Design and Control of Concrete Mixtures - Term Paper Example

Assignment 2 – Building Report Name Instructor Institution Table of Contents Executive Summary 3 Ground Floor 4 Structural Frame Construction 5 Method of construction and jointing of the structural members 6 First Floor Construction 7 Walls - Masonry Wall System 8 Mortar 11 Roofing- Roofing Slate Tiles 11 Conclusion 12 References 14 Executive Summary This report gives details of construction materials and construction system used at different points in a one floor residential house, the reasons for the preference as well as the cost details. The major parts of the building as detailed include the ground floor, the first floor, the structural system, walls, roofing and cladding. Ground floor: Concrete slabs are most ideal for construction in climates which experience large daily temperature swings. The slabs act as regulators in this case and keep the building cool by day and warm by night. Concrete slabs are cast on top of an insulating layer of other materials such as expanded polystyrene, are constructed with under floor heating pipes. The structural system: A concrete structural frame will be most appropriate as compared to the steel structural frames option Cast in place reinforced concrete offers an outstanding resistance to explosion and the impact. Concrete can endure high temperatures in case of fire for a considerable high time. This ensures that the building maintains its structural integrity. First floor: The one way system is the most appropriate for this type of set up because its members can be easily used at the roof level to accommodate drainage requirements. Walls: Masonry walls form a durable cladding system that can attain various aesthetic effects. The walls are also ideal as a part of the structural framing reinforcement. Masonry walls can create different patterns especially when masonry units are oriented in different positions. In this building requirement, concrete masonry units (CMU) are the most ideal because the units will form a load bearing wall as well as interior partitions that will form the various rooms between spaces within the building. Roofing: roofing slate tiles will be the most ideal for this type of roof. A slate roof is beautiful, natural, recyclable, easy to maintain, and environmental friendly. It is less costly modern roofing system and ideal for residential buildings. Ground Floor In modern buildings, concrete slabs are common structural elements. Horizontal slabs are typically made of steel reinforced concrete. These slabs are 100 to 500 millimetres in thickness and ideal for constructing ground floor in domestic buildings (ICT, 2009). In constructing the floors using concrete slabs, thick slabs are supported on foundations or laid on top of subsoil. Reinforced concrete slabs are abbreviated as r.c. slabs. The cost of concrete slab is approximately $560per cubic metre [Pet12]. Concrete slabs are most ideal for construction in climates which experience large daily temperature swings. The slabs act as regulators in this case and keep the building cool by day and warm by night (Kosmatka, 2008). However, concrete slabs can drain heat from the room if cast directly. In such a case, concrete slabs are cast on top of an insulating layer of other materials such as expanded polystyrene, are constructed with under floor heating pipes. In cases where buildings are not cooled or heated to room temperature, the slabs are cast directly on a rocky substrate to keep the floor near the temperature of the substrate throughout the year. This prevents overheating and freezing (Hurd, 2005) . Figure 1 modern layout of concrete slab floor components (ACI, 2008). Structural Frame Construction A concrete structural frame will be most appropriate as compared to the steel structural frames option. According to ground zero developers, concrete is safer. Cast in place reinforced concrete offers an outstanding resistance to explosion and the impact (CRSI, 2009). Concrete can endure high temperatures in case of fire for a considerable high time. This ensures that the building maintains its structural integrity. A structural frame costs approximately $500 per square metre [Pet12]. In addition, concrete does not require additional fire proof treatments to comply with stringent fire codes. Concrete also performs well during natural and manmade disasters (ACI, 2006). Cast in place reinforced concrete can resist wind speed of up to 200 miles per hour and even more and can also perform much better under the impact of falling debris. This is attributed by the concrete’s inherent heaviness, strength and mass (Fanella, 2009). Method of construction and jointing of the structural members The ground floor walls have to be taller than the second floor. The heights may range between 2.5-4.5 metres for the ground floor and 2.8-3.0 for the first floor. Blade columns with an aspect ratio of about 3 will be appropriate for this set up. The plan dimension can range to between 150 mm x 500 mm to 250 mm x 800 mm (ACI, 2008). the longitudinal rebar ratio can range to between 1% and 2%; 12 to 16 mm diameter, smooth rebar are most appropriate. The spacing of transverse ties may range between 200-250 mm along the clear height of individual column (ACI, 2005). Figure 2 Beam and column rebar (ICC, 2009) The beam span may range between 3 and 5 metres with the beam depth and width ranging between 200 and 250, and 500-600 mm respectively. The transverse ties will be smooth rebar of 6-10mm diameter with 90 degrees hooks. The transverse ties may be spaced by 200-250mm along the entire length of the beam (CRSI, 2009). The bent up longitudinal rebar are more economical in providing sheer resistance to gravity loads as well as increasing the negative moment resistance to gravity. The corner column has to be spiced above the floor slab with a lap length of between 40 and 70 bar diameter. The side face column rebar may be terminated above and below the joint using 180 degrees hooks or spliced per corner rebar (Fanella, 2009). Modern methods of construction offer a wide range of construction methods. These include the precast flat panel system, the 3D volumetric construction, the tunnel form, the floor slabs, hybrid concrete construction, the joint masonry and the insulting concrete framework. The hybrid concrete construction is the most appropriate for this set up. This is because the method combines all the benefits of pre casting with the advantages of cast in site construction operations. The hybrid frame ensures quality, overall economy, and a great construction speed. The method keeps the construction cost low as well as ensuring a high quality while providing a simple but competitive structure that can offer quality and consistent performance (ACI, 2005). First Floor Construction There are two widely known types of floor systems; the one way system and the two way system. One type of floor construction system has to be specified on an entire level of the building for cost saving unless on extreme cases where a change of floor design is necessary. The one way system is the most appropriate for this type of set up because its members can be easily used at the roof level to accommodate drainage requirements. Figure 3 One way slab system (Fanella, 2009) The one way roof or floor system consist its members with main flexural reinforcements running in one direction. The reaction from the supported load is transferred primarily in one direction. Members in the one way system are referred to as flexural members because they are subjected to the effects from bending. The load that is supported by the slab is transferred to the spans perpendicular to the slabs. The beams then transfer the load to the girders; the girders transfer the loads to the column. An individual spread footings carries the load to the ground below. The load transfer between the members of this system occurs in one direction only (Fanella, 2009). Walls - Masonry Wall System Masonry walls have been in use for many years in construction. The walls form a durable cladding system that can attain various aesthetic effects. The walls are also ideal as a part of the structural framing reinforcement. Masonry walls can create different patterns especially when masonry units are oriented in different positions. Different types of masonry units are common in the market. The most common in use are the cast stone, silicate, concrete, and clay units. These units may be hollow or solid, unglazed or glazed. In this building requirement, concrete masonry units (CMU) are the most ideal because the units will form a load bearing wall as well as interior partitions that will form the various rooms between spaces within the building. CMUs should meet the ASTM C90 requirements (ACI, 2008). These units come in different categories depending on the application and requirements such as light weight, heavyweight, and normal weight. Heavy weigh units are most ideal for the walls of the building in this case for weight bearing requirements. Clay masonry units are the least applicable for this type of construction because they expand when exposed to moisture (Hurd, 2005). This change in units cause accumulated growth of the wall, a characteristic that is permanent. This may cause cracking, and displacements. The time required for laying the CMU units is usually less as compared to bricks since they are bigger in size. Hollow units with two or three cores with solid ends are most ideal since the cores provide continuous vertical voids that are used for reinforcement. Steel bars are placed in the cores so that the walls can act in the same way as the reinforced concrete elements. Piers and plasters are used to provide lateral support to the walls. They also offer an economic advantage. Concrete masonry units cost approximately $17-20 per square feet [Pet12]. Figure 4 Concrete Masonry Units (CMU) types and sizes Concrete blocks are made in many sizes and shape as shown in the figure above. The most common units size include 7 5/8 by 7 5/8 by 15 5/8 inches. This size is the normal size mostly known as 8 by 8 by 16’’ blocks. Figure 4 Concrete masonry units wall layout Mortar Mortar is made up of cement, lime and sand mixed at proportions whose ratios depend on the desired properties. In this case, type S mortar is the most ideal for it is the recommended mortar for structural masonry application. This type has high proportions of cement and therefore has increased shrinkage of the mortar. A well-built concrete unit’s masonry wall meets the specification covering size, weight compressional strength and moisture content (ACI, 2005). These walls offer a wide range of advantages over other types on walls such as fire safety durability, attractive finishing, utility, acoustics and comfort. Concrete masonry is ideal for firewall construction. It provides a significant improvement in building walls that are safe from fire attacks. Masonry walls require little maintenance as compared to other wall systems. Exterior masonry requires 20-30 years after the initial construction. However, this depends on the quality and the type of the original masonry installation (Kosmatka, 2008). Roofing- Roofing Slate Tiles A slate roof is beautiful, natural, recyclable, easy to maintain, and environmental friendly. It is less costly modern roofing system and ideal for residential buildings. Slates are made from natural stones. The stones are dug from the quarry, and hand split into thin sheets of about ¼ of an inch thick using a hammer and a chisel. Slate shingles are then trimmed into desired shapes and punched holes made for installation (Hurd, 2005). The roof installer will only need to install them into the roof. Standard roof slate sizes are 6 by 10 inches to 14 by 24 inches. For a 6 by 10 slates, 686 slates are required per hundred square feet. Small size slates require more of nails and the more the cost of installation. Natural wood is the best sheath of the slate roof. The roofing sheath is then covered with a 30lb roofing felt paper, nailed to the roof with 1 inch galvanised roofing nails. The felt paper helps in providing a temporary cover especially when it is raining during season installation and also helps in insulating and making the roof waterproof. The cost of slate tiles is approximately $0.2-0.85 per piece; therefore, square feet will cost $137.2-583.1 per square feet [Pet12]. Figure 5 cross section of a slate roof showing how major components intersect (ICC, 2009) Conclusion Concrete slabs are most ideal for construction in climates which experience large daily temperature swings. The slabs act as regulators in this case and keep the building cool by day and warm by night (ACI, 2005). A concrete structural frame will be most appropriate as compared to the steel structural frames option Cast in place reinforced concrete offers an outstanding resistance to explosion and the impact. Concrete can endure high temperatures in case of fire for a considerable high time. This ensures that the building maintains its structural integrity. Masonry walls form a durable cladding system that can attain various aesthetic effects (ICC, 2009). The walls are also ideal as a part of the structural framing reinforcement. Masonry walls can create different patterns especially when masonry units are oriented in different positions. In this building requirement, concrete masonry units (CMU) are the most ideal because the units will form a load bearing wall as well as interior partitions that will form the various rooms between spaces within the building. Roofing slate tiles will be the most ideal for this type of roof. A slate roof is beautiful, natural, recyclable, easy to maintain, and environmental friendly (Hurd, 2005). It is less costly modern roofing system and ideal for residential buildings. References International Code Council (ICC). (2009) International Building Code. ICC,Washington, DC. American Concrete Institute (ACI), (2008)Committee 318. Building Code Requirements for Structural Concrete and Commentary, ACI 318–08. (ACI, Farmington Hills, MI. Fanella, D. A. (2009) Design of Low-Rise Reinforced Concrete Buildings Based on 2009 IBC, ASCE/SEI7–05, ACI 318–08. International Code Council,Washington, DC. American Concrete Institute (ACI), (2005) Committee 301. Specifications for Reinforced Concrete, ACI 301–05. ACI, Farmington Hills, MI. Concrete Reinforcing Steel Institute (CRSI) (2009), CRSI Committee on Manual of Standard Practice. Manual of Standard Practice, 28th ed. CRSI, Schaumburg, IL. American Concrete Institute (ACI), (2006) Committee 117. Specifications forTolerances for Concrete Construction and Materials and Commentary, ACI 117–06. ACI, Farmington Hills, MI. Hurd, M. K. (2005), Formwork for Concrete, SP-4, 7th ed. American Concrete Institute, Farmington Hills, MI. Kosmatka, S., Kerkhoff, B., and Panarese, W. (2008), Design and Control of Concrete Mixtures, 14th ed. Portland Cement Association (PCA), Skokie, IL. 2002 American Concrete Institute (ACI) (2008), Committee 347. Guide for Shoring/Reshoring of Concrete Multistory Buildings (2005), ACI 347.2R-05. ACI, Farmington Hills, MI. Read More