under Thermal and Hydrothermal Conditions

This study is aimed to utilize of the Golden Horn (GH) sediments in briquette production after they were conveyed to a stone quarry in Istanbul, Turkey. Two different types of mixtures were prepared for hydrothermal agglomeration. In the first type, GH sediment and lime and in the second type GH sediment, lime, and quartz were mixed. For thermal agglomeration, GH sediment was used alone. First, physical, chemical, and mineralogical properties of the GH sediments were determined. Then, the prepared briquette samples were agglomerated under 0.5, 1.0, and 1.5 MPa water vapor pressure for 4 h with the hydrothermal method in the autoclave and then under 1,273 °K constant temperature for 2 h in a thermal agglomeration oven. Density change of the briquettes as a result of agglomeration compressive strength were measured and the results of the mechanical data and x-ray analysis of sediments subjected to thermal and hydrothermal treatment are presented. Calcium silicate hydrate peaks were observed only at 1.0 MPa between 423 and 473 K in the first type of mixture and the highest compressive strength value (27 MPa) was observed in briquettes prepared without quartz in the hydrothermal method at 1.5 MPa. This study showed that it is possible to produce briquettes from GH sediments and this will reduce environmental pollution.

An investigation into polypyrrole-coated 316L stainless steel as a bipolar plate material for PEM fuel cells

Increasing attention is being paid to the use of metallic materials as a replacement for non-porous graphite in bipolar plates (BPs) for polymer exchange membrane (PEM) fuel cells. The ideal BP material should demonstrate high values of electrical conductivity, thermal conductivity, corrosion resistance and compressive strength and low values of gas permeability and density. Although metallic materials demonstrate many of those properties, their corrosion resistance can be inadequate, which in turn can lead to unacceptable values of contact resistivity. In this study, polypyrrole was polymerized onto 316L stainless steel using galvanostatic and cyclic voltammometric methods. A dense coating of polypyrrole could be formed on SS316L using both electrochemical methods. The coatings had different morphologies. For galvanostatic coatings, the particle size increases with increasing applied current. For cyclic voltammometric coatings, the particle size increases with increasing the cycle number. The potentiodynamic tests show that the corrosion current density is decreased by about one order of magnitude and polarization resistance is increased by about one order of magnitude by coating with polypyrrole. Optical microscopy showed that there is less intergranular corrosion after coating with polypyrrole. Therefore, these dense polypyrrole coatings much improved the corrosion resistance of SS316L and the coated materials could possibly be used in polymer exchange membrane fuel cells (PEMFCs) as a bipolar plate material.

A study of steel bar reinforcement corrosion in concretes with SF and SRH using electrochemical impedance spectroscopy

Several electrochemical techniques can be used to monitor corrosion, among them are open circuit potential (OCP) and eletrochemical impedance spectroscopy (EIS). Monitoring OCP is the most typical procedure for routine inspection of reinforced concrete structures and can be easily carried out, however it only gives an approximate idea of the corrosion process. EIS is a more complete technique, which supplies information regarding the mechanism and kinetics of reaction electrochemistries, but only used in the laboratory. Based on these two techniques, this study is related to the steel corrosion in high-performance concrete with silica fume and silica from rice husk. The acceleration of the corrosion was carried out using immersion cycles in a 3.5% NaCl solution. As well as high compressive strength values, the addition of silica fume presented low corrosion risks and high impedance module values and significant increases of the concrete resistivity after 22 months of alternate immersion/drying cycles were obtained.

Evaluation of mechanical properties of Z250 composite resin light-cured by different methods

This study evaluated some mechanical parameters of Z250 composite resin using different light-curing methods. Ten specimens were prepared for each mechanical test group with different dimensions according to the test. Light-curing was performed by: a). continuous light (800mW/cm²-40s); b). exponential light (0-800mW/cm²-40s); c). intermittent light (2s-600mW/cm²; 2s without light-80s); d). stepped light (10s-150mW/cm²; 30s-650mW/cm²); e). PAC (1320mW/cm²-3s); f). LED (350mW/cm²-40s). After 24 ± 1 h, the specimens were loaded at a crosshead speed of 0.5 mm/min until fracture. The mechanical properties were calculated and analyzed by ANOVA and Tukey test (5%). The results showed that the highest compressive strength values were found for the continuous, exponential, intermittent and stepped light methods, whereas PAC and LED obtained the lowest values. LED, stepped light, PAC, exponential and continuous light presented the highest values for diametral tensile strength. The intermittent light showed the lowest value, which was significantly lower than the value obtained for LED only. Flexural strength results were not significantly different between all light-curing methods. Finally, the highest modulus of elasticity values were obtained for LED, exponential, continuous and intermittent light, whereas PAC and stepped light showed the lowest values. The mechanical properties were affected by light-curing methods employed.

Mechanical improvement of concrete by irradiated polypropylene fibers

Fiber reinforced concrete (FRC) contains fibers physically mixed with gravel, sand, cement, and water. So far, adequate mechanical performance of FRC has been obtained at high cost and using complex technologies; important here is the geometry and surface characteristics of the polymers. We have modified polymeric-fiber surfaces by using gamma radiation. Irradiated polypropylene (PP) fibers were submitted to 0, 5, 10, 50, and 100 kGy of gamma irradiation dosages. First, tensile strength of PP fibers was evaluated, and then fibers blended at 0, 1.0, 1.5, and 2.0% in volume with Portland cement, gravel, sand, and water. The highest values of compressive strength were obtained with irradiated-fibers at 10 kGy and 1.5% in volume of fiber. The result is 101 MPa, as compared to 35 MPa for simple concrete without fibers. POLYM. ENG. SCI., 45:1426–1431, 2005. © 2005 Society of Plastics Engineers

04/02784 The development of grain-face porosity in irradiated oxide fuel: White, R. J. Journal of Nuclear Materials, 2004, 325, (1), 61–77

A simple one-step method with direct thermal conversion at lower temperatures for preparing a stabile Cs-aluminsilicate phase, known as pollucite, is presented. Cs-exchanged form of Na, Ca-LTA type of zeolite (Cs-LTA) was pressureless sintered and hot pressed at certain temperatures in order to obtain pollucite. XRD and FTIR analysis were used to study structural changes of Cs-LTA before and after thermal treatments. Pressureless sintered sample recrystallized into pollucite phase after heat treatment at 1000 °C (3 h) (PLS1000) and hot pressed sample at 750 °C (3 h) using pressure of 35 MPa (HP750), indicating reduced temperature of 250°. SEM micrographs confirmed that HP750 has higher density than PLS1000 which leads to higher value of compressive strength. The HP750 showed better resistance to Cs leaching than the PLS1000. Base on these results one can conclude that hot pressing is the promising method for the permanent disposal of Cs radionuclides.

Hardness and compressive strength of indirect composite resins: effects of immersion in distilled water

The aim of this study was to evaluate the effect of ageing in distilled water on the hardness and compressive strength of a direct composite resin Z100, a feldspatic porcelain (Noritake) and three indirect composites (Artglass, Solidex and Targis). For the Vickers hardness tests, five disk-shaped specimens (2 x 4 mm) of each material were prepared according to the manufacturers' instructions. The hardness tests were conducted using a Vickers diamond indentor. Compressive strength measurements were recorded on cylindrical specimens with a diameter of 6 mm and a length of 12 mm. The compression tests were carried out with a constant cross-head speed of 0.5 mm min(-1) on a mechanical test machine. For each material, 10 specimens were tested after 7 days of dry storage at 37 +/- 1 degrees C and 10 specimens were tested after water storage at 37 +/- 1 degrees C for 180 days. Noritake porcelain specimens showed higher hardness values than the composites. Among the composite materials, Z100 promoted the highest VHN values, regardless of the ageing periods. The results showed that Solidex and Z100 had the highest compressive strength values. Ageing in water reduced the hardness for all composites, but had no long-term effect on the compressive strength.

Controlled preparation and properties of porous poly( l-lactide) obtained from a co-continuous blend of two biodegradable polymers

This study prepares porous PLLA from a blend of two biodegradable polymers. This approach is based on a detailed and quantitative morphology control of the blends. Co-continuous blends comprised of poly( l-lactide)/poly( ε-caprolactone) PLLA/PCL, were prepared via melt processing. Through a judicious combination of concentration control and a subsequent annealing step it is possible to generate a wide range of sizes for the co-continuous phases. Subsequent extraction of the PCL porogen phase generates a fully interconnected porous PLLA material with a void volume between 50% and 60%. The volume average pore diameter is controlled from 1.5 to 88 μm as measured by mercury intrusion porosimetry. Through static annealing it is also possible to generate porous structures well beyond that upper limit of pore size. The upper limit of pore size reported above is in the range required for scaffolds for tissue engineering. Micrographs of porous polyglycolide and PCL derived from co-continuous blends of PLLA/polyglycolide and PCL/poly(ethylene oxide) are also shown and demonstrate the versatility and wide applicability of this preparation protocol. The porous structures produced from PLLA/PCL blends possess a high level of mechanical integrity and a degree of crystallinity between 25% and 38%. High values of both compressive modulus and strength at 10%-strain are obtained, greater than 190 and 11 MPa, respectively. The compressive modulus is found to be from 10% to 20% of that of the pure PLLA material. A series of loading studies were also carried out and it was shown that under a pressure of 40 atm applied for 1 h, the pores of a 1.5 μm porous PLLA structure were filled to approximately 80% by water. In addition, the loading of an aqueous solution of a model drug compound, bovine serum albumin (BSA), was carried out at 40 atm and the results indicate that large quantities of BSA (up to 25% of the weight of the original porous capsule) can be driven into the pores. These results indicate that the internal porous structure is accessible to aqueous solution and that this material also has potential as a substrate for controlled release applications.

전단보강근이 없는 섬유보강 철근콘크리트 보의 특성에 관한 실험적 연구

This study examines the material characteristics of fibers and their influences on reinforced concrete through the tests of reinforced concrete by the types of fibers including non-reinforced, steel, polypropylene and cellulose fibers and the test of compressive strength and reinforced concrete beam without shear reinforcement and consequently it obtains the following conclusions. As a result of conducting compressive strength by the types of specimens, fiber reinforced specimen with the highest compressive strength value at 28 days of age was cellulose fiber reinforced specimen as 280.4kgf/<TEX>$\textrm{cm}^2$</TEX> and steel fiber specimen had the highest compressive strength of 250.7kgf/<TEX>$\textrm{cm}^2$</TEX> at 180 days of age. In case of non-reinforced specimen, its compressive strength was 277.4kgf/<TEX>$\textrm{cm}^2$</TEX> at 28 days of age and 273.1kgf/<TEX>$\textrm{cm}^2$</TEX> at 180 days of age. Comparing the compressive strength of non-reinforced specimen to that fiber reinforced specimen showed that the compressive strength of fiber reinforced specimen was lower in the passage of age and the results of this experiment showed no effects of fiber reinforcement. As a result of testing reinforced concrete beam without shear reinforcement, ductility factors of specimens were 4.67 for non-reinforced specimen, 8.18 for steel fiber reinforced specimen, 6.20 for polypropylene fiber reinforced specimen and 5.49 for cellulose reinforced specimen, and it is found that steel fiber reinforced specimen was highest. When non-reinforced specimen and steel fiber reinforced specimen were compared, steel fiber reinforced specimen had higher ductility factor of about 75.2% than that of non-reinforced specimen.

Effect of polyester backbone structure on the cured products properties

A new monomer (o-carboxy phthalanilic acid) was prepared by the reaction of o-aminobenzoic acid with phthalic anhydride. This monomer was condensed with different acids and glycols to prepare three unsaturated polyester resins namely, poly (1,2-propylene-maleate-o-carboxy phthalanilate) polyester I, poly (ethylene- maleate- o-carboxy phthalanilate) polyester II and poly (1,2-propylene-itaconate- o-carboxy phthalanilate) polyester III. Infrared (IR) and nuclear magnetic resonance (NMR) spectra were used qualitatively and quantitatively to elucidate the structure of the prepared polyester resins. These unsaturated polyester resins were found to cure with styrene at room temperature in the presence of methyl ethyl ketone peroxide (MEKP) as initiator and Co- naphthenate as accelerator. The effect of concentration of the initiator (MEKP) and the accelerator (Co-naphthenate) on the compressive strength values was studied. The effect of the type of glycol and the unsaturated acid in the styrenated polyester backbone on the chemical resistance, flammability, thermal stability, physical, electrical and weathering properties was also studied. It was found that the styrenated poly (1,2-propylene-maleate-o-carboxy phthalanilate) has the highest compressive strength value and the best chemical resistance and physical properties.

The influence of biogenic micro-silica-rich rocks on the properties of blended cements

Diatomaceous rock samples of a different origin and with amorphous, biogenic micro-silica (opal-A) as their major siliceous constituents were studied and their behaviour as a cement additive was determined. The raw materials were collected from Hungary, Romania and Greece. These diatomite rocks varied in geological age from Miocene to Pleistocene, and were deposited respectively in lacustrine, brackish and marine conditions. The depositional environment affected the size of the opal-A particles, those of lacustrine origin being the smaller (<10 μm). Most of the opal-A particles were represented by disk-shaped diatom frustules. Laboratory tests showed that these diatomite rocks exhibited good pozzolanic properties and could replace the most commonly used natural pozzolanas. The use of diatomaceous rocks as cement additives has drawbacks such as higher water demand, but the compressive strength of the laboratory produced cements exhibit higher values than OPC. The highest compressive strength values were obtained with the use of the Hungarian diatomite rock that had the greatest amount of reactive silica content reflecting its high opal-A content.

VISIBLE LIGHT-CURABLE N-METHACRYLOYL GLUTAMIC ACID MODIFIED POLYELECTRO LYTES FOR USE IN DENTAL APPLICATIONS

The visible light-curable N-methacryloylglutamic acid (MGA) modified polymers (VLC MGA MPs), with the optimal molar ratio of 8:1:1 (acrylic acid: itaconic acid: MGA) in the copolymer backbone, were synthesized by a one pot reaction. The compressive strength (CS) was used as the initial basic screening property to determine the best graft ratio. A statistical design of experiment (DOE) technique was utilized to predict the optimal formulation for the VLC MGA MP with the best graft ratio based on the CS. The VLC MGA MPs were synthesized under the same reaction conditions, using a free-radical polymerization process to produce the copolymers, followed by grafting 2-isocyanatoethyl methacrylate (IEM) onto the copolymer backbone to form the VLC materials. Specimens were prepared by mixing the polymer solutions with the basic glass powders and their strength values were measured after the test specimens were conditioned in distilled water at 37°C for 7 days. In this study, polymer solutions containing VLC MGA MPs were formulated with the glass powder used in the commercial Fuji II LC (GC America) material to determine the CS. Diametral tensile strengths (DTS) of the produced materials were also determined. Based only on the CS value, the VLC MGA MP with 15 molar % of IEM grafting was the best material. The optimal formulation for this copolymer, i. e., the system having the highest CS value, was found to be at the weight ratio of 52.5:18:29.5 (VLC MGA MP:HEMA:water), providing an improvement in CS of 30% compared to the commercial Fuji II LC system. This formulation was also mixed with the glass powder used in the Vitremer™ (3M Dental Products) material to determine its mechanical properties. The MGA monomer was also further evaluated as a reactive diluent/modifier for commercial VLC formulations, such as the Fuji II LC and Vitremer™, as well as the optimal experimental VLC formulation. In the latter effort, the MGA monomer was used to partly replace HEMA in the optimal experimental VLC formulation, providing additional evidence that MGA was useful to formulate improved VLC glass-ionomers.

Strength and water absorption for gypsum—cement—silica fume blends of improved performance

The present work describes results of testing gypsum—cement—silica fume blends having gypsum binder contents of 65, 75 and 85% at various silica fume/Portland cement ratios: 1/4, 2/3, 3/2 and 4/1. Cases of extra expansion and cracking due to ettringite formation were not revealed. It is shown that the hydraulic properties are developed in time in a diflerent manner for various compositions. Some of the blends achieved a high wet/dry strength ratio exceeding 0·6 after 200 days of water curing. This is explained by the development of a microstructure in which gypsum crystals were engulled by C-S-H. The optimum compositions were revealed by high absolute values of compressive strength in the water-saturated state, as well as low values of water absorption. The high values of water absorption for some compositions together with the low values of strength in the wet state are due to the extra content of silica fume, which is not needed for pozzolanic reaction and can be freely removed from the structure by washing.

Problems associated with the compression testing of fibre reinforced plastic composites

Compression testing of thin and slender specimens must take into consideration the inherent instability of such specimens. Four different procedures which address this problem of instability (tendency to buckle) were used to characterise a fibre reinforced plastic (FRP). It is demonstrated that the procedure adopted influences the results obtained. Use of the Celanese antibuckling guide recommended in ASTM standards gave rise to high values of compressive strength whereas complete edge support of specimens gave rise to high secant modulus values. Other guides gave results with much lower coefficients of variation. Possible explanations for these findings are presented and recommendations for use are made.