ECIV 2639ElshaerL11

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School
Lakehead University **We aren't endorsed by this school
Course
ECIV 2639
Subject
Civil Engineering
Date
May 31, 2023
Pages
5
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2/12/2020 1 Lakehead University Cement Dr. Ahmed Elshaer, P.Eng. Civil Engineering Department Feb. 13, 2019 ECIV 2639 - WA - Construction Materials Lecture (11) 124 Lakehead University 2.3 Portland Cement Concrete 125 Volume Change (i) Change in the volume of concrete due to change in temperature . Controlled by the coefficient of concrete expansion typically ~10  m/m/ o C (ii) Shrinkage which occurs as the concrete dries out during curing (unless it is kept continuously under water). The coefficient of concrete shrinkage is 400 to 800  m/m (average 600  m/m) (iii) The third volume change in concrete creep, which is caused by a continuous applied load . It is important in prestressed concrete. 124 125
2/12/2020 2 Lakehead University 2.3 Basic Concrete Tests 126 1) Compressive Strength: The common test uses cylinders 150 mm in diameter and 300 mm high . The strength is usually determined 28 days after casting. 3, 7, or 14 day strength may also be determined to indicate the expected 28 day design strength. Submerging the cylinder in boiling water for certain period is sometimes used to accelerate curing and obtain 28‐day strength measurement in a short period. π‘π‘œπ‘šπ‘π‘Ÿπ‘’π‘ π‘ π‘–π‘£π‘’ π‘ π‘‘π‘Ÿπ‘’π‘›π‘”π‘‘β„Ž ࡌ πΏπ‘œπ‘Žπ‘‘ π‘π‘Ÿπ‘œπ‘ π‘  ࡆ π‘ π‘’π‘π‘‘π‘–π‘œπ‘› π‘Žπ‘Ÿπ‘’π‘Ž Lakehead University 2.3 Basic Concrete Tests 127 2) Flexural Strength : It is how much you can bend something before it starts to break . Flexure strength is specified for concrete that is to be subjected to bending loads , such as pavement slabs . A concrete beam 150 mm ο‚΄ 150 mm and 900 mm long is cast. The beam is loaded using the third‐point loading CSA Test Method A23.2‐ 9C (ASTM C78), shown below, or the center‐point loading (ASTM C 293). The flexural strength or modulus of rupture is obtained by multiplying the failure load by L/wd 2 . L , w , and d are the length, width and depth of the beam. 126 127
2/12/2020 3 Lakehead University 2.3 Basic Concrete Tests 128 3) Consistency or Workability : Slump test, CSA Test Method A23.2‐5C (ASTM C143) is the most generally accepted method used to measure the consistency/workability of concrete. The test equipment consists of a slump cone (a metal conical mold 300 mm high, with 200 mm diameter base and 100 mm diameter top) and steel rod 16 mm in diameter and 450 mm to 600 mm long with a hemispherical tip. The dampened slump cone, placed upright on a flat nonabsorbent rigid surface, should be filled in three layers of approximately equal volume. Lakehead University 2.3 Basic Concrete Tests 129 Therefore, the cone is filled to a depth of 70 mm for the first layer , a depth of 160 mm for the second layer , and overfilled for the third layer. Each layer is rodded 25 times . Following rodding, the last layer is struck off and the cone is slowly raised vertically 300 mm in 5 second. 128 129
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