Search results for " cement"
showing 10 items of 245 documents
USE OF FOAMED END-OF-WASTE PLASTIC AGGREGATES AS INTERNAL CURING WATER RESERVOIR INTO A CEMENTITIOUS MORTAR
2017
Shrinkage phenomena represent an important issue for cementitious materials. There are several procedures able to reduce shrinkage phenomena, in particular, external and internal curing. The latter consider the possibility to add water reservoir that are able to release water during the curing period. In this study, porous plastic aggregates were used as internal curing water reservoir.
Effect of sheep wool fibres on thermal-insulation and mechanical properties of cement matrix
2015
The use of sheep wool as reinforcement of cement in order to produce mortar or plaster involves several advantages for environment and energy. Moreover, in several regions it is treated as a waste and, consequently, its employ is characterized by low cost. Aim of this paper is to evaluate the influence of wool fibres on thermal conductivity and mechanical properties of cement. The samples were prepared using wool fibres, obtained from a breed of Sicilian sheep, with three different length (i.e. 1 mm, 6 mm and 20 mm). Moreover, in order to evaluate the influence of fibre content, the samples were prepared by varying the fibres weight fraction up to maximum level. The thermal conductivity of …
Etude de l'influence de l'hydratation des laitiers sur les propriétés de transfert gazeux dans les matériaux cimentaires
2015
Cements with high slag content are currently studied as possible candidate for nuclear waste containment materials. In this context it is important to know their microstructure and the transport properties (permeability and diffusion) of the gases that are formed by the radiolysis of the water present in this material. According to literature, these properties are strongly impacted by the addition of blast furnace slag. The aim of this work is to correlate the hydration processes of slag blended cements with their transport properties. In the first part of this work, the hydration of the slag blended cements, for which only few results have been reported to date, has been studied. Silicon-2…
Al-27 and Si-29 Solid-State NMR Characterization of Calcium-Aluminosilicate-Hydrate
2012
International audience; Calcium silicate hydrate (C-S-H) is the main constituent of hydrated cement paste and determines its cohesive properties. Because of the environmental impact of cement industry, it is more and more common to replace a part of the clinker in cement by secondary cementitious materials (SCMs). These SCMs are generally alumina-rich and as a consequence some aluminum is incorporated into the C-S-H. This may have consequences on the cohesion and durability of the material, and it is thus of importance to know the amount and the location of Al in C-S-H and what the parameters are that control these features. The present paper reports the Si-29 and Al-27 MAS NMR analyses of …
Effect of postbleaching application of an antioxidant on enamel bond strength of three different adhesives
2010
Objectives: The aim of this study was to compare the shear bond strength (sbs) of three different adhesives on bleached enamel immmmediately after bleaching, bleached/delayed for 1 week, and bleached/applied antioxidizing agent. Study Design: The enamel surfaces of 144 freshly extracted incisors without any caries and restorations were flattened and divided into 12 groups. The following adhesives were investigated: Optibond FL (OFL) (three-step etch&rinse), Optibond Solo Plus (OSP) (two-step etch&rinse), Optibond All-in-One (OA) (one-step self-etch), (Kerr, Orange, USASA). Unbleached enamel groups were prepared as negative controls. The remainder surfaces were bleached with 20% Opalescent P…
Reactive Surface Coatings Based on Polysilsesquioxanes: Controlled Functionalization for Specific Protein Immobilization
2009
The key designing in reliable biosensors is the preparation of thin films in which biomolecular functions may be immobilized and addressed in a controlled and reproducible manner. This requires the controlled preparation of specific binding sites on planar surfaces. Poly(methylsilsesquioxane)-poly(pentafluorophenyl acrylates) (PMSSQ-PFPA) are promising materials to produce stable and adherent thin reactive coatings on various substrates. Those reactive surface coatings could be applied onto various materials, for example, gold, polycarbonate (PC), poly(tetrafluoroethylene) (PTFE), and glass. By dipping those substrates in a solution of a desired amine, specific binding sites for protein ads…
Effect of proanthocyanidin mediated immediate and delayed dentin sealing on the strength of premolars restored with composite resin inlay.
2019
Background Immediate dentin sealing (IDS) with proanthocyanidin (PA) could be used before cementation with a self-adhesive (SA) cement. The aim of this study was to assess the effect of PA treatment on acid-etched dentin before adhesive application, in IDS and delayed dentin sealing (DDS), on the strengthening property of SA-cemented composite resin inlay in premolars. Material and Methods Eighty-four maxillary premolars were divided into 7 groups (n=12): 1) (Intact) Sound teeth served as controls; groups 2-7) After cavity preparation and fabrication of composite resin inlay, temporary inlays were made and cemented. After one week, the inlays were removed and composite inlays were luted wit…
Effects of Different Percentages of Microhydroxyapatite on Microhardness of Resin-modified Glass-ionomer and Zirconomer
2016
Background Hydroxyapatite (HA) is the main mineral component of the tooth structure, which exhibits considerable biological behavior and its incorporation might improve microhardness of dental materials. Microhardness of restorative materials, like glass-ionomer, is critical for the clinical longevity of restorations. The aim of this study was to evaluate the microhardness of two glass-ionomers types by incorporating different percentages of microhydroxyapatite. Material and Methods In this study, 80 disc-shaped experimental specimens (6 mm in diameter, 2 mm in height) were prepared in 8 groups, including resin-modified glass-ionomer (RMGI, GC, Gold Label, Japan), zirconia-reinforced glass-…
THE DURABILITY OF INNOVATIVE CEMENTITIOUS COATINGS: PHOTOCATALYTIC ACTIVITY AND COLOUR
2012
Today, in a world context characterized by high pollution levels and increasingly limited natural resources, even in the building sector, focusing on environmental issues, through energy saving and a more rational use of these resources, both during construction and management, is fundamental. An important contribution in this direction is given by the knowledge of the durability of products and building components, especially when innovative products are applied and no information are available on the reliability and service life. The research concerns the evaluation of the durability of cement-based photocatalytic coatings (“rasanti” in the Italian diction), containing different types of …
Cytotoxicity and bioactivity of various pulpotomy materials on stem cells from human exfoliated primary teeth.
2017
Aims To investigate the cytotoxicity and bioactivity of several pulpotomy materials: Biodentine (Septodont, Saint-Maur-des-Fosses, France) MTA (Angelus, Londrina, PR, Brazil), Theracal LC (Bisco Inc., Schamburg, IL, USA) and IRM (Dentsply DeTrey GmbH, Konstanz, Germany), after contact with stem cells isolated from human exfoliated primary teeth (SHEDs). Methodology SHEDs were cultured in the presence of the eluates of various pulpotomy materials for 24, 48 and 72 h. Cell viability was determined by mitochondrial dehydrogenase enzymatic (MTT) assay. Apoptosis and changes in cell phenotype were evaluated by flow cytometry. Also, an in vitro scratch wound-healing assay was used to determine th…