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Showing 4 results for Cement Matrix

Hasan Ghasemzadeh, Ms. Esmat Akbari Jalalabad,
Volume 9, Issue 3 (9-2011)

In this study compressive strength of carbon nanotube (CNT)/cement composite is computed by analytical method. For this purpose representative elementary volume (REV) as an indicator element of composite is chosen and analyzed by elasticity relationships and Von mises' criterion applied to it. It is assumed that carbon nanotubes are distributed uniformly in the cement and there is perfect bonding in the interface of cement and nanotube. At first for simplicity of computations, carbon nanotubes ( CNTs) are assumed to have unidirectional orientation in the cement matrix. In following, the relations are generalized to consider random distribution of nanotubes in cement, and a new factor suggested for random orientation of fibers in the CNT/cement composite. The results of analytical method are compared with experimental results.

M. Khorami, J. Sobhani,
Volume 11, Issue 4 (12-2013)

Worldwide, asbestos fibers utilized in fiber cement boards, have been recognized as harmful materials regarding the public health and environmental pollutions. These concerns motivate the researchers to find the appropriate alternatives to substitute the asbestos material towards the sustainability policies. In this paper, the applicability of asbestos replacement with three types of agricultural waste fibers, including bagasse, wheat and eucalyptus fibers were experimentally investigated. To this end, the flexural behaviour and microstructure of cement composite boards made by addition of 2 % and 4 % of waste agricultural fibers in combination with and without 5 % replacement of silica fume by mass of cement were evaluated. The results of this study attested the applicability of utilized waste agricultural fibers in production of cement composite boards by improving the flexural and energy absorption characteristics, more or less, depending on the type of fibers. Moreover, it is found that application of silica fume in production of cement composite boards led to an increase in flexural strength.
Hojjatollah Maghsoodloorad, Ali Allahverdi,
Volume 14, Issue 6 (9-2016)

Efflorescence formation is an important soundness issue to be considered with alkali-activated cements. In this study, the impact of activator type on the efflorescence formation severity and methods of efflorescence reduction in alkali-activated phosphorus slag cement are investigated. Different alkaline activators including NaOH, KOH and liquid sodium silicate of different silica modules (Ms = SiO2/Na2O) were used for alkali-activation of phosphorus slag. Additions of high alumina cements (Secar 71 and 80) and application of hydrothermal curing condition at 85 °C for 7 h with different pre-curing times (1, 3 and 7 day) in humid environment (relative humidity of 95 %) and 25 °C were used for efflorescence control in alkali-activated phosphorus slag cement. Sodium containing activators resulted in more severe efflorescence formation compared with those of potassium containing activators. Also presence of liquid sodium silicate intensified efflorescence formation. Based on the results obtained, application of an optimum pre-curing stage in humid environment before hydrothermal curing regime stabilizes the cement matrix and improves the effectiveness of hydrothermal conditions.

Ms Ladan Hatami, Dr. Masoud Jamshidi,
Volume 15, Issue 5 (7-2017)

Colored self-compacting mortar (C-SCM) is a novel cementitious product that has been recently used in decoration and rehabilitation and has improved aesthetic 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 were 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.

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