2 type and surface of aggregate affects the bond

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2. Type and surface of aggregate. Affects the bond strength. 3. Efficiency of curing. Loss in strength of up to 40% may result from premature drying out. 4. Temperature. In general, the initial rate of hardening of concrete is increased by an increase in temperature but may lead to lower ultimate strength. At lower temperatures, the crushing strength may remain low for some time, particularly when cements of slow
E25-0170/05 35 rate of strength gain are employed, but may lead to higher ultimate strength, provided frost damage does not occur. 5. Age. When moisture is available, concrete will increase in strength with age, the rate being greatest initially and progressively decreasing over time. The rate will be influenced by the cement type, cement content and internal concrete temperature. 6. Moisture condition. Concrete allowed to dry will immediately exhibit a higher strength due to the dry process but will not gain strength thereafter unless returned to and maintained in moist conditions. Dry concrete will exhibit a reduced strength when moistened. [2] Figure 10: Concrete compressive test being carried out
E25-0170/05 36 CHAPTER 4: DATA COLLECTION 4.1 Laboratory tests results 4.1.1 Specific Gravity test of wood ash Density bottle no. 30 31 Mass of bottle (m 1 )g 63.0 53.29 Mass of bottle + dry ash (m 2 )g 78.24 70.37 Mass of bottle + dry ash + water (m 3 )g 169.32 163.79 Mass of bottle full of water (m 4 )g 159.50 152.77 Water temp T( o C) 23 o C 23 o C Specific gravity of ash G ash 2.81 2.81 Average specific gravity G ash 2.81 Table 11: specific gravity test results of wood ash Specific gravity of wood ash at 20 o C = 2.81 x 0.9993 = 2.8 4.1.2 Sieve analysis of aggregates 4.1.2.1 Fine aggregates Particle size distribution to BS EN 933 1: 1997 Tests sieves (mm) weight retained (g) weight passing (g) % retained % passing 10 8 1217.5 0.7 99 5 30.5 1187 2.5 96.6 2.36 26.5 1160.5 2.2 94.4 1.2 280 880.5 22.8 71.6 0.6 460.5 420 37.5 34.2 0.3 296.5 123.5 24.2 10.1 0.15 100.5 23 8.2 1.9 0.75 18.5 4.5 1.6 0.4 pan 4.5 TOTALS 1225.5 100 Initial weight was 1230.0g Table 12: sieve analysis results of fine aggregates
E25-0170/05 37 4.1.2.2 Coarse aggregates Particle size distribution to BS EN 933 1: 1997 Tests sieves (mm) weight retained (g) weight passing (g) % retained % passing 30 0 10927.5 0 100 25 244.5 10683 2.3 97.8 20 4964 5719 45.5 52.4 15 1812.5 3906.5 16.6 35.8 10 3124 782.5 28.6 7.2 5 707.5 75 6.5 0.7 2 59.5 15.5 0.6 0.2 pan 15.5 0 0.2 0 TOTALS 10927.5 100 Initial weight was 10930.0g Table 13: sieve analysis results of coarse aggregates 4.1.3 Aggregate Crushing Value BS 812-112 Weight of measure = 3370.5g Weight of measure + aggregate = 5553.5g Weight of measure + aggregate (crushed passing 2.36 sieve) = 3626.5 Hence Wt (A) = 5553.5 3370.5 = 2183g Wt(B) = 3626.5 3370.5 = 256g = 11.73 4.1.4 Bulk density of wood ash, fine and coarse aggregates BS 312, AASHTO Designation: T 19/T 19M-00, ASTM Designation: C 29/C 29M-97 Weight Test 1 Test 2 Wt of container 1544.50g 1544.50g Wt of water 1983.50g 1983.50g Wt of wood ash 1769.50g 1844.0g Bulk density of wood ash 890 kg/m 3 930 kg/m 3 Wt of fine aggregate 3059.0g 3134.0g Bulk density of fine aggregates 1540 kg/m 3 1580 kg/m 3 Wt of container 2 4669.50g 4669.50g Wt of water in container 2 9712.50g 9712.50g Wt of coarse aggregates in container 2 13730.50g 14110.0g Bulk density of coarse aggregates 1413 kg/m 3 1453 kg/m 3
E25-0170/05 38 Table 14: bulk density test results 4.1.5 Consistency and setting time tests Consistency of standard cement paste: BS 12, A.S.T.M: C-187 %cement replacement

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