Papers by Keyword: Cement

Paper TitlePage

Authors: Michiyo Honda, Toshiisa Konishi, Minori Mizumoto, Mamoru Aizawa
Abstract: Cancers frequently metastasize to bone, where it leads to secondary tumor growth, and osteolytic bone degradation. Bone metastases are often associated with fractures and severe pain resulting in decreased quality of life. Accordingly, effective therapies to inhibit the development or progression of bone metastases will have important clinical benefits. Bone cement, one of the powerful tools as bone substitutes, is used to fill the resection voids. The aim of this study was to develop a local drug delivery system using HAp cement as a carrier of chemotherapeutic agents. In the present study, we have fabricated chelate-setting apatite cements (IP6-HAp cements) using HAp particles surface-modified with inositol hexaphosphate (IP6) and evaluated their anti-tumor effect. Human osteosarcoma (HOS) cultured on IP6-HAp cements (over 3000 ppm IP6) resulted in inhibition of cell growth. DNA microarray analysis indicated changes in the expression of apoptosis-related genes on IP6-HAp cement surface-modified with 5000 ppm IP6 compared with HAp cement, suggesting activation of apoptosis machinery by IP6-HAp cement. To clarify the mechanism of anti-tumor effect of IP6-HAp cement, the properties of cement were investigated. The release kinetics of IP6 from IP6-HAp cement showed that the level of released IP6 was insufficient to induce anti-tumor activity. These results led us to consider that locally high concentration of IP6 which was released from cement acts on the cells directly as anti-tumor agent and induces the apoptosis. Consequently, IP6-HAp cement might gain the anti-tumor effect and act as a carrier for local drug delivery system.
173
Authors: Yusuke Nakashima, Michiyo Honda, Toshiisa Konishi, Minori Mizumoto, Mamoru Aizawa
Abstract: In our previous study, silicon-containing hydroxyapatite (Si-HAp) powder was prepared via an aqueous precipitation reaction. The Si-HAp powders were synthesized with desired Si contents (0, 0.4, 0.8, 1.6, and 2.4 mass%) as a nominal composition. Another previous study in our group demonstrated surface-modification of HAp powder with inositol phosphate (IP6) enhanced the compressive strength of apatite cement. Thus, to fabricate the cements with higher bioactivity, the above Si-HAp powders were surface-modified with IP6 (IP6-Si-HAp). The IP6-Si-HAp cements with various Si contents were fabricated by mixing with pure water at the powder/liquid ratio of 1/0.4 [w/v]. In order to clarify biocompatibility of the IP6-Si-HAP cements in the present work, MC3T3-E1 cells as a model of osteoblast were seeded on the cement specimens. As for the numbers of cells cultured on the IP6-Si-HAp cements, the substitution of lower levels of Si into HAp lattice did not greatly influence the cell proliferation. However, the substitution of Si amount over 0.8 mass% enhanced the cell proliferation. Especially, the IP6-Si-HAp cement with the Si content of 2.4 mass% showed excellent cell proliferation among examined specimens. Therefore, to fabricate the cements with higher bioactivity, it is necessary to control the amount of Si in the IP6-Si-HAp cements. The usage of these IP6-Si-HAp cements may make it possible to fabricate the cements with higher bioactivity, compare to conventional pure HAp cements.
183
Authors: Peih Jeng Jiang, Sarika Patel, Uwe Gbureck, Liam M. Grover
Abstract: There is a current need for the localized delivery of antibiotics in order to treat implant based infections. In this study, the efficacy of hydroxyapatite (HA) gels, HA cements, and silica gels in the delivery of vancomycin have been investigated and compared. Vancomycin release was monitored at set time points using a UV/VIS spectrophotometer (288 nm). The activity of the vancomycin released from the cements and gels was assessed using an agar diffusion test with Staphylococcus aureus. Vancomycin was released rapidly from both HA matrices, and the silica gel in the first day of the experiment, but the release rate was slowed considerably after 3 days for the HA gels. Following ten days of aging, 70% of the vancomycin remained in the HA gel matrix and the quantity released from the gel was shown to retain its effectiveness against Staphylococcus aureus.
327
Authors: Hashem Al-Mattarneh, Abdullah Alwadie, Ahmad Malkawi, Muhd Fadhil Nuruddin
Abstract: A new measurement system is developed to monitor the early hydration of cementitious materials based on measured dielectric properties of the material in low electromagnetic frequency range. The objectives of this paper were to evaluate the changes in the electromagnetic properties for samples with different fly ash content and to establish the reliability of the measurement technique by comparing with results obtained by traditional method such as thermal method that is either time consuming or impractical. The method adopted in the present experimental work is a parallel plate electrode system (PPES). The suggested monitoring device for concrete hydration and strength development is based on the relationship between the electromagnetic properties such as dielectric constant, loss factor and the strength development during hydration process and curing time. In this research the electromagnetic properties of concrete is found to be dependent on the hydration and strength of concrete. Therefore the development of microstructure and concrete compressive strength can be determined by monitoring its electromagnetic properties in the frequency range of 1 to 100 kHz.
333
Authors: H.B. Zhu, P.M. Wang, C.S. Wang, G.T. Yan, Y.S. Cheng, L.M. Wu
Abstract: Both of noise and building energy efficiency are attached importance to in the world. A novel material is developed to control noise, save building energy and decorate for buildings. Porous absorber, cavity resonator resonance sound absorber, film resonance sound absorber, functional absorber and high sound absorber are utilized to improve the sound absorbability. Perlite, Ordinary Portland cement, silicon fume, re-dispersible emulsion powder or emulsion, air-entraining agent, superplasticizer, short fiber and mesh fabrics are used to prepare novel material. Organic silicone waterproof material is used to prevent it from destroying, assist for sound absorbability and decorate for surface. After designing wedge sound absorber by mould, forming cavity resonator resonance sound absorber by air-entraining agent, and controlling compression ratio, diameter of perlite grain and cement dosage, final performances of sound absorbability and heat preservation can meet requirements of ASTM C423-84A and GB/T 20473-2006 respectively.
3922
Authors: Ahmad Azrem Azmi, Mohd Mustafa Al Bakri Abdullah, Che Mohd Ruzaidi Ghazali, Andrei Victor Sandu, Kamarudin Hussin
Abstract: This paper aims to investigate the potential use of recycled tire rubber in concrete. In Malaysia, rubber consumption of tires in January – June 2014, rose up to 8.4% from 0.388 million tonnes. These numbers keep on increasing year-over-year with the numbers of vehicles, as do the future problems relating to waste tires. Over the past few years, a number of researchers have studied on incorporated the waste tires into cement based materials. In an attempt to reduce the magnitude of this issue, recycled tire rubber has gained interest in concrete improvement. The used of recycled tire rubber in the reinforcement in concrete is considered as value added materials for sustainable development by reusing waste materials. It is believed that using waste tire rubber in concrete could be an alternative way to replace fine and coarse aggregate (sand and gravel) in improving the properties of concrete. Rubberized concretes can be used in architectural applications such as side walk pavement, nailing concrete, in road constructions where high strength is not necessary, outdoor playground mat, in wall panels that require low unit weight, in sound barriers as sound absorbers, and in railroads to fix the rails to the ground.
249
Authors: Jana Zahálková, Pavla Rovnaníková
Abstract: The production of Portland cement is connected with high emissions of greenhouse gases, especially carbon dioxide, and the intensive consumption of energy and natural resources. The present trend is for the replacement of cement by reactive admixtures, which can include ground waste glass, a material which shows pozzolanic activity. This paper deals with the determination of the mechanical properties of cement pastes in which part of the cement mixture (5 to 30 %) was replaced by borosilicate glass. The process by which the hydration of the cement with ground glass began was monitored by an isothermal calorimeter.
86
Authors: Peng Xuan Duan, Ye Zhang, Yuan Chao Miao, Ying Li
Abstract: This paper describes replacing natural gypsum with FGD gypsum as cement retarder, the influence on the working performance, compressive strength and admixture adaptability of concretes, which were prepared with fly ash cement, slag cement and ordinary Portland cement. The results indict the FGD gypsum instead of natural gypsum used as cement retarder has little difference on the working performance of concrete and additionally the FGD gypsum has no negative influence on the compressive strength and admixture adaptability of concretes.
1311
Authors: Treerat Silatikunsatid, Nittaya Jaitanong, Suparut Narksitipan
Abstract: In this research, the influence of zinc oxide (ZnO) on the phase compositions and crystalline structure and microstructure of cement composite was studied. ZnO powder (0.5-1 wt% of cement) was used as an additive material. The Portland cement and ZnO powder were blended and mixed with water at the ratio constant (W/C) of 0.4. Then, the paste was cast into the molded for 24 hours. After these periods, the samples were dried at temperature 50°C for 24 hours. Those of samples were analyzed of crystalline structure and phase compositions by using X-ray diffraction technique (XRD). Microstructure analysis by using field emission scanning electron microscopy (SEM). It was found that the XRD spectra showed phases of calcium hydroxide (CH) and calcium silicate hydrated (CS), which were hydration products of cementitious material. Moreover, phase of zinc hydroxide (Zn(OH)2) is detected. Zn(OH)2 have affected on the retardation of hydration reaction (more than 48 h). Zn(OH)2 phase was formed on the surface of anhydrous tricalcium silicate (C3S) main compound in cement. The intensity of un-hydration products (C3S and C2S) increased with increasing content of ZnO nanoparticle in cement composites.
95
Authors: I.O. Ogunleye
Abstract: The thermo-physical properties of some varieties of sawdust and some additives are presented. They are thermal conductivity, heat capacity and specific gravity. The methods of investigation used are Lee’s Disc Apparatus, heat balance and gravimetric method respectively. The sawdust specimens were obtained from six varieties of wood. The additives employed on two typical sawdust samples are cement and silica clay. The values of thermal conductivity range between 0.440 and 0.204 W/m K, and heat capacity between 58,644.08 and 29,584 J/kg K. The highest specific gravity is 0.256 and the least value is 0.107. It was observed that as the clay content increases, specific gravity and the thermal conductivity also increases while the specific heat capacity decreases.
752
Showing 1 to 10 of 370 Paper Titles