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
Experimental study on the effect of ambient temperature on ready-mix concrete strength. Part 2: Industrial implementation
Puig Montraveta, J.,Masó Gamell, D.,Ortiz Lozano, J. A.,dos Santos, A. C. P.
Materiales de Construccion , 2010,
Abstract: This paper is the second part of an experimental study about the effect of environmental temperature on the concrete performance, from an industrial perspective. An earlier article on its effect on aggregate, paste, mortar and concrete workability and mechanical properties reported that high temperature had a clearly adverse impact on strength, which can generally be offset with overdoses of both cement and water to maintain the original water/cement ratio. In this second part of the paper the basis of a methodological formulation is presented, with the purpose of carry out the optimization of the overdosage of cement in concrete in hot climates, in order to be industrially implemented in ready mix concrete plants. This proposal has been successfully applied in some ready mix concrete plants of the company Promotora Mediterránea 2, S.A. (PROMSA), considering that the cement content (overdosage) in concrete can be optimized without any adverse effect in its performance, reason why it is possible to reduce the production costs of concrete without reducing its quality. El presente artículo constituye la segunda parte de un estudio experimental sobre la influencia de la temperatura ambiental sobre las prestaciones del hormigón, desde una perspectiva industrial. En la primera, se estudió el efecto sobre las propiedades de trabajabilidad y mecánicas, en áridos, pasta, mortero y hormigones, detectando un claro efecto negativo de la temperatura elevada sobre la resistencia, que se suele solucionarcon una sobredosificación en cemento y agua, para mantenerla relación agua/cemento original.En esta segunda parte del artículo, se presentan las bases de una formulación metodológica para llevar a cabo la optimización de la sobredosificación de cemento en el hormigón en climas cálidos, para ser implementada industrialmente en plantas de hormigón preparado. Dicha propuesta se ha aplicado con éxito a escala industrial en plantas de producción de hormigón preparado de Promotora Mediterránea 2, S.A. (PROMSA), considerando que la sobredosificación de cemento en el hormigón puede ser optimizado sin causar detrimentos en las prestaciones del mismo, lo que permite reducir costes de producción sin castigar la calidad del producto.
Applications and Prospects of Fiber Reinforced Concrete in Industrial Floors  [PDF]
Hesham Alsharie
Open Journal of Civil Engineering (OJCE) , 2015, DOI: 10.4236/ojce.2015.52018
Abstract: Upon the view of this work, industrial floor is a vital structure due to its relation to quality of production, labor comfort, and human health. Flooring costs may reach 20% of single-story building construction expenditure, and the consumption of concrete for floors may come to 40% - 50% of the total size of concrete. Thereby, the efficient design of floor will reduce materials consumption and labor, and will increase the endurance of the floor. Fiber reinforcement reduces the thickness of the subfloor about 20% - 30%, hence enabling to reduce the consumption of cement and fillers. The use of fiber meshes will enable to save 30% - 40% of steel. Despite the flexible use of fiber in concrete reinforcement saves effort and money, still fiber reinforced concrete is lacking additional regulations in Jordan.
A Survey of High Performance Concrete Developments in Civil Engineering Field  [PDF]
Vatsal Patel, Niraj Shah
Open Journal of Civil Engineering (OJCE) , 2013, DOI: 10.4236/ojce.2013.32007
Abstract:

High Performance concrete (HPC) has received increased attention in the development of infrastructure Viz., Buildings, Industrial Structures, Hydraulic Structures, Bridges and Highways etc. leading to utilization of large quantity of concrete. This paper presents a comprehensive coverage of High Performance concrete developments in civil engineering field. It highlights the High Performance concrete features and requirements over conventional concrete. Furthermore, recent trends with regard to High Performance Concrete development in this area are explored. This paper also includes effect of Mineral and Chemical Admixtures used to improve performance of concrete.

Strength properties of glass fibre concrete  [PDF]
Chandramouli K,Srinivasa Rao P,Seshadri Sekhar T,Pannirselvam N
Journal of Engineering and Applied Sciences , 2010,
Abstract: The present day world is witnessing the construction of very challenging and difficult civil engineering structures. Quite often, concrete being the most important and widely used material is called upon to possess very high strength and sufficient workability properties. Efforts are being made in the field of concrete technology to develop such concretes with special characteristics. Researchers all over the world are attempting to develop high performance concretes by using fibres and other admixtures in concrete up to certain proportions. In the view of the global sustainable developments, it is imperative that fibres like glass, carbon, polypropylene and aramid fibres provide improvements in tensile strength, fatigue characteristics, durability, shrinkage characteristics, impact, cavitation, erosion resistance and serviceability of concrete. Fibres impart energy absorption, toughness and impact resistance properties to fibre reinforced concrete material and these characteristics in turn improve the fracture and fatigue properties of fibre reinforce concrete research in glass fibre reinforced concrete resulted in the development of an alkali resistance fibres high dispersion that improved long term durability This system was named alkali resistance glass fibre reinforced concrete. In the present experimental investigation the alkali resistance glass fibres has been used to study the effect on compressive strength, split tensile strength and flexural strength on M20, M30, M40 and M50 grades of concrete.
Effect of size and shape of specimen on compressive strength of glass fiber reinforced concrete (GFRC)  [PDF]
Krishna Rao M.V.,Kumar Rathish P.,Srinivas B.
Facta Universitatis Series : Architecture and Civil Engineering , 2011, DOI: 10.2298/fuace1101001k
Abstract: Concrete is a versatile material with tremendous applications in civil engineering construction. Structural concrete elements are generally made with concrete having a compressive strength of 20 to 35 MPa. Lately, there is an increase in use of high strength concrete (HSC) in major construction projects such as high-rise buildings, and bridges involving members of different sizes and shapes. The compressive strength of concrete is used as the most basic and important material property in the design of reinforced concrete structures. It has become a problem to use this value as the control specimen sizes and shapes are different from country to country. In India, the characteristic compressive strength is usually measured based on 150 mm cubes [1]. But, the ACI code of practice specifies the design compressive strength based on the standard 150x300 mm cylinders [2]. The use of 100x200 mm cylinders gained more acceptance as the need to test high strength concrete increases [3]. In this context the size and shape of concrete becomes an important parameter for the compressive strength. In view of the significance of compressive strength of concrete and due to the fact that the structural elements of different sizes and shapes are used, it is proposed to investigate the effect of size and shape of the specimen on the compressive strength of concrete. In this work, specimens of plain as well as Glass Fiber Reinforced Concrete (GFRC) specimens are cast in order to carry out a comparative study.
The Effect of Accelerators and Mix Constituents on the High Early Strength Concrete Properties  [PDF]
V. M. Sounthararajan,A. Sivakumar
ISRN Civil Engineering , 2012, DOI: 10.5402/2012/103534
Abstract: The present research study focused on the high early strength concrete properties that can be produced with large replacement of cement by fly ash. Also, the effects of adding fibres on the compressive strength gain and early age strength gain properties are determined. Tests were conducted on different high strength concrete specimens, where fly ash was substituted for cement up to 50%. Different types of concrete specimens were casted and tested for different fine-to-coarse aggregate ratio, metallic fibre content, cement-to-total-aggregate ratio, and accelerator dosage. The test results indicated that high early strength concrete (50.7?MPa at 7 days) was obtained for higher F/C ratio of 0.8, C/TA ratio of 0.24, and higher dosage level of steel fibre at 1.5%. 1. Introduction High-early-strength-based cementitious materials are of vital importance for the present expanding civil infrastructure. However, the deterioration of civil infrastructure all over the world has led to the realization that cementitious materials must be improved in terms of their engineering property and durability. The use of admixtures such as fly ash has little effect on pozzolanic properties to improve the engineering properties of fly-ash-substituted concrete. In a structural concrete durability should be high, as presented by water-to-binder ratio (W/B). A concrete structure is said to be durable if it withstands the conditions for which it has been designed, without deterioration for the entire period of life [1–5]. However, use of chlorides may cause corrosion in steel reinforcing and is prohibited in some countries, so that calcium nitrates can be potentially used to achieve high early strength concrete. These techniques are especially useful in the prefabrication industry, wherein high early age strength enables the removal of the formwork within 24 hours, thereby reducing the cycle time, resulting in cost-saving benefits [6]. Pozzolana increases the later age strength of concrete as it reacts with calcium hydroxide and turns it into calcium-silicate-hydrates (C-S-H). However, Portland pozzolana cements have higher activation energy and, therefore, their rate of hydration is lower as compared to ordinary Portland cements [7]. In a similar context, the addition of steel fibers improves the concrete matrix in all mechanical properties of concrete such as compressive strength, spilt tensile strength, flexural strength, and toughness. Steel-fiber-reinforced concrete is made for cement-based composite material reinforced with randomly distributed steel fibers diameter. It
Зал зобетонн рамн конструкц для промислових буд вель REINFORCED CONCRETE FRAME CONSTRUCTIONS FOR INDUSTRIAL BUILDINGS Железобетонные рамные конструкции для промышленных зданий  [cached]
Valery N. Pershakov,Roman V. Borovsky,Oleksandra O. Gorbenko,Nataliya Y. Vrublevska
Proceedings of National Aviation University , 2009,
Abstract: Проведено огляд анал з досв ду проектування буд вництва одноповерхових промислових буд вель з рамними зал зобетонними конструкц ями. Generalization and the analysis of experience of designing and construction of single-storied industrial buildings from reinforced concrete constructions is lead. Проведен обзор и анализ опыта проектирования и строительства одноэтажных промышленных зданий с рамными железобетонными конструкциями.
Early Estimation of Hardened Concrete Strength  [PDF]
Hasan M. Tantawi,Emhaidy S. Gharaibeh
Journal of Applied Sciences , 2006,
Abstract: Due to the large expansion in concrete projects and due to the importance of time and its direct impact on project cost, an essential need to estimate the hardened concrete strength within the first few hours of casting the concrete. In addition to that, it is known that in most concrete projects, casting of concrete is done in a consequence stages, so if the obtained hardened concrete strength is less than the target strength, then the time could be too late to take the necessary and right action. On the other side, if the obtained hardened concrete strength is more than target one then again it is uneconomical and time is done to save the wasted money in getting such a high unnecessary strength. Based on that, in this research the available methods of predicting hardened concrete strength at early stage were reviewed. One of these methods is developed and the effect of water cement ratio and cement dose on early strength estimation is discussed. Using non linear regression analysis, a theoretical model is established to estimate consolidated concrete strength at 7 and 28 days by knowing its strength after 6 h of its casting. Accelerating tests for early determination of concrete strength are used to generate expressions for prediction of hardened concrete strength as composite function of cement content and W/C ratio. By testing more than 200 cubes, the suggested theoretical model shows a good agreement with experimental results.
EFFECT OF SILICA FUME ON STRENGTH AND DURABILITY PARAMETERS OF CONCRETE  [PDF]
N. K. Amudhavalli,Jeena Mathew
International Journal of Engineering Sciences and Emerging Technologies , 2012,
Abstract: Portland cement is the most important ingredient of concrete and is a versatile and relatively high cost material. Large scale production of cement is causing environmental problems on one hand and depletion of natural resources on other hand. This threat to ecology has led to researchers to use industrial by products as supplementary cementations material in making concrete. The main parameter investigated in this study is M35 grade concrete with partial replacement of cement by silica fume by 0, 5, 10,15and by 20%. This paper presents a detailed experimental study on Compressive strength, split tensile strength, flexural strength at age of 7 and 28 day. Durability study on acid attack was also studied and percentage of weight loss is compared with normal concrete. Test results indicate that use of Silica fume in concrete has improved the performance of concrete in strength as well as in durability aspect.
Concrete hardening accelerator containing galvanic sludge (rus)  [PDF]
Stepanov S.V.,Morozov N.M.,Khozin V.G.
Magazine of Civil Engineering , 2012,
Abstract: One of the most effective ways to reduce power inputs to the manufacture of concrete and reinforced concrete products is the use of hardening accelerator additives that reduce the time or lower the temperature of thermal processing. From economic and ecological points of view it is expedient to use the by-products and waste industry for the production of additives. In this paper we propose the use of galvanic sludge, which structure contains oxide, hydroxide and aluminum sulphate. Its use leads to an increase in the strength of cement stone in the first hours and days of hardening, as the number of Ettringite increases in the system. As galvanic sludge is a fine product, it is more effectively used in conjunction with superplasticizer, resulting in a complex chemical additive. Application of such additives enables to triple the durability of the cement stone at the age of 12 hours, and to increase in two times the concrete strength at the age of 1 day of hardening. The effectiveness of additives remains constant when changing the mobility of the mixture, that allows applying it in different ways of forming concrete products.
Page 1 /100
Display every page Item


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