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116 Cards in this Set
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- Back
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Road Pavement |
A sequence of selected and processed materials placed on the natural ground or "subgrade". |
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What does a pavement do? |
The pavement (stiffest layer) spreads out the concentrated load over a large area from the vehicles tires down to each of its layers. Until, the stress on the underlying soil (subgrade - weakest layer) is so small that it isn't affected by the vehicle's load and doesn't rut. |
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Newark New Jersey |
The first asphalt roadway in US (1970). |
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HMA Layer 1 : Wearing Course |
It resists surface distress such as top-down cracking and rutting. |
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HMA Layer 2 : Intermediate Layer |
It carries load. It is stable and durable. |
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HMA Layer 3 : HMA Base (Fatigue Resistance) Layer |
Increase thickness, add as content Avoid tensile strain |
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Rigid Pavement and Joint Types - Jointed Portland Concrete Pavement (JPCP) - Jointed Dowel Reinforced Portland Conrete (JDRPC) - Continuous Reinforced Concrete Pavement (CRCP) - Construction Joint - Expansion Joint Joint |
- JPCP : used to remedy cracking due to shrinkage - CRCP : reinforcements at the bottom will absorb tension due to loading - Construction Joint : chosen over JPCP because only 1 lane is filled which causes a smooth crack - Expansion Joint : used when concrete expands due to heat |
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CRCP Typical Crack Spacing |
1.1 - 2.4 m (3.5 - 8 ft) |
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Federal Highway Association (FHWA) |
The transpo in U.S. which sets the standards we follow. |
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How to transfer load across transverse joints? |
Aggregate Interlock Dowel Bars Reinforcing Steel |
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Tie Bars |
Usually used to hold abutting slabs at the longitudinal joints. It does not provide load transfer. Deformed steel bars. Connectors used to hold the faces of abutting slabs in contact. Usually used between an edge joint and a curb or shoulder. |
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Aggregate Interlock |
Shear between the aggregate particles below the initial saw cut. Cracks develop later on. |
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Mechanical Locking |
It is formed between the fractured surfaces along the crack below the joint saw cut. |
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Dowel Bars |
Usually inserted at mid-slab depth and coated with a bond-breaking substance to prevent bonding to the PCC. It helps to transfer load but allow adjacent slabs to expand and cotract independent of one another. |
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Porous Block Pavement |
It is easily changeable. |
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The Gross Domestic Product (GDP) is directly proportional with the Vehicle-Miles Travelled (VMT). |
This means that more products are transported. National economy is greatly affected by your investment in your roads. |
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What is the Vision of Road Policy of Korea? |
Eco-friendly Road Convenient Road - using technology Safe Road |
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How is the Philippine Pavement? Total Length Covered Concrete Asphalt Gravel Earth |
Total Length Covered : 33 000 km Concrete : 64.44% Asphalt : 29.98% Gravel : 5.41% Earth : 0.16% *Those that are gravel and earth are just waiting to be covered |
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What are the only regions where asphalt pavements are higher than concrete pavements? |
NCR Region 4-A |
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Does the pavement maintenance cost increase every year and at 2018 it is at 11 000 000? |
True |
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Philippine Pavement Issues Yellow Lanes Thirsty Pavement Delayed Flights Road Closure Damaged Road Bridge Deck |
Yellow Lanes Rule - "anti-poor" Thirsty Pavement - absorbs floodwater Delayed Flights - damaged pavement Road Closure - 40 ton 14-wheeler truck caused 20 ton capacity Roxas Blvd road to collapse; but, there should only be minimal damage and not a huge hole Damaged Road - netizens says that the gov't corrupted it because there's no steel inside Bridge Deck - according to DPWH, it's because of the weak subgrade and it's over a fault line which PHIVOLCS denied. Note that there are no earthquake resistant pavements yet. |
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How do you characterize traffic loads? |
The number, configuration and load magnitudes of truck axles. |
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What are some random advanced technologies? |
Technologies transferred from military and aerospace Remote sensing : video & infrared Radar : passive technology Image Processing : autoscope Various Sensor : loop detection Wireless Communication : mobile phone - iridium - IMT2000 Overhead Laser Infrared Radar Installation |
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What are traffic data monitoring equipment distributed over the roadway network used to collect traffic load data? |
Automatic Traffic Recorders (ATR)
Automated Vehicle Classifiers (AVC)
Weigh-in-motion (WIM) Systems
*typically installed in the driving lanes *records data at normal driving speeds *some systems are permanently installed while others are temporarily installed over short periods of time and moved between locations *estimate average traffic volumes from short-term volume counts *traffic data is summarized for pavement design input |
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These are installed in truck inspection stations and are used for load enforcements instead for data collection purposes. |
Static Weigh Scales |
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Automated Vehicle Recorders (ATR) |
It uses an inductive (open wire) loop that is embedded near the pavement surface. Current and voltage are generated due to the passing of vehicles.
Some sensors are placed overhead which can be moved between locations to provide short-term traffic count samples. Cannot be used to differentiate between vehicle types. |
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Automated Vehicle Classifiers (AVC) |
Record vehicle volumes by vehicle classification.
Vehicle classification is defined in terms of the number of axles by axle configuration.
Detect the number of axles and their spacing through a combination of vehicle and axle sensors.
Not all axle sensors can differentiate between two and four tires axle (cannot distinguish Class 3 from Class 5 vehicles) |
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In terms of AVC system accuracy, what is the maximum error unclassified vehicles and mis-classified trucks? |
2% |
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What are the limitations of AVC? |
Classifying vehicles through conventional AVC systems under variable speeds is challenging. Camera-based sensors used for general traffic data collection purposes have been used. Additional independent observers need to collect more accurate traffic data. Although it contains more information than the ATR, it still lacks information about axle loads. |
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What is AADT? |
Annual Average Daily Traffic |
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What's one way of predicting traffic volumes? |
Applying a % growth factor to curren traffic volumes Assuming a linear or exponential growth function over the analysis period (e.g. 30 years) |
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What is axle configuration? |
It is the number of axles sharing the same suspension system and the number of tires in each axle. |
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Traffic Model Gear Naming Convention |
1 tire - single 2 tires - dual 3 tires - triple 4 tires - quadruple Multiple Axles 2 axles - tandem 3 axles - triple 4 axles - quad
*spaced 1.2 - 2.0 m *treated differently than single axles because they impose pavement stresses/strains that overlap |
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How many vehicle classes are there in FHWA and Korea? |
13 12 (no motorcycle) |
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Weigh-in-Motion (WIM) |
Provide the load of each axle passing over the system. Consist of a combination of inductive loops for detecting vehicle speed and one or several axle load sensors. Able to respond/ recover quickly, allowing multiple closely-spaced axles to be weighed individually at highway speeds. |
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WIM Load Sensing Mechanisms |
Load-sensitive strips (piezoelectric or quartz) Strain-gauged plates Load cell supported plates |
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WIM Load Sensing Principles |
The voltage signal being output is electronically processed to yield the load of the tires or axles. WIM systems measure dynamic rather than static axle loads. Dynamic axle loads can be substantially different than the static. |
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Wandering Effect |
A bell curve formed from vehicles that did not only move in 1 lane but also, wandered by curving. |
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Equivalent Single Axle Load (ESAL) |
A dimensionless unit describing the pavement damage from the variety of axle configurations and loads. The reference unit is damage caused by a single axle of 80 kN (18 000 lbs) with tires inflated to 586 kPa (85 lbs /in^2) |
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AASHTO Road Test Equation |
To determine the significant relationships between the number of repetitive applications of specified axle loads of varying magnitude and arrangement and the performance of different thickness of uniformly designed and constructed pavements. |
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Fixed Traffic - Critical Aircraft |
1. Criterion for Stress 2. Deflection 3. Tensile Strain 4. Contact Pressure 5. Contact Radius |
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Structural Considerations / Capability |
ESAL factors depend on this. It is the capability of a pavement to carry the load with its thickness and terminal serviceability. This is measured by the Structural Number (SN). |
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Lab Tests |
Rotational Direct Axial Diametral |
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Fatigue - Lab Test |
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Third - Point Flexural Testing |
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NCHRP 1-37A Pavement Design Approach |
Higher level versions of this design approach require a disaggregate treatment of truck axle loads involving counts of axles by configuration and load magnitude (load spectra). This type of traffic data is assembled by combining data from WIM, AVC and ATR systems distributed throughout a roadway network. This is a significant improvement over the aggregate ESAL approach because it allows mechanistic treatment of load-induced stresses and the resulting fatigue and plastic deformation accumulated over time |
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Level 1 in NCHRP 1-37A |
Project/lane specific data on volume/classification/axle load distribution. Can be collected only with a WIM system operated at the design site over extended periods of time. |
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Level 2 in NCHRP 1-37A |
Project/lane specific data on traffic volumes by vehicle class combined with representative/regional axle load distribution data. It is possible with a site/lane specific installed AVC system combined with WIM installations on roads of similar truck traffic composition as the design site. |
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Level 3 in NCHRP 1-37A |
Site/lane specific data on traffic volumes and an estimate of the percentage of trucks. Possible with a site/lane specific ATR and manual truck percentage observations combined with regional AVC and WIM data. |
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Level 4 in NCHRP 1-37A |
Similar to the Level 3 input, except that national representative or default AVC and WIM data is utilized, where regional data is not available. |
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What are the Interstate maximum allowable loads? Single axles/dual tires Tandem axles/ dual tires Tridem axles/ dual tires GVW |
Single axles/dual tires: 89 kN (20,000 lbs) Tandem axles/dual tires: 151 kN (34,000 lbs) Tridem axles/dual tires: 151 kN (34,000 lbs) (i.e., no additional load) GVW: 356 kN (80,000 lbs) |
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The load on any group of consecutive axles should be lower than the value computed from the what? |
Bridge Formula |
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What type of pavement is it where the base provides strength and reduces stress levels that reach the subgrade? |
Flexible Pavement |
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What type of pavement is it where the base is used for leveling and structural strengthening of weak subgrades? |
Rigid Pavements |
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What materials can provide internal drainage to prevent deleterious effects of water in the subgrade? |
Base/ sub-bases and subgrades |
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The mechanical behavior of bases/sub-bases and subgrades are best described by what theory? |
Shakedown Theory |
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Shakedown Theory : Zone 1. Small Stresses |
The path is the same for unloading and loading. Pure elastic response. |
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Shakedown Theory : Zone 2. Elastic shakedown |
There are small levels of permanent deformation due to limited slipping of particles. Subsequent cycles at the same strain level : no additional plastic deformation. |
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Shakedown Theory : Zone 3 |
The increase in plastic strain ceases: plastic shakedown limit. |
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Shakedown Theory : Zone 4 |
Some aggregates: plastic strain continues after limit (due to gradual and low-level of abrasion of aggregates): plastic creep region. |
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Shakedown Theory : Zone 5. |
Plastic strain at an increasing rate until failure. Aggregates suffer significant crushing, abrasion and breakdown |
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Resilient Response |
It is the typical response of granular materials under one cycle of loading before permanent strain. |
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Resilient Modulus (Mr) |
The elastic-only component of the response of granular materials. It is experimentally determined using a repeated load triaxial test where the cylindrical specimen is subjected to confined triaxial stress state and dynamic axial compressive load. It is the fundamental input to te structural design of pavements. |
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What does the AASHTO T 307-99 standard consists of? |
Mr of untreated granular base-subbase materials Mr of subgrades (i.e. soil compacted before the placement of base-subbases) |
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What are the factors affecting resilient properties? |
Stress level, compaction and aggregate structure, material factors |
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Compaction and Aggregate Structure |
Unbound granular layers: cross-anisotropic properties (layers are stiffer in the vertical direction than in the horizontal direction); Anisotropy is explained by preferred orientation of aggregates within the layer, aggregate shape and compaction forces. |
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What are the material factors? |
Density gradation fines content moisture content physical characteristics |
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Material Factors : Density |
More significant for partially crushed aggregates. NEGLIGIBLE for fully crushed aggregates. At low confinement levels, Mr increases with increase in density. At high confinement levels, Mr is less sensitive to density. |
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Material Factors : Gradation and Fines |
NO CONSENSUS on its effect on Mr. Some studies show that fines contents between 2 and 10% has a SLIGHT effect on Mr and others, found a DETRIMENTAL effect of increase in fines on Mr. WELL-GRADED aggregates have shown to have higher Mr than UNIFORMLY GRADED aggregates. |
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Material Factors : Moisture Content |
Critical in determining Mr. Below the optimal moisture content: Increase in moisture levels causes an increase in Mr. Above the optimal moisture content: Increase in moisture levels causes a decrease in Mr. |
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Material Factors : Physical Characteristics |
Angular and rough-textured particles are related to higher Mr compared to uncrushed or partially crushed particles. |
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Plastic Response |
It is used to estimate the plastic component of the strain in granular materials. It is important for quantifying permanent deformation. |
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What are the 2 approaches that can be used to model the plastic response of unbound aggregate bases/subbases and subgrades? |
Use a 3-D strain-behavior model of the aggregates based on plasticity theory; Use laboratory experiments to obtain a one-dimensional relationship between stress level, number of loading cycles and cumulative permanent strain.
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Modulus of Subgrade Reaction (k) |
Soil spring constant. Material input to the analysis of Portland concrete pavements; Represents the elastic constant of a series of springs supporting the concrete slabs; Measured through plate-loading test: |
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California Bearing Ratio (CBR) |
Defined as a comparison between the bearing capacity of a material with respect to a well-graded crushed stone characterized by a reference CBR of 100% |
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CBR Test |
Measured by applying load to a small penetration piston (1,33 mm per minute) and recording the total load at penetrations ranging from 0.64 – 7.62 mm. |
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R-value (Resistance Value) |
Inferred value of stiffness of unbounded materials based on their resistance to deformation. |
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R-value Test (Hveem Stabilometer) |
Experimental setup includes measuring the lateral pressure transmitted in response to a vertical pressure on a cylindrical sample. |
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Coefficient of Lateral Pressure |
Defined as the ratio of lateral stress by vertical stress; Ranges from 0.4 to 0.6 for unbound materials, subgrades and bedrock materials; |
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What are other aggregate layer indices? 5 common indices used to characterize bases/subbases and subgrades. |
Modulus of Subgrade Reaction CBR R-Value Coefficient of Lateral Pressure Atterberg Limits |
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Dynamic Cone Penetrometer (DCP) |
Device used for measuring in situ (in place) strength (density measurement) of soils Locates different soil layers Correlated to CBR value Developed by Corps of Engineers Quick and inexpensive |
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DCP Operation |
Drop weight : 17.6 lb or 10.1 lb Keep track of displacements and number of blows Plot penetration rate versus depth. |
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Factors affecting Falling Weight Deflectometer (FWD) measurements - FWD Deflection Basin |
Load applied Pavement type/ condition - distress - existence of voids - direction (transverse or longitudinal) - location (midslab, joint, corner.. ) Climatic Condition - moisture, temperature, frost penetration |
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Atterberg Limits |
These are index properties used to determine the soil consistency at different levels of moisture content. |
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What is the order of Atterberg Limits? |
- Solid State Shrinkage Limit - Semisolid State Plastic Limit - Plastic State Liquid Limit - Liquid State |
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Solid State |
Breaks before it will deform; consistency of hard candy |
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Semisolid State |
Deforms permanently but cracks Consistency of cheese |
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Plastic State |
Deforms without cracking Consistency of soft butter to stiff putty |
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Liquid State |
Deforms easily Consistency of pea soap to soft butter |
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Plasticity Index (PI) |
It is the measure of the range of moisture content that defines the plastic state |
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Stabilization |
The procedure to reduce the increased strength and stiffness of materials. |
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How do you stabilize subgrade soils? |
Reduce the volume change potential of the material |
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How do you stabilize granular bases/ subbases? |
Reduce plasticity. |
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Traditional Stabilizers |
Hydrated Lime Portland Cement Fly Ash |
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How do you stabilize with Lime? |
Used in different forms. The most common: hydrated high-calcium lime Ca(OH)2; Lime causes calcium to replace cations (e.g., NA+, K+) in the water system in clays; As a result, particles form a flocculated structure with smaller volume, higher internal friction and better workability; Soil-lime reaction is influenced by many factors (soil pH, drainage, organic carbon content, clay mineralogy, etc.); There exist protocols to design and test soil-lime mixtures.
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How do you stabilize with Cement? |
Soil-cement mixtures are tested using durability and strength tests; Cement stabilization is done to reduce the PI of the soil, increase shrinkage limit, reduce volume change, reduce clay-silt-size particles, improve strength or increase Mr of the soil. |
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How do you stabilize with Fly Ash? |
Fly ash is a synthetic pozzolan resulting from combustion of coal;Its use for stabilization of clay soils only works in combination with lime or cement; Important consider rate of hydration process, influence of moisture content, percent of free lime and percent of sulfates. |
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Construction Process for Lime Stabilization |
1. Scarify-Pulverize Soil 2. Lime Addition 3. Initial Soil-Lime Mixing 4. Final Mixing and and Pulverizing 5. Compact Soil-Lime 6. Cure |
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Moisture Related Strength Loss How? What? |
Moisture infiltration - lubricates particles - weakens materials Expansive/swelling soils Frost penetration |
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Factors for frost heave to develop? |
1. Freezing temperatures 2. Presence of water - when water freezes there is a 10% increase in volume 3. Frost susceptible soils - silts
*ice lenses in the subgrade |
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Indicators of high severity frost heave? |
Differential heaving Surface roughness Cracking Blocked drainage A reduction in bearing capacity in thaw periods |
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How to reduce frost heave and penetration? |
Remove frost susceptible soil Lower water table Add a drainage Restrict truck traffic on roads during spring-thaw season Thicker pavement section - frost protection |
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What about tbe distresses caused by aggregates as seen on highways? (10) Rutting Scaling Polished Aggregate Popouts Mud ball ASR D Cracking Pothole Ravelling Bleeding |
Rutting - wheel tracks Polishing Scaling- looks like fish scales Polished Aggregate- smoothened, no longer angular Popouts- aggregate is removed Mud ball ASR (Alkali-Silica Reaction)- causes a jelly to form so the aggregates fail to fit the concrete - check the alkali content D Cracking- usually happens during winter where concrete undergoes tension and compression Pothole- furthered damage of crocodile cracking Ravelling- loss of large aggregates- binder is being removed Bleeding- binder melted
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How are aggregates made? (5) |
Excavation Crushing Sizing Stockpiling (pinagsasama sizes) Transportation |
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Los Angeles Degradation Test (ASTM C 131): resistance of coarse aggregates to abrasion and impact forces. Los Angeles Abrasion (AASHTO T96 ASTM C 131) - Toughness - LA Abrasion Test |
Sample of coarse aggregates placed within a rotating steel drum with steel balls.
Tumbling causes abrasion between particles and between steel balls and particles.
Sample is removed and sieved.
Percentage passing No. 12 sieve is as a measure of degradation.
Result expressed as % changes in original weight
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How do you measure stength of aggregate for the pavement on a highway? (5) |
Los Angeles Degradation Test (ASTM C 131): resistance of coarse aggregates to abrasion and impact forces. Los Angeles Abrasion (AASHTO T96 ASTM C 131) - Toughness LA Abrasion Test
Page Impact Test (ASTM D 3) Aggregate Impact Value, AIV (BS 812-Part-112, British standard): resistance to impact. Aggregate Crushing Value, ACV (BS 812-Part-110, British standard): resistance to breakage. The Micro-Deval test (ASTM D 6928): French test to measure resistance to abrasion. |
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LA Abrasion Test |
- Approx. 10% loss for extremely hard igneous rocks - Approx. 60% loss for soft limestones and sandstones |
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Page Impact Test (ASTM D 3) |
Resistance of a cylindrical core to impact of a hummer dropped freely from different heights. Height (in / cm) causing fracture: toughness value of the aggregate. |
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Aggregate Impact Value, AIV (BS 812-Part-112, British standard): resistance to impact. |
Sample of coarse aggregates placed in a cylindrical model. Sample subjected to blows from a hammer. AIV = aggregate weight passing a British Standard 2.40-mm sieve (approx. U.S. No. 8 sieve). |
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Aggregate Crushing Value, ACV (BS 812-Part-110, British standard): resistance to breakage. |
Sample in cylindrical model. Sample subjected to continuous load in a compaction machine. Load applied gradually over a specific time. ACV = percentage of fines created passing the British Standard 2.40-mm sieve (approx. U.S. No. 8 sieve). |
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The Micro-Deval test (ASTM D 6928): French test to measure resistance to abrasion. |
Steel balls cause abrasion during the rotation of an aggregate sample introduced in the machine. Sieve analysis is conducted in the sample after the test: Weight loss in coarse aggregate = material passing sieve No. 16
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How do you measure friction coefficient of aggregate for the pavement on a highway? |
British Wheel Device (ASTM D 3319): measures the resistance to polishing.
British Portable Pendulum Tester (ASTM E 303): measures aggregate friction or degree of polishing.
Micro-Deval Voids at nine hours (MDV9): resistance to polishing.
Insoluble Residue in Carbonate Aggregates (ASTM D 3042): used to identify carbonate aggregates that are prone to polishing. |
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Degree of polishing: how to get ow to get |
height reached by the slider as it swings past the point of contact with the test specimen |
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British Portable Pendulum Tester (ASTM E 303): measures aggregate friction or degree of polishing. |
Aggregate coupons before (top) and after (bottom) polishing |
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Micro-Deval Voids at nine hours (MDV9): resistance to polishing. |
Micro-Deval is used to polish an aggregate sample for 9 hours. The voids in an uncompacted sample are used to measure their packing (void ratio). The lower the void ratio: smoother the polished aggregates, lower their polish resistance. |
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Insoluble Residue in Carbonate Aggregates (ASTM D 3042): used to identify carbonate aggregates that are prone to polishing. |
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