Question

Write a detailed essay about the properties of concrete that are needed for a construction of a bridge. How does this bridge function according to these properties

Answer 1

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   4:10 % I Voi) 4G LTE 60% Done 121 Х Properties of concrete that are needed for a construction of a bridge: 1. Workability 2. Durability 3.Compressive strength/grade of concrete 4.Tensile strength 5. Moduluss of elasticity 6.Poisson ratio 7.Shrinkage 8.Creep 9. Curing of concrete 1.workability- The workability of freshly mixed concrete is that property which determines the ease and homogeneity with which it can mixed, placed, compacted and finished. A workability concrete should not show any segregation or bleeding. A workable concrete possesses required lubrication for handling concrete without segregation, can be placed in the form with out loss of homogeneity, compacted with minimum effort and shall be finished easily. Factors that may effect the workability are water cement ratio means it is the ratio of amount of mixing water to the weight of cement required to obtain the desired consistency and workability of concrete mix is known as water cement ratio, the water cement ratio mat varies from 0. 5 to 0.6 times the weight of cement. The other factors which effects the workability are type and grading of concrete, use of admixtures, efficiency of mixing. 2.Durability: 00 OO Wrap Text Tools Keyboard
   
   4:10 2 Voi) 4G LTE 60% Done 21 Х 1/4 concrete, use of admixtures, efficiency of mixing. 2.Durability: It is the property of the concrete by virtue of which it is capable of resisiting its disintegration and decay which may be caused to: a. Use of unsound cement. b. Use of less durable aggregate. c. Entry of harmful gases and salts through the pores and voids present in the concrete. d. Expansion and contraction resulting from temperature changes and alternate drying and wetting. The resistance of concrete to chemical attack, weathering, abrasion and fire etc, mostly depends upon the conditions of exposure, grade of concrete used, quality of its materials and the extent of voids and pores present in the concrete mass. The amount of cover provided over reinforcement and the degree of impervious of concrete mix also influence the durability of concrete. 3.compressive strength/grade of concrete: The compressive strength of concrete is the characteristic compressive(fck) of 150mm concrete cubes at the age of 28days in N/mm2. The characteristic strength is defined as the strength of material below which not more than 5% of the test results are expected to fall. As the grades of concrete varies from 15t080N/mm2 designated as M15 to M80. Based on the compressive strength. 4.tensile strength: The tensile strength of the concrete is very low and hence it is not taken into account in the design of reinforced concrete. But it is an important property which effects the extent and width in the structure. It can be calculated through Fck=0.7(fck) 1/3 OD: OO Wrap Text Tools Keyboard
   
   4:10 2 Voi) 4G LTE 60% Done 21 Х Fck=0.7(fck)^1/3 can be calculated through 5. Modulus of elasticity- Modulus of elasticity is an important property required for computation deflections of structural concrete members. In the absence of test data, the modulus elasticity of concrete is related to compressive strength by following relations as ls456-2000 6.poisson ratio- Poisson ratio varies between 0.1 for high strength concrete and 0.2 for week concrete usually it is taken as0.15 for strength design and 0.2 for serviceability calculations. 7.curing of concrete- Curing is the process of keeping the finished concrete surface moist under ambient temperature soon after its setting, to facilitate the continuation of hydration reaction between cement and water, due to which concrete gains strength. Curing has strong influence on the properties of hardened concrete. Proper curing will increase durability, water tightness, abrasion resistance, volume stability and resistance to freezing and thawing. Methods of curing 1.poding and immersion. 2.fogging and sprinkling. 3.wet coverings. 4.membrance curing. 5.curing with gunny bags. These bridge function according to these properties like this the durability of the concrete is vital with regards to the structure life span. The importance CIU DO 00 Wrap Text Tools Keyboard
   
   4:10 2 Voi) 4G LTE 60% Done 21 Х uurarity of the Concrete is via WILIT Tegarus to the structure nie span. The importance 3/4 Of the concrete durability cannot be underestimated. For many years the design of precast prestressed concrete girders was based on concrete compressive strengths of 34t041 Mpa. The strength level served the industry well and provides the basis for establishing the prestressed Concrete bridge industry. As the concrete cures, water from the prewetted aggregate provides the hydration necessary for curing and also enables curing from the inside. SRAs work by reducing the surface tension of pore water and there by decreasing the capillary stress and shrinkage induced by drying. Several studies have reported that using SRAs in concrete mixtures in one the most effective ways of reducing shrinkage cracking used. Prestress losses assumed for the bridge girder design and deflection girder design and deflection analyses are dependent an the concrete moduluss of elasticity. Ost design specifications, such as the American highways and transportation officials bridge specifications, contain a constant value for the Moe based on the unit weight of concrete and the concrete compressive strength at 28days. It has been shown in the past that Moe age varies with the age of concrete. EIO 00 00 Wrap Text Tools Keyboard