Characteristics Of Cement Research Articles

Dispersion and effects of metal impregnated granular activated carbon particles on the hydration of antimicrobial mortars

Granular activated carbon (GAC) particles impregnated with antimicrobial metals were incorporated into cementitious materials for the express purpose of inhibiting biogenic concrete corrosion. We report herein the influence of such metal-laden GAC particles on the hydration of cement mortars when substituted for fine aggregate, as well as the dispersion of metal in the cured matrix. Isothermal calorimetry was utilized to study the influence of GAC without and with copper and/or cobalt on select hydration characteristics of ordinary portland cement (OPC) mortars. When 1% of the fine aggregate mass was replaced with GAC particles of similar size, total evolved heat in all formulations was similar, regardless of GAC pretreatment. However, as the substitution approached 10% of the fine aggregate mass, metal-laden GAC formulations imparted delays in heat liberation and lowered heat fluxes. Results also substantiate that metal-laden GAC particles participate in the enhanced uptake of the calcium that is normally liberated during cement mixing and that the water delivered with GAC particles is not readily available during the first 142 h of curing. Electron microprobe analysis (EMPA) elucidated that copper and cobalt were homogenously distributed throughout the cement paste with metal-laden GAC, with these metals concentrations localized in a 50–100 μm region surrounding the GAC particles. Compressive strengths were not affected by the presence of metal-impregnated GAC in the concentration ranges tested and reported herein.

Investigating the expansion characteristics of geopolymer cement samples in a water bath and compared with the expansion of ASTM Class-G cement

In selecting the binder composition for oil well application, its stability is an important design parameter. This paper presents the results of an experimental study conducted for comparing the linear expansion characteristics of geopolymer cement with the traditionally used ASTM Class G cement system. The expansion test was done in a water bath at 60 °C subjected to different curing intervals. The linear expansion of a cement system defines as the dimensional changes occur in the system, which is sometimes required to avoid the cement shrinkage during the hydration phase. In the case when the desired level of expansion is not achieved in the system, then the commercially available expandable materials are added in the class G cement system that enables the system to expand to the desired level. Shrinkage in the cementing system causes the formation of a microannulus or induces a gap that may allow the migration of fluid, hence the integrity of the system could be lost. This experimental study has revealed that the geopolymer cement tends to expand 0.15%–0.2% without the addition of any admixture, whereas the ASTM Class G cement has shown a lower value of linear expansion, which was obtained less than 0.1% after 18 days of curing. In the case of Class G cement, the addition of expandable material helped to increase the expansion; in the case of a geopolymer system, the additive has further accelerated the expansion.

Properties of modified asphalt mixtures with additives of fillers materials

In past, the use of by-product materials such as cement kiln dust and fly ash powders, especially in the field of highway pavements has received increasing attention. The aim of this research is to investigate the physical properties of the modified asphalt binder with additives of filler types such as cement kiln dust, fly ash, and metakaolin powder. Then, to assess the Marshall properties of modified asphalt mixtures. Three fillers containing 3%, 5%, and 7% by weight were used. The modified asphalt binder was mixed by a mechanical mixer having a revolution rate of (2000 rpm.), for mixing time (5 to 20) min. at a temperature of 140 °C. Results showed that the use the additives was beneficial in improving the physical characteristics of the asphalt cement. Overall, it was found that the penetration grade reduced and softening point values increased and the susceptibility of temperature was enhanced. Furthermore, the results of the tested specimens, the 5% of CKD, 5% of fly ash and 7% of MK were sufficient to improve the physical characteristics and Marshall properties of modified asphalt binder mixtures. In addition, the results obtained from the Marshall test show that the maximum stability for 7% of MK, 5% of CKD, 5% of fly ash, and control asphalt mixtures are (14.4, 13.6, 11.7 and 10.4) kN, respectively.

A Review of Rheological Modeling of Cement Slurry in Oil Well Applications

The rheological behavior of cement slurries is important in trying to prevent and eliminate gas-migration related problems in oil well applications. In this paper, we review the constitutive modeling of cement slurries/pastes. Cement slurries, in general, behave as complex non-linear fluids with the possibility of exhibiting viscoelasticity, thixotropy, yield stress, shear-thinning effects, etc. The shear viscosity and the yield stress are two of the most important rheological characteristics of cement; these have been studied extensively and a review of these studies is provided in this paper. We discuss the importance of changing the concentration of cement particles, water-to-cement ratio, additives/admixtures, shear rate, temperature and pressure, mixing methods, and the thixotropic behavior of cement on the stress tensor. In the concluding remarks, we propose a new constitutive model for cement slurry, considering the basic non-Newtonian nature of the different models.

Improvement in gas migration reduction in oil wells by using nanoparticles: an experimental investigation

In recent years, improving the quality and modification of the composition of cement slurry in order to reduce the fluid migration behind the well casings is one of the most important challenges for researchers and oil and gas well drilling industries. It has been demonstrated that nanoparticles have made some progresses in the operational characteristics of conventional cement. Various technologies have been developed to solve gas migration where is an important task to design a cement slurry that do not let the hydrocarbon fluid migrate from the cement after its hydration. This research, via 13 experimental attempts, showed that great improvement in compressive strength and rheological properties of cement slurry appears after addition of silicon dioxide nanomaterial to the slurry, on the other hand it did not make any significant change in free water content of the cement and fluid loss. In the case of static gel strength analyzers (SGSA) test, transient time followed a decrementing pattern by increasing nanoparticle. As a result, it met the vital goal in drilling industry via deep reduction in gas migration rate and solves the foregoing problem without having any negative effects on the other properties of cement slurry such as thickening time. Moreover, Mohr circles analysis demonstrated that higher compressive strengths are achieved by adding nanoparticles, especially in the absence of anti-gas migration additive.

Mechanical Properties of Lime-Fly Ash-Sulphate Aluminum Cement Stabilized Loess

Lime-fly ash stabilized loess has a poor early strength, which results in a later traffic opening time when it is used as road-base materials. Consideration of the significant early strength characteristics of sulphate aluminum cement (SAC), it is always added into the lime-fly ash mixtures to improve the early strength of stabilized loess. However, there is a scarcity of research on the mechanical behavior of lime-fly ash-SAC stabilized loess and there is a lack of quantitative evaluation of loess stabilized with binder materials. This research explored the effects of the amount of binder materials, curing time and porosity on the unconfined compressive strength (UCS), splitting tensile strength (STS), cohesion (c) and friction angle (φ) of lime-fly ash-SAC stabilized loess by a series of unconfined compressive tests (UCT) and splitting tensile tests (STT). The results indicate that an increase in curing time and a decrease in porosity lead to a continuous increase in the UCS and STS for lime-fly ash-SAC stabilized loess. The addition of SAC has a prominent enhancement in the early strength of lime-fly ash-SAC stabilized loess. When the curing time, porosity, and binder content were constant, the UCS and STS increase with increasing SAC content; For a stabilized loess with 30% binder content and 5% SAC content after 1 day of curing, the UCS was greater than 0.7 MPa, which meets the requirement of opening traffic, so lime-fly ash-SAC stabilized loess could be used as an excellent maintenance material for road-base; In accordance with the analysis of testing data, empirical relationships between the UCS and STS of lime-fly-SAC stabilized loess and key effect factors (binder materials content, curing time and porosity) were developed, which can provide references for reasonably selecting the amount of binder materials, compaction degree and curing period to meet the required strength of practical engineering. Finally, based on the Mohr-Coulomb theory and the above empirical relationships, a simpler method for calculating the c and φ of stabilized loess was proposed, with which, the shear strength parameters can be determined only by UCT or STT.

Compressive Strength Evaluation of Ordinary Portland Cement Mortar Blended with Hydrogen Nano-Bubble Water and Graphene.

Abnormal climate changes have occurred all over the world due to greenhouse gases (GHGs). Various countries are targeting emission reductions of GHGs in 2020 and trying to GHGs those in multiple fields. Cement-based structures account for a large part in the construction industry. One ton of carbon dioxide is produced during the manufacturing process for a ton of cement. Therefore, decreasing cement usage is essential for carbon dioxide reduction. However, strength characteristics of cement are necessary conditions to meet the required strength of a structure. Therefore, it is necessary to develop cement substitutes and economic additives. In this study, we proposed an eco-friendly blend ratio by comparing the compressive strength of Ordinary Portland Cement (OPC) mortar and two variations. One was a mortar with a small amount of APTMS-sGO added. The other was a mortar mixed with HNBW (hydrogen nano-bubble water) as an enhanced material instead of ordinary water. The mortar added with 0.1% of APTMS-sGO showed improved early strength compared with OPC mortar. Its strength was enhanced 31.1% by using HNBW as functional water. Strength was improved 20.4% for cement mortar added with Graphene Oxide after reacting with SAM containing APTMS. When the texture of both mortars became denser, early compressive strength at 7 days each was 20.4-31.1% higher than that of OPC mortar. Finally, the strength was increased by 10.2% at 28 days.

Study of the influence of properties of dusty ferromagnetic additives on the increase of cement activity

Sustainable development of construction materials is directly related to research on the processes of hydration of binders. Builders need better types of cement, with lower cost and energy consumption in production. The development of spin chemistry methods allows us to consider the processes of hydration and structure formation of binders from the spin state of the elements involved in chemical reactions. Magnetic interactions have a significant effect on the spin dynamics and the control of the spin multiplicity of radical pairs. The practical implementation of magnetic effects on a binder can be carried out in various ways. However, a long-term impact can be achieved only by introducing ferromagnetic substances into the binders. In the paper presented the results of a study of the influence of the characteristics of finely dispersed powdered ferromagnetic additives on the strength characteristics of cement. Ferromagnetic additives regulate the behavior of the reactants during rotation during the hydration of the binders due to magnetic interactions and control the reactivity of the chemical reaction. A comparative analysis revealed that it is most expedient to use as powdery ferromagnetic additives are the waste from mining and processing enterprises of the Krivorozhsky field. The work investigated the magnetic and dispersed characteristics of 12 different dust. The experiments showed that the origin of dust and the method of their capture are determined their magnetic characteristics. Preparation of samples with the dust and determination of the strength characteristics of cement were carried out by standard methods. The results obtained made it possible to reveal the laws of the effect of the dispersed and magnetic properties of various dust on the degree of activation of binders.

Strength Characteristics of Cement Treated and Expanded Polystyrene Mixed Lightweight of Waste Soil from the Construction Site of a Yangtze River Bridge in China

In the past decades, the speed and scale of Chinese infrastructure construction have been enormous, and the resulting construction waste is also quite amazing, which has become a huge threat to environmental protection. If the pollution‐free engineering utilization of the construction waste can be achieved at a low cost, it will undoubtedly be a great benefit for the country and the people. Therefore, a preliminary experimental study was conducted to investigate the strength characteristics of the cement treated and expanded polystyrene mixed lightweight. The waste soil (muddy clay and fine sand) as the main component of the lightweight mixture is taken from a foundation construction site of a Yangtze River Bridge which connects two eastern coastal cities, Zhenjiang and Yangzhou. With different mixture ratios and additives of the cement treated and expanded polystyrene mixed lightweight, a series of cubic samples were tested by the unconfined compressive strength test, and collections of standard cylinder samples prepared by hand were inspected by the conventional triaxial shear test. Then, a good exponential relationship between the uniaxial compressive strength and the cement mixing ration was founded, and a logarithmic relationship was captured between the compressive strength and curing time within a period of 28 days after the specimens were made. Samples made of different soil as raw materials have different strengths, but all of these specimens show a strain‐hardening and stable behavior. Results show that the mechanical strength characteristics of the cement treated and expanded polystyrene mixed waste soil mainly depend on the proportions of lightweight mixture.

Effect of freeze–thaw on fatigue damage characteristics of cement emulsified bitumen mastic

Cement emulsified bitumen mastic (simplified as CEBM) is a type of composite binder composed of cement, emulsified bitumen, water and various additives. Freeze–thaw cycles have an important influence on the fatigue properties of CEBM. In this paper, freeze–thaw test and fatigue test were carried out. Damage variable characterizing freeze–thaw effect and total damage variable characterizing freeze–thaw and fatigue coupling effect were established. They were based on the initial complex modulus and fatigue properties parameters of fatigue test. Effects of freeze–thaw cycles on fatigue properties and damage evolution process were analysed. This study demonstrates that, as freeze–thaw cycles increasing, fatigue life decreases, and the sensitivity of fatigue life with stress level is reduced. With the increase of freeze–thaw cycles, both freeze–thaw damage and total fatigue damage increase, and the proportion of freeze–thaw damage in total damage increases. Effect of freeze–thaw cycles on the fatigue properties of CEBM is enhanced. With the increase of bitumen content, freeze–thaw damage reduces and total damage increases. The increase of bitumen content can improve the frost resistance of CEBM and improve the sensitivity of fatigue properties to freeze–thaw cycles.

Experimental Investigation of the Macroscopic Behavior and Microstructure Property Evolution of Hardened Cement Consolidated Tailings

Surface cement consolidated tailings disposal has recently been proposed to manage tailings in the modern mining industry because it can reduce or eliminate the disadvantages of traditional tailings storage. In this study, the evolution of the macro performance and microstructure characteristics of cement consolidated tailing samples during the curing period were determined by unconfined compressive strength tests, permeability tests, scanning electron microscopy (SEM) observations, and mercury intrusion porosimetry (MIP) tests, respectively. The results show that the curing time notably affected the macro performance and microstructural properties of the hardened cement consolidated tailings samples. As the curing age increases, the compressive strength increases nonlinearly and the growth rate decreases; the permeability decreases rapidly first, then gradually stabilizes, and finally reaches a stable value; the morphology of the hydration products and microstructures continues to evolve with the hydration process; the total pore volume decreases slightly, whereas the critical pore size decreases significantly. The proportion of the pore volume in different pore size ranges can also be affected by the curing age, which results in a large pore (>200 nm) decrease, and the small pores (<200 nm) increased. In this process, the filling effect plays a major role.

Influence of mixing solution on characteristics of calcium aluminate cement modified with sodium polyphosphate

This study investigated characteristics of a calcium aluminate cement modified with a phosphate (CAP) by changing an amount and concentration of mixing solution with sodium polyphosphate. When the amount of mixing solution was increased with a constant amount of sodium polyphosphate, an enhanced consumption of monocalcium aluminate was observed compared with gehlenite in calcium aluminate cement. Formation of gibbsite, Al(OH)3, was also increased as a hydration product in the CAP and a reduction of water in the amorphous gel phase. When the amount of mixing solution was increased with a constant concentration of sodium polyphosphate, the enhanced consumption of monocalcium aluminate was not observed. Neither gibbsite nor any other crystalline hydration products were identified in this series. In addition, unreacted sodium polyphosphate remained in the system. The increased formation of gibbsite and the possible reduction of water from the amorphous gel phase appears to contribute to the improvement of the microstructure in the products.

An approach for quantitative analysis of cementation in sandstone based on cathodoluminescence and MATLAB algorithms

With the development of programming technology and high resolution image analysis, automated image analysis and recognition technology is used in a variety of disciplines, including modern sedimentary. On the basis of cathodeluminescence (CL) images and the algorithm and functions in MATLAB, this paper establishes an analysis method of quantitative calculation for the distribution, content and radius of siliceous cement, calcareous cement, kaolinite cement with various occurrence types in sandstone. Taking the Upper Paleozoic sandstone of Ordos Basin as the research object, the CL image was converted to the binary image which contained the color and pixel information of cement by the built-in application “Color Thresholder” in MATLAB. Further, through the functions such as ‘bwarea’, ‘bwlabel’, ‘bwboundaries’, the area in which the cement feature pixels were stored was calculated and analyzed in turn. The results show that this characterization method can automatically distinguish and calculate the content and radius of various cementation, even quartz overgrowth, in different diagenetic periods. The cement radius of quartz overgrowth, calcite and kaolinite are distributed at 0–150 μm, 0–300 μm and 0–200 μm. Comparing the content results measured by X-ray diffraction (X-RD) analysis with CL-MATLAB algorithm, the calculation results with a single CL image are suitable for siliceous cement, grain-replaced calcareous cement and pore-cemented kaolinite with linear coefficient R2 0.841, 0.562 and 0.236. For the radius distribution of cement, the average grain radius and pore radius, corresponding to the grain-replaced cementaion and the porous cementation, are used as the comparison parameters of cement radius. The appropriate objects for the method are grain-replaced and porous calcareous cement and pore-cemented kaolinite cement with R2, 0.7797, 0.4987 and 0.289. In addition, four color modes of image binarization, YCbCr, RGB, L*a*b*, HSV, are explored in this paper. It is clarified that the calcareous cements with orange-red color are most suitable under L*a*b* mode, while the siliceous and kaolinte with blue-purple color are most appropriate under RGB mode. The analysis method of CL image -MATLAB algorithm can not only accurately identify and quantitatively output the distribution, content and pore radius of cements in a single CL image, but also reflect the distribution characteristics of cements of the whole formation with superposed results of all the samples.

Fatigue damage and creep characteristics of cement emulsified asphalt composite binder

Cement emulsified asphalt composite binder (simplified as CEACB) is a kind of viscoelastic material composed by cement, emulsified asphalt and various admixtures. Fatigue damage caused by dynamic loading affects the viscoelastic properties of CEACB. In this paper, evolution process of fatigue damage was analyzed by fatigue test. Based on the four-element model with five parameters and creep damage evolution equation, CEACB creep equation, single damage creep equation and double damage creep equation were established, and the effect of fatigue damage on the creep behavior of CEACB was analyzed. The damage rate of CEACB increases with the increase of stress level. With the increase of asphalt content, the sensitivity of fatigue properties change with stress level increases. With the increase of fatigue damage, instantaneous elastic deformation and creep rate increase in steady creep stage during creep process. The ability of CEACB to resist deformation is reduced by fatigue damage, and CEACB shows a tendency of softening. The damage of elastic and viscous properties of CEACB are different.

Analysis of loess sediment texture in Golestan province according to the microstructure parameters

This study was performed to recognize the loess texture in Golestan Province, Iran using the microstructure analysis according to the electron microscopic images. Loess microstructure study allows for investigating the characteristics of particle shape, fabric, cement and porosity in microscopic images. In recent years, computer analysis has been replaced with manual calculation due to its high speed, precision and ease of use. Since the scanning electron microscope (SEM) digital image analysis method can quantitatively determine the loess microstructure and identify the microstructure changes, it was used to analyze the loess texture. The obtained results showed that the loess microstructure changed from north and northeast to south and southwest of Golestan Province. According to microstructural and sedimentology parameters, Golestan Province loess can be divided into 4 zones. The results also showed that microstructural study of loess sediments in Golestan Province could be a useful tool for loess zoning and separating loess sediments from loess-like deposits.

Research on durability and microscopic mechanisms of the portland slag cement stabilized soil under carbonation condition

In this study, physical-mechanical properties and microscopic characteristics of the slag Portland cement stabilized soil and the normal Portland cement stabilized soil after carbonization were investigated and compared through carbonization depth tests, unconfined compression tests, XRD and SEM tests. Results showed that carbonation depth of the slag Portland cement stabilized soil was lower than that of the normal Portland cement stabilized soil on each carbonization stage. Results of XRD and SEM tests showed that the normal Portland cement stabilized soil were decomposed into Cal after carbonization, which lead to loosened structure and strength retrogression.

AN INNOVATION OF HIGH PERFORMANCE CONCRETE BY REPLACING CEMENT WITH NICKEL SLAG POWDER

ABSTRACT
 Nickel slag is a solid waste produced from the nickel smelting process. At present, In Indonesia, the total capacity of domestic nickel smelting reaches 5 million tons/year with the assumption of NPI or FeNi production with a Ni level of 10%, requiring the input of Ni ore raw materials around 40 million tons/year in which around 30 million tons will become waste/slag. Currently, the area of Southeast Sulawesi has a potential of huge nickel resources of 97.4 billion tons, which spread over 480 thousand hectares of land. This has led to a continuous increase in the demand of concrete towards infrastructural development in Indonesia. Therefore, the aim of this research is to reuse nickel slag powder in the context of environmentaly friendly by analyzing the tensile strength using nickel slag powder (NSP) as a cement substitution material for the manufacture of high-performance concrete. Specimens were made with water-cement ratio of 0.31 and compared with 100% OPC Type 1 cement (as reference). Furthermore, the NSP substitution of cement were 5%, 10%, 15%, 20%, 25% and 30% with a concrete age of 3, 7, 14 and 28 days. Analysis of physical characteristics of nickel slag powder and cement were carried out by using the Le Chatelier method, while the mechanical characteristics comprised ease of work in the field (workability) and split tensile strength. The manufactured concrete was made by using Sika Viscocrete 8015 superplasticizer admixture with split tensile strength test results for NSP substitution at 28 days ≥ 5% of the value of compressive strength.
 
 Keywords: High-performance concrete, Nickel slag powder, Split tensile strength,

The hydration properties of blended cement containing ultrafine fly ash with particle size less than 17 μm from the circulating fluidized bed combustion of coal gangue

This paper presents the proposal of the particle size range of circulating fluidized bed fly ash (CFA) that was positively associated with properties of blended cement by gray correlation analysis. Then, the hydration characteristics of blended cement containing ultrafine CFA (UCFA) with the above-suggested particle size distribution are studied from the physical and mechanical properties, hydration heat, non-evaporable water content, morphologies and pore structure. The results show that there is a positive association between CFA particles of less than 17 μm (especially 3–8 μm) and property of blended cement, while there is a negative association for particles of more than 17 μm, so the particles content of less than 17 μm should be improved in CFA as much as possible. The industrial UCFA, whose particle content of less than 17 μm reaches 98.18%, is prepared. The blended cement containing 10% UCFA possesses excellent properties, which ever surpasses pure portland cement. Furthermore, the physical and mechanical properties of blended cement containing no more than 30% UCFA meets the Chinese cement standard of 42.5 grade. With increase in the addition amount of UCFA, the hydration rate and degree of blended cement are gradually decreased and the influence is small at the addition amount of no more than 30%. The addition of 10% UCFA can optimize the pore structure of cement system, and the effect of 30% UCFA on the microstructure of cement gradually decreases with ages.

Carbonation of magnesium oxysulfate cement and its influence on mechanical performance

In order to popularize magnesium oxysulfate (MOS) cement in civil engineering, it is very necessary to investigate its carbonation related durability. It was found that carbonization can increase compressive and flexural strength of MOS cement to some extent and compressive strength of MOS cement increases gradually at first, then decreases during carbonation process. The displacement to ultimate compressive force of hardened MOS cement paste carbonated for 28 days is larger than that of non-carbonated one at the same age. Evaporable water testing and X-ray computed tomography (X-CT) were adopted to examine the porous structure of MOS cement paste with and without carbonation. It was found that carbonation refines the meso-pore (≧38 µm meters) volume ratio of hardened MOS cement with 0.5 water-to-cement ratio by about 17%. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were adopted to analyze the carbonation characteristics of MOS cement. The results indicate that magnesium hydroxide and some basic magnesium oxysulfate phase are obviously neutralized with carbon dioxide to form magnesium carbonate phases in the hardened MOS cement, which leads to the refined porous structures and corresponding increased toughness.

Mud-to-cement conversion of non-aqueous drilling fluids using alkali-activated fly ash

Driven by the needs for reduced waste disposal and a sustainable environment, many efforts have been made to recycle coal combustion products. Fly ash, for instance, has been well-researched and successfully re-used in various industries and fields. Despite the potential for various applications, only 1% of the recycled fly ash has been directed to the oil and gas industry. The present study evaluated the feasibility of using alkali-activated fly ash (AAF) as an alternative cementitious material in well cementing applications.The key finding of this study is that AAF slurries provide improved compatibility with oil-based and synthetic-based drilling muds (OBM/SBM) in comparison to Portland cement slurries. Benefits of using AAF go beyond mere OBM/SBM compatibility: it is in fact possible to incorporate large amount of non-aqueous drilling fluids (NAF) such as SBM and OBM into AAF formulations while maintaining necessary well cement characteristics. This also means that NAF-associated waste can be disposed of in a more cost-effective way, which presents a viable option for environmentally acceptable on-site or off-site disposal of drilling muds and cuttings.In the present work, a novel mud-to-cement conversion method was achieved by blending varied amounts of AAF and SBM. The consolidated AAF/mud mixture was named “AAF hybrid cement”. In an effort to develop the AAF hybrid system as a novel well cementing material, fresh state properties, such as slurry rheology and thickening time, and hardened state mechanical properties, such as compressive strength, were comprehensively studied. The laboratory evaluations showed that the AAF hybrid cement could meet the typical characteristics and requirements of a well cementing slurry. By changing the relative amount of AAF and SBM in the slurry, the AAF hybrid can be deliberately designed with high compressive strength for primary cementation, or with lower compressive strength for lost circulation control.