Characteristics Of Cement Research Articles

Electrical resistivity and setting characteristics of some biomaterials

Cement base materials are used under metallic restorations to minimize pain due to galvanic current. The setting time - current characteristics of dental cements show that, immediately after mixing of the powder-liquid, the resistivity of dental cements such as Zinc Polycarboxylate, Zinc Phosphate and Glass Ionomer is of the order of 103 Ω - m. The resistivity of these fully set cement is high and of the order of 107 Ω - m. Glass ionomer cement show prolonged conductivity suggesting that, clinically when used as bases under metallic fillings, they may not function adequately as insulators against the effects of galvanic currents on the pulp.

Radiological characteristics of endodontic materials and fragments of broken instruments in the canals of extracted teeth according to computed tomography

Microfocus cone-beam computed tomography (micro-CBCT) combines the technology of cone beam-computed tomography (CBCT) with a microfocus X-ray tube. Micro-CBCT is used in medicine in a relatively small number of experimental scientific works, the results of which demonstrate that micro-CBCT is a promising new diagnostic technique. The purpose of this work is a comparative analysis of the results of CBCT and micro-CBCT studies of the roots of extracted teeth before and after endodontic treatment, identification of the radiological characteristics of endodontic materials. Materials and methods. Devices Kavo OP 3D Vision (USA) and “Micron” (Russia) were used in order to scan 136 untreated and 91 endodontically treated roots of extracted teeth. A comparative analysis of the acquired CBCT and micro-CBCT reconstructions was performed. Results and discussion. Additional canals in the apexes of the roots, contents of the root canals and longitudinal fractures of the roots were imperceptible on the CBCT images of the untreated roots, but could be discovered with the help of micro-CBCT. The radiological characteristics of calcium-aluminosilicate cement, gutta-percha pins for lateral condensation of cold gutta-percha, zinc oxide-eugenol sealer, thermoplasticized gutta-percha on a plastic carrier, and epoxy resin-based sealer were determined for both of the computed tomography techniques. The microscopic structure of the materials could only be observed using the micro-CBCT reconstructions. A comparative analysis of the CBCT and micro-CBCT scans of the roots which contained intentionally broken metal instruments was performed. The presence of metal fragments resulted in stronger distortions on CBCT images compared to the results of micro-CBCT. Conclusion. Compared to CBCT, micro-CBCT is characterized by a higher spatial resolution and clarity of images, less pronounced artifacts from metal, allows to detect additional root canals, fracture lines and inclusions in root canals, makes it possible to characterize the structure of filling materials at the microscopic level.

Influence of Plastifying Additives on the Properties of Cement Stone

The article presents the results of research work on the development of the properties of binders with chemical additives and determines the optimal compositions. Today, along with water, filler and binder, additives have become an indispensable component of the concrete mix. Among the many types of chemical additives, plasticizers occupy a separate place, especially the most effective of them are superplasticizers. The most important physical and mechanical characteristics of cement with chemical additives are discussed below

Experimental constraints on nonskeletal CaCO3 precipitation from Proterozoic seawater

Abstract Precambrian carbonates record secular variations in the style of CaCO3 nucleation and growth, yet the geochemical conditions recorded by some enigmatic textures remain poorly quantified. Here, we performed CaCO3 nucleation experiments in synthetic seawater in order to constrain the mineralization pathways of synsedimentary calcite microspar cement, a prolific component of Proterozoic carbonates. We found that dissolved PO4 above ∼12 μmol/L (µM) inhibits the nucleation of aragonite and calcite and permits the formation of an amorphous Ca-Mg carbonate (ACMC) precursor once CaCO3 supersaturation (Ωcal) is ≥ 45. Depending on seawater Mg/Ca, ACMC then rapidly recrystallizes to monohydrocalcite and/or calcite. This precipitation mechanism is consistent with sedimentological, petrographic, and geochemical characteristics of Proterozoic synsedimentary calcite microspar cement, and it suggests that kinetic interactions among common seawater ions may open nontraditional CaCO3 mineralization pathways and sustain high CaCO3 supersaturation.

Experimental investigation of crack propagation behavior and failure characteristics of cement infilled rock

A detailed understanding of the failure characteristics of infilled jointed rock is a key concern in underground engineering and is critical to the design, construction and maintenance of relevant projects. In this paper, uniaxial compression tests were performed to investigate the effect of the joint arrangement (different rock bridge angles) on the strength and crack propagation of red sandstone containing a set of preexisting infilled flaws of the same sizes and angles, while the crack fracturing process was observed by AE and strain monitoring. When the angle between the rock bridge and loading stress was less than 24°, the rock mass failure form was tensile failure with some localized shear failure occurring in the rock bridge damaged by crack penetration, leading to an overall decrease in the carrying capacity. The turning points of the strain and AE signal were clearly observed to be caused by the initiation and propagation of cracks, and the energy consumed by the initiation of shear cracks was greater than that of tensile cracks. The study was further conducted using the fracture mechanics numerical code FRACOD to investigate the crack propagation law and failure mechanism under different loading stress conditions. Simulation results from three 2D similar models showed that the percentage of open fractures decreased, but slipping increased; in addition, the total length of the fractures was greatly reduced with increasing confining stress. These results are important and valuable for understanding the crack mechanism of rock engineering in deep underground mining excavations.

Influence of Rice Husk Ash on Characteristics of Earth Cement Blocks

AbstractThis paper presents an experimental study on the characteristics of earth cement blocks with Rice Husk Ash (RHA) as a partial replacement to cement. The replacement of RHA content is limited to 0%, 5%, 10%, 15% and 20% by mass of the total binder in the earth cement block. The experiments on earth cement blocks investigate the compressive strength and flexural tensile strength for mechanical properties and water absorption, sorption rate and erosion against water spray for its durability. Due to the high content of SiO2 in RHA with great reactivity, a significant increase in the compressive and flexural tensile strength of earth cement blocks was observed up to 10% RHA content. However, the durability of earth cement blocks becomes adverse with the increasing percentage of RHA replacement, but within the allowable limit. The experimental results indicate that to some extent, RHA based earth cement blocks have a significant potential for reduction in cement used in the construction industry.

Influence of Soil Grading on the Mechanical Behavior of Earth Cement Blocks

AbstractThe characteristics of earth cement blocks depend on soil composition, grading of the soil, cement-soil ratio and water content, etc… In the present study, an experimental program is conducted to evaluate the influence of soil grading in the mechanical properties of earth cement blocks. Five gradings of soil used for the preparation of earth cement blocks. Soil grading effect on following properties of earth-cement blocks such as block density, compressive strength in wet and dry condition, flexural tensile strength in wet and dry condition, and water absorption was compared. Results show that the properties of the earth cement blocks are dependent upon the fine content and uniformity coefficient of the soil. The increase in the finer content in mortar improves water absorption, compressive strength and flexural tensile strength.

The Effect of Various Milling Time Duration On The Characteristic of Glass Ionomer Cement (GIC) with The Addition of Liquid Pmve-Ma

A study entitled The Effect of Milling Time Duration on the Characteristics of Glass Ionomer Cement (GIC) Dental Cement with the Addition of Liquid PMVE-MA aims to determine the effect of milling time duration on the physical and mechanical properties of Glass Ionomer Cement, and to determine the optimum milling time duration in order to obtain GIC dental cement with the best characteristic to be applied as a dental restoration material. The duration of the milling time was 80 minutes, 90 minutes, 100 minutes, and 110 minutes. After the milling process, the next process was sintered at a temperature of 1200 for 1 hour to form Powder Glass Ionomer. Then Powder Glass Ionomer was added with Poly Methyl Vinyl Ether-Maleic Acid (PMVE-MA) to form a paste. The mixed paste was then formed. Sample characterization was the density test, the compressive strength test, and the vickers hardness test. The results of the density test obtained the highest value of 1.683 gram / cm3, the compressive strength test of 71.841 MPa, and the highest value of the hardness test of 92.3 Kg / mm2. These results increased as the increasing milling time duration up to 110 minutes.

Distribution and cementation characteristics of beachrocks along southern, southwestern and western coast of Sri Lanka

Beachrocks are sedimentary structures where gravelly or sandy beaches have been transformed into rock outcrops formed through precipitation of connective cements amid their interstices. They are well-noted coastal features along the coastal belt of Sri Lanka due to the prevalent tropical climate. This study was aimed at gathering data on surface nature and cementation characteristics of beachrock occurrences along a part of Sri Lankan shoreline through field observations and a series of analyses including X-ray diffraction, X-ray fluorescence, scanning electron microscopy (SEM) techniques and petrographic thin-section analysis. The combined research findings from different techniques are also employed as a preliminary step to determine the formation mechanism of the studied beachrocks. The seaward-inclined low-angle beds running parallel to present shoreline are composed mostly of sandstone with occasional conglomerate. Almost all the beachrocks are made of quartz grains amalgamated by cement. One remarkable feature of Sri Lankan beachrocks is the presence of heavy minerals generally in thin lamina form. The cementing agents are predominantly composed of metastable carbonate phases, high magnesium calcite (HMC) and aragonite (Ar) with varying microfabrics and textures. From SEM examinations and thin-section images, main morphologies identified are acicular Ar, scalenohedral magnesium calcites along with bridge cements and micritic coatings which are typical of a marine-phreatic precipitation with the exception of occasional meniscus cements. Further, the presence of evidences of living organisms may be an indication of influence from the biological aspects which can be confirmed by more detailed analyses.

Strength and Permeability Characteristics of Superfine Cement and Fine Fly Ash Mixture Grouted Sand

Strength and Permeability Characteristics of Superfine Cement and Fine Fly Ash Mixture Grouted Sand

The Release Behavior, Biocompatibility and Physical Properties of Ald-loaded Strontium Doped Calcium Phosphate Cement

The effect of concurrent attendance of two inhibitors of bone degradation, namely Alendronate (Ald) sodium trihydrate and Strontium (Sr), on Calcium Phosphate Cement (CPC) characteristics was explored. To this aim, 5 wt% Strontium and 21 mM Alendronate sodium trihydrate were used in calcium phosphate cement and setting time, ion and drug release were analyzed. RAW264.7 and G cell were cultured on cement samples and Tartrate-Resistant Acid Phosphatase (TRAP), Alkaline phosphatase (ALP) activity and MTT assay were studied. The results of structural analysis indicated that 21 mM Ald did not let the cement set. Therefore, colloidal silica was added to the cement formula and successfully decreased the setting time. In vitro tests showed Sr-loaded sample had a greater inhibitory effect on biocompatibility of G cells than Ald-loaded and Sr-Ald-loaded samples. In addition, the findings about osteoblast MTT and ALP activity indicated that Sr was more effective in osteogenic activity of G cells. The simultaneous presence of Ald and Sr in Calcium Phosphate Cement (CPC) was not as effective in its biocompatibility as the presence of Sr alone.

Study of the Incorporation of Ladle Furnace Slag in the Manufacture of Cold In-Place Recycling with Bitumen Emulsion.

Cold in-place recycling with bitumen emulsion is a good environmental option for road conservation. The technique produces lower CO2 emissions because the product is manufactured and spread in the same location as the previous infrastructure, and its mixing with bitumen emulsion occurs at room temperature. Adding materials with cementitious characteristics gives the final mixture greater resistance and durability, and incorporating an industrial by-product such as ladle furnace slag (of which cementitious characteristics have been corroborated by various authors) enables the creation of sustainable, resistant pavement. This paper describes the incorporation of ladle furnace slag in reclaimed asphalt pavements (RAP) to execute in-place asphalt pavement recycling with bitumen emulsion. Various test groups of samples with increasing percentages of emulsion were created to study both the density of the mixtures obtained, and their dry and post-immersion compressive strength. To determine these characteristics, the physical and chemical properties of the ladle furnace slag and the reclaimed asphalt pavements were analyzed, as well as compatibility with the bitumen emulsion. The aforementioned tests define an optimal combination of RAP (90%), ladle furnace slag (10%), water (2.6%), and emulsion (3.3%), which demonstrated maximum values for compressive strength of the dry and post-immersion bituminous mixture. These tests therefore demonstrate the suitability of ladle furnace slag for cold in-place recycling with bitumen emulsion.

Interface characteristics of oil-well cement and rock asphalt coated by dicalcium silicate

Rock asphalt can be used feasibly to toughen oil-well cements. However, the interface between non-hydrophilic rock asphalt and cement is poor, which reduces the overall mechanical properties of the composites. Therefore, in this study, the sol–gel method was used to synthesise dicalcium silicate (C2S), which was applied as a coating on the surface of rock asphalt to improve its interfacial bonding with cement. Our analysis indicated that the formed C2S consisted of β crystals with an average particle size of 13.622 µm. Infrared testing showed the presence of O–Si–O, Si–OH, and Si–O bonds in C2S-coated rock asphalt. Scanning electron microscopy and energy-dispersive X-ray analysis indicated that C2S has been grafted on the surface of rock asphalt. Compared to untreated rock asphalt, the surface free energy of C2S-coated rock asphalt increased from 12.71 to 35.83 mJ/m2 while the interfacial binding energy with cement increased from 45.61 (untreated rock asphalt) to 84.76 (C2S-coated rock asphalt) mJ/m2. In addition, mechanical testing showed that the tensile strength and toughness of C2S-coated rock asphalt-containing cement composites were very high. This is because C2S-coated rock asphalt formed an excellent transition zone at the interface with the cement matrix, resulting in a strong and durable interface.

Hydration characteristics of calcium sulfoaluminate (CSA) cement/portland cement blended pastes

The hydration characteristics of calcium sulfoaluminate cement (CSA) and ordinary Portland cement (OPC) blended pastes incorporating calcium sulfate (CS‾) are investigated. The experimental characterization techniques were employed and complemented with thermodynamic calculations to provide in-depth understanding of the hydration of CSA/OPC blended system. The results showed that the hydration of C3S in the CSA/OPC blended pastes was significantly delayed in comparison with the sole OPC paste. The delayed hydration of C3S negatively affected the strength development of the CSA/OPC pastes. As the amount of CS‾ increases, the induction period occurring between the initial peak and the intermediate peak was extended, thus increasing the initial setting time. The addition of CS‾ to the CSA/OPC blends led to the two phenomena in the hydration of C4A3S‾, (1) retardation of C4A3S‾ hydration, and (2) formation of more ettringite after a few hours of hydration. The thermodynamic calculations indicated that the setting of the CSA/OPC blended system is mainly facilitated by hydration of C4A3S‾ and by the formation of ettringite, while the major strength-giving phase is C–S–H that originates from the hydration of C3S.

Effects of activator properties and GGBFS/FA ratio on the structural build-up and rheology of AAC

The effects of ground granulated blast furnace slag/fly ash (GGBFS/FA) ratio, mass ratio of SiO2 to Na2O (Ms) of activator solution and sodium silicate dosage on structural build-up, flow properties and setting characteristics of alkali-activated cement (AAC) mixtures were investigated. The solid-like behavior becomes more dominant with increasing GGBFS/FA ratio. Ms value had significant effect on the structural build-up. Significantly higher initial storage modulus with a low increasing rate was observed for the Ms values lower than 0.8. However, for higher Ms values, a sudden increase in storage modulus was observed after negligible initial structuration. An increase in sodium silicate dosage caused a considerable delay in the abrupt increase in the structural formation. It was observed that flow curves of AAC fit the Herschel-Bulkley model with shear-thickening behavior. ICP-OES tests revealed the lower release of aluminum and calcium into the pore solution of GGBFS/FA mixtures with low Ms values.

Absorption characteristics of composite ordinary portland cement (OPC)/Fe2O3/BaO X-ray shield applications

AbstrakComposite materials for X-ray shield aplications have been synthesized used the ordinary portland cement (OPC) as matrix material and Fe2O3 and BaO as fillers material. There are four compositions of the (Fe2O3 + BaO); namely OFB 1 for 0%, OFB 2 for 5%, OFB 3 for 10%, and OFB 4 for 15%. The chemical composition of the composites were determined by X-ray fluorescence (XRF) spectroscopy and for structural properties determined by X-ray diffraction (XRD). For the absorption characteristics were determined by using mobile X-Ray and analysis the linear coefficient attenuation (μ), the half value layer (HVL), the tenth value layer (TVL), and the absorbed dose (S) for various of the tube voltage; 60 kV, 70 kV and 80 kV. The absorption dose was increase with increasing the amount of (Fe2O3 + BaO) as fillers at the same tube voltage, but decreasing the absorption dose for the tube voltage of radiation source increased. The best absorption dose is for composite OFB 4 on the source tube voltage of 60 kV with the value of μ, HVL, TVL and S are 0.32 mm−1, 2.13 mm, 7.09 mm, and 99.85%, respectively.

Initial curing characteristics of composite cements under ceramic restorations.

To assess the degree of conversion (DC) of dual-curing composite cements when cured through ceramic-veneered zirconia disks. Portions of mixed cement, either G-CEM LinkForce (GC), Panavia V5 (Kuraray Noritake) or ResiCEM (Shofu), were placed on the ATR crystal of a Fourier Transform Infrared Spectroscope (FTIR; iS50, Thermo Scientific) and squeezed to a 100-µm film thickness using a microscopy cover glass. DC (%) of the composite cements applied in self-curing mode was measured in the dark at 37°C. Following the dual-curing mode, the cements were light-cured directly (positive control) or through a ceramic-veneered zirconia disk (0.5-mm thick zirconia with a 1.0-mm thick veneering ceramic) for 40 sec using two light-curing units (G-Light Prima 2, GC; PenCure, Morita). Per experimental group, 5 tests were conducted to measure DC in self-cure and dual-cure mode (n=5). FTIR spectra of the composite cement films were acquired to determine DC every min up to 30 min. DC of the composite cements was statistically compared using two-way repeated-measures ANOVA (α=0.05). For all cements investigated, the self-curing mode resulted in significantly lower DC at 10, 20 and 30 min than the light-curing mode. When the composite cements were light-cured through the zirconia disk, DC at 30 min dropped significantly for ResiCem (Shofu), while not for Panavia V5 (Kuraray Noritake) and G-CEM LinkForce (GC). Self-curing slows down polymerization but does not reach for all composite cements the highest (light-cured) DC. Ceramic-veneered zirconia-based restorations may affect DC of some composite cements.

Analysis of frost resistance of basalt fiber cement solidified aeolian sand subgrade

Through the freeze-thaw cycle test, the damage characteristics of basalt fiber cement solidified aeolian sand with different basalt fiber and cement content, different freeze-thaw cycles and curing age were analyzed. The test results show that with the increase of the basalt fiber content, the damage degree of the basalt fiber cement solidified aeolian sand under the action of freeze-thaw cycle first decreases and then increases, and the damage degree is minimum when the basalt fiber content is 0.5%; The 90-day-old specimens were more resistant to freeze-thaw damage than the 28-day specimens. By establishing the damage model of unconfined compressive strength loss rate and freezing and thawing times of basalt fiber-solidified aeolian sand, it was found that it obeyed the quadratic polynomial change trend, and the fitting accuracy was greater than 0.9. The gray entropy analysis method was used to find that the amount of cement had the greatest influence on the mass loss rate and unconfined compressive strength of basalt fiber-solidified aeolian sand specimens.

Influence of coir fiber reinforcement on shear strength parameters of cement modified marginal soil mixed with fly ash

In the context of paucity for suitable granular soils at various work sites, it has become inevitable for the use of marginal soils (low quality soils) and has been being used for different types of constructions. With the advent of reinforcing soil, a wide variety of materials such as geosynthetics are used for reinforcement. Apart from geosynthetics, coir fiber is also been used for soil strength improvement for their engineering practice. Coir fiber is randomly distributed in soil mass for the purpose of reinforcement. Fly ash has been used at several work sites due to its abundant availability as a waste material. The effective use of Fly ash has an advantage over saving and preserving natural resources, leading in the reduction in cost of the project. Apart from various other techniques of soil modification such as chemical stabilization, lime stabilization etc; the cement modification has got prominence. In the present study, the marginal soil is treated with 3% cement that could able to make it non–plastic. An attempt was made to investigate the effectiveness of coir fiber as reinforcement for locally available cement modified marginal soil and mixed with Fly ash. The intention of the work is to study the effectiveness of coir fiber as a randomly distributed reinforcement on shear strength and strength characteristics of cement modified marginal soil mixed with Fly ash. A series of laboratory tests such as direct shear and unconfined compressive strength tests were conducted using marginal soil. The shear strength of this marginal soil reinforced with 2% coir and mixed with 10% Fly ash was 1.5 to 2 times the shear strength of plain marginal soil. Hence, the experimental study provides an approximate solution for enhancement of shear strength of marginal soil, that marginal soil could be used in construction of reinforced soil structures.

Eksplorasi Material Semen untuk Pengembangan Produk Elemen Estetik

Cement is a unique material, initially as the base material with the mainfunction as an adhesive for other materials whose existence is always covered. Nowdays, the application of cement materials in interior elements appears to be more honest. Natural ash color and cement characteristics are interesting things to be exposed. The use of cement material has also grown not only limited to the elements that make up space (floors, walls and ceilings), but has stepped into space facilities (furniture) and aesthetic elements. Through a series of experiments with the "design by doing" method, experiments were carried out by giving chemical treatments such as foam agents, adding magnesium carbonate powder and adding magnesium oxide to the base materials (cement, cement + sand) to explore and discover various potentials, uniqueness, peculiarities and lighter feature as new ideas in aesthetic elements product development in interior design. The results obtained from a series of experiments showed differences in the cement concrete characteristics through its texture, shape, number and size of pores and difference in weight .