Corrosion Of Reinforcement In Hvfa Concrete
Introduction
Corrosion of reinforcements has been one of the major challenges that the civil engineers have been facing. Corrosion leads to the formation of rust which results in the spalling of concrete which in turn leads to the exposure of rebars to the aggressive environment. This will accelerate the ill effects and ultimately leads to the break down of the structure. Corrosion mainly occurs in areas of aggressive environment such as coastal regions. It is very important that corrosion of reinforcement must be prevented in order to have a durable structure. Even though there are many methods to prevent corrosion, most of them are uneconomical and requires great skill.
Some of the recent studies in various parts of the world have revealed that High Volume Fly Ash (HVFA) concrete can protect the steel reinforcement more efficiently, so that it can resist corrosion, and thus the structure as a whole. HVFA concrete is a type of concrete in which a part of the cement is replaced by fly ash, which is an industrial waste. Thus the implementation of H V F A concrete can minimize corrosion in an effective way. Moreover it can lead to much durable structure without considerable increase in cost. .
Silica Fume Concrete
Silica Fume Concrete
Introduction
Silica fume is also referred to as micro silica or condensed silica fume but the term silica fume has been generally accepted. It is a by-product of manufacture of silica and ferrosilicon alloys from high purity quartz and coal in a submerged arc electric furnace. It is reported that the addition of ultra fine particle in HPC improves the strength of concrete. The optimum silica fume proportions in between 20% and 25% by weight of concrete. In it self silica fume does not have any binding properties, but it reacts with calcium hydroxide on hydration of cement and produces the gel i.e. calcium silicatehydrate which has good binding properties. Silica fume has been used in manufacture of high strength concrete.. .
Self Compacting Concrete
Self Compacting Concrete
Introduction
Self Compacting Concrete (SCC) is defined as a category of High Performance Concrete that has excellent deformability in the fresh state and high resistance to segregation, and can be placed and compacted under its self weight without applying vibration. SCC was first developed in Japan in mid 1980. Since then, it has found applications in reinforced concrete sections containing congested reinforcements. Poor quality of vibration of concrete, in congested locations, has often been a shortcoming of traditional concrete. In such situations, SCC, which flows under its self weight and does not require any external vibration, has revolutionized the concrete placement.
Fatigue Behaviour Of Steel Fibre Reinforced Concrete Beams
Fatigue Behaviour Of Steel Fibre Reinforced Concrete Beams
Introduction
Construction material subjected to repetitive or cyclic loading have to be qualified for their fatigue behaviour. Generally their behaviour is considered satisfactory if they withstand two million cycle of repetitive loading without distress or failure at that required mean stress level and range stress.
The recent research in reinforcing Portland cement based material with randomly distributed fibres was spurred by pioneering research or fibre reinforced concrete (FRC) conducted in the United state in the 1960s.The addition of fibre in the concrete matrix improves the monotonic flexural strength, flexural fatigue strength, impact strength, shock resistance, ductility, and flexural toughness in concrete, besides delaying and arresting crack proportion.
Fatigue is often described by a parameter ËœFatigue lifeâ„¢ which essentially represents the number of cycles the material can withstand under a given pattern of repetitive loading, before falling. This paper presents the details of the experimental investigations carried out at the structural engineering research centre (S E R C) to study the behaviour of reinforced concrete beam cast at different types of steel fibre in the concrete matrix and subjected to Fatigue loading.. .
Stress Ribbon Bridges
Stress Ribbon Bridges
Introduction
Philosophers, thinkers, intellectuals all appeal, please build bridges and not walls between different communities, nationalities, countries, languages etc, to achieve universal brotherhood. This can be achieved by constructing stress ribbon bridges.
Stress ribbon bridges are very economical, aesthetical and almost maintenance free structure. They require minimal quantity of materials. They are erected independently from the existing terrain and therefore they have minimum impact upon the environment during construction.
Stress ribbon bridge is the term used to describe structures formed by a very slender concrete deck in the shape of a catenary. They can be designed with one or more spans and are characterized by successive and complementary smooth curves. These curves blend in to natural environment and their forms, the most simple and basic of structural solutions. The stress ribbon bridge can be erected without undue pressure on the environment.
Stress ribbon bridges looks at how slender concrete deck are used in the design of suspension and cable stayed structures. It looks at their characteristic feature; their rigidity, which is mainly given by the tension stiffness of prestressed concrete decking so much so that movement caused by pedestrians or wind does not register as discomfort by users. As opposed to suspension bridges, where the cables carry the load, in stress ribbon, by tensioning the cables and the deck between the abutments, the deck shares the axial tension forces. Anchorage forces are unusually large since the structure is tightly tensioned.
At present studies on combining stress ribbon bridges with cables or arches, to build most economical stress ribbon bridges. It makes the study of features of stress ribbon bridges as an important one. .
Passive Solar Buildings
Passive Solar Buildings
Introduction
Passive solar heating and cooling represents an important strategy for displacing traditional energy sources in buildings. Passive solar techniques make use of the steady supply of solar energy by means of building designs that carefully balance their energy requirements with the building's site and window orientation. The term passive indicates that no additional mechanical equipment is used, other than the normal building elements.
In this approach, the building itself or some element of it takes advantage of natural energy characteristics in materials and air created by exposure to the sun. Passive systems are simple, have few moving parts, and require minimal maintenance and require no mechanical systems. All solar gains are brought in through windows. All passive techniques use building elements such as walls, windows, floors and roofs, in addition to exterior building elements and landscaping, to control heat generated by solar radiation. Solar heating designs collect and store thermal energy from direct sunlight. Passive cooling minimizes the effects of solar radiation through shading or generating airflows with convection ventilation.
The benefits of using passive solar techniques include simplicity, price and the design elegance of fulfilling one's needs with materials at hand. As a design approach, passive solar design can take many forms. It can be integrated to greater or lesser degrees in a building. Key considerations regarding passive design are determined by the characteristics of the building site. The most effective designs are based on specific understanding of a building site's wind patterns, terrain, vegetation, solar exposure and other factors often requiring professional architectural services. However, a basic understanding of these issues can have a significant effect on the energy performance of a building. . .
New Techniques Of Erosion Control On Hill Roads
New Techniques Of Erosion Control On Hill Roads
Introduction
Transportation contributes to all round development of a country and hence plays a vital rate towards its progress. India, being predominantly rural in nature, road links is found to have distinct advantages over other modes of transportation. The impact of highway location on the environment is a major concern of the highway engineer and the public. If the highways are not properly located and designed it will subject to erosion and may contribute sediments to streams. The control of soil and water is basic to the protection of the road structure and therefore highway design, construction and maintenance procedure must be continually evaluated to minimize erosion and sedimentation problems.
Erosion can be controlled to considerable degree by geometric design and with proper provision for drainage and fitting landscape development. Although some standardization of methods for minimizing soil erosion is also possible. Also erosion process is a natural phenomenon accelerated by manâ„¢s activity, technical competency is evaluating the severity of erosion problem and the planning and design of preventive and corrective measures is essential in obtaining economical and environmental satisfactory methods for erosion control.
Application Of Infrared Thermography In Concrete Engineering
Application Of Infrared Thermography In Concrete Engineering
Introduction
Different types of Non-Destructive tests (NDT) are there to detect voids and cracks in concrete such as Ultrasonic Pulse Echo, Ultrasonic Pulse Velocity, Ground Penetrating Radar, Impact Echo Method, X-ray Scanning Method, Rebound Hammer Method, Infrared Thermography Method .In which Infrared Thermography method is discussed in this paper As concrete is used in newer areas and evidence is coming to light of premature deterioration in concrete structures there is a need to develop new methods for quality control at the time of concrete construction and for the evaluation of existing structures .
Concrete specimens were designed and conditioned to represent some of the anomalies that may be found during construction and also in hardened concrete. From the study it emerges that Infrared Thermography is an effective tool for concrete placement and identifying location of voids and cracks in fresh and hardened concrete. It could be effectively used to narrow down areas that needed closer attention during an in-service inspection of concrete structures.
Trenchless Technology
Trenchless Technology
Introduction
Trenchless technology is a relatively new term that describes the installation of conduits beneath roadways without open-cutting. The term has been used on a global basis since the mid-1980s. However, some of the methods referred to as trenchless methods are not new. For example, auger boring and slurry boring have been used since the 1940s, and pipe jacking has been used since the early 1900s. These methods are referred to as road boring techniques or horizontal earth boring techniques. Nevertheless, many new trenchless techniques have been introduced and many advancements have taken place with the more traditional techniques. Although most of these methods require excavation for shafts, shaft locations usually can be selected to avoid or minimize traffic disruption.
It is anticipated that the use of trenchless technology will continue to increase because of its inherent advantages of minimizing disruption to society and reducing environmental impact. Another driving force behind this increase is the benefit of avoiding or minimizing the handling, volume, treatment and/or disposal of contaminated soil. In many situations, these techniques have become cost-effective alternatives to traditional open-cutting methods
Plastic As Soil Stabilizer
Plastic As Soil Stabilizer
Introduction
Use of plastic products such as polythene bags, bottles, containers and packing strips etc. is increasing day by day. As a result amount of waste plastic also increased. This will leads to various environmental problems. Many of the wastes produced today will remain in the environment for many years leading to various environmental concerns.
Therefore it is necessary to utilize the wastes effectively with technical development in each field. Many by-products are being produced using the plastic wastes. This paper presents the details of studies, conducted by various researchers on the possible use of waste plastic for soil stabilization. The results of the studies indicate that by adding plastic strips in soil; shear strength, tensile strength and California bearing ratio (CBR) value of the soil increases.
Evacuation Patterns In High Rise Buildings
Evacuation Patterns In High Rise Buildings
Introduction
This topic deals with the evacuation pattern in high rise buildings mainly on the onset of fire. The ability to warn population of the impending disasters has become a reality only in the last few years. The ability to track and warn must be complimented with the capability of effecting a timely evacuation of potentially threatened areas. The two problems that exist are the ability to adequately disseminate a warning of an impending disaster and that of producing an evacuation once the warning has been received. These problems can be overcome by the development of a timely and accurate warning system, identification of escape routes, and establishment of a policy wherein every one within a threatened area is required to evacuate when an order is given..
Superplasticisers For Ready Mix Concrete Plants
Superplasticisers For Ready Mix Concrete Plants
Introduction
Superplasticisers are high range water reducing admixtures..Admixture is defined as a material other than cement ,water and aggregate that is used as an ingredient of concrete and is added to the batch immediately before or during mixing. The development of superplasticisers is one the major break throughs in concrete technology, which will have a significant effect on the production and use of concrete in the next millennium. Superplasticisers have been greatly responsible for development of the following connects.
1) High performance connects
2) High strength concrete
3) High durability concrete
4) Self compacting concrete
5) High volume flyash /slag concrete
6) Fibre reinforced concrete
7) Anti washout concrete under water.
A superplasticiser is one of a class of admixtures called water reducers that are use to lower the mix water requirement of the concrete. They are chemically different from normal water reducers and are capable of reducing water contents by about 30 percent. They are variously known as superplasticisers, super fluidizers , superfluidifiers, super water reducers or high range water reducers.
In Japan, during the late 1960â„¢s superplasticisers were developed. Ready mix concrete incorporating water reducers and workability enchancers make use of superplasticisers and delivers increased workability without loss of ultimate strength or durability. The role of superplasticisers in ready mix concrete industry is essential where ordinary as well as high strength or high performance concrete with slump retention capability are to be produced. Superplasticisers can be used to reduce the amount of water to produce high strength concrete and to reduce the amount of cement.
Mobile Inspection Platform
Mobile Inspection Platform
Introduction
There is a need for reliable and economic Mobile Inspection Platform (MIP) for the inspection of Bridges. We have in our country, a large number of road bridges. Every year new road bridges are added to the existing bridges. The older bridge require maintenance to continue to permit serviceability. For proper maintenance, assessment is to be done. Inspection for assessment is to be done not only from the top of the carriageway, but also from the side and bottom of the deck, and also around the sub-structure. The MIP provides a very economic and convenient means of producing such inspection data. Minor maintenance can also be carried out using MIP... .
Engineering Aspects Of Reinforced Soil
Engineering Aspects Of Reinforced Soil
Introduction
Reinforced soil is composite material which is formed by the associating of frictional soil and tension resistant elements in the form of sheets, strips, nets or mats of metal, synthetic fabrics or fibre reinforced plastics and arranged in the soil mass in such a way as to reduce or supress the tensile strain which night develop under gravity and boundary forces. It is well known that most granwar soils are strong in compression and shear and weak in tension. The performance of such soils can be improved by introducing reinforcing elements in the direction of tensile straine in the same way as in reinforced concrete.
The variety and range of application of reinforced soil is unlimited severs field applications include retaining walls, abutments, away walls, embankments dams, hill roads, housing, foundations, railways, industry, pipe works, waterway structure and under ground structures. The soil reinforcement technique results in
(i) a simple , composite material, quick and easy to make
(ii) a flexible material, able to withstand important deformation without damage.
(iii) A heavy material both from the technical and architectural paint of view and
(iv) An economical material.
These merits of reinforced soil enabled its use in almost all civil engineering structures.
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