Application Of Cement Research Articles

Potential application of Portland cement-calcium sulfoaluminate cement blends to avoid early age frost damage

This paper aims to investigate mechanical strength and hydration behavior of Portland cement (PC) and calcium sulfoaluminate (CSA) cement mixtures when exposed to different temperatures from −5 °C to 20 °C. Setting time and compressive strength were evaluated for mixtures with different PC-CSA ratios. The exothermic hydration heat flow, hydration products, pore size distribution and microstructure for typical samples were determined by using isothermal calorimetry measurement, TG/DTG, XRD, MIP and SEM facilities. The results indicate that the setting time of PC-CSA blends decreases with the higher dosage of CSA cement. Compressive strength of cement mortar is increased by the higher incorporation of CSA cement (5–10%) at early ages, but it is decreased by CSA cement at late ages. This negative effect on late age strength is alleviated by the lower curing temperature. The compressive strength degradation of Portland cement induced by early age exposure to −5 °C is improved by the addition of 5–10% CSA cement. Moreover, the negative effect can be avoided by the incorporation of 20% CSA cement due to the achievement of critical strength after 6 h pre-curing. The hydration of CSA cement during the first several hours is accelerated by the existence of PC and this is favorable for improve the resistance to early age frost. The pore structure and porosity of cement paste under room temperature is aggravated when the incorporation of CSA is higher than 5% due to the fast formation of massive AFt crystals. But the pore structure and microstructure is improved after exposure to early age frost due to the higher resistance to frost damage. Therefore, the incorporation of suitable content CSA provides a potential method for avoiding early age frost damage for cement concretes under minus temperatures.

Preparation of cellulose nanofibers by TEMPO-oxidation of bleached chemi-thermomechanical pulp for cement applications

Hardwood bleached chemi-thermomechanical pulp (BCTMP) was converted to cellulose nanofibers by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) catalyzed oxidization along with mechanical defibrillation process. The TEMPO reaction was evaluated based on the delignification, carboxylate content of cellulose and the yield of the insoluble component. Cellulose nanofibers were characterized by conductometry, Fourier transform infrared spectroscopy (FT-IR), scanning electronic microscopy (SEM), thermogravimetric analysis (TGA) as well as X-ray diffraction (XRD) techniques. Minimum 10 mmol/g NaClO addition was needed to obtain meaningful carboxylate content and easy defibrillation by using high shear mixing. TEMPO-catalyzed oxidization process removed 74% of pentosans and 80% of lignin from bleached chemi-thermomechanical hardwood pulp while 13% of cellulose was also lost. CNF with 1.44 mmol/g carboxylate content resulted high level of water retention (13.4 g/g fiber) Cellulose nanofibers were used in cementitious mixtures. CNF with carboxyl groups resulted in better flow control in wet cement paste and reduced the crack growth in concrete.

Influence of the conditioning technique of a lithium disilicate vitroceramic

Introduction: Lithium disilicate reinforced glass ceramics are materials that require good adhesion to ensure clinical success. Objective: To evaluate the bond strength of resin cements to lithium-disilicateenhanced vitroceramics using different cleaning techniques of recently conditioned ceramics. Material and methods: Twelve ceramic discs (IPS Empress II) were made and inserted into PVC pipes using acrylic resin. The ceramic surface was designed and submitted to a 10% hydrofluoric acid conditioning process for 20s. Then, the specimenswere divided into 3 groups (n = 16) according to the cleaning techniques of recently conditioned ceramics: 1) control - conventional technique (no cleaning after the conditioning process); 2) application of 37% phosphoric acid for 20s; 3) 90% ethyl alcohol bath in a ultrasound tub for 4 min. After cleaning, the silane agent was applied for 1 minute and silicon matrices (1 mm in diameter x 1 mm in height) were made for further application of the resin cement (Vitique, DMG), which was handled according to the manufacturer’s instructions. Four cylinders were prepared on each ceramic surface. The specimens were storedin distilled water for 48 hours and subjected to the micro-shear test in a universal testing machine. After the micro-shear test, a failure analysis of the specimens was performed. Data were submitted to ANOVA (analysis of variance for a criterion) with a significance level of 5%. Results: There was no significant difference between groups (p > 0.05). Conclusion: the cleaning technique of the recently conditioned ceramics does not interfere with the resin/cement bond strength values

Hydration mechanism of a calcium phosphate cement modified with phytic acid

Calcium phosphate cements composed of β-tricalcium phosphate (β-TCP) and phosphoric acid were modified by addition of 5, 10, 12.5, 15 and 20 wt% phytic acid (IP6) related to the β-TCP content and compared to a reference containing 0.5 M citric acid monohydrate solution as setting regulator. The hydration reaction of these cements was investigated by isothermal calorimetry and in-situ X-ray diffraction at 23 °C and 37 °C. The cements were further characterized with respect to their injectability, rheology, zeta potential and time-resolved compressive strength development.Injectability was strongly improved by IP6 addition, while the maximum effect was already reached by the addition of 5 wt% IP6. This could be clearly related to an increase of the negative zeta potential leading to a mutual repulsion of cement particles. A further increase of the IP6 content had a detrimental effect on initial paste viscosity and shifted the gelation point to earlier time points. IP6 was further proven to act as a retarder for the cement setting reaction, whereas the effect was stronger for higher IP6 concentrations. Additionally, IP6 favoured the formation of monetite instead of brushite and a better mechanical performance compared to the IP6 free reference cement. Statement of SignificanceCalcium phosphate cements (CPCs) are clinically applied for bone repair due to their excellent biocompatibility and bone regeneration capacity. A deep understanding of the setting mechanism is the prerequisite for the targeted fabrication and application of such bone cements, whereas setting characteristics are usually adjusted by additives. Here, novel injectable CPC formulations were developed by modifying a cement composed of β-tricalcium phosphate and phosphoric acid with phytic acid (IP6). A detailed investigation of the setting mechanism of the IP6 modified CPCs is provided, which demonstrated the effectiveness of IP6 as setting regulator to adjust the reaction time and kind of setting product. Additionally, the high surface charge of cement particles after IP6 addition was effective in dispersing cement particles leading to low viscous cement pastes, which can be directly applied through a syringe for minimal invasive surgery.

Application of a direct pulp capping cement containing S-PRG filler.

To evaluate new pulp capping cements containing surface pre-reacted glass ionomer (S-PRG) filler and to investigate ion release kinetics and pH shift of eluates from the cement. Molars of Wistar rats were directly pulp capped using three kinds of cement containing S-PRG filler and mineral tri-oxide aggregate (MTA) was used as a control. After 1, 2, or 4weeks, histological evaluation was performed and differences of tertiary dentin formation were analyzed. Release of Sr2+, BO33-, SiO32-, Na+, and Al3+ ions was determined by inductively coupled plasma-atomic emission spectrometry, and F- ion release was measured using a fluoride ion selective electrode. The pH of the eluate from each cement after mixing was measured with a pH electrode. One of S-PRG cements promoted tertiary dentin formation to the same extent as the control (p > 0.05) and it showed a tendency of less inflammatory response. This cement released more BO33- and SiO32-, but less Sr2+, Na+, and F- than other S-PRG specimens. Each cement recovered nearly neutral compared with glass ionomer cement. S-PRG cement induced tertiary dentin formation based on multiple ion releases, suggesting that it is suitable as a pulp capping material. This new material can be an alternative pulp capping agent to MTA.

Tuning of emission color in the germanate luminescent materials for cement application

Nowadays, tunable luminescence that can be only pumped upon excitation at an invisible single ultraviolet (UV) wavelength has attracted great attentions in the lighting fields. Unlike most of previous works which focus mainly on the application of luminescent phosphor materials for phosphor converted white light-emitting diodes (pc-wLEDs), a new type of germanate phosphor luminescent material, which can emit a broadly tunable spectral range and show the promising for cement application, has been reported in this work. As for the structure purity of the as-obtained germanate phosphor materials, we, based on the XRD results, reveal that they belong to a trigonal structure with the space group of R3 (No. 146). The luminescent centers, i.e., the +3 europium and +3 bismuth ions, which tend to substitute the Lu sites in the germinate crystal host, can emit the blue emission and the red emission upon excitation at 297 nm and 393 nm, respectively. Due the great spectral overlapping between the excitation wavelength of +3 europium and the emission wavelength of +3 bismuth, the energy transfer from +3 bismuth to +3 europium is demonstrated. More remarkable, fixing the doping content of +3 bismuth yet changing the doping content of +3 europium can induce the emission color tuning from blue, white and to red. In order to explain the PL results we achieved, here we also construct a mechanistic pattern based on the energy transfer from +3 bismuth to +3 europium. Our results show that such germanate materials can suggested for cement application.

Design of the composition of alkali activated portland cement using mineral additives of technogenic origin

This paper reports results of the development of cement compositions and production technology for common cement systems cement clinker – mineral additives – alkaline activator – water-reducing admixture, which contain more than 60 % by weight of mineral additives. The additives have been selected from the group: granulated blast furnace slag, ash from thermal power plants (fly ash and disposed ash) and red mud (waste of alumina production). The relevance of the work relates to the need to improve a number of indicators that limit the widespread application of traditional cements, highly filled with waste (slag portland cement), in particular, early strength and setting terms. We have devised basic principles of the structural arrangement of cement compositions, as well as show the technology of their production. It was established that in terms of the requirements based on acting Ukrainian and European standards, in particular EN 197-1, the designed cements are not inferior to the EN cements, CEM I, CEM II, CEM III, in their characteristics, but even outperform them for strength. The developed cement compositions, which contain the portland clinker in the amount not exceeding 40 % by weight, meet the requirements of the EN standard for the classes of compressive strength (at the age of 28 days) 32,5N − 32,5R; 42,5R − 52,5R. We have investigated the influence of alkaline components on the structure formation processes of artificial stone in the alkaline activated cement at different levels. It was established that an increase in the alkalinity of a cement environment predetermines a decrease in the basicity of the phase composition of neo formations of cement at the micro level, as well as contributes to increasing the total porosity of an artificial stone, which, at the same time, tends to closing and decreases over time.

3D FE analysis of the behavior of elliptical cracks on orthopedic cement of the total hip prosthesis

An explicit analysis conducted on the crack behavior in chirurgical cement (Polymethylme- thacrylate – PMMA) used for Total Hip Prosthesis (THP) is of great importance in collecting information about the nature of the phenomenon of loosening of the cement application. The rupture of the orthopedic cement is practically the main cause of this loosening. Understan- ding different rupture mechanisms give a great value in advancing the durability of the cemented total prosthesis. The purpose of this study is to analyse cracks behavior, initiated in the cement that links the femoral-stem with the bone, using the Finite Element Analysis Method (FEM). The present study brings into focus the variation of the stress intensity factor in modes I, II and III. This rupture criterion is used according to the nature of crack, its orientation and its location in the orthopedic cement. At first, the level and distribution of the equivalent von Mises stress is analysed, which is induced in the medial, proximal and distal parts of the bone cement. Then, the behavior of different geometric forms of an elliptical crack is evaluated which are located and initiated within the body of these three parts.

Use of clay-based construction and demolition waste as additions in the design of new low and very low heat of hydration cements

In light of the large amounts of cement used in plain concrete and given the exothermal reactions involved in its hydration, the control and assessment of heat of hydration are instrumental to prevent future shortcomings in structural durability. This article describes the design of new eco-efficient cements containing different percentages of fired clay-based construction and demolition waste (CC&DW). The new cements (CCDWC) were characterised for pozzolanicity and their heat of hydration was assessed based on a semi-adiabatic method described in European standards. The inclusion of CC&DW retarded the heating of mortar and lowered its maximum temperatures, more significantly with the increase of replacement ratios. The design of such CC&DW-bearing low and very low heat of hydration cements may well prompt the introduction of new applications of bulk cement or cement-high mixes, in which heat may have adverse effects on durability.

Utilization of converter steel slag by remelting and reducing treatment

In China, as by-products of iron and steel industry, the utilization rate of steel slag is still relatively low and its open-air stacking occupies a lot of land, where there is a quite different situation of blast furnace slag as supplementary cementitious material in concrete. Considerable amount of metallic iron and iron oxide are lost within slag. In addition, undesirable volume change occurs when slag used as admixture in construction due to high free-CaO content, limiting its application in cement and concrete industry. In this study, remelting and reducing treatment was conducted to recycle iron and modify the chemical composition of the residue. Results showed that iron oxide could be reduced to iron and adjusting materials were found to promote reduction of iron oxide and stability of slag and separation of iron and slag.

Influence of the conditioning technique of a lithium disilicate vitroceramic

Lithium disilicate reinforced glass ceramics are materials that require good adhesion to ensure clinical success. Objective: To evaluate the bond strength of resin cements to lithium-disilicateenhanced vitroceramics using different cleaning techniques of recently conditioned ceramics. Material and methods: Twelve ceramic discs (IPS Empress II) were made and inserted into PVC pipes using acrylic resin. The ceramic surface was designed and submitted to a 10% hydrofluoric acid conditioning process for 20s. Then, the specimens were divided into 3 groups (n = 16) according to the cleaning techniques of recently conditioned ceramics: 1) control - conventional technique (no cleaning after the conditioning process); 2) application of 37% phosphoric acid for 20s; 3) 90% ethyl alcohol bath in a ultrasound tub for 4 min. After cleaning, the silane agent was applied for 1 minute and silicon matrices (1 mm in diameter x 1 mm in height) were made for further application of the resin cement (Vitique, DMG), which was handled according to the manufacturer’s instructions. Four cylinders were prepared on each ceramic surface. The specimens were stored in distilled water for 48 hours and subjected to the micro-shear test in a universal testing machine. After the micro-shear test, a failure analysis of the specimens was performed. Data were submitted to ANOVA (analysis of variance for a criterion) with a significance level of 5%. Results: There was no significant difference between groups (p > 0.05). Conclusion: the cleaning technique of the recently conditioned ceramics does not interfere with the resin/cement bond strength values.

Study on application of cement substituting mineral fillers in asphalt mixture

Abstract In order to investigate the potential of cement fillers applying in asphalt pavement instead of mineral fillers, this research did a comprehensive study, including the raw materials properties tests, mix design, and verification of mixture performance. Results show that in terms of the physical and volumetric properties, the cement fillers are similar with mineral fillers. The mix design process of asphalt mixture containing cement fillers can refer to the common asphalt mixture. The optimum asphalt/aggregate ratio was 5.0% for the materials and gradation selected in this research. The residual stability of immersion Marshall stability test was 78.9%, and the TSR of freeze–thaw splitting test was 74.4%. Both of them meet the specification requirements. The dynamic stability was 1169 time/mm, the seepage coefficient was 63.4 ml/min. These larger data than the required values demonstrated the good functional performance of asphalt mixture containing cement fillers, including the rutting resistance and the anti-permeable ability.

Cement-augmented sacroiliac screw fixation with cannulated versus perforated screws – A biomechanical study in an osteoporotic hemipelvis model

IntroductionCement-augmentation is a well-established way to improve the stability of sacroiliac screw fixation in osteoporosis-associated fragility fractures of the posterior pelvic ring. However, to date little is known about the influence of different techniques of cement augmentation on construct stability. The aim of this study was to evaluate the primary stability of cement-augmented sacroiliac screw fixation with cannulated versus perforated screws under cyclic loading. Materials and MethodsA total of eight fresh-frozen human cadaveric hemipelvis specimens with osteoporosis were used. After generating ventral osteotomies on both sides of the sacrum, each specimen was treated using a cement-augmented cannulated screw on one side and a cement-augmented perforated screw on the other side. Afterwards, axial cyclic loading was performed. ResultsNo statistically significant difference was found between cannulated and perforated screws concerning maximum load (356.25 N versus 368.75 N, p = 0.749), plastic deformation (1.95 mm versus 1.43 mm, p = 0.798) and stiffness (27.04 N/mm versus 40.40 N/mm, p = 0.645). ConclusionsConsidering the at least equivalent results for perforated screws, cement augmentation via perforated screws might be an interesting option in clinical practice because of potential advantages, e.g. radiological control before cement application, reduced risk of cement displacement and time saving.

Dilatometric behavior and crystallographic characterization of Portland-polyurethane composites for oilwell high-temperature cementing applications

In order to improve the behavior of Portland-based oilwell sheath to high-temperature applications and the corresponding thermal gradients, polymeric admixtures can be added. Steam injection, for instance, raises the cement sheath-steel casing interface temperature to ∼300 °C which can be deleterious to the mechanical stability and zonal isolation provided by the cement sheath as a result of cracking of the cement. Polyurethane can be added to the cement to improve its plastic behavior and reduce the thermal expansion mismatch between casing and sheath. However, the use polymeric admixtures, especially as aqueous dispersion, can affect the kinetics of the hydration reactions and, as a consequence, the crystallographic composition and coefficient of thermal expansion of the material. Therefore, the present study aimed at evaluating the effects of the addition of different concentrations of polyurethane on the thermomechanical properties of Portland cement pastes cured at 300 °C from 14 to 90 days. Formulations containing 1 gpc (0.052 kg), 2 gpc (0.102 kg) and 3 gpc (0.153 kg) of polyurethane, respectively named PU1, PU2 and PU3 were prepared according to the American Petroleum Institute guidelines. A standard PU-free slurry was also prepared. X-ray diffraction and dry dilatometric tests were carried out. The results revealed that the curing time does affect the kinetics of hydration of Portland-polyurethane composites, retarding the formation of high-temperature stable phases, i.e., tobermorite and xonotlite. Moreover, longer curing times were necessary to reveal the improved expansion of the composites with respect to the standard sample. The addition of polyurethane can be pointed as an approach to high-temperature oilwell cement applications, since it reduces the thermal mismatch between cement sheath and steel casing for and retards but do not prevent the formation of xonotlite.

Re-examination of the β→γ transformation of Ca2SiO4

Dicalcium silicate finds applications in different fields (cement, bio-ceramics, refractories). In the case of Portland cement, its interest is its lower sintering temperature compared to tricalcium silicate and therefore an interesting compound for low CO2 cements. Dicalcium silicate goes through different polymorphic forms, namely α, α'H, α'L, β and γ, as the temperature decreases. In theory, only the γ-phase is stable at room temperature. In a polycrystalline material, the different polymorphs can co-exist depending on several factors (sintering conditions, presence of impurities, grain size) and the interpretations given in the literature are sometimes contradictory. For cement applications, only the α, α' or β polymorphs react with water to give hydrates while γ does not. Therefore, this paper focuses specifically on the effect of grain size on the β to γ transformation. We also propose that the transformation is semi-reconstructive and not martensitic as suggested by some authors.

Penyerapan Air Dan Kelarutan Bahan Semen Ionomer Kaca Sebagai Penutup Pit Dan Fisur Gigi

BACKGROUND: Pit and fissure sealants are materials that are often used for preventive maintenance, especially on occlusal surfaces of teeth that are susceptible to caries. All restoration materials that come into contact with water will experience 2 mechanisms, namely the absorption of water, which causes matrix swelling and increased mass and water solubility, namely the release of components from unreacted monomers and causing reduced mass. OBJECTIVE: Measure the value of water absorption and solubility of glass ionomer cement as a cover of the pit and fissure of the tooth. METHODS: 18 specimens of glass ionomer cement sealant material manipulated according to the manufacturer's instructions consisted of six specimens measuring 15 mm in diameter and 1 mm in thickness made for each immersion time. The specimen was put into a desiccator at 37°C for 22 hours and then put into another desiccator with a temperature of 23°C for 2 hours. The specimen was weighed with a precision scale of 0.1 mg. Measurements are carried out repeatedly until a constant mass is obtained (M1). Next, the specimen was put into 40 ml of aquabides and stored in a desiccator at 37°C for 1 day, 2 days and 7 days. At the end of each immersion time, the specimen was removed from aquabides, dried with suction paper and vibrated in the air for 15 seconds. Specimens are weighed to get M2. The specimens were reconditioned to the desiccator at 37°C for 22 hours and then put into another desiccator with a temperature of 23°C for 2 hours and this procedure was repeated one day later, then the mass was weighed repeatedly until a constant mass was obtained (M3). RESEARCH RESULTS: The Kruskal-Wallis statistical test shows that there is no significant difference in the average water absorption value and solubility of materials for immersion for 1 day, 2 days and 7 days. CONCLUSIONS AND RECOMMENDATIONS: The absorption rate of glass ionomer cement as a cover of dental pit & fissure decreased until the second day and increased until the seventh day, with an average absorption of water for 1 day immersion of 42.68mg/mm³, 2 days 40, 53mg/mm³ and 7 days 42.99mg/mm³. Solubility value in water of glass ionomer cement as a cover of dental pit & fissure decreased until the second day then increased until the seventh day, with an average solubility of material for immersion for 1 day at 41.46mg/mm³, 2 days 39.39mg/mm³ and 7 days 41,91mg/mm³. It was said that there was no significant difference in the value of water absorption and solubility of materials during the immersion period of 1, 2 and 7 days. It is recommended that in the application of glass ionomer cement as a cover of dental pits and fissures, please note in the provision of varnish or protector to reduce the occurrence of water absorption and solubility of the material. In addition, the pit and fissure of the tooth that has been covered should be controlled 3 months later to find out if the cover is still intact or has been damaged or loose. It is also recommended that there is further research to determine the value of water absorption and solubility of ingredients if soaked in artificial saliva for more than 7 days.

Effect of Light-Cured Resin Cement Application on Translucency of Ceramic Veneers and Light Transmission of LED Polymerization Units.

To evaluate the effect of light-cured resin cement application based on etching and silanization on the translucent property of ceramic veneers in different thicknesses, testing the hypothesis that the surface treatment and subsequent resin cement application could influence the translucency of ceramic veneers. The relationship between translucency of ceramic veneers and light transmission irradiated by LED polymerization units was also determined. 40 specimens (10 mm diameter) were fabricated from IPS e.max Press HT A2 ceramic ingots, and polished to 0.3 ± 0.01 mm, 0.5 ± 0.01 mm, 0.7 ± 0.01 mm, 1.0 ± 0.01 mm, and 1.5 ± 0.01 mm thick (n = 8/group). One surface of each disc was etched with HF acid, silanized with Monobond-S, and applied with a light-cured resin cement (Variolink N Transparent Base). Before and after the above procedure, the total luminous transmittance (τ) of all specimens was assessed by a spectrophotometer in a wavelength range of 380-780 nm. A handheld radiometer was used to measure the light intensity irradiated by three LED polymerization units. Light transmission (LT) through ceramic specimens after resin cement application was calculated. Data were statistically analyzed using two-way ANOVA (p = 0.05) and Tukey's test. The correlation between translucency (τ) of ceramic veneers after resin cement application and light transmission (LT) of curing units was statistically evaluated using Spearman correlation test (p = 0.05). With the increase of ceramic thickness, the transmittance decreased significantly (p < 0.05). For the 0.3-mm, 0.5-mm, and 0.7-mm-thick groups, the transmittance of ceramic specimens was statistically significantly lower after resin cement application (p < 0.05). The r value of Bluephase C8 was 0.988, 0.977 for Bluphase, and 0.883 for Bluephase 20i, indicating that the light transmission (LT%) was positively correlated to the translucency of ceramic veneers, regardless of the type of curing units. After the light-cured resin cement application based on etching and silanization, the ceramic veneers (less than 0.7-mm thick) were less translucent, and the translucency decreased when the thickness increased. Because of the lower translucency of ceramic veneers, the light intensity of LED units transmitted to resin layer would decrease when curing.

Rammed earth blocks with improved multifunctional performance

Rammed earth is a traditional construction technology that has proven to be sustainable. This paper explores further improvement of its multifunctional performance by increasing the strength, reducing moisture permeation and increasing the thermal resistance. Surface application of microbial cementation was found to increase the strength by 25%. The water permeability and erosion of the blocks also reduced by 24% and 62% respectively, due to surface application of microbial cementation. The thermal test showed that addition of crumb rubber resulted in a temperature difference of around 30 °C even after 6 h. However, the addition of crumb rubber also reduced the strength. This research demonstrates that significant improvement of overall performance of rammed earth materials can be achieved through various treatments. However, the overall performance requirements are specific to the engineering application and synergistic and antagonistic interactions must be considered to obtain an optimal performance.

Diagnostic Accuracy of Fluoroscopy, Radiography, and Computed Tomography in Detecting Cement Leakage in Kyphoplasty.

Cement leakage is a typical complication of kyphoplasty for vertebral fractures. It is unclear if cement application intraoperatively can be improved by using other techniques of visualization and which kind of postoperative imaging should be recommended to detect cement extravasation accurately. To compare the rates of cement leakage detected by intraoperative fluoroscopy, postoperative radiography, and postoperative computed tomography (CT) in a retrospective study. The study included 78 patients (60 women and 18 men; 115 vertebral bodies) who were treated with two kinds of kyphoplasty. The patients underwent intraoperative fluoroscopy and postoperative radiography and CT. After surgery, the images were evaluated to compare cement leakage rates and locations in the three visualization techniques. Leakage locations were described as epidural, intradiskal, extravertebral, or intravascular. Compared with CT, intraoperative fluoroscopy regularly detected intradiskal leakage (75%) but had a considerably lower sensitivity for visualizing epidural (21%), extravertebral (31%), and intravascular (51%) cement leakages. A comparison of radiography and CT showed that radiography had a high sensitivity for detecting intradiskal (82%) and intravascular (70%) cement extrusions but a lower sensitivity in identifying epidural (42%) and extravertebral (50%) leaks. Therefore, the CT scan overall was best in detecting location and accuracy. CT detected more cement leaks than any of the other investigated techniques, especially epidural, extravertebral, and intravascular cement leakages. To achieve the best accuracy, only CT provides complete information.

Use phase assessment of photocatalytic cool pavements

Abstract Pavement Life Cycle Assessment (LCA) can be used to evaluate the environmental benefits of photocatalytic, cool concrete overlays. The use phase assessment of concrete overlays made of gray and white cement incorporating titanium dioxide (TiO2) was investigated to quantify their environmental impact on vehicular pollutant removal, Urban Heat Island (UHI) effect, and building energy consumption. Pollutant removal was estimated, with a higher decrease in NOx removal for white cement than gray cement. The UHI effect was quantified through a microscale thermal model with white cement concrete overlays resulting in five times less Global Warming Potential (GWP) than gray cement. Building energy consumption was evaluated using air temperature obtained from the ENVI-met model and empirically-derived relationships. White cement significantly decreased the cooling load in summer but increased the heating load in winter as compared to gray cement, with a net decrease in energy consumption of 9.5 kWh per capita per year. These impacts were then converted into ten Normalized Environmental Impact Parameters (NEIPs) and a single-score Net Environmental Impact (NEI) for comparison. As compared to gray cement without TiO2, the application of white cement with TiO2 led to a decrease in all NEIPs and NEIs. The largest reduction in NEI was for white cement with TiO2 at − 1.16 × 10 − 2 and the least reduction in NEI was for gray cement with TiO2 at − 5.35 × 10 − 4 .