Unit 1 Construction Technology

Unit 1 Construction Technology

1. Strength and Stability

   • Testing and Grading Materials
     • Slump Test
       • Checks the Ratio of Water and Cement in wet concrete is correct
         • If wet concrete loses its shape it means that the balance is not correct.
     • Compressive Strength Test
       • Checks that the hardened concrete is strong enough to withstand loads
     • Timber
       • Is used in structures such as frames of buildings or roof trusses, as well as in doors and windows. The strength of various types of timber is tested. Timber is then sorted into various groups. this process is called stress grading or strength grading
     • Mortar
       • Is tested by making cubes of mortar to check how much water can pass through it, or if there are any gaps causing leakage
   • Dead
     • Dynamic
       • Impact
         • This is when something hits the building or falls on it, such as a heavy object
       • These are loads that can change during the use of a building, such as the load from people and furniture
     • This is a load, that does not move, such as the weight of the building itself
   • Specifying and Grading Materials
     • For any building, the designer tells the construction team clearly about the type of material to be used. This is called material specification
     • The materials selected will comply with either British or European Standards.
       • These are standards that ensure the quality of materials used in all sorts of industries, including construction.
         • It is important to use materials that meet these standards because this makes sure that the building has the right strength to support the loads.
         • The material specification will also confirm the strength of material needed. Most materials are graded or classified according to their strength
           • The strength of a material is calculated by working out how much pressire it can take. This pressure is measured in Newtons per square millimetre. (N/mm²), which means the amount of pressure that a piece of material measure g 1mm buy 1mm can resist. So if the strength of a concrete mix is 30N/mm², a piece of that concrete measuring 1 mm by 1 mm could withstand 30 Newtons of pressure before it broke. The strengths of different materials are as followed.
             • Concrete
               • When specifying materials, concrete with a strength of 25 N/mm² is written as C25. the higher the number that is next to the letter , the stronger the concrete is. If concrete is to be used to take a load of a structure, its strength should be at least 25N/mm². the standard that is relevant to concrete strengths is BS EN 206-1
               • Timber
                 • timber strengths ranges from 14N/mm² to 70n/mm². when it is being specified