White Cement Research Articles

Cement‐based solidification/stabilization of phenol‐contaminated soil by bentonite and organophilic clay

AbstractThe performance of ordinary and organophilic clays in the solidification and stabilization process was investigated with respect to the unconfined compressive strength (UCS) and leaching of phenol‐contaminated soil. The samples contained 2,000 mg/kg of phenol. White cement (15 and 30 percent by weight [wt%]) was used as binder, while ordinary and organophilic clays (8, 15, and 30 wt%) were applied as additives for reducing the harmful effects of phenol interference in cement hydration with a 28‐day curing time. The results revealed that the UCS is reduced by increasing the amount of clays. The values of UCS of all samples met the minimum standards specified for disposal in sanitary landfills determined by developed countries. The leaching test demonstrated that the degree of leaching diminished with increased clay content in all samples of both clay types. This reduction was observed to be greater in samples containing organophilic clay than in bentonite clay samples. Furthermore, the best composition of the materials tested was determined to be 30 wt% white cement plus 13.3 wt% organophilic clay with a compressive strength of 3,839 kPa, phenol removal percentage of 80 percent, and a cost of $67 per ton of contaminated soil.

Influence of Using White Cement Kiln Dust as Mineral Filler on Hot Asphalt Concrete Mixture Properties

The White Cement Kiln Dust (WCKD) as a byproduct material, formed in cement factories during cement production operation, is categorized by Environmental Production Agency (EPA) as a non hazardous solid waste material. In highway construction process, the WCKD can be used in different ways such stabilizing the subgrade soil and also instead of mineral filler in Hot Mix Asphalt (HMA) production which results in more economy and leads to keeping the environment more clean and healthy. In Iraq, there are two common types of fillers that are Portland cement and lime stone powder. In this research, various percentages of WCKD taken from Fallujah cement plant were used in addition to two filler types(100%WCKD, 50%WCKD+50%Cement (C) ,100%C ,50%WCKD+50%Limestone (L), and 100%L to prepare asphaltic concrete mixes. Five tests were used to evaluate the performance of these different asphaltic concrete mixes, standard Marshall Test at 60 O C and 70 O C, to test immersed samples for four days in water at room temperature (24 O C) , Indirect Tensile Strength Test(ITST) to test conditioning and un-conditioning samples. All the test results were acceptable and within the AASHTO and Iraqi roads specifications. The results showed that using WCKD as a filler could conserve the environment and encourage the HMA producers to use this inexpensive material in their works.

Photocatalytic, hydrophobic and antimicrobial characteristics of ZnO nano needle embedded cement composites

In this work, ZnO nanoneedles were synthesized employing a co-precipitation method. Further, white cement composites were prepared with ZnO filler of 5%, 10% and 15% by weight ratio. With the increasing concentration of ZnO in cement matrix the synergetic effect between ZnO and white cement matrix was observed through FE-SEM and UV–visible. We studied the photocatalytic degradation of pollutant (Rhodamine 6G) using ZnO nano-needles embedded in white cement matrix under ultraviolet irradiation (UV) along with enhanced hydrophobic nature and the antimicrobial property of the cement. The pseudo-first order kinetics was found in a photocatalytic process, and degradation rate constant was enhanced up to 0.147 min−1 for ZnO modified cement which was significantly higher than the pure cement (0.037 min−1). Antimicrobial studies were performed using bacterial strains Escherichia.coli (JM109, Promega Gram negative), Bacillus subtilis (MTCC121, Gram-positive) and fungal strain Aspergillus niger (MTCC281) for all the composites. A significant improvement in bacterial and fungal degradation was observed in ZnO modified cement than control and pure cement in a dose-dependent manner.

The “Terranova” render of the Engineering Faculty in Bologna (1931–1935): reasons for an outstanding durability

In the first half of the twentieth century, a variety of dry-mix renders with different trade marks spread across Europe. Their stated performance made them attractive for buildings where the overhanging eave was absent, hence they found broad application in rationalist buildings and districts. However, their composition and properties are barely known. In this paper, the Terranova render of the Engineering Faculty in Bologna was characterised, to investigate the reasons for its outstanding durability. Unexpectedly, the render was found to be constituted by dolomitic lime and only a small amount of white cement and exhibited a remarkable strength. The presence of air voids seems due the use of air entraining agents and may have contributed to the frost resistance of this render during 80 years. The results are expected to contribute not only to the knowledge of Terranova render, but also to a better understanding of durability issues for new renders.

Dentinogenic differentiation potential of fast set white portland cements of a different origin on dental pulp stem cells

Abstract Background: Advances in endodontic biomaterials are at the forefront of endodontic research. Purpose: This study aimed to compare the dentinogenic differentiation potential of extracts of two formulations (normal and fast set [FS] by the addition of calcium chloride dihydrate (CaCl2.2H2O) of white Portland cements (WPCs) of a different origin (Aalborg, Malaysia, and Egypt) on dental pulp stem cells (DPSCs). Materials and Methods: The material extracts at 12.5 mg/ml were applied on DPSCs cultured in 96-well plates. After 1, 3, 7 and 14 days of incubation, the RNA was extracted, cDNA was prepared, and the expression of four dentinogenic gene markers (bone gamma-carboxyglutamate protein, dentin sialophosphoprotein, runt-related transcription factor 2, and secreted phosphoprotein 1 [SPP1]) was examined using the real-time polymerase chain reaction. One-way analysis of variance was used for statistical analysis, and the level of significance was set at 0.05 (P = 0.05). Results: Significant differences were observed between Malaysian WPC (MAWPC) and Egyptian WPC (EGWPC) and FS MAWPC), FS EGWPC in 7 out of 15 and 6 out of 10 comparisons, respectively. While more expressions in EGWPC group were observed in four comparisons and three for MAWPC, all FS formulations showed higher expressions for FS MAWPC compared to FS EGWPC (P < 0.05). The addition of CaCl2.2H2O to MAWPC and EGWPC increased the upregulation of SPP1 gene at all-day intervals, which was not observed with other genes. Conclusions: The dentinogenic differentiation of DPSCs shows different expression profiles to extracts of normal and fast formulations of WPC. Extracts of WPC of different origin have different dentinogenic differentiation potential on DPSCs.

Why permeability to water is anomalously lower than that to many other fluids for cement-based material?

The intrinsic permeability of porous medium is theoretically independent of percolating fluids. While concerning cementitious material, its water permeability is anomalously lower than that to many other fluids. To discover the responsible physical background, the permeability coefficients of two mature white cement mortars are measured using water, isopropanol and nitrogen gas. Their pore structures are also tested on specimens at various states through low-field NMR and MIP methods. It is found that the pore structures of water-saturated mortars are remarkably coarsen due to the contraction of C-S-H gel enforced by water removal through drying or isopropanol exchange. The coarsening of pore structure fundamentally increases the intrinsic permeability by 2–4 orders of magnitudes, which can be approximately quantified through the Katz-Thompson equation. The anomalous low water permeability is physically rooted in the swelling of C-S-H gel specific to water, which is intimately linked to the disjoining pressure of aqueous pore solution.

Human Resources Information Systems and their Impact on Competitive Advantage: An Empirical Study on Cement Companies in the Hashemite Kingdom of Jordan

The study identifies human resources information systems (HRIS) and their impact on the competitive advantage of Jordanian cement companies (Lafarge Cement Company, Arab White Cement Company, Manaseer). To achieve the objectives of the study, a questionnaire was developed for data collection, and then the Statistical Package for Social Sciences (SPSS.16.1) was used to analyze the data of the questionnaire. The study produced a series of results, the most prominent of which are: The level of importance of human resources information systems (the efficiency, integration, and response of human resources information systems) in Jordanian cement companies according to the respondents' perceptions was “medium”. Moreover, human resources information systems had an effect on competitive advantage. Human resources information systems accounted for 69.8% of the variation in competitive advantage in Jordanian cement companies. In the light of the study’s results, the study produced several recommendations, the most important of which is to design training programs for employees and users of human resources information systems. The study also stressed on the importance of providing and constantly upgrading and maintaining the basic infrastructure for hardware, equipment, and software used in human resources information systems, to minimize the occurrence of potential errors that may disrupt required work.

Characterization of pore structures of hydrated cements and natural shales by 129Xe NMR spectroscopy

129Xe NMR of adsorbed xenon gas is a sensitive tool for the characterization of porous materials. Here we exploit, for the first time, 129Xe NMR to investigate the nanoscale porous structures in hydrated white cements and natural shale. Signals of xenon in mesopores and larger voids are well resolved in the spectra of the cement samples, and the exchange rate between these sites was determined to be 100−300 s−1 at room temperature. The spectra imply that the mesopore size is the smallest and the exchange rate is the highest in the sample with the lowest initial water/cement ratio. The heat of adsorption of xenon in the cements is similar to that in silica gels, about 12 kJ/mol. The shale spectra include a very broad signal, covering a range of about 600 ppm, implying that the adsorbed xenon interacts with the paramagnetic impurities present in the samples.

Optical Properties and Failure Load of Thin CAD/CAM Ceramic Veneers.

This study aimed to compare optical properties and failure load of leucite (IPS Empress CAD LT) and lithium disilicate glass ceramic (IPS e.max CAD LT) materials in incisor veneers. Four groups of veneers were made on 36 bovine incisors with Cerec 3D milling unit (n=9/group): 0.5 and 0.3 mm thick leucite glass and 0.5 and 0.3 mm lithium disilicate glass veneers. The optical features were measured with CM-700d spectrophotometer using white and yellow try-in pastes. Differences were determined by means of ΔE value and luminance. The bovine teeth with veneers were mounted on acrylic resin blocks (Palapress, Heraeus Kulzer) and static loading test was conducted (LR30K plus, Lloyd Instruments). The color difference of veneers could be noticed with yellow and white cements when the material thickness increased from 0.3 to 0.5 mm (leucite ΔE yellow 4.4, white 6.0; lithiumdisilicate ΔE yellow 2.1, white 4.1). Both materials showed similar failure load with 0.5 mm veneers (leucite 1906 +/-319 N; lithiumdisilicate 2098 +/- 309 N). The failure load of 0.3 mm thick lithium dilisilicate veneers (2002 +/- 427 N) was comparable with the 0.5mm veneers. Ultrathin lithium disilicate glass ceramic veneers (0.3 mm) could be a potential option for clinical use.

Use of Late-Barremian sands from Central Tunisia in white cement clinker

The present work focuses on the ability of Late-Barremian sands from Ouaddada Mountain (Central Tunisia), to produce high-quality white cement clinker. Results indicate that these sands are particularly characterized by their fineness of grains (mean grain-size 90–140 μm), high cleanness (sand equivalent 88–98%), extremely low coloring oxides and volatiles levels (less than 0.03 and 1.9% respectively) and high values of whiteness and lightness indices (more than 86 and 90% respectively). Studies based on Bogue calculation, X-ray diffraction (XRD), burnability of raw mixes, Point Counting and Scanning Electron Microscopy (SEM) with Energy-Dispersive X-Ray Spectroscopy (EDS) methods, reveal that the Late-Barremian sands from Ouaddada Mountain can be used in the production of white Portland clinker by mixing with 70.8–75.6% of local limestones and 3.5–24.8% by weight of common Mediterranean kaolins from Guadalajar province (Central Spain), Tamazert (North-East Algeria), Şile (North-West Turkey), Sebha (South-West Libya), and Abu Zanima area (West-Central Sinai, Egypt). Synthesized clinkers are composed largely of alite (75–76.2%), belite (12.8–16.5%) and aluminate (7.4–8.9%) with subordinate quantities of ferrite (less than 1%), slightly harder to burn and seem to be much whiter than Mediterranean ones with a whiteness index β more than 86%.

Combined use of waste glass powder and cullet in architectural mortar

The use of 100% waste glass cullet (WGC) as fine aggregates in architectural cement-based mortar had been proven to be feasible in previous works. This paper reports a further study on investigating the influence of using waste glass powder (WGP) as a supplementary cementitious material on the properties of glass-based architectural cement mortars. The experimental results showed a good linear relationship between the particle size of WGP and the flow values of the fresh mortar, revealing that the particle size of WGP played an important role in controlling the workability. For the hydration of white cement, the inclusion of WGP not only affected the second exothermic peak of hydration but also changed the third peak. In particular, the result indicated that the use of finer WGP had an advantage in increasing the flexural strength of the cement mortar when compared with the corresponding compressive strength, which was attributed to the morphological and pozzolanic effect of WGP. In addition, the very fine WGP could act as micro-fibers and micro-aggregates in filling the microstructure of the mortar. At 90 days of curing, the mortar prepared with finer WGP showed a distinct improvement in strength due to the improved interfacial transition zone and the pore-size refinement.

Temperature and moisture evolution beneath an aerogel based rendering applied to a historic building

Retrofitting of buildings defined as cultural heritage with respect to energy consumption and thermal comfort of the occupants is a demanding endeavor due to the additional requirements of the conservation aspect. Within a pilot project an inhabited mill in Sissach/Switzerland whose first mention dates back to the 14th century has been retrofitted by using a highly insulating external rendering containing SiO2 aerogel and mainly mineral admixtures namely hydraulic lime, calcium hydroxide, white cement, aerogel granules, light mineral aggregate, water retaining agent, air-entraining agent, except the organic hydrophobic agent. By a rendering thickness of 5–6cm, the thermal transmittance through the walls was reduced to one third of its original value and the thermal comfort in the 6 apartments improved substantially including a reduction in mold growth risk. The characteristics of the aerogel based rendering have been discussed especially with respect to preservation aspects. By installing temperature and moisture sensors on the original wall and beneath the insulating rendering it was shown that its application on the original walls fulfils the requirement for avoiding moisture accumulation. Further, hygro-thermic simulations were performed extrapolating temperature evolution and water content for a period of 5 years. The object represents a new paradigm in the energy efficient restoration of the built heritage and simultaneously respecting the conservation aspects. The project has been carefully monitored by the state office (Basel-Landschaft) for preservation of monuments.

An anthropomorphic abdominal phantom for deformable image registration accuracy validation in adaptive radiation therapy.

To design and construct a three-dimensional (3D) anthropomorphic abdominal phantom for geometric accuracy and dose summation accuracy evaluations of deformable image registration (DIR) algorithms for adaptive radiation therapy (ART). Organ molds, including liver, kidney, spleen, stomach, vertebra, and two metastasis tumors, were 3D printed using contours from an ovarian cancer patient. The organ molds were molded with deformable gels made of different mixtures of polyvinyl chloride (PVC) and the softener dioctyl terephthalate. Gels with different densities were obtained by a polynomial fitting curve that described the relation between the Hounsfield unit (HU) and PVC-softener blending ratio. The rigid vertebras were constructed by molding of white cement and cellulose pulp. The final abdominal phantom was assembled by arranging all the fabricated organs inside a hollow dummy according to their anatomies, and sealed by deformable gel with averaged HU of muscle and fat. Fiducial landmarks were embedded inside the phantom for spatial accuracy and dose accumulation accuracy studies. Two channels were excavated to facilitate ionization chamber insertion for dosimetric measurements. Phantom properties such as deformable gel elasticity and HU stability were studied. The dosimetric measurement accuracy in the phantom was performed, and the DIR accuracies of three DIR algorithms available in the open source DIR toolkit-DIRART were also validated. The constructed deformable gel showed elastic behavior and was stable in HU values over times, proving to be a practical material for the deformable phantom. The constructed abdominal phantom consisted of realistic anatomies in terms of both anatomical shapes and densities when compared with its reference patient. The dosimetric measurements showed a good agreement with the calculated doses from the treatment planning system. Fiducial-based accuracy analysis conducted on the constructed phantom demonstrated the feasibility of applying the phantom for organ-wise DIR accuracy assessment. We have designed and constructed an anthropomorphic abdominal deformable phantom with satisfactory elastic property, realistic organ density, and anatomy. This physical phantom can be used for routine validations of DIR geometric accuracy and dose accumulation accuracy in ART.

The impact of cooling water types on the cement clinker properties

This paper studied the influence of the different water types on clinker properties. It concern with cement plants which are using the water for cooling the clinker (El-Minia white cement plant). The water types are Nile, ground and deionized water. The cooling was mad suddenly for clinker by three water types at the same time. The paper discusses the physical and chemical analysis and algal detection of all water types. It also discusses the chemical and physical analysis for kiln feed, clinker. The analysis of water showed that the concentration of dissolved salts in groundwater is higher than Nile water. The concentration of algae gave opposite direction; the algae concentration in Nile water is higher than groundwater. While the deionized is completely free from dissolved salts and algae. The cement tests for clinker which treated by the different water types showed that the cement strength was reducing when used the Nile water with high algae count. From another side, the high concentration of dissolved salts in groundwater does not affect on strength. The water contained the algae prevent the complete crystallization of calcium silicate for clinker. The results also showed that the best type of water, which improved cement compressive strength ranged according to algae count by the sequence deionized water>groundwater>Nile water.

Influence of Pigment Content and Cement Type on Appearance and Performance of Colored Self-Compacting Mortars (C-SCMs)

Colored self-compacting mortar (C-SCM) is a novel cementitious product that has been recently used in decoration and rehabilitation and has improved esthetic quality of architectural constructions. C-SCM is susceptible to strength decrease due to excessive pigment presence in the mixture. Optimum pigment content with respect to color intensity and mechanical performance is an important matter that should be determined to prevent mortar failure after construction. In this research, two inorganic pigments in production of colored self-compacting mortar were utilized. The impact of titanium dioxide (TiO2) and iron hydroxide (FeO(OH)) contents on behavior of C-SCMs was investigated in white and gray cement matrixes. Experiments included measurements of compressive strength of mortar cubes and cylinders, flexural strength and colorimetric properties. Analyses on compressive and flexural toughness were applied, as well. It was concluded that pigment content in mix design of colored self-compacting mortar could be optimized with regard to color quality in surface and mechanical strength of the product. Results implied that 5 and 2% of titanium dioxide were the saturation points of color and strength, respectively, and iron hydroxide at 10% was unsurpassed in C-SCMs containing white cement. Application of both pigments in gray SCMs caused the saturation points of color and strength to occur at 10 and 2%, respectively.

Synthesis of a Goethite Pigment by Selective Precipitation of Iron from Acidic Coal Mine Drainage

Conventional treatment of acid rock drainage (ARD) from coal mines generates large volumes of sludge, which requires further treatment and disposal. The aim of this work was to study the recovery of iron by selective precipitation to synthetize goethite for use as pigment. Goethite particles were successfully produced, and presented a particle distribution in the range of nano- and micro-sizes, varying from 0.04 to 5.0 µm when produced as paste suspension, or from 0.04 to 25.0 µm when dried at 60 °C and converted to a solid powder. The pigment was used to color a white cement paste, giving it a yellow ochre color. ARD treatment plants can adopt this process to reduce waste disposal issues and produce a valuable mineral (e.g., yellow pigment for concrete).

Investigation on preparation of pyrite tailings-based mineral admixture with photocatalytic activity

In this study, we prepared a mineral admixture with photocatalytic activity by acid leaching-hydrolyzation and single calcination method, using industrial waste pyrite tailings and high titanium slag as raw materials in which pyrite tailings were substrate and high titanium slag was the source of titanium. The compressive strength of the cementitious materials with the admixture, and the photocatalytic activity of the admixture and white cement with admixture were also studied. The results demonstrated that the optimum conditions for preparing admixture were that the mass ratio of acid and slag is 8:1; the temperature of acid leaching is 85°C; the time of acid leaching is 250min; the content of distilled water is 40%; the mass ratio of filtrate and tailings is 8:1; the loading temperature is 105°C; the loading time is 3.5h; at last, the precursor of admixture is calcined in 800°C for 2h. The admixture prepared in this method showed a superior crystallinity of anatase with the particle size of about 100nm. Comparing with the cement paste without the admixture, the 3, 7 and 28days compressive strength of the cement paste with 30% admixture were found to be increased by 40.92%, 44.57% and 37.74%, respectively. The photocatalytic degradation rate of methylene blue(MB) reached 95.28% after irradiation for 5h, and white cement with the admixture manifested perfect photocatalytic performance under irradiation by 300W high-pressure mercury lamp.

Effect of Blood Exposure on Push-Out Bond Strength of Four Calcium Silicate Based Cements.

Introduction:The purpose of this study was to compare the push-out bond strength of white ProRoot Mineral Trioxide Aggregate (MTA), Biodentine, calcium-enriched mixture (CEM) cement and Endosequence Root Repair Material (ERRM) putty after exposure to blood. Methods and Materials:A total of 96 root dentin slices with a standardized thickness of 1.00±0.05 mm and standardized canal spaces were randomly divided into 4 main experimental groups (n=24) according to the calcium silicate based cement (CSC) used: white ProRoot MTA, CEM Cement, ERRM Putty and Biodentine. Specimens were exposed to whole fresh human blood and then subdivided into two subgroups depending on the exposure time (24 or 72 h). Push-out bond strength was measured using a universal testing machine. Failure modes were examined under a light microscope under ×10 magnification. Data were analyzed using the two-way ANOVA test. Results:Biodentine exhibited the highest values regardless of the exposure time. The lowest push-out strength values were seen in white ProRoot MTA and CEM cement in both post exposure times. After exposure to blood, the push-out bond strength of all materials increased over time. This increase was only statistically significant in white ProRoot MTA and ERRM specimens. The dominant failure mode in all CSCs was the adhesive mode. Conclusion:Biodentine showed the highest values of push-out bond strength and may be better options for situations encountering higher dislocation forces in a short time after cement application.

Manufacturing of Thermal and Acoustic Insulating from (White Cement and Hemp Short Fibers) by using Recycled Paper

Manufacturing of Thermal and Acoustic Insulating from (White Cement and Hemp Short Fibers) by using Recycled Paper

The Discoloration effect of White Mineral Trioxide Aggregate (WMTA), Calcium Enriched Mixture (CEM), and Portland Cement (PC) on Human Teeth.

BackgroundThe aim of this study was to evaluate the discoloration induced by CEM cement, Portland cement (PC) and MTA mixed with propylene glycol (MTA-PG) in comparison to White MTA.Material and MethodsNinety extracted premolar and canine teeth were resected 2 mm below the CEJ. The coronal part of crown was prepared with peeso reamer and Gates-Glidden drills, and the specimens were randomly divided into 4 experimental (n=20) and one control (n=10) groups. The tooth crowns in experimental groups 1 to 4 were filled with White MTA, PC, CEM cement and MTA-PG, respectively; and in group 5, the teeth were kept empty. After incubation, digital photographs of teeth were acquired at 4 time points (before, immediately after placing the materials, 3 and 6 months afterwards). Images were transferred to Adobe Photoshop CS4 and CIE L*a*b color space was used for tooth shade assessment. One-Way ANOVA and One-Sample t-test were used to compare discoloration of teeth between groups.ResultsSignificant statistical discoloration was only observed in the cervical one third of all groups at each time points (except between 3 and 6 months). Tooth discoloration was greatest in PC and lower in MTA and MTA-PG at the end of 6 months. The tooth discoloration between immediately and 3 months after placing the materials had significant difference only between MTA and PC; and also the tooth discoloration between immediately and 6 months after placing the materials was observed only between PC and MTA, and PC and MTA-PG.ConclusionsAll of the experimental biomaterials caused tooth discoloration after 6 months, of those, PC had the most and MTA and MTA-PG had the least discoloration effect. Key words:Mineral trioxide aggregate (MTA). Calcium enriched mixture (CEM). Propylene glycol. Portland cement.