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COMPOSITE CEMENT MODIFIERS

As a recent trend, there have been a few attempts to use polymer latexes with chemical admixtures such as superplasticizers,( l alkyl alkoxy silane,[ J and amino alcohol derivativel l at low polymer-cement ratios of 5.0% or less. A trM to inhibit alkali-aggregate reaction with chemical admixtures and SBR latex has also been done.I I When such attempts are completed, new polymeric chemical admixtures for ordinary cement concrete may successfully be developed in the near future. [Pg.217]

Type of Wood Specific Gravity (20°C) Flexural Strength (kgf/cm2) Modulus of Elasticity (kgf/cm2) Compressive Strength (kgf/cm ) Length Change (%) [Pg.218]


Acrylic latices have been used successfully for more than 35 years to modify portland cement composites. The use of solid grade acrylic cement modifiers has become common during the past few years. Both of these types will be discussed later in this section. The level of polymer modification is measured as a ratio of polymer solids by weight of cement. A 15%-20% modification represents the range for optimum performance lower modification levels may prove acceptable for certain product applications (Rohm Haas, 1989). [Pg.116]

Inclusion of porosity, with the aim to improve the osteoconductivity, can be introduced by the addition of soluble inclusions such as sucrose, sodium hydrogen carbonate, sodium hydrogen phosphate (Takagi and Chow 2001), or calcium carbonate that reacts to evolve carbon dioxide (Walsh et al. 2001). These reactants produce ionic substitutions in the structure and further improve the resorbability. Another example is that of strontium, which has been shown to be incorporated at low concentrations, while higher concentrations require a heat treatment (Leroux and Lacout 2001b). Since the cement is designed to harden in the body, the composition is modified in situ by reaction with the physiological solutions. [Pg.638]

The effects of the influence of NS at their interaction into liquid medium depend on the type of NS, their content in the medium and medium nature. Depending on the material modified, FS of NS based on different media are used. Water and water solutions of surface-active substances, plasticizers, foaming agents (when modifying foam concretes) are applied as such media to modify silicate, gypsum, cement and concrete compositions. To modify epoxy compounds and glues based on ERs the media based on polyethylene polyamine, isomethyltetrahydrophthalic anhydride, toluene and alcohol—acetone solutions are applied. [Pg.226]

Polymer-modified or polymer cement mortar (PCM) and concrete (PCC) are a category of concrete-polymer composites which are made by partially replacing the cement hydrate binders of conventional cement mortar or concrete with polymers, i.e., polymeric admixtures or cement modifiers, thereby strengthening the binders with the polymers. Polymer-modified or polymer cement paste, which is prepared widiout any aggregate, is sometimes used. [Pg.240]

The potential compound composition of a cement or cement clinker can be calculated from the oxide analyses of any given raw materials mixture, or from the oxide analyses of the cement clinker or finished cement. The simplest and most widely used method is the Bogue calculation (23). The ASTM C150 (24) calculation is somewhat modified. [Pg.286]

One approach for ameliorating the highly brittle nature of these cements has involved the use of tougher, more ductile fillers (62,63). Another approach for improving the overall properties of traditional glass—ionomer cements involves the development of hybrid cement-composites and resin-modified cements (64—68). [Pg.473]

A fundamental criticism of the resin-modified glass polyalkenoate cements is that, to some extent, they go against the philosophy of the glass polyalkenoate cement namely, that the freshly mixed material should contain no monomer. Monomers are toxic, and HEMA is no exception. This disadvantage of composite resins is avoided in the glass polyalkenoate cement as the polyacid is pre-polymerized during manufacture, but the same cannot be said of these new materials. For this reason they may lack the biocompatibility of conventional glass polyalkenoate cements. These materials also absorb excessive amounts of water because of the hydrophilic nature of polyHEMA (Nicholson, Anstice McLean, 1992). [Pg.175]

One method of overcoming some of the instability and loss in strength of oxychloride cements when exposed to water has been to modify them by impregnation with sulphur (Beaudoin, Ramachandran Feldman, 1977). The resulting material appears to be a composite in which the respective components complement each other. The magnesium oxychloride part has relatively poor resistance to water as initially formed, whereas the sulphur is difficult to wet and is completely insoluble in water. [Pg.297]

A polymeric composition for reducing fluid loss in drilling muds and well cement compositions is obtained by the free radical-initiated polymerization of a water-soluble vinyl monomer in an aqueous suspension of lignin, modified lignins, lignite, brown coal, and modified brown coal [705,1847]. The vinyl monomers can be methacrylic acid, methacrylamide, hydroxyethyl acrylate, hydroxypropyl acrylate, vinylacetate, methyl vinyl ether, ethyl vinyl ether, N-methylmethacrylamide, N,N-dimethylmethacrylamide, vinyl sulfonate, and additional AMPS. In this process a grafting process to the coals by chain transfer may occur. [Pg.46]

Polymethylmethacrylate can be modified with monoethanolamine to form a water-soluble polymer (Deman). Deman is used as a cement additive to increase the strength in amounts smaller than 0.5% of the total weight of the composition [1595]. The produced plugging stone has improved strength characteristics within a temperature range from —30° to -1-300° C. [Pg.279]

Y. V. Vasilchenko and I. G. Luginina. Binder for cementing low-temperature wells—contains modified lignosulphonate(s), potash and cement of specified composition, to increase bending strength of cement rock. Patent SU 1749199-A, 1992. [Pg.473]

Since we have no direct information about the chemistry of the Fountain fluid, we assume that its composition reflects reaction with minerals in the evaporite strata that lie beneath the Lyons. We take this fluid to be a three molal NaCl solution that has equilibrated with dolomite, anhydrite, magnesite (MgCC>3), and quartz. The choice of NaCl concentration reflects the upper correlation limit of the B-dot (modified Debye-Hiickel) equations (see Chapter 8). To set pH, we assume a CO2 fugacity of 50, which we will show leads to a reasonable interpretation of the isotopic composition of the dolomite cement. [Pg.380]

We chose to modify the anhydride monomers with photopolymerizable methacrylate functionalities. Methacrylate-based polymers have a long history in biomedical applications, ranging from photocured dental composites [20] to thermally cured bone cements [21]. Furthermore, photopolymerizations provide many advantages for material handling and processing, including spatial and temporal control of the polymerization and rapid rates at ambient temperatures. Liquid or putty-like monomer/initiator... [Pg.187]

Compomers are properly called polyacid-modified composite resins and are a group of aesthetic materials chemically similar to the well-established composite resins [266], They were introduced to the dental profession in the early 1990s [267], and were intended to combine the benefits of traditional composite resins and glass-ionomer cements, and their trivial name reflects this, being derived from the names of these two parent materials, the comp coming from composite, and omer from ionomer [268], These materials are now considered a distinct class of dental restorative, with well established uses in clinical restoration, particularly in children s dentistry [269],... [Pg.362]

R.M.H. Verbeeck, E.A.P. De Maeyer, L.A.M. Marks, R.G.J. De Moor, A.M.C.J. De Witte, L.M. Trimpeneers, Fluoride release process of (resin-modified) glass-ionomer cements versus (polyacid-modified) composite resins. Biomaterials 19 (1998) 509-519. [Pg.376]

The incorporation of fly ash into Portland cement has been identified as one of the treatment parameters of cement composition to be evaluated. There is already an extensive experience database on the performance of fly-ash-modified Portland cement for heavy-metal immobilization and the solidification/stabilization (S/S) of radioactive waste. The United Kingdom (Wilding, 1992) and the United States (Huang et al., 1994) have used these materials, in the form of cement grouts, for the S/S of low- and intermediate-level radioactive wastes. In this section, we will review the known benefits of fly-ash-modified Portland cement over unmodified Portland cement, along with the anticipated improvements expected by the supercritical C02 treatment of modified Portland. [Pg.252]


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