2 (i) What is the cause of reflective cracking visible at the surface of a flexible pavement? [1 mark] (ii) State two (2

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2 I What Is The Cause Of Reflective Cracking Visible At The Surface Of A Flexible Pavement 1 Mark Ii State Two 2 1 (49.95 KiB) Viewed 43 times

2 (i) What is the cause of reflective cracking visible at the surface of a flexible pavement? [1 mark] (ii) State two (2) functions of the subbase in a flexible pavement structure [2 marks] (iii) Determine the optimum bitumen content of an asphaltic concrete surfacing on a heavily- trafficked road using the following Marshall test data and specifications: 2 marks] Bitumen Content StabilityFlow Units % Air Voids in the % Voids Filled with Unit Weight % (0.25 mm) total mix Bitumen Kgm 4.5 2.280 7.500 7.300 14.6 2.325 2.220 6,800 N 7.100 3 4 5 9.6 11.8 4.0 2.355 3.8 75 78 80 85 88 6 6.900 2.8 16.6 18.5 7 22 2,109 Mix Criteria Light Traffic Medium Traffic Heavy Traffic |< 10 ESALS) 10-10 ESAL 10 ESALE Min. Max. Min. Max. Min. Max. Compaction (number of blows on each end of the sample) 35 50 75 Stability (minimum) 4224 N 6300 N 7072 N Flow (0.25 mm) 8 20 8 18 8 16 Percent Air Voids 3 $ 3 5 3 $ Percent Aggregate 75 85 75 85 75 85 Voids Filled with Bitumen