Compressive Strength Of Samples Research Articles

Influence of carbonated pozzolana on sulfate attack of cement stone at low temperatures

This study investigates the influence of natural pozzolana (opoka) additive on the sulfate attack process of Portland cement stone at low temperatures. In the samples, 5%, 15% and 25% (by weight) of the Portland cement is replaced with additive. The specimens are then hardened for 28 days in water and then soaked in a 5% sodium sulfate (Na2SO4) solution for 6 months at 4°C. It is estimated that under normal conditions, opoka decreases the compressive strength of cement stone. A decrease in strength is the result of the slow pozzolanic reaction; moreover, part of the pozzolana carbonate component acts as an inert filler. In this study, however, pozzolana additive increased the compressive strength of samples after treatment for 3 months in a 5% sodium sulfate solution at 4°C. This effect is related to the ongoing pozzolanic reaction and the formation of a greater amount of calcium silicate hydrates. With increasing maintenance of samples for up to 6 months in a 5% sodium sulfate solution, it is found that pozzolana promotes the formation of thaumasite. This process is initiated by calcite, which is an integral part of pozzolana, and there is a greater formation of calcium silicate hydrates in samples with opoka.

Preparation and properties of reticulated porous γ-Y2Si2O7 ceramics with high porosity and relatively high strength

Dense γ-Y2Si2O7 ceramics are promising silicates with very low thermal conductivity, good damage tolerance and hot corrosion resistance. However, processing of porous γ-Y2Si2O7 was not reported in early literatures. In this paper, reticulated porous γ-Y2Si2O7 ceramics with high porosity (~85%) and relatively high compressive strength (~1.28MPa) are successfully fabricated by the polymeric sponge impregnation method. The main compositions of the slurry are Y2SiO5 and silica sol. Samples are sintered at the temperature of 1550°C to obtain porous γ-Y2Si2O7 ceramics by reaction bonding; and the samples are recoated 3 times to enhance the compressive strength of porous ceramics. Scanning electron microscopy and X-ray tomography investigations show that the pore size distribution of the as-prepared porous γ-Y2Si2O7 ceramic ranges from 200 to 700μm; meanwhile, the sample possesses fully open and highly interconnected pores. Influences of pretreatments of sponge on the compressive strengths of samples are also investigated. This work reports a new porous ceramic material (γ-Y2Si2O7) with high permeability, high strength and controllable macrostructure.

Comparative Study of in-vitro Behavior of Tetracalcium Phosphate-based Cement: Ringer’s Solution versus Human Blood Plasma

Apatite formation ability of an implant in a supersaturated solution has been widely used to investigate its bioactivity. However, the method may provide incomplete information, because it is determined only by solution supersaturation, irrespective of biological factors. In this study, apatite-forming ability of calcium phosphate cement (CPC) was evaluated in two different media; human blood plasma and Ringer’s solution. The CPC samples were stored in human blood plasma and Ringer’s solution for different intervals and change in phase composition, microstructure and compressive strength were investigated. The reactants could be transferred to apatite phase in both Ringer’s solution and human blood plasma but the crystallinity and size of the apatite crystals was higher for the former. Furthermore, the compressive strength of sample fourteen days after soaking in Ringer’s solution was 1.6-fold of that in human blood plasma. Overall, the in vitro tests in human blood plasma which is more similar to real conditions can produce some results different from Ringer’s solution.

Research on the Mechanical Properties and Micro-Morphology of the Cement Stabilized Gravel with Rubber Particles

The primary objective of this paper was to study the mechanical properties of the cement stabilized gravel by different compact method which added rubber particles by using macroscopic and microscopic test. Through test of compression, relationships of mechanical properties of samples were studied. Pore structure and fractal characteristic of mixture was analyzed quantitatively using mercury intrusion porosimetry (MIP), scanning electron microscope (SEM) was applied to analyze the micro-morphology of samples. The tests results showed that the compressive strength of samples which prepared by using vibrating method was greater than that by static pressure method. Compressive strength of samples from vibrating method or static pressure method decreased with the rubber particles volume fraction increase. MIP tests showed that the mean pore diameter and porosity of mixture increased from about 70nm to 250nm and 9% to 24% with the rubber particles content increasing, respectively. SEM tests showed that the interface bonding between sand and hardened cement paste was better than that of between rubber particles and hardened cement paste.

Novel glass ceramic foams materials based on red mud

Glass ceramic foams were prepared using red mud and fly ash with added CaCO3 as foaming agents. The aim of the present work was to investigate the possibility of adding red mud, an alkaline leaching waste, in the raw material for the preparation of glass ceramic foams. The results of mineralogical analyses as well as the microscopic examination showed that the use of the red mud affect the mineralogical characteristics and structures of the as produced foams. The influence of amount of red mud on the bulk density and compressive strength of samples was further evaluated. The experimental results showed that relatively low bulk density foams (0.33–0.41g/cm3) could be obtained by using low sintering temperature (760–840°C) when the red mud/fly ash ratio does not exceed 40:60. The reduction of sintering temperature or, above all, the reduction of the holding time, was found to limit the coalescence and significantly improve the compressive strength of the foams (0.33–2.74MPa).

The effects of nanoscale expansive agents on the mechanical properties of non-shrink cement-based composites: The influence of nano-MgO addition

The mechanical properties and permeability of cement-based composites containing nano-MgO were studied and the experimental results indicated that the mechanical strength of the composites mixed with the nano-MgO, measured at different ages, were higher than those of a plain composite. The results from the treated composites compared to those of the plain composite indicated that the compressive strength of sample containing 1% nano-MgO of binder by weight (MGC1) increased by 103% and 80% at 7days and 28days, respectively, and that the flexural strength of MGC1 equaled 4.66 and 5.1MPa, which were 95% and 70% higher than those of the plain composite (PC), respectively. SEM revealed that the microstructure of the composites with nano-MgO were more compact and homogeneous than that of plain composite because of expansive effect of nano-MgO. This paper describes the mechanism of the nano-MgO effects on composites’ nanostructure.

ИССЛЕДОВАНИЕ КОРРОЗИОННОЙ СТОЙКОСТИ МОДИФИЦИРОВАННОГО БЕТОНА В СРЕДЕ СТОЧНЫХ ВОД

The objective of the research project was to design multi-component concrete with an optimized pore structure designated for sewage water treatment facilities. It was followed by the study of their stability in aggressive environments. Measurement of mesopores and macropores with diameters of 0.0055 to 360 mcm was taken using AutoPore IV 9500 porosimeter. X-ray analysis of samples was performed using diffractometer ARL X’TRA produced by Thermo Scientific (Switzerland). Modified 28-day concrete cubes were exposed to aggressive environments for 1 year at low (+4 ± 2 °C) and high temperatures (+20 ± 2 °C) to identify their linear deformation characteristics. Compressive strength of samples was tested upon completion of each three-month period.The authors have found out that degradation of concrete samples in the corrosive environment of waste waters accompanied by generation of thaumasite is less intensive than that in the waste waters that have ettringite generated. Thus, the authors have discovered that the lower the temperature of the aggressive environment of the waste water, the more intensive the formation of ettringite that causes destruction of the concrete. Optimization of the concrete structure is attained through the optimization of the concrete composition. Application of fine-grained silica causes generation of concrete that is highly resistant to the aggressive effects of sulfates and chlorides.

Study on Preparation of Solid Concrete Brick with Recycled Aggregate

The construction waste was processed into recycled aggregate to produce solid construction waste brick with grade of MU20. The preparation process of recycled aggregate and the optimal value of mass ratio of water to cement (water cement ratio) and mass ratio of recycled aggregate to cement was studied. The results shows that when the water cement ratio is 0.86 and the mass ratio of recycled aggregate to cement is 5.5 and the dosage of activator is 0.25% (mass fraction with recycled aggregate), the compressive strength of sample is 22.5MPa and can be satisfied with the requirement of MU20 solid concrete brick.

Soil Stabilizer Prepared with Saline Soil and Industrial Solid Wastes

A soil stabilizer was prepared by mixing saline soil, slag, desulfurization gypsum and clinker. The compressive strengths of samples is up to 6.11MPa when the mixing amount of slag, desulfurization gypsum and clinker at 14% after 7 days curing. Results show that the stabilizer can meet the sub-base engineering applications, is an ideal stabilizer.

Effect of AlF3 Production Waste on the Properties of Hardened Cement Paste

The possibility to use by-product SiO2·nH2O (often called AlF3 production waste) in cement casting has been attracting the interest of researchers for many years, although high content of fluorine makes the use of amorphous SiO2 problematic. Finding the way of utilizing waste products is a very important research topic at the moment. In this study AlF3 production waste was investigated as the basic ingredient of a new pozzolanic material. The goal of this study is to investigate the possibilities of using AlF3 production waste, washed in ammonia solution, in cement stone specimens. Chemically treated silica gel additive was proved to reduce the amount of Ca(OH)2 and CaCO3 in hardened cement paste samples. Experimental research has revealed that the density in hydrated samples reduces from 2220 kg/m3 to 2030 kg/m3 with the increase of silica gel content from 0 % to 35 %. The compressive strength of samples containing 10 % of silica gel additive increased by 8.04 % compared to the samples without the additive. SiO2 additive used at 10 % and 20 % increased the maximum hydration temperature. In this case, the additive modifies the hydration kinetics.DOI: http://dx.doi.org/10.5755/j01.ms.18.2.1925

Floating porous alumina from protein foaming-consolidation technique for cell culture application

Floating porous ceramics have been successfully fabricated using protein foaming-consolidation method. Alumina powder and yolk as the pore creator were mixed while stirring and the resulting slips were poured into cylindrical shaped molds followed by drying for foaming-consolidation process. The dried green bodies were then burned at 600°C for 1h to remove the pore creating agent and finally sintered at 1550°C for 2h. The sintered alumina ceramics with shrinkage in the range of 29–40vol.% and pore sizes of 250–500μm were obtained. The compressive strength of sample was 1.1 at 70.6% porosity and it increased to 1.7MPa at 52.8% porosity. The density varied in the range of 0.8–1.1g/cm3 depending on the composition of the slurry. Preliminary cytotoxicity test of the samples conducted using DF-1 cell culture showed promising results.

Preparation and cellular response of porous A-type carbonated hydroxyapatite nanoceramics

Microwave sintering using the activated carbon as embedding material was applied in preparation of porous A-type carbonated hydroxyapatite ceramics with nano(nCHA) and submicron (mCHA) structure. By examining the linear shrinkages and the compressive strengths of samples at different temperatures, a suitable microwave sintering temperature was achieved. The microwave sintering method was successfully used to prepare A-type CHA with nano or submicron structure, and the mechanism of the formation of A-type carbonate groups was discussed also. Compared with the samples prepared by the conventional sintering method (mHA), the nCHA bioceramics synthesized by the microwave sintering approach had smaller grain size and more uniform microstructure, and showed a compressive strength similar to the conventional samples. In vitro dissolution test proved that nCHA exhibits better degradation property in comparison to pure HA. Rat osteoblasts were cultured with nCHA, mCHA and mHA to evaluate their biocompatibility, and nCHA showed significant enhancement of cells in attachment, proliferation and differentiation. In conclusion, carbonate groups can be easily introduced to HA crystal structure using the activated carbon as embedding material, and microwave sintering is an effective and simple method in preparing A-type CHA with a nanostructure. Results from this in vitro biological study suggest that porous A-type carbonated hydroxyapatite nanoceramics may be a much better candidate for clinical use in terms of bioactivity.

Investigation of Mechanical Behavior of Stir Casted Al Based Composites Reinforced With B<sub>4</sub>C Nanoparticles

In this study, aluminum alloy (Al-2wt. % Cu) matrix composites reinforced with 1, 2 and 4 wt. % boron carbide nanoparticles with average size of 80 nm were fabricated via stir casting method at 850 °C. The microstructures of composites were studied by scanning electron microscope (SEM). Density measurement, tensile and compressive tests were carried out to identify the mechanical properties of composites and effect of B4C nanoparticles amount. In all fabricated composites, severe agglomeration was observed in the micrographs. With increasing the amount of B4C nanoparticles up to 2 wt. %, yield and tensile strength increased but with more increasing B4C content they were decreased. Also, the compressive strength of samples was increased with increasing weight percentage of B4C nanoparticles.

Use of Oil Drill Cuttings as an Alternative Raw Material in Sandcrete Blocks

This research has investigated the use of waste oil drill cuttings treated by thermal desorption in sandcrete, a major construction material used throughout Nigeria and much of West Africa. Sandcrete samples were prepared using a sand to cement ratio of 6:1. The results show that replacing up to 50 wt% of sand by treated oil drill cuttings produced sandcrete with reduced water absorption and reduced sorptivity, increased density and reduced thermal conductivity. In addition, the compressive strengths of samples containing oil drill cuttings were comparable to control samples. The work demonstrates the potential for the beneficial reuse of waste oil drill cuttings treated by thermal desorption in the production of sandcrete blocks with improved properties.

Influence of Flux on Sintering Property of Imported Hematite Ore

The microstructure and compressive strength were investigated by means of optical microscopy, X-ray diffraction, and tensile testing machine. The influence of basicity, SiO2 and Al2O3 content on sintering property of hematite ore was studied. The results show that when the silica content was either 5.3% or 5.6%, the best result of the compressive strength of samples obtained at middle basicity. While the silica content was up to 5.9%, the greatest value of the compressive strength of samples attained at lower basicity.

Modification of strength properties of lime-stabilized laterites with sawdust ash

The potential of sawdust ash as a stabilizer for lateritic soils was investigated to determine the modifying effects on strength properties required for road construction. Three laterite samples, A, B and C were collected respect- ively from Akoda, Osogbo and Ile-Ife (Nigeria). Atterberg limits and strength tests were performed on the raw samples and stabilized samples A and B only. Sample C exhibited Plastic Index > 15 and required no stabilizat-ion. Stabilization was performed at lime optimum of 6 % for sample A and 8 % for sample B using 2, 4, 6, 8, and 10 % of sawdust ash by weight of the samples. The unsoaked California Bearing Ratio increased from 1.69 to 4.64 % for sample A, but decreased from 2.62 to 1.92 % for sample B. The compressive strength of sample A increased from 34.25 to 73.26 kN/m2, but decreased from 53.27 to 50.43 kN/m2 for sample B. The shear stre-ngth increased from 28.49 to 46.70 kN/m2 for sample A, but decreased from 84.19 to 34.08 kN/m2 for sample B. Therefore, sawdust ash could be used to modify the strength properties of lime-stabilized lateritic soils for road construction.

Thermal insulation and strength of autoclaved light concrete

The primary objective of this study was to develop an autoclaved light concrete (ALC) material with ultra-thermal insulation property and to investigate the relationship between its physical characteristics and mechanical properties. Through tests of dry bulk density and compressive strength, relationship of physical characteristics and mechanical properties of samples were studied, resulting in a material with ultra-thermal insulation property. Scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDX) were applied to analyze the micro-morphology and elemental composition of samples. To identify the product phases, X-ray diffraction (XRD) was engaged. The test results showed that compressive strength and thermal coefficient were reduced with the increasing of aluminum powder within the mixtures. As a result the optimal thermal coefficient and compressive strength of samples were improved to 0.061 W/(m·k) and 1.2 MPa, respectively. SEM, EDX and XRD analyses showed that calcium silicate hydrate and tobermorite crystal were main resultant phases.

Study on Crystallinity Degree of Hydration Products in Autoclaved Samples with Solid Wastes

The ratio of the dissolved amount difference between in cool hydrochloride and hot hydrochloride to the bound water amount of the samples is regarded as crystallinity degree; approximate expressed the proportion relation of crystal and gel in the samples. And studied the relationship of compressive strength and dissolved amount difference, bound water amount and crystallinity degree of autoclaved silicate products using solid waste. The results shown, dissolved amount difference, bound water amount and crystallinity degree of autoclaved samples are related to kinds of hydration products. When well-crystallized hydrated amount is smaller, the crystallinity degree and its change are also smaller, and compressive strength of the sample increases with bound water amount increasing. When well-crystallized hydrated amount is larger, dissolved amount difference is larger, and crystallinity degree is larger, compressive strength of the sample increases with crystallinity degree decreased. There is an optimal value of crystallinity degree for compressive strength of the autoclaved samples.

Effects of Carbonation on Steel Slag Products

The effects of carbonation on structure and properties of steel slag specimens are evaluated by some different testing technologys in this paper. The experimental results of strength and soundness show that the compressive strength of samples is improved 6-8 times due to carbonation, and carbonated specimens have qualified autoclave soundness. Also the carbonation reactions of steel slag and the reason that why strength and soundness improved are analyzed by chemical titration, XRD, TG, SEM and MIP etc. Experimental results indicate that in steel slag specimens, f-CaO, f-MgO, partial C2S and C3S minerals could be carbonated, and 105～110 gram CO2 gas could be sequestrated after carbonating per kilogram of steel slag specimens.

Effect of nanodisperse particles of silicon and aluminum oxide hydrosols on structure formation of clay minerals in aqueous medium

The effect of nanodisperse particles of Al and Si oxide hydrosols on structure formation of minerals in aqueous suspensions of bentonite and refractory clays was examined. The following were determined during formation of the structure of the ceramic material: pH and structure of clay suspensions, slip fluidity, shrinkage and compressive strength of samples poured from slips made of dried and thermally activated (350°C) clays.