Construction Material Project - Report Example

Materials design project Name; Course: Instructor: Date: Contents 1.0.Introduction 6 This project requires that the material engineer comes up with a design of a 100m span steel arch bridge which should incorporate a 6-lane carriage way, and measuring 24 m in width. Similarly, the bridge should consist of reinforced concrete abutment on each side of the river. The abutment measurements of the design are supposed to measure 28m by 24 m. the steel arch bridge should also include a large angle and flat box section for fabrication of the various structural components of the bridge. In the design, the engineer is expected to provide support for high loading impact on the bridge which therefore calls for the incorporation of rail connections in the bridge design. Finally, high bolts are expected to provide anchorage as well as the rail connections at various points. The aim of the report is this to present a design concept that incorporates concrete mix design, the selection of steel to be used and the specifications for both concrete and steel preferred for the intended project. 6 2.0.Concrete mix design 6 The design will require two types of concrete mixes, each 24m*24m*24m* in measurement. One mix will be made up of fly ash/cement as the binding material while the other one will have slug/cement as the binding component. The two mixes will then be subjected to various tests to establish their comparative performance in terms of proportions of the ingredients used and the heat dehydration measures in each mix. 6 2.1.Abutment in the Arch Bridge 7 Most contemporary construction methods for bridges often incorporate abutment an abutment arch at each end of the bridge. The reason behind the inclusion of the abutment arch at each end I to counter the horizontal movements that occurs within the arch bridge when transferring exerted weight of the external load and even the weight of the bridge (Eleni, 2012). The abutment arc acts by way of restraining the resultant horizontal movements of the structure to maintain stability. Hence, concrete will be used to make the abutment arch. The concrete will subsequently have strength of 40Mpa, a 60 degree Celsius maximum internal temperature alongside a 100mm mix slump. 7 2.2.Concrete mix design with Fly Ash 7 2.2.1.Design strategies and Solutions 7 Fly ash is the preferred binder for this design since it significantly reduces the quantity of cement used hence a very important environmental conservation measure. Whenever used alone, cement has been associated with environmental degradation as it emits significant amounts of carbon (IV) oxide, a greenhouse gas, into the atmosphere. Hence, the fly ash is used to reduce the quantity of emitted gases as well as suppress their effects in the atmosphere. In this project therefore, the concrete mix design with fly ash will use a C40 sample. The target mean strength of the concrete as indicated on the requirements for this project is 49.9MPa. The mathematical formulae for calculating the target mean strength is as shown below. 8 fcu,0 = fcu,k+1.645. 8 Where: p is the percentage of the SCM: W is the free water content 8 The following ingredients will thus be required for the concrete mix to be used in this design :, 275.2 kg/m3 of cement (11.75%), 119.25 kg/m3 of fly ash (5.09%) , 614.87 kg/m3 of fine aggregates (26.24%), 1175.14 kg/m3 of coarse aggregates (50.15%), 154.7 kg/m3 of free water (6.60%), 3.9445 kg/m3 of water reducer (0.17%) and a water-cement ratio to be used will be 0.4. 8 2.3.Concrete Mix Design with Slag 8 2.4.Heat of Hydration 9 A combination of fly ashes and slag cement is used to reduce heat dehydration in typical concrete mixes for most construction projects. However, it has been found out with time large quantities of the two ingredients cause thermal cracking in concrete. In this effect, it is preferred that concrete designs use moderate amounts of both slag cements and fly ash in a mixture, principally to reduce the internal temperature of the concrete (Civil Engineers Forum, 2016). Hence, the concrete design will establish ingredient proportions that do not lead to thermal cracking. 9 2.5.Considerations for Durability 9 Durability is a common and major consideration for all construction projects. The principle aim of the design will thus be to produce a concrete structure capable of withstanding all the environmental conditions through its lifespan. According to the descriptions, the intended bridge is expected to be located in a coastal region with a high exposure to both sulphates and alkali salts. Hence, there is a need for the bridge design to incorporate the various preventive mechanisms so as to enhance the durability of the bridge. 9 2.5.1.Alkali-Silica Reaction 9 Alkali-silica reaction is also referred to as concrete cancer. The term refers to a chemical reaction that occurs as a result of continued exposure of concrete to alkaline cement paste, mostly compounds of sodium and potassium salts. For the purpose of this design, Petrography ASTM C 295 and Mortar-bar tests will be used to test aggregate for its affinity to alkalis. A special requirement on pozzolans and slags through ASTM C 1567 will be used to improve concrete effectiveness should the results show a reactive concrete. In the same manner, should the tests indicate a successful ASR mitigation, then mitigation options will be used. The design further recommends the limitation of concrete alkalis to a level to control ASR (Portland Cement Association 2016). 9 2.5.2.Reinforcement corrosion 10 The major effect of corrosion on steel and steel reinforced structures is that it eats away the concrete reinforcements (steel) thereby affecting the overall durability. Once the reinforcement steel has been eaten away by the corrosive chemicals, the resultant rust takes up the volume that was initially occupied by steel hence causing an expansion of concrete. The expansion process lead to a build-up of tensile forces within the structure and hence the cracks that occurs in concrete. Unlike the alkali-silicon reaction, corrosion can be easily prevented through various methods. However, this design specifically recommends the provision of adequate concrete cover over the steel and the use of galvanized high quality steel to offer sufficient protection against corrosion (American Galvanizers Association, 2016). 10 2.6.Material specification 10 A combination of Fly ash and slag has been extensively used in construction projects of this nature and magnitude upon the recommendation of the various authorities. Standard mixtures use 318 kg/m3 sulphate resisting Portland cement for a low C3A content. However, a different measure may still be chosen depending on the resistance of the sulphate of C3A used. A corresponding 747 kg/m3 of steel slag is subsequently used along as a fine aggregate in the concrete mix. Steel slag is majorly used to chloride-induced corrosion, sulphate attack and alkali-silica reaction in the concrete. Slag cement in the mixture is added to reduce the heat hydration than fly ash since it occupies a larger proportion in the mixture. Research on qualities of different types of concrete have further revealed that slag cement increases the strength and durability of concrete due to the presence of the Due to its secondary C-S-H bond found in its structure. Furthermore, Limestone between 5-15 mm is preferred as the most suitable coarse aggregate since it has the acceptable result of 110 mm from the slump test and has also been associated with ability to reduce the binder required for lubrication purpose. 10 3.0.Steel Arch Design 11 When carrying out the design specification for steel, the main aim will be to identify the steel characteristics and specifications that offer sufficient resistant to the various environmental conditions as well as can effectively sustain the continuous internal and external loadings. The part of the report will therefore majorly dwell on the design and fabrication of the steel arch and structural components 11 3.1.Main Arch 11 According to the conditions of the intended location of the bridge, the design of the bridge will take a tied arch in which all the outward-directed horizontal forces will be sustained by the deck as opposed to ground borne forces or foundation supported designs. The major reason for the above choice is that the tri-box section design inherently uses tough materials with ability to withstand large bending moment, flexural strength and fatigue stress. The materials should also be protected from rusting and corrosion. The design will therefore incorporate High Strength Low Alloy Steels (HSLA) as the preferred material for the main arch. Generally, High Strength Low Alloy Steels (HSLA) is associated with extremely low levels of alloy content in its structure. High Strength Low Alloy Steels (HSLA) also offers significantly improved mechanical properties and greater resistance to atmospheric corrosion than conventional carbon steels (Teychenné, 1988). 11 3.2.Structural Components 12 3.3.Hand Rails 12 The main function of the hand rails in this bridge design is to offer a safe hold along the stairways thereby providing a significant resistance to the effects of the weight from external loads. According to the standards set by the Occupational Safety and Health Administration, the minimum withstanding load for steel hand rails is set at 890 N (The Linde Group, 2016). 12 3.4.Material Specifications 12 In order to achieve the various specifications as required for the bridge, High Strength Low Alloy Steels (HSLA), HSLA –V will be used as the primary materials of the main arch. High Strength Low Alloy Steels (HSLA) has been picked on because this type of steel contains a low percentage of micro alloying elements (below 0.15% in total) and it is specifically made in a form that offer improved mechanical properties. For instance, High Strength Low Alloy Steels (HSLA), contain 0.07% to 0.12% carbon, up to 2%% manganese and small additions of niobium, vanadium and titanium in various combinations (The Linde Group, 2016,). HSLA – V has numerous industrial applications in structural engineering, especially in the construction of bridges. Nevertheless, a universal testing machine will be sued to test the High Strength Low Alloy Steels (HSLA) before they are finally used up in the project. 12 4.0.References 13 1.0. Introduction This project requires that the material engineer comes up with a design of a 100m span steel arch bridge which should incorporate a 6-lane carriage way, and measuring 24 m in width. Similarly, the bridge should consist of reinforced concrete abutment on each side of the river. The abutment measurements of the design are supposed to measure 28m by 24 m. the steel arch bridge should also include a large angle and flat box section for fabrication of the various structural components of the bridge. In the design, the engineer is expected to provide support for high loading impact on the bridge which therefore calls for the incorporation of rail connections in the bridge design. Finally, high bolts are expected to provide anchorage as well as the rail connections at various points. The aim of the report is this to present a design concept that incorporates concrete mix design, the selection of steel to be used and the specifications for both concrete and steel preferred for the intended project. 2.0. Concrete mix design The design will require two types of concrete mixes, each 24m*24m*24m* in measurement. One mix will be made up of fly ash/cement as the binding material while the other one will have slug/cement as the binding component. The two mixes will then be subjected to various tests to establish their comparative performance in terms of proportions of the ingredients used and the heat dehydration measures in each mix. 2.1. Abutment in the Arch Bridge Most contemporary construction methods for bridges often incorporate abutment an abutment arch at each end of the bridge. The reason behind the inclusion of the abutment arch at each end I to counter the horizontal movements that occurs within the arch bridge when transferring exerted weight of the external load and even the weight of the bridge (Eleni, 2012). The abutment arc acts by way of restraining the resultant horizontal movements of the structure to maintain stability. Hence, concrete will be used to make the abutment arch. The concrete will subsequently have strength of 40Mpa, a 60 degree Celsius maximum internal temperature alongside a 100mm mix slump. 2.2. Concrete mix design with Fly Ash Typical fly ash is a fine powder which is a byproduct from burning pulverized coal in electric generation power plants. The term is also used to refer to the residue that is left from burning coal and this is formed when the gaseous releases of the coal is efficiently cooled (Civil Engineers Forum 2016). The major characteristics of fly ash that makes it the preferred material for thus project is that is has a low calcium oxide content ( Civil Engineers Forum, 2016, Fly Ash Concrete – Advantages and Disadvantages of Using Fly ash In Concrete, viewed 2 May 2017, http://civilengineersforum.com/fly-ash-in-concrete-advantages-disadvantages/ D C Teychenné, R E Franklin & H C Erntroy, 1988, Design of normal concrete mixes, Building Research, viewed 2 May 2017, http://www.icie.ir/files/filebox/design%20of%20normal%20concrete%20mixes%20BRE.pdf DoItYourself, 2016, Strength Tests for Handrails, viewed 2 May 2017< http://www.doityourself.com/stry/strength-tests-for-handrails> Eleni, G 2012, Use of High Strength Steel Grades for Economical Bridge Design, TU – Delft & Iv – Infra, viewed 2 May 2017, < https://www.scia.net/sites/default/files/thesis/reportgogou.pdf> Jingfei X, Tingjiang Z & Yaguang H, C40 Concrete with Fly Ash Mix Design (1), viewed 2 May 2017, < http://wenku.baidu.com/link?url=vv0QDCDFx1jTTq85v9W3u9fLV_ek8tzlK4An_ILuxNOYvuip267ZZ8dH7FlN-Mpi42NSTqu34Id4BFBJowVj4ZJ3TzKsf7_FGubB7lxOXTG> Portland Cement Association, 2016, Alkali-Aggregate Reaction, viewed 2 May 2017< http://www.cement.org/for-concrete-books-learning/concrete-technology/durability/alkali-aggregate-reaction> The Linde Group, 2016, Manual Metal Arc (MMA) Welding, viewed 2 May 2017, < http://www.linde-gas.com/en/processes/cutting_joining_and_heating/welding/manual_metal_arc_welding/index.html Read More