Characteristics Of Cement Research Articles

Hydration heat evolution and kinetics of blended cement containing steel slag at different temperatures

Hydration heat characteristics of blended cement containing up to 50% steel slag were studied at 25°C, 45°C and 60°C by isothermal calorimeter. Kinetics equations were used to explore kinetics of blended cement. Kinetics parameters, n, K, and Ea, were calculated and analyzed. Results indicated that the activity of steel slag was very low. Steel slag accelerated the hydration of aluminates but decelerated the hydration of silicates in cement clinker. Small amount of steel slag affected little the hydration process of cement. Elevated temperature obviously promoted the hydration of blended cement. The hydration of blended cement containing no more than 35% steel slag was controlled by nucleation of hydrates in acceleration period and by diffusion of ions in decay period. The hydration of blended cement containing 50% steel slag was mostly dominated by phase boundary reaction, then directly by diffusion. Ea increased with increasing steel slag content.

Influence of Mineral Admixtures on Early-Age Behavior of Calcium Sulfoaluminate Cement

Calcium sulfoaluminate (CSA) cements were developed for shrinkage compensation of concrete. This study investigates the expansion characteristics of CSA-portland cement (CSA-OPC) systems in the presence of mineral admixtures (MA). Unrestrained expansion of CSA-based cement pastes incorporating Class C fly ash (FA), Class F FA, and silica fume (SF) were monitored at water-cementitious material ratios (w/cm) of 0.34 and 0.44. Despite the same amount of expansive component, CSA-OPC-MA mixtures exhibited noticeable difference in expansion. The Class F FA increased the unrestrained expansion at early age for both w/cm, which was attributed to lower material resistance (that is, stiffness) due to the presence of Class F FA. Furthermore, the expansion of the Class C FA-based mixture ceased at 2 days at both w/cm due to faster consumption of ye'elimite. A calorimetric study of Class C FA-based mixture revealed early depletion of sulfates, which correlated well with the completion time of expansion. Additionally, the presence of SF lowered the expansion, which was attributed to the lower alkalinity of pore solution, incomplete hydration of ye'elimite, and increased material stiffness.

Shrinkage cracking of cement treated demolition waste as a road base

This paper presents the shrinkage cracking characteristics of cement treated demolition waste as a road base layer, which was produced by using recycled crushed concrete and masonry aggregates from construction and demolition waste (CDW). The developed method to estimate the crack pattern was based on the structural properties of cement treated demolition waste measured in the laboratory and the average climatic conditions recorded in the Netherlands. The influences of four mixture variables (masonry content, moisture content, cement content and degree of compaction) on the crack pattern were investigated. Results show that the proposed estimation model can predict the crack pattern of cement treated demolition waste comparable to the crack spacing observed in the field. The masonry variation in CDW is a key factor to determine its shrinkage cracking characteristics.

Influence of the Unburned Residues in Fly Ash Additives on the Mechanical Properties of Cement Mortars

The cement companies have found in natural and artificial pozzolans a very good option for partial replacement of cement in concrete. Fly Ash is a type of artificial pozzolan, which improves the microstructure of hydrated cement and its durability. Because it is a byproduct of coal combustion, it is economical and abundant for use as an addition to mortars and concrete, making this byproduct a recoverable residue, favoring the environment.The main objective of this study was to evaluate the changes of the microstructural and mechanical strength occurring in portland cement mortars when different proportions of fly ash are added, comparing the effects of adding fly ash in its original state of industrial waste with those of adding fly ash with a reduced content of unburned residues. For the preparation and strength determination of the mortars, cubes of 50x50x50mm were cast, using as references standards ASTM C305 and ASTM C109, respectively. Compressive strength was evaluated in curing times of 1, 3, 7, 28, 56, and 118 days. The characteristics of fly ash and Portland cement were evaluated using X-ray Fluorescence (XRF) and X-ray Diffraction (XRD) techniques, and Scanning Electron Microscopy (SEM).Given that unburned residues in fly ash are defined as the sum of the percentages of volatile matter and fixed carbon contained by it, proximate analyses were carried out - as it is for coal (ASTM D 3172) - to determine the percentage of unburned carbon that is eliminated during the process. As a result, better compressive strengths were obtained when ash containing fewer amounts of unburned carbon was added to mixtures. It is also evident that the optimal amount of fly ash that may be added to mixture of mortar without greatly affecting the mechanical strength is 20 percent.

Influence of irradiation on bonding characteristics of self-adhesive resin cements

Influence of irradiation on bonding characteristics of self-adhesive resin cements

Hydration characteristics of cement for co‐sintered from washed‐fly ash and waste sludge

The purpose of this study is to co‐sinter washed‐fly ash, limestone sludge, stone sludge, and iron‐oxide sludge to fabricate 4 types of eco‐cement clinkers. The compound raw materials were burned for 2 h at 1400°C to form the eco‐cement clinkers, all of which met the toxicity characteristic leaching procedure requirements. The results show that the major components of ordinary Portland cement (OPC), C3S, C2S, C3A, and C4AF, were present in the eco‐cement clinkers. The compressive strength development indicated that the EcoA pastes were similar to those of commercial OPC products. The compressive strength in the EcoG pastes decreased because of the amount the α‐C2S increased. The mercury intrusion porosimetry results showed that the pore volume in the pastes gradually decreased when the curing time increased. Additionally, from the X‐ray diffraction results, all the eco‐cements produced Ca(OH)2 during hydration, which also increased with curing age. The scanning electron microscopy images of OPC and EcoA pastes showed that the pore volume decreased and the denser structural increased with the curing time increased. In addition, adding higher amounts of 1% washed‐fly ash caused to increase the content of α‐C2S. The result show that this co‐sintered process from 1% washed‐fly ash and 99% waste sludge (77% limestone sludge, 19.51% stone sludge and 2.49% iron‐oxide sludge) to produce eco‐cement with excellent mechanical characteristics. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 964–972, 2015

Preparation of polymer-based cement grinding aid and their performance on grindability

This paper described a chemical process called water-based free radical polymerization to synthesize a polymer-based grinding aid (PGA), which was characterized by infra-red spectroscopy (FT-IR) and used for the production of Portland cement (ground in a ball mill at a laboratory stage). For this purpose, reference cement was also produced without using PGA. All the cement mixtures were tested for specific surface area and particle size distribution. The changes of shape of particles and repose angles of ground cement were also tested to evaluate the flow characteristics of ground cement. Compared to a reference cement admixture, the addition of PGA led to significant gains in specific surface area, a fact that was attributed to the PGA’s ability to prevent agglomeration and powder coatings of ball. The results also indicated that PGA had obviously influences on particle size distribution of ground cement, which showed a narrower grading spectrum as the PGA dosage increased. Test results by SEM and repose angle method showed that PGA resulted in improvement of roundness and fineness of cement grains and fluidity of ground cement.

Intensification of Cement Grinding with Apply Grinding Aids with Modify Effect

For over 60 years technological additives used in process of grinding cement. Application of cement grinding aids can improve performance of ball mills, reduce specific energy consumption, and increase fluidity of cement during transportation and processing. Construction practice is characterized currently emergence and increasing use of so-called high-tech (effective) a new generation of concrete, suggesting the use of high quality cement. In work presents results of impact intensifiers on the grindability of cement based on different mineralogical composition of clinker. Offers original methodology for assessing of indicators intensifiers action on grinding process and qualitative characteristics of cement. Knowing positive and negative sides of each constituent component it is possible to try selection of compositions intensifiers with synergies effect considering mineralogical composition of clinker and material composition of cement. The presence of modifying component allows not only render intensifying effect in milling process, but to increase both early and late strength due to the formation of more dense and homogeneous structure of cement stone. It is shown that intensifiers with modifying additives allow not only affect on grinding process, but also on the process of hydration and morphology crystal hydrates, strength characteristics. In process of work we had determined, that among researched additives for two different cements, which differ from each other mineralogical composition, best results were obtained with used AI8 intensifier.

A gas adsorption porosimetry analysis of Portland cement prepared by compaction vs. compaction with indirect ultrasonic agitation

Background: Mineral trioxide aggregate (MTA), is commonly used in endodontic and restorative procedures. Objective: Our objective was to introduce gas adsorption porosimetry as a viable method for evaluation of general porosity and specific pore characteristics of set Portland cement used in substitute for MTA, to investigate the effect of two different obturation methods (compaction and compaction in conjunction with indirect ultrasonic agitation of the cement paste), and to evaluate the correlation between the specific pore characteristics to compressive strength in general. Material and Methods: Portland cement samples were prepared and divided into two groups based on compaction techniques. An initial stereomicroscopic evaluation was done to assess any differences in appearance of pores randomly selected from either of the two experimental groups. Specific pore characteristics and compressive strength were quantified by a gas adsorption porosimeter and an Instron universal testing machine. A two tailed student t-test was used for statistical comparison of data, and a regression analysis was done to evaluate the correlation between each specific pore characteristic and compressive strength in general. Results: The gas porosimetry method provided measurable values relating to specific pore characteristics of Portland cement. The stereomicroscopy evaluation revealed marked differences between samples from the two groups, namely visibly larger pores both on the outside surface and in cross-sections of specimens prepared by the indirect ultrasonic activation method. Conclusions: Gas adsorption porosimetry is a feasible method for evaluation of specific pore characteristics of Portland cement and potentially other dental materials as well.

Biomechanical comparison of the strength of adhesion of polymethylmethacrylate cement to zirconia ceramic and cobalt–chromium alloy components in a total knee arthroplasty

Purpose The purpose of this study was to clarify the biomechanical characteristics of cement–material interfaces for the zirconia ceramic and cobalt–chromium (Co–Cr) alloy femoral components used for total knee arthroplasty.Methods In the first sub-study, we compared the strength of adhesion of the cement to flat plates, by tensile testing under dry and moistened conditions. In the second sub-study, we compared the maximum load of the cement–component complex by tensile testing. In the third sub-study, we compared the fatigue characteristics of the cement–component complex by use of a dynamic tensile testing machine.Results Under dry conditions, the maximum strength of adhesion to the zirconia ceramic plate was the same as that to the Co–Cr alloy plate. Under moistened conditions, however, the strength of adhesion to the zirconia ceramic plate was significantly lower (p = 0.0017) whereas the strength of adhesion to the Co–Cr alloy plate was not reduced. Maximum load for the cement–component complexes for zirconia ceramic and Co–Cr alloy was no different under both dry and moistened conditions. Fatigue testing showed that cement–zirconia adhesion was stronger than cement–Co–Cr alloy adhesion (p = 0.0161).Conclusions The strength of adhesion of cement to zirconia ceramic is substantially weaker under wet conditions than under dry conditions. The mechanical properties of cement–zirconia ceramic component complexes and cement–Co–Cr alloy component complexes are equivalent.

The effect of using fly ash on the strength and hydration characteristics of blended cements

The present study is aimed at investigating the combined effects of the compressive strength and hydration development of blended cements which contain fly ash. In the first stage, chemical, physical, X-Ray diffraction (XRD) and Fourier transforms infrared spectroscopy (FT-IR) analysis were performed in order to determine the characteristics of Portland cement and fly ash. In the second stage, the compressive strength of cement mortars and setting time, water demand and volume expansion of cement pastes were identified according to the standard cement experiments. In the last stage, XRD, FT-IR, thermal and scanning electron microscope analyses were performed in order to determine the hydration of cement pastes. Consequently, the addition of FA in Portland cement contributes to the consumption of Ca(OH)2 which is formed during the hydration of cement and leads to the formation of cementitious products, like C–S–H. Therefore, the compressive strength of fly ash blended cement mortars increased at later ages compared to the early ages.

Study on the Calcinations of Recycled Cement Clinker Using Waste Concrete and Waste Clay Brick

Utilizing construction waste, mainly waste concrete, to produce recycled cement, provides possibility for realizing the closed circulation between concrete and cement, which is an effective way for sustainable development of cement and concrete industry. Waste clay brick (WCB) and its surface-coated waste mortar are inevitably introduced into the raw meals while waste concrete is used in cement production. So on the basis of the composition characteristics of construction waste, considering of optimizing the performance of recycled cement and improving the adaptability of recycled cement to complex raw material, it's necessary to study the effect of raw meal mixing waste concrete and WCB on sintering process and property of recycled cement clinker. Mixing waste concrete and WCB in three different proportions, the burnability of raw meal, clinker mineral composition, clinker mineral morphology and hydration characteristics of recycled cement have been studied in this paper. The results indicate, the presence of WCB is beneficial for the generation and development of silicate minerals; with increasing proportion of WCB, the content of f-CaO in recycled cement clinker rises, the structure of C-S-H gel from hydration product presents higher densification and the compression strength of 3d and 28d curing period are enhanced.

Utilization of Circulating Fluidized Bed Combustion (CFBC) Fly Ash and Coal-Fired Fly Ash in Portland Cement

Circulating fluidized bed combustion (CFBC) fly ash is a promising admixture for construction and building materials due to its pozzolanic activity and self-cementitious property. In this study, CFBC fly ash and coal-fired fly ash were used in Portland cement to investigate the pozzolanic and cementitious characteristics of CFBC fly ash and the properties of cement-based composites. Tests show that CFBC fly ash has the potential instead of cementing materials and as an alternative of pozzolan. In fresh specimens, the initial setting time of mortars increases with the increasing amount of cement replacement by CFBC fly ash and coal-fire fly ash. In harden specimens, adding CFBC fly ash to replace OPC reduces the compressive strength. Meanwhile, CFBC fly ash would results in a higher length change when adding over 30%. Based on the results, the amount of CFBC fly ash replacement cement was recommended to be limited below 20%.

Hydration characteristics of slag-blended cement at different temperatures

The compressive strength of mortar, pore structure, hydration heat, and non-evaporable water content of slag-blended cement used to prepare self-consolidating concrete were investigated. The blended cement pastes were cured at different temperatures to simulate the condition of real concrete structure. The blended cement containing 30% of slag possesses almost same characteristics as pure Portland cement. Incorporation of 70% of slag shows much lower properties than them. The dosage of slag in blended cement should be controlled in a reasonable range. Elevated temperature activates the hydration of binders but shortens the hydration continuing time, which results in a coarse paste microstructure and a low final strength.

Performance Studies on Cement Stabilized Gravelly Soil Exposed to Sulfate Environment

Soil is being used as construction material worldwide since decades for construction of flexible pavements, embankments and brick making. Many methods have been tried for improving the characteristics of soil to make it suitable for intended purpose. Stabilization of soils in order to improve strength and durability properties often relies on additives such as cement, lime, fly ash, and asphalt emulsion. These materials are low-priced, relatively easy to apply and provide benefits to different soils. In the present study, comprehensive laboratory work is carried out on the durability characteristics of cement stabilized gravelly soils exposed to three sodium sulfate solutions with sulfate concentrations of 1, 3 and 5 %, with exposure periods up to 6 months. Two types of soils, namely clayey gravel (GC) and silty gravel (GM) are stabilized with varying cement content ranging from 4 to 14 % by dry weight of the soil in increments of 2 %. As per the results, the compressive strength gain of CSGM cubes with age continued with addition of cement whereas compressive strength gain of CSGC cubes with age increased with increase in cement content up to 6 % and thereafter decreased.

Comparing PMMA and calcium sulfate as carriers for the local delivery of antibiotics to infected surgical sites.

Antibiotic-loaded bone cement is a primary option for treatment of orthopedic infections. Poly(methyl methacrylate) (PMMA) is a widely used cement that, when loaded with antibiotics in spacer or bead form, has been shown to reduce infection rates. However, PMMA is not resorbable and requires a second surgery for removal, while also acting as a potential foreign body for bacterial colonization. Alternatively, resorbable bone cements, such as calcium sulfate, have been proposed and present the advantage of being completely reabsorbed. It is unknown whether the antibiotic elution characteristics of absorbable bone cements are similar to PMMA. This study (1) characterized antibiotic elution from synthetic, highly purified calcium sulfate cement beads of varying sizes against pathogenic bacteria both in liquid culture and seeded on agar plates, (2) tested calcium sulfate beads against PMMA beads loaded with the same antibiotics, and (3) analyzed the structural differences between how PMMA and calcium sulfate bind to antibiotics. In every assay, the calcium sulfate beads performed as well as, or better than, the PMMA beads in inhibition of bacterial growth and elution of vancomycin in vitro with complete elution observed from calcium sulfate within three days. These data suggest that calcium sulfate, functions, as well as PMMA in the patient setting for infection control.

Nanoindentation Characteristics of Cement with Metakaolin Under Different Curing Systems

Nanoindentation Characteristics of Cement with Metakaolin Under Different Curing Systems

Shrinkage Characteristics of Alkali-Activated Slag Cements

AbstractRecent interest in creating green construction materials has sparked the development of portland cement–free binders. Alkali-activated slag (AAS) concrete has a low embodied energy and comparable or superior strengths to ordinary portland cement (OPC) concrete. However, one factor limiting AAS usage is its durability performance, specifically its susceptibility to shrinkage. Before declaring AAS a marketable product, the mechanisms behind its volumetric instability need to be understood. This paper presents a preliminary study of the shrinkage deformations of various AAS mixtures, wherein four unique AAS mortars were designed and tested for autogenous, chemical, and drying shrinkage; time of setting; and compressive strength. All results were compared to those obtained for a control OPC mortar. Alkali-activated slag mixtures with comparable strength to OPC show a higher autogenous and drying shrinkage. A lower elastic stiffness, higher degree of saturation, and potentially higher chemical shrinkag...

Characteristics of CFBC fly ash and properties of cement-based composites with CFBC fly ash and coal-fired fly ash

The aim of this study is to investigate the pozzolanic and cementitious characteristics of circulating fluidized bed combustion (CFBC) fly ash and the properties of cement-based composites with various combinations of CFBC fly ash and coal-fired fly ash. Setting time test, compressive strength test and length change test were performed to measure fresh and hardened properties. Test results showed that the CFBC fly ash cannot meet the chemical and physical requirements in ASTM C821-09 (Standard specification for lime for use with pozzolans), but is consistent with the requirements of ASTM C593-11 (Specification for fly ash and other pozzolans for use with lime for soil stabilization). It indicates that CFBC fly ash has the potential instead of cementing materials and as an alternative of pozzolan. The initial setting time increases with an increasing amount of cement replacement by CFBC fly ash and coal-fire fly ash. The lower compressive strength has been obtained in mortar with various combinations of coal-fired fly ash and CFBC fly ash than the comparable ordinary Portland cement (OPC) mortar. Coal-fired fly ash can be effectively used in reducing the length change. However, CFBC fly ash would results in a higher length change when adding over 30%. Thus, the amount of CFBC fly ash replacement cement was recommended to be limited below 20%.

Characterization of a Limestone Powder Residue for Recycling as a Concrete Block Incorporation

The mining and processing of limestone in the state of Rio de Janeiro, southeast of Brazil, generates a considerable amount of small particles, like a powder ,which is commercialized as a by product. In principle, this inert limestone powder could be recycled as part of another civil construction material. Thus, the objective of this work was to characterize a limestone powder by its physical properties, chemical analysis and microstructural aspects. The results were compared with the characteristics of a common cement and a conventional sand to be possibly applied in the fabrication of limestone incorporated concrete blocks. It was found that the limestone powder has physical, chemical and microstructural characteristics satisfactory for concrete blocks incorporation.