The Effect Of Fiber Volume On Tensile Strength

Ultra high performance concrete (UHPC) represents a major progress step over normal strength concrete (NSC) and high strength concrete (HSC), through the achievement of very high strength and very low permeability. Basically, the UHPC is a concrete with compressive strength ranging 120 to 400 MPa, this “ultra” high strength is achieved through different techniques including the use of improved materials, ultra-fine pozzolans (e.g. silica fume), low water-cement ratio, improved quality and higher dosage of superplasticizer, use of fibers (metallic or synthetic) to increase the energy absorption capacity and decrease brittleness, high cementitious materials content, longer mixing time and heat treatment [1]. UHPC tensile strength varies from 10 to 30 MPa; and the modulus of elasticity is in the range of 60 – 100 GPa [2].

Concrete: - It is one of the most widely used construction materials and has a long history of use. Cement is a very important material. Therefore it is necessary to know about it in some details. Generally, cement has been classified by different types depending upon its strength e.g. grade 43, grade 44 etc. Depending upon the requirement of strength of the structure the contractor decides as to which grade is to be used and where. It can be mixed by simple hand mixing method or for large quantities in a computer control batching plants. It is a solid hard mixture produced by adding Portland cement, coarse and fine aggregates and water in proper proportions.

Concrete is an artificial material in which the aggregates are bonded together by the cement when mixed with water. With the advancement of technology and increased field of application of concrete and mortars, the strength, workability, durability and other characteristics of the ordinary concrete can be made suitable for any situation. For this, definite proportions of cement, water, fine aggregate, coarse aggregate, mineral admixtures and chemical admixtures are

is result and discussion and it shows the compressive strength of bricks at 7 days and 28 days, and comparison between strengths. Its shows table and graph of strengths. it also deliberate the results of test performed on soil in the starting of

Concrete is the second most utilized substance in the world after water and is the most widely used construction material with an annual global production of about 10 billion tonnes. It is preferred in most structures because of its unique properties such as durability and high compressive strength. It is however relatively weak in tension, its tensile strength being about 10-15 % of its compressive strength requiring that it be reinforced with materials such as steel rods, glass or plastic fibers in order to improve its ductility. It is also prone to slight shrinkage during the drying process and may lead to cracking especially in normal strength concretes. (R. I. Gilbert, 2001). As defined by the Portland Cement Association, the durability of concrete is its ability to counteract abrasion, weathering action and chemical attack, and still maintain its desired engineering properties. The proportioning and interactions between concrete ingredients, placement and curing practices as well as the service environment determine this ultimate durability and life. The ideal situation therefore in any construction project is to choose the correct concrete type which will be more durable based on the project requirements.

Concrete is one of the essential component of public infrastructure and most buildings. It can only be more effective if we used reinforcement with it, because tensile strength without reinforcement is very low. It usually get cracked with time as it is brittle in property. There are some more causes of these cracks are shrinkage, inadequate water for hydration… etc. these cracks causes reinforcement exposes to atmosphere now reinforcement come into contact of O2 & H2O. That can cause corrosion which results in weaken of structure. That being said concrete is a high maintenance material. Concrete cracks and suffer wear and tear. Concrete is not as much flexible that it can handle significant amount of strain.

Concrete samples are considered over different time period for example the fresh concrete,7 days as well as 28 days and tested after keeping those specimens under different weather conditions. In lab, samples were kept under different conditions as follows:-

The aim of this research as discussed previously in chapter one is to investigate the use of recycled concrete aggregates in the building construction projects and relate it to the structural performance requirements, which will give a better understanding on the concrete made by using recycled concrete aggregates.

ABSTRACT Self compacting concrete with suitable chemical admixtures like Super Plasticizer and viscosity modifying agent can be cured, alternatively by addition of an internal curing agent instead of using large quantities of water. Steel fibers on the other hand have been used in cement and concrete composites for more than four decades, most of the steel fibers were introduced in the market prior to 1980. This is in sharp contrast to the continuous progress and development in the cement matrix itself. The proposed aim of the experiment is to examine the behavior of self compacting self-cured concrete by changing the steel fiber content. The mix incorporated 40 % replacement of cement with fly ash. The compressive strength and flexural strength of concrete were compared with conventional concrete by adding 0.5%, 1% and 1.5% of steel fibers and a notable accession of 79% in flexural strength was observed without compromising with the compressive strength.

Strength is defined as the maximum load that a material can carry. The strength of concrete usually increases when other properties of the material improves. Combined with the simple tests for strength, it makes strength a common and reliable way of measuring the quality of concrete.

There is a strong correlation between the compressive strength and other mechanical properties of concrete (Neville, 1996, Mehta and Monterio, 2005). Compressive strength is used as an index of flexural strength, tensile strength and shear strength of concrete. The flexure strength or modulus of rupture of normal concrete is approximately 7.5 to 10 times the square root of the compressive strength. Similarly, the tensile strength is about 8 to 12% of the compressive strength and is often estimated as 5 to 7.5 times the square root of the compressive strength. The shear strength of concrete is about 20% of the compressive strength (PCA, 1988). These correlations between compressive strength and flexure, tensile and shear strength varies with concrete ingredients and environment.

Reinforced concrete is one of the most important available materials for construction in Egypt and all over the world. It is used in almost all structures as: buildings, shells, bridges, tunnels, tanks and retaining walls. Concrete is made by mixing binding materials as sand and gravel held together with a paste of cement and water. The used of admixture is to change certain characteristic of concrete such as workability, durability and time of hardening. Some of concrete advantages are its high compressive strength, its ability to cast in almost any desired shape, its economical and fire resistance. Low tensile strength, low ductility and cracking consider one of its disadvantages. Regardless of this disadvantages, concrete still the materials of choice in construction.

Now a day, civil engineering structures require high strength and high durability concrete for construction, but at the same time concrete should be economical. This requirement leads to the development of concept of Self Compacting Concrete [1]. As Self Compacting Concrete completely fills the formwork by virtue of its own weight without segregation so dense matrix is formed which increase the strength and durability of structure [2]. But Conventional Self Compacting Concrete has low tensile strength, little cracking resistance and limited ductility. This limitation can be eliminated by addition of fibers [3]. Fibers have the potential to increase the post cracking energy absorption and enhancing the ductile character of concrete structure [4,5]. Also when, Steel Fiber Reinforced Self

Infrastructure development across the world created demand for construction materials. Concrete is the most important construction material. Concrete is a mixture of various ingredients like aggregates, water and admixture. Aggregate form is the major part of concrete among the entire ingredients used in concrete. The use of normal weight of aggregate such as gravel and granite probably reduces the natural stone deposits and it cause effect on environment. Therefore, it is necessary to explore and to find out suitable material for the replacement and to substitute the natural stone. In foreign countries, the natural and artificial light weight aggregate has been identified

Concrete as is well known is a heterogeneous mix of cement, water and aggregates. The admixtures may be added in concrete in order to enhance some of the properties desired specially. In its simplest form, concrete is a mixture of paste and aggregates. Various materials are added such as fly ash, rice husk, and admixture to obtain concrete of desired property. The character of the concrete is determined by quality of the paste. The key to achieving a strong, durable concrete rests in the careful proportioning, mixing and compacting of the ingredients.