Showing papers on "Cement published in 2006"
TL;DR: In this paper, a field trial was conducted using a 40 MPa concrete mixture, incorporating various proportions of glass powder (0, 20, and 30%) as cement replacement, and the results demonstrated that GLP can be incorporated into 40MPa concrete at dosage rates of 20-30% to replace cement without harmful effects.
369 citations
TL;DR: In vivo and in vitro studies show calcium phosphate cement as a promising material for grafting applications and the resorption/replacement by bone capability of the cement remains controversial.
Abstract: Purpose Calcium phosphate cement is a bioactive and biodegradable grafting material in the form of powder and liquid, which when mixed, sets as primarily hydroxyapatite, sometimes mixed with unreacted particles and other phases. This material has been extensively investigated due to its excellent biological properties, potential resorbability, molding capabilities, and easy manipulation. Because the material can potentially be replaced with bone after a period of time, it could retain the short-term biological advantages of hydroxyapatite without the long-term disadvantages. Although little is known about this material in the dental community, in vivo and in vitro studies show calcium phosphate cement as a promising material for grafting applications. In the following article, the authors review the biological and mechanical properties of calcium phosphate cement, as well as its potential use in clinical applications. Materials and methods A Medline search was performed (timeline: 1980 to 2003) using the following keywords: calcium phosphate cement, hydroxyapatite cement, HA cement, and hydroxyapatite. The search was limited to the English language. The patent literature as well as a limited number of master's theses and books were reviewed after using the electronic database search service from a dental school library. Results Calcium phosphate cement appears to have excellent biological properties. At only 2 weeks, spicules of living bone with normal bone marrow and osteocytes can be seen. Excellent moldability is a desired clinical characteristic; however, further research is necessary in order to improve the mechanical properties of the cement. The resorption/replacement by bone capability of the cement remains controversial. Further research is needed to clarify this issue. Due to poor mechanical properties, clinical applications are currently limited to craniofacial applications. Further research is necessary to take advantage of the excellent biological properties of this cement under clinical applications. Conclusion Further research is necessary to understand and improve the behavior of this type of cement under clinical situations.
348 citations
TL;DR: In this paper, the effect of nano-alumina on the elastic modulus and compressive strength of cement composite, cylindrical specimens ( Φ 20 × 40 mm) with different volume fractions of nano alumina at different curing days (3 days, 7 days, 28 days).
332 citations
TL;DR: In this paper, the effect of metakaolin replacement of cement on the durability of concrete to sulfate attack was investigated by measuring expansion of concrete prisms, compressive strength reduction, and visual inspection of concrete specimens to cracks.
302 citations
TL;DR: It is concluded that alkali-activated cements are better matrix for solidification/stabilization of hazardous and radioactive wastes than Portland cement.
296 citations
TL;DR: In this paper, the effects of decalcification under saturated conditions on the dimensional stability of cement paste were investigated, and it was found that the decalcation shrinkage is due initially to these structural changes in C3S-H at Ca/Si ´1.2 and eventually to the decomposition of C−S−H into silica gel.
281 citations
25 May 2006-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, a liquid-form of nanosilica particle with a spherical diameter of about 20 nm was incorporated into the Portland cement paste at five different dosages and analyzed at four different ages to identify the nanosizing effects on the microstructures and material properties of composite cement paste.
Abstract: Both the filling effect and the pozzolanic reaction make siliceous materials as one of major ingredients of high-performance Portland cement-based composites. Hence, the introduction of nanosilica with finer particle size and larger silicon dioxide to the composite becomes a great deal of interest in recent years. In this study, a liquid-form of nanosilica particle with a spherical diameter of about 20 nm was incorporated into the Portland cement paste at five different dosages and analyzed at four different ages to identify the nanosizing effects on the microstructures and material properties of composite cement paste. Experimental results show that the Portland cement composite with 0.60% of added nanosilica by weight of cement has an optimum compressive strength, in which the increase of compressive strength is about 43.8%. Moreover, the corresponding nanosilica paste of one portion of water mixed with nanosilica of 1.08 wt.% of water has the maximum absolute value of zeta potential of 41.3 mV. Properties through the analyses of NMR, BET and MIP also indicate that the microstructure of Portland cement composite with nanosilica evidently has a more solid, dense and stable bonding framework.
275 citations
TL;DR: The treatment of hazardous wastes using cement-based solidification-stabilization (S-S) is of increasing importance as an option for remediating contaminated sites as discussed by the authors. But this method is not suitable for all applications.
Abstract: The treatment of hazardous wastes using cement-based solidification–stabilization (S–S) is of increasing importance as an option for remediating contaminated sites. Indeed, among the various treatm...
271 citations
TL;DR: In this article, a systematic study of slag concrete behavior under severe test conditions was performed to evaluate the internal expansivity of the slag, its chemical reactivity with some components of the cement and its resistance to environmental agents, ice and moisture.
Abstract: Electric arc furnace (EAF) slag, a by-product of steelmaking recovered after the oxidizing process, is useful when employed as aggregate in hydraulic concrete and bituminous mixtures. Concrete made with EAF oxidizing slag as an aggregate shows good physical and mechanical properties and further study of its durability will ensure greater reliability in its usage. This paper details a systematic study of slag concrete behaviour under severe test conditions. The tests were designed to evaluate the internal expansivity of the slag, its chemical reactivity with some components of the cement and its resistance to environmental agents, ice and moisture. The results indicate that the durability of slag concrete is acceptable, though slightly lower than that of conventional concrete. When the mix proportions are adequate, both the mechanical strength and the durability of slag concrete are satisfactory, although in less care mixes durability is likely to be impaired. Finally, leaching tests were performed to determine the environmental impact of the concrete, which, in comparison to results obtained directly from the slag, confirmed an important cloistering effect of the cementitious matrix on contaminant elements.
267 citations
TL;DR: In this article, a multi-method approach was used for the investigation and comparison of alkali-activated slag binders (AAS), pure slag and ordinary Portland cement (OPC).
Abstract: A multi-method approach was used for the investigation and comparison of alkali-activated slag binders (AAS), pure slag and ordinary Portland cement (OPC). X-ray fluorescence, X-ray powder diffraction, granulometry, calorimetry, thermo-gravimetric analysis and environmental scanning electron microscope investigations of the microstructure with energy dispersive X-ray analyses were used to characterise the cements and their hydrate phases. In addition, the chemical composition of the pore solution, including the different sulphur-containing ions, was analysed. The precipitation mechanisms during binder hydration in the AAS and OPC systems exhibit significant differences: in AAS the formation of the ‘outer product’ C-S-H is much faster than in OPC. The high Si concentrations in the pore solution during the early hydration of AAS are related to the fast dissolution of Na-metasilicate. The fast reaction of Na is an important factor for the voluminous precipitation of C-S-H within the interstitial space alread...
262 citations
TL;DR: In this paper, a linear relationship between the fractional change in resistivity and compressive strain was observed for cement-based composites containing a large amount of carbon black (CB), suggesting that this kind of composite was a promising candidate for strain sensors used in concrete structures.
Abstract: This paper investigates the strain sensing properties of carbon black (CB)-filled cement-based composites which were prepared with 120 nm CB. A linear relationship between the fractional change in resistivity and compressive strain was observed for cement-based composites containing a large amount of CB, suggesting that this kind of composite was a promising candidate for strain sensors used in concrete structures. Tunneling effect theory and percolation theory are employed to interpret the conductivity and electromechanical properties of CB-filled cement-based composites.
TL;DR: Formations of calcite along with precipitate formation of calcium arsenite were found to be responsible for low leaching of arsenic from the stabilized/solidified samples.
TL;DR: The influence of using GGBFS in reinforced concrete structures from the durability aspects such as chloride ingress and corrosion resistance, long term durability, microstructure and porosity of GGB FS concrete has been reviewed and discussed.
TL;DR: In this article, the authors present some of the results of an investigation on the possible application of RCA in asphalt concrete and find that all the volumetric properties (except the percentage of air voids), resilient modulus and creep values of asphalt specimens containing RCA as coarse aggregates were relatively lower compared with the values found for similar specimens made with only fresh aggregates.
Abstract: Recycled concrete aggregates (RCA) are produced by crushing demolished concrete elements. RCA differ from fresh aggregates due to the cement paste attached to the surface of the original natural aggregates after the process of recycling. This highly porous cement paste and other contaminations contribute to the lower particle density and higher porosity, variation in the quality of the RCA and the higher water absorption. This paper presents some of the results of an investigation on the possible application of RCA in asphalt concrete. It was found that all the volumetric properties (except the percentage of air voids), resilient modulus and creep values of asphalt specimens containing RCA as coarse aggregates were relatively lower compared with the values found for similar specimens made with only fresh aggregates. Some of these measured properties were within the acceptable recommended limits, for the RCA sample used in this study.
TL;DR: In this article, the interaction of municipal solid waste incinerator bottom ash (MSWI bottom ash), when utilized as an aggregate in concrete, with the cement matrix was investigated, and the most prominent reaction observed in lab and field concrete was the formation of aluminium hydroxide and the release of hydrogen gas from aluminium grains reacting in the alkaline environment.
TL;DR: A strong relationship was found between the uniformity of the filling pattern and the elapsed time from cement mixing and viscosity, respectively, and high-viscosity cement seems to stabilize cement flow.
Abstract: STUDY DESIGN Experimental study using a laboratory leakage model. OBJECTIVE To examine the working hypothesis that high-viscosity cements will spread uniformly, thus significantly reducing the risk of leakage. SUMMARY OF BACKGROUND DATA In vertebroplasty, forces that govern the flow of bone cement in the trabecular bone skeleton are an essential determinant of the uniformity of cement filling. Extraosseous cement leakage has been reported to be a major complication of this procedure. Leakage occurs due to the presence of a path of least resistance caused by irregularities in the trabecular bone or shell structure. Ideally, cement uniformly infiltrates the trabecular bone skeleton and does not favor specific paths. Cement viscosity is believed to affect the infiltration forces and flow during the procedure. Clinically, altering the time between cement mixing and delivery modifies the viscosity of bone cement. METHODS An experimental model of the leakage phenomenon of vertebroplasty was developed. A path, simulating a blood vessel, was created in the model to perturb the forces underlying cement flow and to favor leakage. Cement of varying viscosities was injected in the model, and, thereafter, the filling pattern, cement mass that has leaked, time at which leakage occurred, and injection pressure were measured. RESULTS A strong relationship was found between the uniformity of the filling pattern and the elapsed time from cement mixing and viscosity, respectively. Specifically, 3 distinct cement leakage patterns were observed: immediate leakage was observed when cement was injected 5-7 minutes following mixing. The cement was of a low viscosity and more than 50% of the total cement injected leaked. Moderate leakage was observed when injection occurred 7-10 minutes following mixing. Less than 10% of the cement leaked, and the viscosity was at a transient state between the low viscosity of immediate leakage and a higher viscosity, doughy cement. Cement leakage ceased completely when cement was delivered after 10 minutes. The viscosity of the cement in this case was high, and the cement was of a dough-like consistency. CONCLUSIONS High-viscosity cement seems to stabilize cement flow. However, the forces required for the delivery of high-viscosity cement may approach or exceed the human physical limit of injection forces. Although the working time of the cement is about 17 minutes, it may not be manually injectable with a standard syringe and cannula after 10 minutes, at which time cement leakage ceased completely.
TL;DR: In this paper, the CEMHYD3D computer model was extended and preliminarily validated for the incorporation of limestone at substitution levels up to 20% by mass fraction, and the influence of limestone substitutions on hydration rates was observed to be a strong function of water-to-solids ratio (w/s).
Abstract: The ASTM C150 standard specification for Portland cement now permits the cement to contain up to 5% of ground limestone. While these and much higher levels of limestone filler substitution have been employed in Europe and elsewhere for many years, changing the ASTM standard has been a slow process. Having computational tools to assist in better understanding the influence of limestone additions on cement hydration and microstructure development should facilitate the acceptance of these more economical and ecological materials. With this in mind, the CEMHYD3D computer model for cement hydration has been extended and preliminarily validated for the incorporation of limestone at substitution levels up to 20% by mass fraction. The hydration model has been modified to incorporate both the influence of limestone as a fine filler, providing additional surfaces for the nucleation and growth of hydration products, and its relatively slow reaction with the hydrating cement to form a monocarboaluminate (AFmc) phase, similar to the AFm phase formed in ordinary Portland cement. Because a 20% limestone substitution substantially modifies the effective water-to-cement ratio of the blended mixtures, the influence of limestone substitutions on hydration rates is observed to be a strong function of water-to-solids ratio (w/s), with significant acceleration observed for lower (e.g., 0.35) w/s, while no discernible acceleration is observed for pastes with w/s = 0.435. Published by Elsevier Ltd.
TL;DR: In this article, the authors examined the compressibility and strength characteristics of high water content cement-admixed clay in deep mixing applications and found that both cement content and total clay water content of the clay-water-cement mixture significantly affect the strength and compressibility of the resulting stabilized clay.
Abstract: This paper examines the compressibility and strength characteristics of high water content cement-admixed clay in deep mixing applications. During curing time, both cement content and total clay water content of the clay–water–cement mixture significantly affect the strength and compressibility of the resulting stabilized clay. To ensure optimum improvement, the selection of an appropriate total clay water content for a mixture with a certain cement content is crucial. Furthermore, the fundamental parameters such as the ratio of after-curing void ratio ( eot ) and cement content ( Aw ) have been found sufficient to characterize the strength and compressibility of cement-admixed clay. The results of unconfined compression and consolidated–undrained tests have proven that the ratio eot ∕ Aw combines together the influences of clay water content, cement content, and curing time as well as curing pressure on the strength of cement-admixed clay. In addition, useful empirical relationships on deep mixing applic...
TL;DR: In this article, the effect of the cement retarders tartaric acid, sucrose, and lignosulfonate with tricalcium silicate (C3S) and ettringite formation was studied by 27Al and 29Si MAS NMR spectroscopy.
Abstract: The reaction of the cement retarders tartaric acid, sucrose, and lignosulfonate with tricalcium silicate (C3S), tricalcium aluminate (C3A), and C3A/gypsum have been studied by 27Al and 29Si MAS NMR spectroscopy, SEM, XRD, and XPS to gain an understanding of the effect on the individual minerals prior to studying a typical sample of portland cement. Tartaric acid is the most effective at retarding C3A hydration and ettringite formation, while sucrose and the lignosulfonate accelerate ettringite formation but are more effective at retarding C3S hydration. We have confirmed that sucrose acts via nucleation poisoning/surface adsorption while lignosulfonates involve the formation of a semipermeable layer on the cement grains. The formation of calcium tartrate is clearly the most important step in tartaric acid inhibition; however, tartaric acid only exhibits a dissolution−precipitation mechanism for C3A. Under conditions of excess calcium, the formation of a calcium tartrate overlayer does not require the pred...
TL;DR: In this paper, the authors developed a simple spatial model to describe the hydration kinetics of portland cement and compared it to existing experimental data, particularly in terms of the influence of the starting water-to-cement ratio (w/c) on hydration rates.
TL;DR: Results provide encouragement for the idea that CS A cement can provide a possible alternative to PC in the immobilisation of difficult and reactive wastes, although further investigation is needed.
TL;DR: Results are very encouraging for the reuse of such TFA in cement-based materials because they can be considered as pozzolanic additions and could advantageously replace a part of the cement in cement -based materials.
TL;DR: In this paper, a broad experimental study has been performed, from the end of mixing up to 2 years, on a set of plain cement pastes prepared with the same type I ordinary portland cement (OPC) and various water-to-cement ratios (W/C), and cured at various constant temperatures.
TL;DR: In this article, four stabilizers have been used: cement, lime, cement plus lime and cement plus resin and then evaluated by various laboratory tests as well as in real climatic conditions.
TL;DR: In this article, the effect of cooling rate on mineralogy and cementing characteristics of normal BOF slags as well as iron oxide-devoid slag was investigated. But, it was found that the slowly cooled slags did not show any cementing properties.
TL;DR: In this paper, the effect of copper slag (CS) and cement by-pass dust (CBPD) addition on concrete properties was studied, and two different trial mixtures were prepared using different proportions of CS and CBPD.
TL;DR: In this article, the authors evaluated the effect of OMMT micro-particles on the improvements of strengths and permeability of cement mortars and found that the optimal dosage gave higher compressive and flexural strength and a lower coefficient of permeability.
TL;DR: The porosimetric behavior of calcium sulfoaluminate-based cement is related to its very fast hydration rate and to the lack of water needed to continue the hydration reactions as discussed by the authors.
TL;DR: The results showed that the matrixes with heavy metals-bearing sludge and MSWI fly ash have a strong fixing capacity for heavy metals: Zn, Pb, Cu, Ni and Mn.
TL;DR: In this article, wood waste ash (WWA) of pretreated timber of 0, 5, 10, 15, 20, 25, and 30% by weight of cement was added as a supplement to a concrete of mix proportion 1:2:4:0.56 (cement:sand:coarse aggregate:water cement ratio), and the strengths and the water absorption of the matrix were evaluated.
Abstract: The enormous amount of wastes produced during wood processing operations in many countries provides challenging opportunities for the use of wood waste as a construction material. In this research, wood waste (sawdust and wood shaving) ash (WWA) of pretreated timber of 0, 5, 10, 15, 20, 25, and 30% by weight of cement was added as a supplement to a concrete of mix proportion 1:2:4:0.56 (cement:sand:coarse aggregate:water cement ratio), and the strengths and the water absorption of the matrix were evaluated. Also, the metal leachability of WWA was analyzed. The compressive and the flexural strengths of WWA concrete for the ages investigated ranged from 12.83 to 28.66 N∕ mm2 , and 3.65 to 5.57 N∕ mm2 , respectively, with the lowest values obtained at 30% additive level of ash. When compared with the strength of plain concrete (control), the compressive and flexural strengths of WWA concrete were between 62 and 91% and 65 and 98%, respectively, of the former. The trend of the water absorption of WWA concrete...