CE-T3 Quiz 2 Review PDF

**MODULE 7: Highway Maintenance and Rehabilitation** Highway Maintenance - Routine work performed to keep a pavement under normal conditions of traffic and normal forces of nature, as nearly as possible in its original condition (monitoring pavement health) - Maintenance actions help...

**MODULE 7: Highway Maintenance and Rehabilitation** Highway Maintenance - Routine work performed to keep a pavement under normal conditions of traffic and normal forces of nature, as nearly as possible in its original condition (monitoring pavement health) - Maintenance actions help slow the rate of deterioration by identifying and addressing specific pavement deficiencies that contribute to overall deterioration Maintenance Operations - Surface maintenance - Road side maintenance - Shoulder and approaches maintenance - Bridges, tunnels, and drainage structure maintenance - Traffic controls and safety devices (road signs, pavement markings, traffic signals, and road lighting) Maintenance of Road Surfaces 1. Bituminous Surfaces - failures due to weathering, failure of base or subgrade due o material quality or compaction or improper drainage - Repairs: - Patching - Scarifying - Resealing - Non skid surface treatment 2. PCC Surfaces - Repairs: - Filling and sealing of joints and cracks - Repairing spalled, scaled, and map cracked areas - Patching areas where failure has occurred - Reaping areas damaged by settlement and pumping - Treating buckled pavement 3. Maintenance of Shoulders and Approaches - Approaches include public side roads, private driveways, ramps. Speed change lanes, and turnouts - Approach maintenance is similar to main roadway maintenance 4. Maintenance of Roadsides - Roadside include area between traveled surface and the limit of the right-o-way (medians, roadside parks, ROW fences, etc.) - Vegetation management and control (include mowing, weed eradication and control, seeding, planting vegetations, and care of trees and shrubs) - Maintenance of rest areas 5. Maintenance of Bridges, Tunnels, and Drainage Structures - Bridges need to minimize deterioration or repair damage caused by accidents, floods, or other unforeseen events - Steel bridges need to be cleaned and painted to precent erosion - Concrete bridge decks may deteriorate due to the corrosion of reinforcement bars due to penetration of water and de-icing salts or chemicals - Bridge deck with minor deterioration is to be patched with special concrete - For major deterioration it is to be overlayed or removed and constructed - Tunnels (special attention areas): - Supports -- check for decays - Tunnel walls and ceilings -- check for leaks - Portals -- free from loose rocks - Lighting -- for visibility - Ventilation - Drainage Structures (following should be kept in good condition:) - Surface drainage - Ditches - Culverts - Traffic Control and Safety Devices - Guardrails, barriers, impact attenuators, pedestrian overpasses and underpasses, fence to restrict access of pedestrians and animals - Safety devices should be frequently and systematically inspected and repaired Pavement Rehabilitation - Proper maintenance to extend pavement life - However, the best-maintained pavements will deteriorate with time and will need rehabilitation - Conventional rehabilitation: - Reconstruct with all new materials - Patch and overlay with new wearing surface - Due to high construction cost, new methods of rehabilitation are raised: - Pavement Milling -- surface layers can be removed with a milling machine and replace with new hot-mix - Pavement Recycling -- technique where an existing degraded pavement is modified and transformed into a homogeneous structure that can support the traffic requirements **MODULE 8: Recycling Equipment and Methods** Recycling - Action or process of converting waste into reusable material Recycling Highways - Using recovered concrete, brick, and asphalt materials for the construction of pavements, earthworks, and drainage - This provides potential cost savings and conservation of natural resources Pavement Recycling - Technique where an existing degraded pavement is modified and transformed into a homogeneous structure that can support the traffic requirements - A report from the Federal Highway Administration shows that 80 percent of asphalt pavement that's removed each year during widening and resurfacing projects is reused Asphalt Pavement Recycling - Four primary methodologies in pavement recycling 1. Hot Recycling - Hot Mix Asphalt or Warm Mix Asphalt containing Recycled Asphalt Pavement (RAP) 2. Hot In-place Recycling (HIR) 3. Cold Recycling - Cold In-place Recycling (CIR) - Cold Central Plant Recycling (CCPR) 4. Full Depth Reclamation (FDR) Hot Mix Asphalt (HMA) and Warm Mix Asphalt Recycling - Process in which Reclaimed Asphalt Pavement (RAP) is combined with new materials to produce HMA/WMA mixes - RAP material can be obtained by milling or a crushing operation - RAP percentages range from 10 to 50 percent - Produced by batch plants or drum plants - Batch Plant -- make small accurate batches of asphalt mixture through a process that is repeated over and over until the total tonnage for a project has been manufactured - Drum Plant -- prepare the asphalt mix through a continuous process and require the use of silos for temporary storage prior to the mix being trucked to the paving location Hot In-place Recycling (HIR) - Method where the existing pavement is heated and softened, and ten scarified/milled to a specified depth - New HMA/WMA (with or without RAP) and/or recycling agent may be added to the scarified RAP material during the recycling process - HIR can be performed either as a single pass or as a multiple pass operation - Single Pass -- scarified in-place material can be combined with new material if needed or desired - Multiple Pass -- restored RAP material is recompacted first, and a new wearing surface is applied later - Three HIR Processes: 1. Surface Recycling 2. Repaving 3. Remixing Surface Recycling - Primary purpose of the surface recycling process is to eliminate surface irregularities and cracks - Equipment consists of the following: 1. Preheating unit 2. Heating and recycling unit 3. Rubber-tired roller Repaving - Useful when the surface recycling process is not sufficient to restore the pavement's desirable surface requirements or when a conventional HMA overlay is impractical or not needed - Equipment: 1. Preheating unit 2. Heating and recycling unit 3. Rubber-tired roller 4. Paver Remixing - Used when repaving method is not sufficient to restore the pavement to its desirable properties and additional aggregates or new HMA mix are required to provide strength and stability to the existing pavement - Process can effectively eliminate rutting, cracking, and oxidation (hardening) in the upper 50 mm (2 in) of the pavement surface - Asphalt pavements with one seal coat are remixable and the seal coat may help in softening the recycled binder - Pavements with multiple seal coats can create smoke and fire t the surface and act as an insulator against the heating of the underlying pavement Cold In-place Recycling - Existing pavement is pulverize in-place and recompacted into a pavement layer - Either as foamed asphalt binder or an asphalt emulsion is added as a recycling agent or binder Cold Central Plant Recycling (CCPR) - Material removed from an existing pavement I transported to a central location -- either on the project site or an existing asphalt plant - Either a foamed asphalt binder or an asphalt emulsion is added as a recycling agent or binder Full Depth Reclamation (FDR) - Recycling method where all of the asphalt pavement section and a predetermined number of underlying materials are mixed and manipulated in-place and treated t produce a stabilize base course - Steps: 1. Pulverization 2. Introduction of additive 3. Shaping of the mixed material 4. Compaction 5. Application of a surface or a wearing course - Performed at a depth of 4 to 12 inches **MODULE 9: Flexible Pavement Design** ***(not including all equations)*** Flexible Pavement - A pavement constructed of bituminous and granular materials - Structure that maintains intimate contact with subgrade and distribute loads to it, and depends on aggregate interlock, particle friction, and cohesion for stability Layers of Flexible Pavement (from top to bottom): 1. Seal Coat (on surface of surface course) 2. Surface Course 3. Tack Coat (on surface of binder course) 4. Binder Course 5. Prime Coat (on surface of base course) 6. Base Course 7. Subbase Course 8. Compacted Subgrade 9. Natural Subgrade Principles of Flexible Pavement Design - The maximum vertical stresses are compressive and occur directly under the wheel load - Stresses decrease with increase in depth from the surface - Maximum horizontal stress also occurs directly under the wheel load but can be either tensile or compressive - When the load and pavement thickness are within certain ranges, horizontal compressive stresses will occur above the neutral axis, whereas horizontal tensile stresses will occur below the neutral axis - Temperature distribution within the pavement structure will also have an effect on the magnitude of the stresses Elements of Thickness Design for Flexible Pavement 1. Traffic Loading 2. Climate or Environment 3. Material Characteristics 4. Others: Cost, Construction, Maintenance, Design Period Traffic Loading - Pavement must withstand the large number of repeated loads of variable magnitudes - Equivalent Standard Axle Load (ESAL) is 80Kn single axis load - Total no. of ESAL is used as a traffic loading input in the design of pavement structure Climate or Environment - Can affect the behavior of materials used in pavements through: 1. Temperature -- high temp. cause asphalt to lose stability, low temp. cause asphalt to become hard and stiff 2. Moisture -- frost related damage, volume changes due to saturation, chemical stability problems with moisture existence (stripping) Material Characteristics - Required Materials Characteristics: 1. Asphalt Surface -- material should be strong and able to resist repeated loading (fatigue) 2. Granular Base and Subbase -- gradation, stable and strong to resist shears from repeated loading 3. Subgrade -- soil classification, strong and stable AASHTO Design Method - Incorporates various design inputs including: 1. Pavement Performance 2. Traffic Characteristics 3. Subgrade Soil Properties 4. Materials for Construction 5. Environmental Effects 6. Drainage 7. Reliability 8. Serviceability Pavement Performance 1. Structural Performance - Related to the physical condition of the pavement with respect to the factors that have negative impact on the capability of the pavement to carry the traffic load 2. Functional Performance - Indication of how effectively the pavement serves the user - Main factor considered under functional performance is riding quality 3. Serviceability - Pavement ability to serve traffic during its design life Traffic Characteristics - Determined in terms of number of repetitions of an 80kn single axle load applied to the pavement on two sets of dual tires (ESAL) 1. Traffic Analysis - Estimate the number of vehicles of different types expected to use the pavement over the design period - Estimate the percentage of total truck traffic expected to sue use the road 2. ESAL Calculations - Total ESAL applied on the highway during its design period can be determined only if the following are known: 1. Design Period -- no. of years that the pavement will last before requiring rehabilitation or repairs 2. Traffic Growth Factor -- estimated using historical records or comparable facilities or obtained from other studies Subgrade Soil Properties - AASHTO method used the subgrade Resilient Modulus (Mr) to define its property - Mr is a measure of stiffness of subgrade, and it is an estimate of its Modulus of Elasticity - Resilient Modulus is determined using cyclical version of the triaxial test Materials for Construction - Structural Number, SN - Quality of the material - Subbase Construction Materials - Quality of the materials is determined in terms of the layer coefficient (a3) - Base Course Construction Materials - Materials should satisfy general requirements for base course - Quality of the materials is determined in terms of the layer coefficient (a2) - Surface Course Construction Materials - Layer Coefficient (ai) - Measure of the relative effectiveness of a given material to function as a structural component of the pavement - Structural Number, SN in inches - Indicative of the total thickness required - Drainage Requirements, m - Expected drainage condition will have a direct impact on the performance of the pavement - To factor this effect into the pavement design, use table below. Environmental Effects - Temperature and rainfall are the two main environmental factors used in evaluating pavement performance in the AASHTO method - Effect of temperature include: - Stresses induced by thermal action - Changes in creep properties - Effects of rainfall is due mainly to penetration of the surface water to the underlying material - If penetration occur, the properties of the underlying material will alter Design Reliability, R - Probability that a pavement section using the process will perform satisfactorily over the traffic and environmental conditions for the design period or design life (AASHTO) - Reliability is the probability that the design road will outlast its deign lie before major rehab is required Serviceability - Ability to serve high-speed, high-volume automobile and truck traffic - Selection of the terminal serviceability index, Pt, is based on the lowest index that will be tolerated before resurfacing or reconstruction becomes necessary - For major highways (80kph or over) -- index of 2.5 - For lesser volume highways -- index of 2.0 - Highest value is 5 and lowest is 0 - At opening year, the Po of highways is suggested to have a value of 4.2 Mcleod's Method for Base Course Thickness - developed by Norman Mcleod in 1969 - empirical method used for design of flexible pavements - uses results from plate load bearing test Tri-axial Test Method for Thickness of Base Course - Developed by L. A Palmer and E. S Barber in 1910 - A lateral pressure of 1.4kg/cm\^2 is applied to the soil when conducting triaxial test US Corps of Engineers Method for Pavement Thickness - Developed by United States Army Corps of Engineers - Pavement design appropriate for low-volume road applications because they were developed from traffic tests using relatively low traffic volumes and thin pavement sections on low-strength subgrades - Equation developed is only valid for CBR values less than or equal to 12% California Resistance Value Method - F. M Hveem and R. M Carmany - Gives the R-value and it is an indication of the stiffness of the material - R-value is measured using a Stabilometer -- used to measure the resistance of soil, aggregate base, or subbase by applying exudation pressure Road Widening at Curve Sections of a Two-lane Road - Two-lane Road -- one lane per direction of travel - Road Widening at Curves - Due to the fact that on curves the rear wheels of motor vehicles do not ordinarily travel in the same radius as the front wheels, it is desirable to widen the road along sharp curves - The minimum widening recommended on curves is 0.60m