Sharif Digital Repository

The aim of the present study was to experimentally investigate the interaction between a low replacement ratio of different nano-particles (SiO2, Al2O3, clay, and CaCO3) and aminosilane in the matrices of cement paste and mortar. Results showed that the optimum content of aminosilane for improving the 28-day compressive strength of cement mortar was 0.75% (by weight of the total binder). The utilization of nano-SiO2 and nano-clay particles improved the strengths of the cement mortar containing hybrid systems of nano-particles/aminosilane at early (7 days) and middle curing ages (28 and 91 days). The 28-day compressive strength enhancement of cement mortar with hybrid systems of nano-SiO... 

The behavior of a cemented gravely sand is studied using triaxial tests. Undrained tests were performed on saturated specimens, and stress-strain characteristics of the soil, along with volumetric and pore pressure changes, were recognized. Artificially cemented samples are prepared using calcite crystallization as the cementing agent in different percentages. The tests were done in usual range of confining pressures, from 50 to 1200 kPa. The results shows that dilation occurs even at highest confining pressure and least cement content. Also the friction angle of soils increases slightly with cement content, but cohesion intercept increasing is more noticeable  

In this study, the effect of agglomeration and non-uniform dispersion of silica particles on the mechanical and microstructural properties of cement paste incorporating silica fume and nanosilica (NS) with various specific surface areas (SSA) is experimentally investigated. The SSA and replacement percent of silica particles were considered as test variables and four series of mixes were made including one set of mixes for silica fume with a SSA of 20 m2/g and three sets of mixes for three different types of NS with SSA equal to 90, 200 and 380 m2/g. In each series of mix designs three different cement replacement percents of 1.5%, 3% and 5% were applied. The results indicate that as the SSA... 

This study concentrates on the industrial waste materials which have pozzolanic and / or cementitious property and can possibly be used in concrete mixtures or in controlled low strength material (CLSM) mixes. These materials as a cementitious or pozzolan not only reserve the environment but can replace Portland cement or reduce it. As in production of one tonne of Portland cement about one tonne of carbon dioxide is released into the environment, the aim is to reduce the amount of the Portland cement use in construction materials as much as technically possible. The research shows that some of the industrial waste materials or by-product materials which are produced in a vast amount per... 

The uniaxial viscosity and sintering stress of WC-10Co-0⊙ 9VC (wt-%) were obtained by a loading dilatometer as functions of fractional density (0⊙ 64< ρ< 0⊙ 93) and temperature (1084< T< 1297° C) according to a Newtonian constitutive law commonly used to simulate sintering. The viscosity is suggested to follow In η= a+ Q/RT+ bρ with the values of a= 52⊙ 3±4⊙ 5 and b= 16⊙ 8±0⊙ 2. Q reflects the temperature dependence of η and estimated to be 502±52 kJ mol-1. The sintering stress exhibited almost a constant value in the range of 0·05–0·4 MPa. It is shown that Rahaman's model best fits the experimental results. This paper describes experiments performed on nanostructured WC–Co feedstock to... 

Developments in the field of green cement-based products are characterized as an important approach to sustainable development and are being devoted much attention by the construction industry. Numerous types of materials are utilized; however, based on other published studies, the use of waste material as a filler normally deteriorates the performance of cementitious products. Appropriate additives thus need to be employed to improve the performances and properties of green products. As a consequence, the aim of this study has been to investigate the properties of a novel green cement-based composite-a hybrid system composed of cement, waste natural fiber, silica nano-particles, and... 

A new cationic flocculant was synthesized by graft copolymerization of acrylamide (AM) and 3-(methacryloylamino)propyl]trimethylammonium chloride (MAPTAC) onto salep using free radical polymerization initiated by ammonium persulfate (APS) to produce cationic salep [S-g-P(AM-co-MAPTAC)]. Reaction parameters (monomers/salep ratio, concentration of reactants, MAPTAC/AM ratio, and APS) were optimized using a full factorial experimental design to obtain the highest settling rate for cement suspensions. The best performing product was characterized by gel permeation chromatography (GPC), FTIR, 1H NMR spectroscopy, and thermogravimetric analysis (TGA). The resulted cationic flocculant may be... 

Cement kiln dust (CKD) is one of the most important waste materials in the cement industry. The large amount of this material, has encouraged researchers to propose new ways to recycle and reuse it. In this paper, effects of adding cement kiln dust to the ordinary Portland cement, on the physical and mechanical properties of ordinary and lightweight concrete were investigated. Results showed that concrete containing CKD, presents lower workability and modulus of elasticity; however, improvements in strength was observed by adding particular amounts of CKD. Eventually, it was found that adding 10% of cement weight CKD is the appropriate percentage for utilizing in manufacturing ordinary and... 

In this research, formation of aluminide/silicide diffusion coatings on γ -TiAl[Ti-48Al-2Nb-2Cr (at.%)] alloy using gasphase diffusion pack cementation process has been investigated. The application of powder mixtures with various chemical compositions in the pack cementation process performed at 1000°C for 6 hours in order to achieve simultaneous diffusion of Al and Si, showed that the composition of the powder mixture could have a significant effect on the structure and thickness of the aluminide/silicide coatings. The identification and analysis of aluminide/silicide microstructures formed as a result of simultaneous diffusion of Al and Si, which was comprehensively and qualitatively done... 

The behavior of a cemented gravely sand is studied using triaxial tests. Drained and undrained tests were performed on dry and saturated specimens, and stress-strain characteristics of the soil, along with volumetric and pore pressure changes, were identified. The gypsum plaster was used as the cement agent and was mixed with the soil in different percentages. The tests were done in the usual range of confining pressures, from 25 to 500 kPa. Test results show that dilation occurs even at the highest confining stress and the least cement content. The behavior of the cemented soil is found to be more brittle in drained condition than the undrained one. However, the brittleness of soil... 

Cemented coarse-grained alluvium is present in a vast area of Tehran city. Iran including its suburbs. This deposit consists of gravely sand to sandy gravel with some cobbles and is dominantly cemented by carbonaceous materials. In order to understand the mechanical behaviour of this soil, a series of triaxial compression tests were performed on uncemented, artificially cemented and destructured samples. Hydrated lime was used as the cementation agent for sample preparation to model the Tehran deposit. The tests were performed on cemented samples after an appropriate time for curing. The tests on cemented samples show that a shear zone appears as the shear stress approaches the peak shear... 

A study was conducted to select the best alternative for the development of construction panels as well as investment in its manufacturing in Iran. Three alternatives are considered, cement-bonded wood composite product, substituted products (such as concrete panel) sandwich panel and a mixture of them. We apply the analytic network process (ANP) to achieve this goal. A hierarchy is designed to prioritize benefits, opportunities, costs and risks (BOCR) by using the Analytic Hierarchy Process (AHP) ratings approach. To evaluate the "control criteria" of the system, a control hierarchy is also created and prioritized by applying the Analytic Network Process (ANP). A total of four major control... 

Because of their unique physical and chemical properties, nanoparticles have been gaining increasing attention and have been used in many fields to fabricate new materials with novel functions. If nanoparticles are integrated with cement-based building materials, the new materials might possess some outstanding properties. Ferrocement is a type of thin-wall reinforced concrete commonly constructed of hydraulic cement mortar reinforced with closely spaced layers of continuous and relatively small-sized wire mesh. The low level of technical skill required to make ferrocement and the ready availability of its materials make ferrocement suitable for a wide variety of applications. This study... 

The relatively new applications of superabsorbent polymers (SAPs) in cement based materials call for investigations regarding their behaviors in relation to other constituents in the system. Colloidal silica nanoparticles (CS) are becoming increasingly important for the improvement of strength and durability of cement based materials. In this study, a poly (AA-co-AM) SAP was synthesized by free radical polymerization, and its behaviors in cement based composites incorporating CS were investigated. These included swelling behavior, setting time, mechanical performance in different curing conditions, and rheological properties of fresh pastes. The observation of an unusual reduction in... 

An experimental study is conducted to measure small-strain shear modulus of clay-cement mixture using bender element apparatus setup in a triaxial cell. Bender element tests were conducted on cement-treated soils and the results were analyzed to study the variation of shear modulus properties of soil specimens at different cement contents, confining pressures, curing times, and compaction moisture contents. Based on the obtained results increasing the cement ratio has a significant effect on the small-strain shear modulus of the treated soils, and this effect signifies with increasing the moisture content and curing time. Rates of shear modulus enhancements due to cement content, curing... 

One of the most conventional and energy efficient methods to improve the engineering properties of concrete is the utilization of waste materials and by-products. Among agricultural wastes, rice husk ash (RHA) has exhibited the greatest potential to enhance the characteristics of cement mixtures. However, the investigations on the properties and performance of RHA are slim compared to its potential advantages and few systematic studies can be found in the literature regarding parameters influencing the chemo-physical and microstructural characteristics of RHA along with its performance in cement mixtures. In this study, the effect of retention time of rice husk is systematically... 

In this paper, the effect of dolomite type and Al2O3 content on the phase composition in aluminous cements containing MA spinel is investigated. For this reason, the raw and calcined dolomites are used as raw materials along with calcined alumina in the preparation of the cement. Then, different compositions are prepared at 1350 °C using the sintering method and their mineralogical compositions are investigated using the diffractometric technique. Also, their microstructures arre evaluated. The results indicate that raw materials used have great effect on the type and amount of formed phases in cement composition. Independently of the dolomite type used, a mixed phase product consisting of...