AGGREGATE Aggregates may be NATURAL or MANUFACTURED Natural aggregates: sand, gravel, crushed rock Manufactured aggregates: blast furnage slag Aggregates may also be COARSE or FINE or FILLER Coarse aggregates: > 4.76mm Fine aggregates: 0.075mm – 4.76mm Filler: < 0.075mm

COARSE AGGREGATE properties Strength (kekuatan) and toughness (kekerasan) Particle shape Porosity Surface texture Surface coatings Specific gravity Gradation

FINE AGGREGATE properties Hard Non-plastic (clean & free from organik materials) Gradation Salt content

Strength and toughness - to prevent breakdown under traffic and subsequent loss of stability no truly satisfactory test to measure the effective strength and toughness Measured by abrasion test using the Los Angeles Machine

Particle shape - to provide aggregate interlock and stability of mixture Crushed aggregates give a better interlocking than rounded gravels Rounded gravels produce a more highly stable surface mixture than crushed aggregates. (adhesi antara agregat dan aspal agregat bulat lebih baik daripada batu pecah) Thin and elongated aggregates are being subject to size segregation in the mixing process and tend to be of low strength.

Porosity - Porosity gives a proper adhesion between aggregate and bitumen Porosity affects the economic of mixture High porosities cause more bitumen will be absorbed into the aggregate (desired around 0.5% of bitumen is absorbed into aggregate) High porosities generally do not affect the quality of mixture. It could be noted that if more bitumen is absorbed into aggregate this will leave a hard residue on the surface of aggregate particle and then lead to raveling and stripping.

Surface texture The rougher the surface texture of aggregate gives the higher the stability and durability A rough aggregate surface reduces the displacement under pavement loading and then increases the stability of mixture Is important to adhesion between aggregate and bitumen. This will increase the durability of mixture

Surface coatings Aggregate may be coated by clay, silt, calcium carbonat, iron oxides, gypsum and other subtances in varying thiskness and hardness. Surface coatings has responsible for aggregate stripping due to disturb the bitumen to seal the aggregate

Specific gravity Specific gravity is importand for mixture calculation such as to determine the void content of the compacted bituminous mixture 3 (Three) types of aggregate specific gravity: Bulk specific gravity (Graviti spesifik bulk) SSD (Saturated Surface Dry) specific gravity (Graviti spesifik kering permukaan jenuh) Apparent specific gravity ( Graviti spesifik semu) There is also known ‘effective specific gravity’. It is used to estimate the amount of bitumen absorbed by aggregate

Specific gravity Bulk specific gravity : perbandingan antara berat kering agregat dan volume total agregat SSD specific gravity : perbandingan antara berat agregat kondisi permukaan jenuh dan volume total agregat Apparent specific gravity: perbandingan antara berat kering agregat dan volume kedap air agregat Effective specific gravity: perbandingan antara berat kering agregat dan volume kedap aspal agregat

Volume of aggregate to calculate Specific gravity Volume agregat tanpa pori/ solid (Vs) Volume agregat kedap air/ impermeable (Vi) Volume agregat rembes air/ permeable (Vp) Volume total agregat (V) Volume agregat rembes aspal (V-Vs-Vi-Vp)

Measuring Specific gravity Diukur Ws= berat kering partikel agregat γw= berat volume air Bk= berat agregat kering Ba= berat agregat di dalam air Bj= berat agregat jenuh air (SSD) Vi Vp Vs Ws Bk Bulk SG = = (Vs+Vi+Vp)/γw Bj - Ba Vs Ws Bj SSD SG = = (Vs+Vi+Vp)/γw Bj - Ba

Measuring Specific gravity Diukur Ws= berat kering partikel agregat γw= berat volume air Bk= berat agregat kering Ba= berat agregat di dalam air Bj= berat agregat jenuh air (SSD) Vi Vp Vs Ws Bk Apparent SG = = (Vs+Vi)/γw Bk - Ba Bulk SG + App SG Estimasi Effective SG = 2

Gradation Gradation is size distribution of aggregate particles Gradation can be assessed by sieve analysis

Aggregate specification Specification for aggregate is some requirements that to be fulfilled by aggregate properties to ensure the performance of bituminous mixture For examples Item Requirement Apparent Specific gravity min 2.50 Absorption max 3.0% Abrasion loss max 35% Elongated and flat particles max 25% Soundness loss max 12%

Sieving analysis ¾’ ½’ No saringan Berat tertahan (g) % tertahan % lolos ¾’ 100 ½’ 89.2 4.3 95.7 3/8’ 159.7 7.7 88.0 No.4 238.5 11.5 76.5 No.8 311.1 15.0 61.5 No.16 300.7 14.5 47.0 No.30 398.2 19.2 27.8 No.50 327.7 15.8 12.0 No.100 149.3 7.2 4.8 No 200 16.6 0.8 4.0 Pan 83.0 Total 2074.0 2 1/2 inch (63 mm) 2 inch (50 mm) 1 1/2 inch (37.5 mm) 1 inch (25 mm) 3/4 inch (19 mm) 1/2 inch (12.5 mm) 3/8 inch (9.5 mm) No.4 (4.75 mm) No.8 (2.36 mm) No.16 (1.18 mm) No.30 (0.6 mm) No.50 (0.3 mm) No.100 (0.015 mm) No.200 (0.0075 mm)

Making gradation curve No saringan % lolos ¾’ 19 mm 100 ½’ 12.5 mm 95.7 3/8’ 9.5 mm 88.0 No.4 4.75 mm 76.5 No.8 2.36 mm 61.5 No 10 2.00 mm 57.5 No.16 1.18 mm 47.0 No.30 0.6 mm 27.8 No.50 0.3 mm 12.0 No.100 0.015 mm 4.8 No 200 0.0075 mm 4.0

Type of gradation GAP GRADED UNIFORMLY GRADED WELL GRADED

Finer or coarser aggregate Agregat semakin halus (finer)

Blending two aggregates (1) Sieve no Grad A Grad B Specification Mean spec (target gradasi) 2 in 100 1.5 in 95 90 – 100 ¾ in 63 85 65 – 80 72.5 No 4 25 50 30 – 45 37.5 N0.10 15 36 20 – 35 27.5 No 200 3 7 0 – 5 2.5

Blending two aggregates – metode grafis (2) Hasil blending A: B = 37 : 63 1.5 in 3/4 in No 4 No 10 No 200 A = 37%