CIV3703 Transport Engineering
CIV3703 Transport Engineering
Module 4 – Part 1 Road Materials Dr. Andreas Nataatmadja
4.1 Pavement Natural soil usually not strong enough to withstand repeated application of vehicle wheel loads. Need to protect natural soil from the wheel loading effects by placing a structure - pavement.
Example (Construction of Residential Road)
Materials Used in Pavements Bituminous materials Unbound granular materials Cemented materials Cement concrete
Pavement Layers
Subgrade may consists of several selected materials on top of natural subgrade
Pavement Types Flexible • Asphalt/Seal on unbound granular • Asphalt on stabilised subbase • Full-depth asphalt Rigid • Concrete base with joints and/or steel reinforcement • Using Lean Mix Concrete (LMC) subbase Composite • Flexible pavement with an LMC subbase • Designed as a flexible pavement
4.2 Pavement Materials Flexible Pavements: •
Granular materials: used in base, sub-base, selected material layers e.g. crushed rock, soil-aggregate (unmodified/modified) May be covered with sprayed seal or asphalt
•
Stabilised/cemented aggregate: used as sub-base e.g. cement treated crushed rock (CTCR) – subject to fatigue Requires at least 175 mm asphalt base to stop reflective cracking
• Bituminous materials: used as surfacing or base e.g. sprayed seal, asphalt (open graded, stone mastic, dense graded)
4.2 Pavement Materials Rigid Pavements: • Concrete: used as base in • Plain Concrete Pavement (PCP) • Jointed Reinforced Concrete Pavement (JRCP) • Continuously Reinforced Concrete Pavement (CRCP): has no joint • Fibre Reinforced Concrete Pavement (FRCP) • Lean Mix Concrete (LMC): used as subbase Rigid Pavement is • Provides uniform support to the base outside the scope of • Resists erosion and pumping CIV3703 • Enhances load transfer across joints • Granular materials: used in selected material layers
4.3 Gravels Crushed rock Soil aggregate mixtures: In Queensland, observe the following terms gravel: max size > 5mm loam: max size < 5mm Includes: pit, ridge, creek or waterworn gravels crusher products mixed with a soil binder decomposed rock sedimentary or metamorphic rocks fine grained materials (loam, sand clay mixtures)
4.4 Factors Influencing Selection of Pav. Materials Type of pavement
(surfaced vs unsurfaced)
Position in the pavement
( base vs sub-base)
Climatic conditions
(wet vs arid)
Traffic
(low vs high volumes; light vs heavy)
Availability of materials
(untreated vs stabilised)
Stress Distribution within a Flexible Pavement
Stronger materials are used to handle higher stresses (near the surface)
4.5 Location & Investigation of Natural Gravel Deposits Search, based on available information, local knowledge maps (soil, geological), aerial photos similar locations to existing deposits geology Vegetation types
Preliminary examination visual, sampling, laboratory tests
Detailed investigation detailed sampling, testing, determination of variation
4.6 Testing of Granular Materials PROPERTIES OF IMPORTANCE: 1. Stability ability to resist deformation and change Strength (c, φ, UCS, CBR) an important component of stability strength depends on moisture, voids, conditions under which stress is applied strength tested e.g. California Bearing Ratio (CBR) or inferred from classification tests
2. Resistance to Wear not easily measured inferred from classification and index tests
3. Permeability inferred from classification and index tests
4. Workability: ease of spreading & compaction inferred from classification tests
4.6.1 Particle Size Distribution Determined by sieving and hydrometer analysis for finer fraction
4.6.2 Consistency Limits (Atterberg Limits) Plastic limit (PL) Liquid limit (LL) Typical max 25% to 35% Plasticity Index (PI) = Liquid limit - Plastic limit Typical maximum for aggregates 6% Weighted PI (WPI) = % passing sieve 0.425 mm x PI Typical maximum = 200 - 400
4.6.3 Linear Shrinkage •
Gives indication of volume change with moisture variation.
•
Maximum allowable 3% to 6%, depending on purpose of use and climatic condition.
4.6.4 California Bearing Ratio (CBR) Test originally developed by California Highways Department to assess quality of fine crushed rock base materials Test compares strength of a material to a standard crushed rock material. Standard material has CBR of 100. Good quality crushed rock has CBR ≥ 80.
Test Procedure Material compacted into steel mould sample 152 mm dia; 127 mm high 3 layers, 53 blows per layer for standard compaction
50mm steel plunger forced into material at constant penetration rate rate of penetration 1 mm/min recording of load versus penetration
CBR value calculated
CBR Calculation CBR at 2.5 mm penetration
Standard material requires load of 13 .3 kN for 2.5 mm penetration. Value for CBR at 5 mm penetration calculated using a value of 20 kN for standard material.
4.6.5 Ten Percent Fines & Wet/Dry Strength Variation Ten percent fines value test measures resistance of rock to crushing. a variation of the Aggregate Crushing Value test. load to produce 10% fines measured.
Wet/Dry strength variation looks at 10% fines value difference for the material in wet and dry conditions.
4.6.6 Washington Degradation Test Used to assess the extent of alteration or weathering of igneous or metamorphic source rocks. Sample crushed to pass 19 mm sieve Shaken in water for 20 minutes Sample washed with flocculating agent Amount of sediment measured Test value calculated (using a complex scale) Values < 60 a concern. Values of 30 to 40 may be okay for subbases.
4.7 Bituminous Surfacing Materials All bituminous road surfacings consist of 2 essential components: •
mineral aggregate - resists the wearing effect of tyres
•
bituminous binder - acts as adhesive or glue, to hold aggregate particles in place, and to bond surfacing to underlying base.
http://www.highway1.co.nz/sma-fibres.html
Commonly Used Bituminous Surfacings in Australia Bituminous seal or sprayed seal Thin layer of bitumen sprayed on the road surface to hold a layer of relatively large aggregate particles.
Asphalt, plant mix, or bituminous concrete Intimate mixture of aggregate particles and bitumen binder, produced in a mixing plant.
Sprayed (Chip) Seal Surface
4.8 Road Surfacing Aggregates Functions are to resist abrasion by traffic, and to transmit wheel loads to base. Aggregate needs to be durable, to possess hardness, toughness, wearing resistance, crushing strength and polishing resistance (to withstand traffic). In addition, aggregates should have good microstructure that provides skid resistance.
Source of Aggregates Naturally occurring unconsolidated sediments gravels & sands
Crushed quarried rock typically igneous rocks - basalt, gabbro or granite metamorphic rocks - quartzite, schist
Crushed artificial rocks blast furnace slag steel slag
Size/Grading of Aggregate for Surfacing Narrow particle size distribution (PSD) used for sprayed seal applications (i.e. one sized aggregate) In plant mix (asphalt) a wide partial distributions is used to form interlocking (except Open Graded Asphalt or OGA) Aggregate greater than 37.5 mm is not normally used for surfacing Coarse aggregate > 4.75 mm; fine aggregate is between 4.75 and 75 µm; passing 75 µm is known as fillers.
4.9 Desirable Properties of an Aggregate Mechanically strong Resistant to wear Resistant to degradation by weather Good shape (angular, near cubical shape) Provides surface texture (microtexture) for skid friction Clean, ready to be mixed with binder
4.10 Testing of Aggregates 4.10.1 Strength & Resistance to Wear Los Angeles Abrasion Test; Agg. Crushing Value
4.10.2 Resistance to Decomposition Soundness; Wet/Dry strength variation
4.10.3 Particle Shape and Surface Texture Flakiness, Angularity, ALD
4.10.4 Resistance to Polishing by Traffic Polished Aggregate Friction Value
Los Angeles Abrasion Test 5,000 g of coarse aggregate is rotated for 500 revolutions with either 10 or 11 steel balls. Amount of generated fines is determined (passing 1.7mm sieve) i.e. percent loss Typical maximum loss: 25% for seal coat
Aggregate Crushing Value Sample: aggregate passing 13.2 mm and retained on 9.5 mm Constant loading for 10 minutes up to 400kN Passing 2.36 mm sieve is determined
Flakiness Index (FI) Percent by mass of aggregate particles having a least dimension < 60% of the mean aggregate size. Determined as the ratio of the mass passing a specific slot to the total mass of the aggregate fraction. Low FI (e.g. 15%) → cubical shaped stone (desirable) High FI (e.g. 30%) → flaky shaped stone (undesirable) QDTMR Spec MRTS22 → FI ≤ 35%
Angularity Number Highly angular fine aggregates are used to produce high stability asphalt concrete mixes. Crushed fine aggregates (manufactured) tend to be more angular than natural ones. Angularity number is the amount of voids exceeding 33%
Average Least Dimension (ALD) must be representative poor practice to use “assumed ALD” check prior to sealing Used to calculate: Binder spray rate Aggregate spread rate Design assumes seal thickness equal to ALD after some trafficking
What happens with non-single sized aggregate ?
Source: Austroads
Skid Resitance Test Pendulum skid resistance tester: measures the polished aggregate friction values (PAFV).
End Module 4, Part 1
Module 4 – Part 1 Road Materials Dr. Andreas Nataatmadja
4.1 Pavement Natural soil usually not strong enough to withstand repeated application of vehicle wheel loads. Need to protect natural soil from the wheel loading effects by placing a structure - pavement.
Example (Construction of Residential Road)
Materials Used in Pavements Bituminous materials Unbound granular materials Cemented materials Cement concrete
Pavement Layers
Subgrade may consists of several selected materials on top of natural subgrade
Pavement Types Flexible • Asphalt/Seal on unbound granular • Asphalt on stabilised subbase • Full-depth asphalt Rigid • Concrete base with joints and/or steel reinforcement • Using Lean Mix Concrete (LMC) subbase Composite • Flexible pavement with an LMC subbase • Designed as a flexible pavement
4.2 Pavement Materials Flexible Pavements: •
Granular materials: used in base, sub-base, selected material layers e.g. crushed rock, soil-aggregate (unmodified/modified) May be covered with sprayed seal or asphalt
•
Stabilised/cemented aggregate: used as sub-base e.g. cement treated crushed rock (CTCR) – subject to fatigue Requires at least 175 mm asphalt base to stop reflective cracking
• Bituminous materials: used as surfacing or base e.g. sprayed seal, asphalt (open graded, stone mastic, dense graded)
4.2 Pavement Materials Rigid Pavements: • Concrete: used as base in • Plain Concrete Pavement (PCP) • Jointed Reinforced Concrete Pavement (JRCP) • Continuously Reinforced Concrete Pavement (CRCP): has no joint • Fibre Reinforced Concrete Pavement (FRCP) • Lean Mix Concrete (LMC): used as subbase Rigid Pavement is • Provides uniform support to the base outside the scope of • Resists erosion and pumping CIV3703 • Enhances load transfer across joints • Granular materials: used in selected material layers
4.3 Gravels Crushed rock Soil aggregate mixtures: In Queensland, observe the following terms gravel: max size > 5mm loam: max size < 5mm Includes: pit, ridge, creek or waterworn gravels crusher products mixed with a soil binder decomposed rock sedimentary or metamorphic rocks fine grained materials (loam, sand clay mixtures)
4.4 Factors Influencing Selection of Pav. Materials Type of pavement
(surfaced vs unsurfaced)
Position in the pavement
( base vs sub-base)
Climatic conditions
(wet vs arid)
Traffic
(low vs high volumes; light vs heavy)
Availability of materials
(untreated vs stabilised)
Stress Distribution within a Flexible Pavement
Stronger materials are used to handle higher stresses (near the surface)
4.5 Location & Investigation of Natural Gravel Deposits Search, based on available information, local knowledge maps (soil, geological), aerial photos similar locations to existing deposits geology Vegetation types
Preliminary examination visual, sampling, laboratory tests
Detailed investigation detailed sampling, testing, determination of variation
4.6 Testing of Granular Materials PROPERTIES OF IMPORTANCE: 1. Stability ability to resist deformation and change Strength (c, φ, UCS, CBR) an important component of stability strength depends on moisture, voids, conditions under which stress is applied strength tested e.g. California Bearing Ratio (CBR) or inferred from classification tests
2. Resistance to Wear not easily measured inferred from classification and index tests
3. Permeability inferred from classification and index tests
4. Workability: ease of spreading & compaction inferred from classification tests
4.6.1 Particle Size Distribution Determined by sieving and hydrometer analysis for finer fraction
4.6.2 Consistency Limits (Atterberg Limits) Plastic limit (PL) Liquid limit (LL) Typical max 25% to 35% Plasticity Index (PI) = Liquid limit - Plastic limit Typical maximum for aggregates 6% Weighted PI (WPI) = % passing sieve 0.425 mm x PI Typical maximum = 200 - 400
4.6.3 Linear Shrinkage •
Gives indication of volume change with moisture variation.
•
Maximum allowable 3% to 6%, depending on purpose of use and climatic condition.
4.6.4 California Bearing Ratio (CBR) Test originally developed by California Highways Department to assess quality of fine crushed rock base materials Test compares strength of a material to a standard crushed rock material. Standard material has CBR of 100. Good quality crushed rock has CBR ≥ 80.
Test Procedure Material compacted into steel mould sample 152 mm dia; 127 mm high 3 layers, 53 blows per layer for standard compaction
50mm steel plunger forced into material at constant penetration rate rate of penetration 1 mm/min recording of load versus penetration
CBR value calculated
CBR Calculation CBR at 2.5 mm penetration
Standard material requires load of 13 .3 kN for 2.5 mm penetration. Value for CBR at 5 mm penetration calculated using a value of 20 kN for standard material.
4.6.5 Ten Percent Fines & Wet/Dry Strength Variation Ten percent fines value test measures resistance of rock to crushing. a variation of the Aggregate Crushing Value test. load to produce 10% fines measured.
Wet/Dry strength variation looks at 10% fines value difference for the material in wet and dry conditions.
4.6.6 Washington Degradation Test Used to assess the extent of alteration or weathering of igneous or metamorphic source rocks. Sample crushed to pass 19 mm sieve Shaken in water for 20 minutes Sample washed with flocculating agent Amount of sediment measured Test value calculated (using a complex scale) Values < 60 a concern. Values of 30 to 40 may be okay for subbases.
4.7 Bituminous Surfacing Materials All bituminous road surfacings consist of 2 essential components: •
mineral aggregate - resists the wearing effect of tyres
•
bituminous binder - acts as adhesive or glue, to hold aggregate particles in place, and to bond surfacing to underlying base.
http://www.highway1.co.nz/sma-fibres.html
Commonly Used Bituminous Surfacings in Australia Bituminous seal or sprayed seal Thin layer of bitumen sprayed on the road surface to hold a layer of relatively large aggregate particles.
Asphalt, plant mix, or bituminous concrete Intimate mixture of aggregate particles and bitumen binder, produced in a mixing plant.
Sprayed (Chip) Seal Surface
4.8 Road Surfacing Aggregates Functions are to resist abrasion by traffic, and to transmit wheel loads to base. Aggregate needs to be durable, to possess hardness, toughness, wearing resistance, crushing strength and polishing resistance (to withstand traffic). In addition, aggregates should have good microstructure that provides skid resistance.
Source of Aggregates Naturally occurring unconsolidated sediments gravels & sands
Crushed quarried rock typically igneous rocks - basalt, gabbro or granite metamorphic rocks - quartzite, schist
Crushed artificial rocks blast furnace slag steel slag
Size/Grading of Aggregate for Surfacing Narrow particle size distribution (PSD) used for sprayed seal applications (i.e. one sized aggregate) In plant mix (asphalt) a wide partial distributions is used to form interlocking (except Open Graded Asphalt or OGA) Aggregate greater than 37.5 mm is not normally used for surfacing Coarse aggregate > 4.75 mm; fine aggregate is between 4.75 and 75 µm; passing 75 µm is known as fillers.
4.9 Desirable Properties of an Aggregate Mechanically strong Resistant to wear Resistant to degradation by weather Good shape (angular, near cubical shape) Provides surface texture (microtexture) for skid friction Clean, ready to be mixed with binder
4.10 Testing of Aggregates 4.10.1 Strength & Resistance to Wear Los Angeles Abrasion Test; Agg. Crushing Value
4.10.2 Resistance to Decomposition Soundness; Wet/Dry strength variation
4.10.3 Particle Shape and Surface Texture Flakiness, Angularity, ALD
4.10.4 Resistance to Polishing by Traffic Polished Aggregate Friction Value
Los Angeles Abrasion Test 5,000 g of coarse aggregate is rotated for 500 revolutions with either 10 or 11 steel balls. Amount of generated fines is determined (passing 1.7mm sieve) i.e. percent loss Typical maximum loss: 25% for seal coat
Aggregate Crushing Value Sample: aggregate passing 13.2 mm and retained on 9.5 mm Constant loading for 10 minutes up to 400kN Passing 2.36 mm sieve is determined
Flakiness Index (FI) Percent by mass of aggregate particles having a least dimension < 60% of the mean aggregate size. Determined as the ratio of the mass passing a specific slot to the total mass of the aggregate fraction. Low FI (e.g. 15%) → cubical shaped stone (desirable) High FI (e.g. 30%) → flaky shaped stone (undesirable) QDTMR Spec MRTS22 → FI ≤ 35%
Angularity Number Highly angular fine aggregates are used to produce high stability asphalt concrete mixes. Crushed fine aggregates (manufactured) tend to be more angular than natural ones. Angularity number is the amount of voids exceeding 33%
Average Least Dimension (ALD) must be representative poor practice to use “assumed ALD” check prior to sealing Used to calculate: Binder spray rate Aggregate spread rate Design assumes seal thickness equal to ALD after some trafficking
What happens with non-single sized aggregate ?
Source: Austroads
Skid Resitance Test Pendulum skid resistance tester: measures the polished aggregate friction values (PAFV).
End Module 4, Part 1
