Chapter 4 Unbound Pavement Materials.pptx

Pavement material

1. SCHOOL OF CIVIL ENGINEERING & ARCHITECTURE 1 1 HIGHWAY ENGINEERING I I CENG 4 20 5 Chapter 4 UNBOUND GRANULAR MATERIALS ASTU CIVIL ENGINEERING 2016 E.C

2. 2 Introduction

3. 3 Sources of Aggregates

4. 4 Sources of Aggregates

5. 5 Aggregates Test

6. 6 Aggregates Test Particle Size

7. 7 Aggregates Test Particle Size

8. 8 Aggregates Test Particle Size

9. 9 Aggregates Test Particle Size

10. 10 Aggregates Test Particle Size

11. 11 Aggregates Test Toughness and Abrasion Test

12. 12 Aggregates Test Toughness and Abrasion Test

13. 13 Aggregates Test Toughness and Abrasion Test

14. 14 Aggregate Crushing Value (ACV) Test: evaluates the resistance of aggregates against the gradually applied load . using a metal plunger to apply gradually a standard load of 400kN to a sample of the aggregate (10 – 14 mm) The amount of material passing 2.36 mm sieve in percentage of the total weight of the sample is referred to as the Aggregate Crushing value (ACV ). Aggregates Test Toughness and Abrasion Test

15. 15 Aggregate Impact Test : evaluating the resistance of aggregates to sudden impact loading. filling a steel test mould with a sample of aggregate (10 – 14 mm) and then the impact load applied is by dropping hammer at a height of 380 mm . Aggregate Impact Value (AIV) is the percentage of fines passing 2.36 mm sieve after 15 blows Aggregates Test Toughness and Abrasion Test

16. 16 Aggregates Test Durability and Soundness Test

17. 17 Aggregates Test Durability and Soundness Test

18. 18 Flakiness index Angularity number Elongation index Aggregates Test Shape & Texture Test

19. 19 Aggregates Test Specific Gravity Test

20. 20 To meet the gradation requirements of aggregates for particular uses in pavement construction, it is often necessary to blend two or more aggregates together. Charts and diagrams are available to do this blending, but the trial-and-error method is simpler . The following equation may be written to apply the procedure to any given sieve : Where: A and B are percentages from aggregates A and B a and b are the respective sieve analysis values for a given sieve X, expressed as a decimal fraction, T is the sieve analysis value in the blended aggregate. The equation can be used for gradation expressions Blending Aggregates

21. 21   Sieve % Passing Aggregate A Aggregate B Specification Mid-point Combined aggregate 12.5 mm 100 100 90-100 95 100 No. 10 100 40-55 48 48 No. 200 14 5-10 8 7 Blending Aggregates Example 1:

22. 22 Three aggregates are to be blended to meet a specification. The aggregates, gradations, and the specification are given in the table below: Sieve size   Aggregate A Aggregate B Aggregate C Specification Spec. Mid-point Combined gradation (1 st trial) Passing 12.5 mm 100     100 100 100 9.5 mm 62   100 72-88 80 79 4.75 mm 8 100 78 45-65 55 46 2.36 mm 2 91 52 30-60 45 34 1.18 mm 73 36 25-55 40 25 600  m   51 29 16-40 28 18 300  m   24 24 8-25 16.5 11 150  m   4 20 4-12 8 6 75  m   1 18 3-6 4.5 5 Blending Aggregates

23. Blending Aggregates 23

24. 24 Graded crushed aggregate: This material is produced by crushing fresh , quarried rock usually termed a 'crusher-run‘. The rock used for crushed aggregates should be hard and durable After crushing, the material should be angular in shape with a Flakiness Index of less than 35%, and preferably of less than 30 %. Grading limits for graded crushed stone base course materials Base Course Materials Test sieve (mm) Percentage by mass of total aggregate passing test sieve Nominal maximum particle size 37.5 mm 28 mm 20 mm 50 100 - - 37.5 95 – 100 100 - 28 - - 100 20 60 – 80 70 - 85 90 – 100 10 40 – 60 50 - 65 60 – 75 5 25 - 40 35 - 55 40 – 60 2.36 15 – 30 25 - 40 30 – 45 0.425 7 – 19 12 - 24 13 – 27 0.075 1 5 – 12 5 - 12 5 – 12

25. 25 The sub-base is an important load spreading layer which enables traffic stresses to be reduced to acceptable levels on the subgrade . working platform for the construction of the upper pavement layers Bearing capacity: A minimum CBR of 30% Filter or separating layer Sub-base Course Materials Typical particle size distribution for sub-bases Test Sieve (mm) Percentage by mass of total aggregate passing test sieve (%) 50 100 37.5 80 – 100 20 60 – 100 5 30 – 100 1.18 17 – 75 0.3 9 – 50 0.075 5 – 25 Where: D15 is the sieve size through which 15% by weight of the material passes and D85 is the sieve size through which 85% passes.

26. 26 These materials are often required to provide sufficient cover on weak subgrades . Thick sub-base to reduce costs, and a cost comparison should be conducted to assess their cost effectiveness A minimum CBR of 15 % Grading or plasticity criteria are not given for these materials Least change in bearing capacity from dry to wet is also beneficial. Selected subgrade materials or capping layers

27. 27 Generally roads which are constructed and maintained at low cost Coarse well graded gravel designed for AADT between 350 and 400 The general soil-aggregate mixture used for constructing gravel roads should be stable Gravel Surface Roads Gradation requirements for gravel wear course (ERA, 2001) Test Sieve Size(mm) Percent(%) by mass of total aggregate passing test sieve   Type 1 Type 2 Type 3 Type 4 Type 5 Type 6 50 - - - 100 - - 37.5 100 - 100 80-100 - - 28 - 100 95 - 100 - - - 20 80 - 100 95 - 100 85-100 60-80 100 - 14 - 80-100 65 - 100 - - - 10 55 - 100 65 - 100 55 - 100 45-65 80 - 100 100 5 40 - 60 45 - 85 35-90 30-50 60 -85 80-100 2.36 30 - 50 - - 20-40 45-70 50-80 2 - 30 - 65 22-75 - - - 1 - 25-55 18-60 - - - 0.425 15 - 30 18 - 45 15-50 10-25 25-45 25-45 0.075 5 - 15 12-32 10-40 5-15 10-25 10-25

28. THANK YOU ! 28 QUESTIONS?