Construction Materials and Testing PDF

CHAPTER 1 Introduction to Construction Materials and Testing Every construction project is intended to result in a finished structure which will perform certain functions in conformance with the project design requirements. The designer, the builder, and the user...

CHAPTER 1 Introduction to Construction Materials and Testing Every construction project is intended to result in a finished structure which will perform certain functions in conformance with the project design requirements. The designer, the builder, and the user must all understand construction materials to produce the finished facility and to use it to best advantage. The Construction Process ​ The construction process is initiated when a person or organization, which may be public or private, decides to improve the land with permanent or semipermanent additions. The initiator of a construction project, hereafter called the owner, therefore has a need, as well as the required financing, to complete the process. ​ After a need is established, and financing has been obtained, the owner contracts with a design professional. The architect or engineer prepares plans, called working drawings, showing details and how the completed project will look. The plans indicate and briefly explain the various materials required. The specific details related to materials are covered in the specifications. The designer also incorporates in the specifications and working drawings all of the necessary building code, zoning, wetland, and other governmental requirements, where applicable. ​ The contractor, selected by bid on public works projects, and by bid or negotiation on private projects, enters into a contract with the owner to provide a completed project in accordance with the project contract documents. Two most common contracts: a.​ Lump sum estimate – It requires the contractor to estimate all of the material quantities, installation, labor, and equipment costs to complete the project. The contractor then adds an overhead and profit figure to the total estimated cost. b.​ Unit price system - The owner supplies all of the quantities to the contractor in the bid documents. The contractor calculates cost factors for each material quantity unit as well as overhead and profit values. To protect both parties, the contract includes, ​ General conditions - a set of guidelines developed by the design and construction communities to ensure fair practices. ​ Change orders – It cover additional work, deleted work, or changed conditions. The construction delivery system selected requires the contractor to deliver to the owner a completed project on time as scheduled, within budget, and at the specified quality levels. Requirements: ​ Impose Occupational Safety and Health Administration (OSHA) regulations. ​ Maintain current Manufacturer’s Safety Data Sheet (MDS) file - Obtained from suppliers, cover potential material hazards and required safe handling techniques, as well as what should be done in case an accident occurs while using the material. ​ Submit a project schedule to the designer for approval. ​ Basic materials and combinations of materials should be in one assembly (shop assembled or jobsite assembled). ​ Select materials for the project that comply with the technical specifications, because nothing may be incorporated into the project without the designer’s review and/or approval. ​ The owner is represented during the construction stage by an agent, usually the designer, who administers the contract impartially, by approving or rejecting materials and workmanship, by approving final construction, and by determining the amount of payment due. o​ Inspectors – Are present at the jobsite to inspect the work in progress and perform field tests as part of construction supervision. o​ Independent testing laboratory – Where Laboratory testing and field testing is performed. It reports whether or not materials comply with specifications. CONSTRUCTION MATERIALS AND TESTING​ ​ ​ ​ ​ Engr. Jaide A. Daguinotas  o​ Suppliers or vendors - Those who supply materials and partially or fully assembled components to be used in construction. Need for Materials with Various Qualities ​ The construction industry requires materials for a vast range of uses. The qualities these materials possess are as varied as the strength and flexibility required of an elevator cable or the warm, wood grain appearance and smooth finish of a birch or maple cabinet. ​ The construction of a simple building, such as a house, requires selection of materials to perform the following tasks: 1.​ Footing a.​ Distribute the weight of the building to the soil b.​ Resist cracking despite uneven soil settlement c.​ Resist corrosive attack from soil and water 2.​ Basement floor a.​ Provide a smooth surface b.​ Resist wear c.​ Resist cracking despite upward water pressure or uneven soil settlement d.​ Keep moisture out e.​ Resist corrosive attack from soil and water 3.​ Basement walls a.​ Support the rest of the building b.​ Resist lateral side pressure from the earth c.​ Keep moisture out d.​ Resist corrosive attack from soil and water 4.​ Other floors and ceilings a.​ Provide a smooth surface b.​ Resist wear c.​ Support furniture and people without sagging excessively or breaking d.​ Provide a satisfactory appearance e.​ Clean easily f.​ Insulate against noise transmission 5.​ Outside walls a.​ Support floors and roof b.​ Resist lateral wind pressure c.​ Provide a satisfactory appearance inside and out d.​ Insulate against noise and heat transmission e.​ Keep moisture out 6.​ Partitions a.​ Support floors and roof b.​ Provide a satisfactory appearance c.​ Insulate against noise transmission 7.​ Roof a.​ Keep moisture out b.​ Support snow and other weights c.​ Resist wind pressure and wind uplift d.​ Provide a satisfactory appearance e.​ Insulate against noise and heat transmission Selecting Materials ​ A designer is selected who, among other things, is responsible for selection of all construction materials to achieve the desired performance within the budget cost. He considers the service each component must perform, appearance, original cost, maintenance expense, and useful life expectancy. Maintenance includes such operations as cleaning, preventing and repairing corrosion damage, and repairing or replacing damaged material. ​ Material Specification – It is the specification prepared in a way where the designer also misses the opportunity of using something that is more economical or performs better. CONSTRUCTION MATERIALS AND TESTING​ ​ ​ ​ ​ Engr. Jaide A. Daguinotas  ​ Performance Specification - specifies performance in terms of appearance, strength, corrosion resistance, and other features, he has the benefit of the builder’s and vendor’s experience in selecting the most economical materials. Life-cycle cost analysis: 1.​ Analysis of the problem 2.​ Comparison of available materials or products with the criteria of step 1. 3.​ Design or selection of type of material, size, shape, finish, method of preserving, and method of fastening in place. Sustainability ​ The concept of sustainability in building design and construction has grown out of concerns about better utilizing material and energy resources, enhancing the environment, and even creating jobs and lowering construction and operating costs. The fundamentals of sustainability are formed around several related concepts: 1.​ We must design and construct new and renovated buildings through the most efficient use of finite material, energy, and labor resources. 2.​ We must seek to operate these facilities in a way that significantly reduces energy consumption and the production of greenhouse gases which can contribute to climate change. 3.​ We need to choose construction materials which can be recycled and reused when facilities must be reconstructed. Longevity ​ In selecting materials today, designers must be aware of their appropriate use and inherent characteristics that will promote longevity of the buildings where they will be used. Energy Efficiency ​ All of the materials have properties relative to their energy footprint. Asphalt, concrete, and steel products use significant amounts of energy in their production. Wood products are, by contrast, a renewable resource, but must be carefully managed. Reusability and Recycling ​ Virtually, all of the construction products can be recycled to create new materials. Properties of Materials 1.​ Thermal Expansion - All building materials change size with a change in temperature, becoming smaller when colder and larger when hotter. In order to predict amounts of expansion and contraction to be expected, a coefficient of expansion is determined for each material. Materials to be used together in an assembly must have approximately the same coefficients of expansion, or else some provision must be made for their different expansions. 2.​ Thermal Conductivity - Heat flows to a cooler area much like water flows to a lower level. The flow continues until outside and inside temperatures are equal. Heat movement takes place by conduction through any solid object separating areas of different temperatures. The rate is measured as thermal conductivity (U) in British thermal units (Btu) of heat transmitted per square foot of cross section per hour per °F difference in temperature between the two sides of the material. a.​ Insulation – It is used to line large surfaces to lessen the rate of heat flow. b.​ Thermal Resistance - The resistance that construction materials offer to the flow of heat. 3.​ Strength and Stress - A force is a push or pull that has a value and a direction. Loads on structures are separated into dead loads and live loads. Dead loads include the weight of the structural elements as well as permanent equipment such as boilers and air-conditioning units. Live loads are those imposed loads which may or may not be present and include occupants, furniture, wind, earthquake, and other variable load conditions. a.​ Stress - is force per unit area over which the force acts. It is obtained by dividing the force by the area on which it acts and is expressed as pounds per square inch (psi) or kips per square inch (Ksi). A kip is equivalent to 1000 lb. b.​ Strength of material - The ability to resist a force. That ability depends on the size and shape of the object as well as on the material of which it is made. the strength of a material in technical terms is equal to the stress that the material can resist. Strength has the same units as stress, that is, psi, Ksi, or megapascals (MPa). CONSTRUCTION MATERIALS AND TESTING​ ​ ​ ​ ​ Engr. Jaide A. Daguinotas  𝑃 σ= 𝐴 c.​ Deformation - A change in the outside dimensions of an object caused by a force. The amount of deformation depends on the size and shape of the object as well as on the material of which it is made. d.​ Strain - A change in the outside dimensions of an object caused by a force. The amount of deformation depends on the size and shape of the object as well as on the material of which it is made. e.​ Allowable stress – The maximum stress allowed. Several reasons for not designing material to be stressed close to the failure stress: 1.​ The actual force (and therefore stress) on a structure may exceed expectations. 2.​ True failure stress may be somewhat less than that determined experimentally. 3.​ The simplified procedures used in design predict approximate stresses which may be exceeded somewhat in actuality. 4.​ Materials may be weakened by rusting (steel), rotting (wood), or spalling (concrete). f.​ Safety factor - The failure stress is greater than the allowable stress by a factor. Failure stress divided by the allowable stress. Important factors considered in deciding on a safety factor are as follows: 1.​ How exactly loads can be predicted and calculated. 2.​ How exactly acting stresses can be calculated. 3.​ How exactly failure stresses can be determined. 4.​ How consistently the material conforms to the experimental strength. 5.​ How serious the consequences of a failure are. 6.​ How much warning the material gives before failing. 7.​ How much the material is likely to deteriorate under the conditions of use. Three kinds of stresses: 1.​ Compressive and tensile stress - act on the cross-sectional area perpendicular to the direction of the force. 2.​ Shearing stress - act on the cross-sectional area parallel to the direction of the force. g.​ Creep - A material, even if brittle, deforms slowly when a force is applied to it for an extended period of years, even though the force is too small to cause failure in a short time. h.​ Fatigue - Although a force of a certain amount may not cause breaking no matter how long it is applied, it may be large enough to cause breaking if it is applied and removed many times (tens of thousands of times), even if over a shorter time. i.​ Endurance limit - There is a stress below which the material will not fail at any number of cycles. j.​ Toughness - The capacity of a material to absorb energy while a force is applied to it. Toughness is the product of stress and strain up to the point of fracture. k.​ Modulus of toughness – The result of multiplying the average stress by the total strain (force times distance) l.​ Impact load or shock load - The toughness of a material indicates its ability to withstand a sudden force. CONSTRUCTION MATERIALS AND TESTING​ ​ ​ ​ ​ Engr. Jaide A. Daguinotas  m.​ Resilience – Is the ability of a material to recover its original size and shape after being deformed by an impact load. n.​ Modulus of resilience - The product of stress and strain up to the elastic limit. It is computed by determining the area under the stress–strain curve from zero to the elastic limit. 4.​ Modulus of Elasticity – The constant value of stress divided by strain. σ 𝐸= ε ​ Proportional limit – The stress at which strain just begins to increase at a rate greater than in the proportional range, CONSTRUCTION MATERIALS AND TESTING​ ​ ​ ​ ​ Engr. Jaide A. Daguinotas Elastic and Plastic Properties ▪​ Elasticity - the property of a material that enables it to return to its original size and shape after a force is removed. ▪​ Plasticity - The property that enables a material changed in size or shape by a force to retain the new size and shape when the force is removed. ▪​ Elastic Limit - Many materials are completely elastic (i.e., return exactly to original size and shape upon removal of a force) throughout a range of stress from zero to a stress. ▪​ Permanent set or plastic deformation – At stresses greater than the elastic limit, the deformation of material remains even if the force is removed. ▪​ Yield Point - the lowest stress at which an increase in strain occurs with no increase in stress. It is therefore at a point of zero slope in the stress–strain curve. ▪​ Yield strength - The stress at which the excessive plastic deformation is reached. ▪​ Offset yield strength – The stress corresponding to a permanent deformation of 0.20 percent. ▪​ Yield stress – It include the yield point or yield strength. It is the stress or strength at yielding point of a material. Sources of information 1.​ PCA – Portland Cement Association 2.​ NCPI – National Clay Pipe Institute 3.​ AISI – American Iron and Steel Institute 4.​ Asphalt Institute 5.​ NSGA – National Sand and Gravel Association 6.​ APA – American Plywood Association 7.​ NRMCA – National Ready Mix Concrete Association 8.​ ASTM – American Society for Testing and Materials 9.​ ASA – American Standards Association 10.​AASHTO – American Association of State Highway and Transportation Officials 11.​AISC – American Institute of Steel Construction 12.​ACI – American Concrete Institute 13.​UL – Underwriters Laboratories 14.​ASCE – American Society of Civil Engineers 15.​AIA – American Institute of Architects Inspection and Testing ▪​ Inspection - Examining a product or observing an operation to determine whether or not it is satisfactory. ▪​ Test - consists of applying some measurable influence to the material and measuring the effect on the material. Inspection and tests can be categorized according to purpose as follows: CONSTRUCTION MATERIALS AND TESTING​ ​ ​ ​ ​ Engr. Jaide A. Daguinotas  o​ Quality assurance or acceptance - Inspection and tests performed to determine whether or not a material or product meets specific requirements in order to decide whether or not to accept or reject the material or product. o​ Quality control - Inspection and tests performed periodically on selected samples to ensure that the product is acceptable. o​ Research and Development - Inspection and tests performed to determine the characteristics of new products and also to determine the usefulness of particular inspection procedures and tests to judge characteristics or predict behavior of materials. Two reasons why samples of material from the same source do not yield exactly the same results for each sample: 1.​ No material is perfectly homogeneous. 2.​ The testing methods, although performed according to standard procedures, cannot be duplicated exactly each time. Standards ​ The designer or builder may desire any number of properties in the material she is going to use. The supplier must be able to prove to the buyer that the material possesses the properties desired to the degree desired. ▪​ Testing method - A specification explaining how to perform a test and how to measure the results. Activity 1: Assignment - Make a list of the kinds of materials used in: a)​ A water distribution system, b)​ A city street pavement, c)​ A sewage collection system, and d)​ A roofing system. Activity 2: Assignment - Discuss in front of the class the advantages of Material Specifications versus Performance Specifications. Research an actual project specification and identify the types of specification formats used and the reasons they were used. This should be done in a group of at least 3 – 5 members. Grading Criteria: Presentation 20% Content 30% Overall Performance 50% TOTAL 100% CONSTRUCTION MATERIALS AND TESTING​ ​ ​ ​ ​ Engr. Jaide A. Daguinotas