Cross section elements. Roads are defined as routes or paths that begin at one destination and lead to another.

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1 Cross section elements What is Road? Roads are defined as routes or paths that begin at one destination and lead to another. Roadway: The portion of a highway, including shoulders, for vehicular use. Traveled way (Carriage way): The portion of the roadway, for the movement of vehicles, exclusive of shoulders. Highway Cross Section Elements: divided in two types 1- Principle elements Travel Lanes Shoulders Medians 2-Secondary elements Roadside Barriers Curbs Right of way Side slopes Cross (Side) Slope or Camber Sidewalks Pavement types Commonly, there are three types of pavements, these are flexible pavement (asphalt concrete), rigid pavement (Portland cement concrete) and composite pavement (rigid over flexible). The selection of pavement type is determined

2 based on the traffic volume, traffic composition (i.e. proportion of trucks and buses), soil characteristics, weather, availability of material, and the initial and maintenance costs. Typical cross section in flexible pavement broken line: Line demarcating the two lanes of the roadway and showing that passing is permitted. solid line: Line demarcating the edge of the roadway or, when in the center of the roadway, indicating that passing is prohibited. Ditch: Ditch parallel to the roadway; surface water drains into it.

3 Subgrade: Layer supporting the base course and the subbase and providing drainage. subbase: Base of a roadway, made up of coarse compacted gravel, making the roadway solid and stable. base course: Top foundation layer, made up of fine compacted material; the driving surface lies on it. surface course: Roadway s driving surface; it is smooth, impermeable and provides a good grip for vehicles. Travel Lanes Lane width greatly influences the safety and comfort of driving. Lane widths of m are generally used. The 3.6m value is the preferred width since it provides desirable clearance between large commercial vehicles. Narrow lanes force drivers to operate their vehicles closer to each other than they would prefer. Shoulders A shoulder is It is the side of the road. Sometimes it is paved. Sometimes it is gravel. Sometimes it is dirt or grass. Main advantages for the use of a shoulder Provide a space for vehicles to make emergency stop Sight distance is increased and therefore improve safety Rain water can be discharged farther from the traveled way, and seepage adjacent to the traveled way can be minimized Structural support for pavement structure Space is provided for pedestrian and bicycle use. Shoulder width Shoulder width varies from 0.6m to 3.6m.

4 A vehicle stopped on the shoulder should clear the edge of travel way by at least 0.3m and preferably by 0.6m. Therefore, the normal shoulder width of 3.0m is recommended. For low-volume highways, the minimum shoulder width is 0.6m and a 1.8 to 2.4m shoulder width is preferred. For high-volume highways carrying large numbers of trucks, the minimum shoulder width is 3m and a 3.6m shoulder width is preferred. Shoulder slope Concrete and bituminous shoulders (paved shoulders) should be sloped from 2 to 6% Crushed rock shoulders (unpaved shoulders) should be sloped from 4 to 6% Median A median is the section of a divided highway that separates the lanes in opposing directions. The width of a median is the distance between the edges of the inside lanes, The functions of a median include: Separating opposing traffic Providing stopping areas during emergencies Providing refuge for walkers Reducing the effect of headlight glare Median Barriers and Roadside barriers A median barrier is defined as a longitudinal system used to prevent vehicles from crossing the portion of a divided highway separating the traveled ways for traffic in opposite directions. Roadside barriers, on the other hand, protect vehicles from obstacles or slopes on the roadside. They also may be used to use to protect walkers.

5 SIDE SLOPES in Roadway Cross Section The graded area immediately adjacent to the graded roadway shoulder is called side slope Types of Side slopes: BACKSLOPE: - Slopes back to natural topography are known as back slope. FARESLOPE: - Slopes down to ditch are called fare slope. Slope depend upon soil characteristics and the geographic location of the highway.

6 Cross (Side) Slope or Camber What is the Road Camber? Raise the middle portion of all highways with respect to the edges. This cross slope in transverse direction is known by Camber. Why must we provide? Camber (Cross slope) helps in rain water drainage from road surface. Remember Water deforms the highways.

7 A value of 2% is usually used for highways with good pavement quality. Typical cross slope of 1.5 to 3% is recommended. Cross slopes greater than 2% should be avoided (for safety). Cross slope for divided highway -Each pavement slopes one way: a -All lanes are crowned toward outer edge b -All lanes are crowned toward inner edge -Each pavement slopes two way Its types of Camber Sloped Camber Parabolic Camber

8 Composite Camber Curbs (Kerb) A line of stone or concrete forming an edge between a pavement and a roadway. So that the pavement is some 15 cm an above the level of the road. That are used mainly on urban highways to: - planning pavement edges and pedestrian walkways control drainage Types of curbs Curbs can be generally classified as either vertical and sloping. Vertical curbs, (which may be vertical or nearly vertical), range in height from 6 to 8_ with steep sides, and are designed to prevent vehicles from leaving the highway. Sloping curbs are designed so that vehicles can cross them if necessary.

9 Right of way Area of the road gained for road (carriages way + other necessities + future extension), along its alignment.

10 PAVEMENTS AND BITUMINOUS MATERIAL (as binder) Binder: A material used to hold solid particles together, like a bitumen and tar. Objectives this lecture: To introduce types of pavements To explain various bituminous materials To explain properties of asphalts Pavement is defined as a road or highway with hard, smooth, and leveled surface made using a suitable material such as Portland cement concrete or asphalt concrete Pavements are classified as flexible or rigid depending on how they distribute surface loads. Flexible pavements are those which are surfaced (paved) with bituminous materials such as asphalt concrete Rigid pavements are those which are surfaced (paved) with Portland cement concrete. Portland cement concrete possess a substantially higher stiffness (EI) than asphalt concrete due to higher modulus of elasticity of Portland cement concrete as compared to asphalt concrete BITUMINOUS MATERIALS Introduction Bitumen is hydrocarbons material, has strong adhesive properties with colors ranging from dark brown to black, and soluble in carbon disulfide. The consistency of the bitumen is solid, semi-solid, or viscous liquid. The solid form is usually hard and brittle at normal temperatures but will flow when subjected to long, continuous loading. The liquid form is obtained from the semisolid or solid forms by heating or dissolving in solvents. The bituminous materials used in highway construction are either asphalts or tars.

11 Asphalts Asphalts are the most common and most widely used bituminous materials The term asphalt refers to a black cementitious material which varies widely in consistency from solid to semisolid at normal temperatures Asphalts are found as natural deposits or are produced from petroleum crude. Tars do not occur in nature and are obtained as condensates in the processing of coal, petroleum, oil-shale, wood or other organic materials. Sources of asphalt 1. Natural asphalt a. Native asphalt: The largest amounts of native asphalt have existed in Iraq several thousand years ago. b. Rock asphalt: it is sandstone or limestone rocks filled with asphalt. c. Petroleum asphalt: Obtained from refining (distillation) of petroleum. The refining process mainly removes the volatile materials in the crude oil at higher temperatures until the petroleum asphalt is obtained as residue. Petroleum asphalt These asphalts are used as the most common bituminous paving materials.

12 TYPES OF PETROLEUM ASPHALTS Following types of petroleum asphalts are used in pavement construction: 1- Asphalt cement 2- cutback asphalt 3- Emulsified asphalt 1- Asphalt cement (also called paving asphalt) are the primary asphalt products produced by the distillation of crude oil. At ambient temperatures asphalt cement is a black, semisolid and a highly viscous material It is strong and durable cement with excellent adhesive and waterproofing characteristics. It is also highly resistant to the action of most acids, alkalis and salts The largest use of asphalt cement is in the production of asphalt concrete, which is primarily used in the construction of flexible pavements throughout the world The asphalt cement can readily be liquefied by applying heat for mixing with mineral aggregates to produce asphalt concrete. 2-Cutback asphalt Cutback asphalt is liquid asphalt which is a blend of asphalt and petroleum solvents (such as gasoline and kerosene). Cutback asphalt uses mainly in cold mixes, road mixes (mixed-in-place), and as surface treatments. Cutback asphalt placed with little or no application of heat. After cutback asphalt is applied and exposed to the atmosphere, the solvent will gradually evaporate, leaving the asphalt cement to perform its function as a binder. Cutback asphalt is divided into three types, based on type of volatility of the solvent used in curing, these are: a. Slow-Curing asphalt (SC) Can be obtained directly through the distillation of crude petroleum or as slowcuring cutback asphalts by cutting back asphalt cement with a heavy distillate, such as diesel oil. SC has lower viscosity than asphalt cement and is very slow to harden. b. Medium-Curing cutback asphalt (MC) Medium-curing (MC) asphalts are produced by fluxing, or cutting back, the residual asphalt (usually 120 to 150 penetration) with light fuel oil or kerosene.

13 The term medium refers to the medium volatility of the kerosene-type diluter used. Medium curing cutback asphalts (MC) harden faster than slow-curing liquid asphalts. These medium-curing asphalts can be used for the construction of pavement bases, surfaces, and surface treatments and also as a prime coat between base course and binder layers in flexible pavements. 3- Emulsified asphalt (also simply called emulsion) is a mixture of asphalt cement, water, and emulsifying agent Because the asphalt cement will not dissolve in water, asphalt cement and water exist in separate phases to mix the asphalt cement with water, an emulsifying agent (usually a type of soap) is added Process of manufacture of emulsified asphalt consists passing the hot asphalt cement and water containing the emulsifying agent under pressure through a colloid mill, as the colloid mill breaks up the asphalt cement and disperses it, in the form of very fine droplets, in the water carrier The emulsified asphalt when used, the emulsion sets as the water evaporates the emulsion usually contains 55-75% asphalt cement and up to 3% emulsifying agent, with balance being water. Emulsified asphalts are increasingly being used instead of cutback asphalts for the following reasons: Emulsions are relatively pollution free When cutback asphalts cure, the diluents which are high energy, high price products are wasted into atmosphere Emulsions are safe to use Lower application temperature: Emulsions can be applied at relatively without use any heat this lead to save the fuel costs. Emulsions can also be applied effectively to a wet pavement, whereas dry conditions are required for cutback asphalts PROPERTIES OF ASPHALT MATERIALS

14 The properties of asphalt materials used for pavement construction can be classified into four main categories: Consistency Aging and temperature sustainability Rate of curing Resistance to water action 1- Consistency The consistency properties of an asphalt material usually are varying with temperature and also the consistency of several types of asphalt are not similar even at a same temperature. 2- Aging and Temperature Sustainability When asphaltic materials are exposed to environmental elements, natural deterioration gradually takes place, and the materials eventually lose their plasticity and become brittle. This change is caused primarily by chemical and physical reactions that take place in the material. This natural deterioration of the asphalt material is known as weathering. The ability of an asphalt material to resist weathering is described as the durability of the material. Factors affect weathering 1- Oxidation: Oxidation is the chemical reaction that takes place when the asphalt material is attacked by oxygen in the air. This chemical reaction causes gradual hardening (eventually permanent hardening) and considerable loss of the plastic characteristics of the material. 2- Volatilization: Volatilization is the evaporation of the lighter hydrocarbons from the asphalt material. The loss of these lighter hydrocarbons also causes the loss of the plastic characteristics of the asphalt material. 3- Temperature:

15 It has been shown that temperature has a significant effect on the rate of oxidation and volatilization. The higher the temperature, the higher the rates of oxidation and volatilization. 4- Surface area: The exposed surface of the material influences the rate of oxidation and volatilization. There is a direct relationship between surface area and rate of oxygen absorption and loss due to evaporation in grams/cm3/minute. This fact is taken into consideration when asphalt concrete mixes are designed for pavement construction in that the air voids are kept to the practicable minimum required for stability to reduce the area exposed to oxidation. 3- Rate of curing Curing is defined as the process through which an asphalt material increases its consistency as it loses solvent by evaporation. Factors affect curing Volatility of the solvent Quantity of solvent in the cutback Consistency of the base material Temperature Ratio of surface area to volume Wind velocity across exposed surface 4- Resistance to water action When asphalt materials are used in pavement construction, it is important that the asphalt continues to adhere to the aggregates even with the presence of water. If this bond between the asphalt and the aggregates is lost, the asphalt will strip from the aggregates, resulting in the deterioration of the pavement. The asphalt therefore must sustain its ability to adhere to the aggregates even in the presence of water.

16 AGGREGATES A combination of different sizes and shapes normally of stones. Maximum size is 75 mm. USES OF AGGREGATES As a main material for foundations and pavements. As a component in Portland cement concrete and asphalt concrete. Importance of Aggregate in AC Supports the main stresses occur within the pavement (load carrying) Resist the wear due to abrasion by traffic Selection of aggregates Aggregates shall be hard, durable and clean and free from organic matter and shall not contain appreciable amount of clay. Aggregates shall not contain harmful impurities such as iron pyrites, alkalis, salts or other materials which will affect hardening and attack reinforcement. Classification of aggregates

17 1- Based on size: classified into 2 categories: fine aggregates - those aggregates which pass through 4.75 mm sieve or aggregates with size less than 5 mm. Coarse aggregates those aggregates Passing through 75 mm sieve and retained on 4.75 mm sieve OR those aggregates with size greater than 5 mm. 2- Based on source: classified into 2 categories: Natural aggregate/uncrushed aggregate- Those from the riverbeds, river sand. Normally rounded in shape and have smooth surface texture. Manufactured aggregate / crushed aggregate those obtained by mechanically crushing rocks. Normally angular in shape and have rough surface texture Recycled materials: such as glass and plastic materials 3- Based on Density: Based on specific gravity or density measured in bulk, aggregate is divided into 3 types: Lightweight aggregate Normal-weight aggregate Heavyweight aggregate Normal-weight aggregate Crushed stone, gravel and ordinary sand are examples of normal weight aggregate. They are commonly used in manufacture of normal weight concrete, asphalt concrete and roadway sub-base. Bulk density of normal weight aggregate is around 1520 to 1680kg/m3. Lightweight aggregate

18 Lightweight fine aggregate is any aggregate with bulk density less than 1120kg/m3 and lightweight coarse aggregate is any aggregate with bulk density less than 880kg/m3. They are commonly used as components in the manufacture of lightweight concrete, for making lightweight masonry blocks (to improved their thermal and insulating properties), and lightweight floor and roof slabs. 2 types of lightweight aggregate: Natural lightweight aggregates (rice husk, etc). Manufactured (also called synthetic) lightweight aggregates. Heavyweight aggregate Those aggregate with high density and is used primarily in the manufacture of heavyweight concrete, employed for protection against nuclear radiation and as bomb shelter. The unit weight of heavyweight concrete varies from 2400kg/m3. Physical properties of aggregates Strength Texture Durability Porosity and Permeability Water absorption 1- Strength of aggregates It represents the ability of road aggregate to resist the fracture under an applied load, resist abrasion due to moving traffic and resist of aggregate crushing. 2- Texture It is the measure of degree of roughness or smoothness of the aggregate. Surface texture plays a big role in developing the bond between an aggregate particle and a binder. A rough surface texture gives the cementing material something to grip, producing stronger bond, and thus creating stronger hot mix asphalt. 3- Durability of aggregates

19 Durability is ability of the aggregate to resist external or internal damaging attack. 4- Porosity and Permeability Aggregate normally have pores of various sizes. Aggregates will absorb water when it is dry but normally release water in the concrete mix when it is wet. The amount of water and its rate of permeation depends on the size and volume of aggregate Since the aggregate comprises 75% of the concrete volume, it is essential to note that porosity of an aggregate contribute to the overall porosity of concrete. Permeability: refers to the particle's ability to allow liquids to pass through it. 5- Water absorption Absorption relates to the particle's ability to take in a liquid Aggregate moisture status 1. Oven-dry (OD). All moisture is removed by heating the aggregate in an oven at 105 C. All pores are empty and the aggregate is fully absorbent. 2. Airdry (AD). All moisture is removed from the surface, but pores are partially filled with water. The aggregate is somewhat absorbent. 3. Saturated surface dry (SSD). All pores are filled with water, but the surface is dry. The aggregate is neither absorbent nor does it contribute water to the concrete mixture. 4. Wet. All pores are filled with water and there is excess moisture on the surface. The aggregate contributes water to the concrete mixture. Density and specific gravity Density is the weight per unit of volume of a substance. Specific gravity is the ratio of the density of the substance to the density of water.

20 The density and the specific gravity of an aggregate particle is dependent upon the density and specific gravity of the minerals making up the particle and upon the porosity of the particle. Aggregate Specific Gravity Types Several different types of specific gravity are commonly used depending upon how the volume of water permeable voids (or pores) within the aggregate. 1- Bulk Specific Gravity (Bulk Dry Specific Gravity), G sb. The volume measurement includes the overall volume of the aggregate particle as well as the volume of the water permeable voids. bulk specific gravity will be less than apparent specific gravity 2- Bulk Saturated Surface Dry (SSD) Specific Gravity. Volume measurement includes the overall volume of the aggregate particle as well as the volume of the water permeable voids. The mass measurement includes the aggregate particle as well as the water within the water permeable voids. It is formally defined as the ratio of the mass of a unit volume of aggregate, including the weight of water within the voids filled to the extent achieved by submerging in water for approximately 15 hours, to the mass of an equal volume of gasfree distilled water at the stated temperature. 3- Apparent Specific Gravity, G sa. The volume measurement only includes the volume of the aggregate particle; it does not include the volume of any water permeable voids. The mass measurement only includes the aggregate particle. Apparent specific gravity is intended to only measure the specific gravity of the solid volume therefore; it will be the highest of the aggregate specific gravities. Calculations: A = mass of oven-dry sample in air (g) B = mass of SSD sample in air (g) C = mass of SSD sample in water (g)

21 Specific gravity of coarse aggregate test s procedure: 1- Obtain a sample of coarse aggregate material retained on the No. 4 (4.75 mm) sieve. 2- Wash the aggregate retained on the No. 4 (4.75 mm) sieve. 3- Immerse the aggregate in water at room temperature for a period of 15 to 19 hours. 4- Dry the sample to a saturated surface dry (SSD) condition. Rolling up the aggregate into the towel, shaking and rolling the aggregate from side to side. Once there are no visible signs of water film on the aggregate particle surfaces, determine the sample mass (B). 5- Place the entire sample in a basket and weigh it underwater (C). Shake the container to release any entrapped air before weighing. 6- Remove the aggregate from the water and dry it until it maintains a constant mass. This indicates that all the water has left the sample. Drying should occur in an oven regulated at 230 F (110 C). 7- Cool the aggregate in air at room temperature for 1 to 3 hours then determine the mass. Examples Example (1) During a specific gravity test for coarse aggregate, the following weights were given: Mass of oven dry= 2000gm, mass of SSD= 2020 gm and mass of sample in water=1300gm. Find Gsb, Gsa and percent of absorption. Answer: Gsb=2000/( )=2.77 Gsa=2000/( )=2.85 % of absorption=(( )/2000)*100%=1%

22 Example(2): The dry mass of a sample of aggregate is 1850 gm. The mass in a saturated surface dry condition is 1900 gm. The net (dry) volume of the aggregate is 700 cm3. Find the apparent and bulk specific gravity and also find the percentage of water absorption. Answer: Apparent density=dry mass/dry volume = 1850/700=2.643gm/cm3 Apparent specific gravity=apparent gravity of aggregate/gravity of water = 2.643/1=2.643 Mass of absorbed water= =50gm Mass of absorbed water=50/1=50 cm3 SSD volume (bulk volume) = dry volume +absorbed volume=700+50=750cm3 Bulk density=dry weight/bulk volume=1850/750=2.466gm/cm3 Bulk specific gravity=2.466/1=2.466 % of absorbed water=(50/1850)*100%=2.7%