oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Mechanical Properties of Polymer Concrete  [PDF]
Raman Bedi,Rakesh Chandra,S. P. Singh
Journal of Composites , 2013, DOI: 10.1155/2013/948745
Abstract: Polymer concrete was introduced in the late 1950s and became well known in the 1970s for its use in repair, thin overlays and floors, and precast components. Because of its properties like high compressive strength, fast curing, high specific strength, and resistance to chemical attacks polymer concrete has found application in very specialized domains. Simultaneously these materials have been used in machine construction also where the vibration damping property of polymer concrete has been exploited. This review deals with the efforts of various researchers in selection of ingredients, processing parameters, curing conditions, and their effects on the mechanical properties of the resulting material. 1. Introduction Polymer concrete is a composite material which results from polymerization of a monomer/aggregate mixture. The polymerized monomer acts as binder for the aggregates and the resulting composite is called “Concrete.” The developments in the field of polymer concrete date back to the late 1950s when these materials were developed as replacement of cement concrete in some specific applications. Early usage of polymer concrete has been reported for building cladding and so forth. Later on because of rapid curing, excellent bond to cement concrete and steel reinforcement, high strength, and durability, it was extensively used as repair material [1]. Precast polymer concrete has been used to produce a variety of products like acid tanks, manholes, drains, highway median barriers, and so forth. The properties of polymer concrete differ greatly depending on the conditions of preparation. For a given type of polymer concrete, the properties are dependent upon binder content, aggregate size distribution, nature and content of the microfiller, curing conditions, and so forth [2]. The most commonly used resins for polymer concrete are unsaturated polyester resin, methyl methacrylate, epoxy resins, furan resins, polyurethane resins, and urea formaldehyde resin [3]. Generally, more than 75–80% volume in polymer concrete is occupied by the aggregates and fillers. The aggregates are normally taken as inert materials dispersed throughout the polymer matrix. Normally aggregates are added in two size groups, that is, coarse aggregates comprising material of more than 5?mm size and fine aggregates having size less than 5?mm. The grading of aggregates in the case of polymer concrete is nonstandardized till date and varies widely from system to system. In addition to the coarse and fine aggregates, microfillers are also added sometimes to the polymer concrete
Effect of textile waste on the mechanical properties of polymer concrete
Reis, Jo?o Marciano Laredo dos;
Materials Research , 2009, DOI: 10.1590/S1516-14392009000100007
Abstract: the mechanical behavior of polymer concrete reinforced with textile trimming waste was investigated. two series of polymer concrete formulations were studied, with different resin/sand (i.e. binder/fine aggregate) weight ratios. in each series, recycled textile chopped fibers at 1 and 2% of the total weight was used. flexural and compressive tests were performed at room temperature and load vs. displacement curves were plotted up to failure. in the study, both the influence of fiber content and resin/sand weight ratio were considered relative to the behavior of polymer concrete reinforced with textile fibers. a decrease in properties was observed as function of textile fibers content. when specific properties were considered, this tendency was kept. however, higher textile fibers content lead to a smoother failure, unlike brittleness failure behavior of unreinforced polymer concrete.
Investigation of Crushing Type of Concrete s on Mechanical Properties of Concrete
International Journal of Materials Engineering , 2012, DOI: 10.5923/j.ijme.20120202.02
Abstract: In this study, determination of the effects of concrete aggregates on mechanical properties of concrete due to crushing type was investigated. For this purpose, mechanical properties of concrete mixtures such as strength and flow are determined by using aggregates crushed by two different types of crusher. Different types of concrete mixtures are prepared by using aggregates developed by vertically shafted (VS) and impact crushers (IC). Properties of concrete compounds such as water, cement are kept constant for each crushing type to determine the aggregate effect for concrete sets having different mixture rates. Four different types of concrete sets with two different aggregate types have been produced to prevent the predominant influences of concrete compounds except aggregate on mechanical properties. Thus, there was no mineral and chemical admixture used in the mix to obtain the nominative effect of aggregates produced with different crushing types, on strength and flow. Strength values for 7 and 28 days are obtained and comparisons have been made according to crushing type.
Mechanical Properties of Plastic Concrete Containing Bentonite  [cached]
Peng Zhang,Qiaoyan Guan,Qingfu Li
Research Journal of Applied Sciences, Engineering and Technology , 2013,
Abstract: Plastic concrete consists of aggregates, cement, water and bentonite, mixed at a high water cement ratio, to produce a ductile material. It is used for creating an impermeable barrier (cut-off wall) for containment of contaminated sites or seepage control in highly permeable dam foundations. The effects of water to binder ratio and clay dosage on mechanical properties of plastic concrete were investigated. The results indicate that the water to binder ratio and clay dosage have great influence on the mechanical properties of plastic concrete. There is a tendency of decrease in the compressive strength, splitting tensile strength, shear strength and elastic modulus of plastic concrete with the increase of water to binder ratio and clay dosage, while, the internal friction angle of the shear specimens is increasing gradually. To improve the resistance to deformation of cut-off walls constructed with plastic concrete, the higher water to binder ratio and clay dosage can be selected to decrease the elastic modulus of plastic concrete in the practical design and applications of plastic concrete on condition that the plastic concrete has enough compressive strength, tensile strength and shear strength.
Effect of Modifying Additives on Mechanical Properties of Refractory Concrete
Regina KALPOKAITE-DICKUVIENE,Kristina BRINKIENE,Algis MAKSTYS,Jurate CESNIENE
Materials Science , 2012, DOI: 10.5755/j01.ms.18.3.2442
Abstract: This experimental study presents the results of the combined effect of micro fibre and micro silica content on physical and mechanical properties of refractory concrete after exposure to high temperatures. A complex binder together with firestone aggregates was used for production of refractory concrete, which was reinforced simultaneously with micro fibre (1 wt % and 3 wt %) and micro silica (1.5 wt %, 3.5 wt % and 5 wt %). Unmodified concrete was produced as well. The results show that simultaneous modification with micro silica and micro fibre improves the flexural strength of the refractory concrete at all the temperatures investigated: 100 °C, 600 °C, 800 °C and 1000 °C. Contrary, the advantage of reinforcing agents on cold crushing strength of concrete was observed above 800 °C. It was determined that the mechanical strength of the refractory concrete increases with the increasing content of micro silica and reduces with the increasing content of micro fibre. DOI: http://dx.doi.org/10.5755/j01.ms.18.3.2442
Mechanical properties of recycled PET fibers in concrete
Pelisser, Fernando;Montedo, Oscar Rubem Klegues;Gleize, Philippe Jean Paul;Roman, Humberto Ramos;
Materials Research , 2012, DOI: 10.1590/S1516-14392012005000088
Abstract: fiber-reinforced concrete represents the current tendency to apply more efficient crack-resistant concrete. for instance, polyethylene terephthalate (pet) is a polyester polymer obtained from recyclable bottles; it has been widely used to produce fibers to obtain cement-based products with improved properties. therefore, this paper reports on an experimental study of recycled-bottle-pet fiber-reinforced concrete. fibers with lengths of 10, 15 and 20 mm and volume fractions of 0.05, 0.18 and 0.30% related to the volume of the concrete were used. physical and mechanical characterization of the concrete was performed, including the determination of compressive strength, flexural strength, young's modulus and fracture toughness as well as analysis using mercury intrusion porosimetry (mip) and scanning electron microscopy (sem). flexure and impact tests were performed after 28 and 150 days. no significant effect of the fiber addition on the compressive strength and modulus of elasticity was observed. however, the young's modulus was observed to decrease as the fiber volume increased. at 28 days, the concrete flexural toughness and impact resistance increased with the presence of pet fibers, except for the 0.05 vol.% sample. however, at 150 days, this improvement was no longer present due to recycled-bottle-pet fiber degradation in the alkaline concrete environment, as visualized by sem observations. an increase in porosity also has occurred at 365 days for the fiber-reinforced concrete, as determined by mip.
Properties of Concrete at Elevated Temperatures  [PDF]
Venkatesh Kodur
ISRN Civil Engineering , 2014, DOI: 10.1155/2014/468510
Abstract: Fire response of concrete structural members is dependent on the thermal, mechanical, and deformation properties of concrete. These properties vary significantly with temperature and also depend on the composition and characteristics of concrete batch mix as well as heating rate and other environmental conditions. In this chapter, the key characteristics of concrete are outlined. The various properties that influence fire resistance performance, together with the role of these properties on fire resistance, are discussed. The variation of thermal, mechanical, deformation, and spalling properties with temperature for different types of concrete are presented. 1. Introduction Concrete is widely used as a primary structural material in construction due to numerous advantages, such as strength, durability, ease of fabrication, and noncombustibility properties, it possesses over other construction materials. Concrete structural members when used in buildings have to satisfy appropriate fire safety requirements specified in building codes [1–4]. This is because fire represents one of the most severe environmental conditions to which structures may be subjected; therefore, provision of appropriate fire safety measures for structural members is an important aspect of building design. Fire safety measures to structural members are measured in terms of fire resistance which is the duration during which a structural member exhibits resistance with respect to structural integrity, stability, and temperature transmission [5, 6]. Concrete generally provides the best fire resistance properties of any building material [7]. This excellent fire resistance is due to concrete’s constituent materials (i.e., cement and aggregates) which, when chemically combined, form a material that is essentially inert and has low thermal conductivity, high heat capacity, and slower strength degradation with temperature. It is this slow rate of heat transfer and strength loss that enables concrete to act as an effective fire shield not only between adjacent spaces but also to protect itself from fire damage. The behaviour of a concrete structural member exposed to fire is dependent, in part, on thermal, mechanical, and deformation properties of concrete of which the member is composed. Similar to other materials the thermophysical, mechanical, and deformation properties of concrete change substantially within the temperature range associated with building fires. These properties vary as a function of temperature and depend on the composition and characteristics of concrete. The strength
The Mechanical Properties of High Strength Concrete for Box Girder Bridge Deck in Malaysia  [cached]
Azlan Adnan,Meldi Suhatril,Ismail Taib
Concrete Research Letters , 2010,
Abstract: This paper presents an experimental investigation of the mechanical properties of high strength concrete for box girder bridge deck in Malaysia. To study the Malaysia condition, high strength concrete samples were obtained from a Malaysian precast concrete factory that provides precast and in-situ concrete for box girder bridge deck construction. The mixed design properties of this type of concrete mixture were investigated; including the slump test, compressive strength, flexural strength, static modulus elasticity and Poisson’s ratio. Stress-strain curve relationship was produced as well, to be used for non-linear behaviour study.
Experimental Research on the Mechanical Properties of PVA Fiber Reinforced Concrete  [cached]
Wei Hu,Xingguo Yang,Jiawen Zhou,Huige Xing
Research Journal of Applied Sciences, Engineering and Technology , 2013,
Abstract: This study reports an experimental study on mechanical properties of concrete prepared by polyvinyl alcohol (PVA) fibers. Concrete mixtures are prepared under the same proportions, but by addition of different fibers content. Compressive, splitting tensile and directly tensile tests are carried out for concrete. Primary test results show that, the unit water consumption of mixture was increased with the dosage of PVA fibers, but the slump of concrete mixture was decreased. Experimental results show that, the compressive strength and splitting tensile strength are increased very quickly at the early ages (before the age of 28 days). The compressive strength of concrete is decreased with the increasing of fibers content, but the splitting tensile strength of concrete is increased with the increasing of fibers content. The elastic modulus of concrete was decreased with the dosage of PVA fiber, but the limit tensile strain was increased with the dosage of PVA fiber.
Mechanical Properties of Recycled Aggregate Concrete at Low and High Water/Binder Ratios  [PDF]
Gai-Fei Peng,Yan-Zhu Huang,Hai-Sheng Wang,Jiu-Feng Zhang,Qi-Bing Liu
Advances in Materials Science and Engineering , 2013, DOI: 10.1155/2013/842929
Abstract: This paper presents an experimental research on mechanical properties of recycled aggregate concrete (RAC) at low and high water/binder (W/B) ratios. Concrete at two W/B ratios (0.255 and 0.586) was broken into recycled concrete aggregates (RCA). A type of thermal treatment was employed to remove mortar attached to RCA. The RAC at a certain (low or high) W/B ratio was prepared with RCA made from demolished concrete of the same W/B ratio. Tests were conducted on aggregate to measure water absorption and crushing values and on both RAC and natural aggregate concrete (NAC) to measure compressive strength, tensile splitting strength, and fracture energy. The mechanical properties of RAC were lower than those of NAC at an identical mix proportion. Moreover, the heating process caused a decrease in compressive strength and fracture energy in the case of low W/B ratio but caused an increase in those properties in the case of high W/B ratio. The main type of flaw in RCA from concrete at a low W/B ratio should be microcracks in gravel, and the main type of flaw in RCA from concrete at a high W/B ratio should be attached mortar. 1. Introduction Recycling of demolished concrete is an important way of utilizing building waste as a resource of the whole society and an important part of the recycling process in the building and construction field. There are a great number of publications on research of recycling of demolished concrete, of which most are in regard to recycled concrete aggregate (RCA) made from demolished concrete [1–6]. Generally RCA is different from natural aggregate so that the properties of recycled aggregate concrete (RAC), which employs RCA as coarse aggregates, are also different from those of ordinary concrete which employs natural aggregates [7–11]. It is commonly believed that RCA has high porosity, low apparent density, and high water absorption. The normally used mechanical process of breaking blocks of demolished concrete into relatively small grains may cause RCA suffering internal damage such as microcracks [12–15] so that RAC has relatively lower strength compared to natural aggregate concrete (NAC) at the same water/binder (W/B) ratio [8, 12, 14, 16]. Some investigations found that a couple of approaches such as particle shaping and heating plus grinding can considerably improve the quality of RCA, in the forms of enhanced density and lowered crushing value of RCA, and hence improve mechanical strength of RAC [16–18]. However, there is a lack of understanding of the characteristics of flaws in RCA composed of original coarse aggregate
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.