How to grade bitumen

Bitumen used for paving grades are categorized according to viscosity (degree of fluidity) gradings. The higher the grade, the stiffer the bitumen gets.

Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms (and for fluids only), viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity. Put simply, the less viscous the fluid is, the greater its ease of movement (fluidity).


The test procedures used for paving grades of bitumen are as follows:

• Penetration Test;  used to determine the consistency of bitumen by measuring the distance that a standard needle will penetrate vertically into a sample
• Viscosity Test; is a more scientific measure of consistency than Penetration. Various tests are used to measure the resistance to flow of bitumen and to thereby define its consistency.
• Flash Point: used to measure the temperature to which a sample of bitumen may be safely heated by establishing the temperature at which a small flame causes the vapour above the sample to ignite or flash.
• Ductility: gives an indication of the extent to which a sample of the material can be stretched before breaking. A standard briquette of bitumen, placed in a mould in a water bath heated to 15°C, is pulled apart, usually at a speed of 5 cm per minute. The length of the thread of bitumen at the moment when it breaks, expressed in centimetres, is the ductility of the sample.
• Solubility and the Presence of Insolubles: indicates the degree of contamination of the bitumen by other matter and therefore the presence of pure bitumen. The Australian test measures the percentage of matter that is insoluble in toluene.
• Effect of Heat and Air: is determined to simulate the conditions obtained when the bitumen is used to manufacture hot-mix. In the Rolling Thin Film Oven Test a moving film of bitumen is heated in an oven at 163°C for 60 minutes. The viscosity is measured before and after treatment.
• Softening Point: a measurement of the temperature at which a sample of bitumen held in a ring in a water bath allows a steel ball of specified weight to fall to a point at a specified distance below it.

The chart below shows typical applications for paving grade of BP bitumens:

Applications for Bp class
Bitumen class	Sprayed Sealing	Asphalt
		Light	Medium	Heavy	Extra Heavy
Class 170	ok	ok
Class 320		ok	ok	ok
Class 600				ok	ok

AASHTO M 226 and ASTM D 3381 Viscosity Grades

Standard	Grading based on Original Asphalt (AC)						Grading based on Aged Residue (AR)
AASHTO M 226	AC-2.5	AC-5	AC-10	AC-20	AC-30	AC-40	AR-10	AR-20	AR-40	AR-80	AR-160
ASTM D 3381	AC-2.5	AC-5	AC-10	AC-20	AC-30	AC-40	AR-1000	AR-2000	AR-4000	AR-8000	AR-16000

Following table is the specification for performance grade bitumen

PROPERTY	GRADES				STANDARD
	PG 76-10		PG 82-10
	Min	Max	Min	Max
Flash Point, COC, °C	230	-	230	-	T48
Viscosity @ 135°C, Pa·s	135°C	3.0	135°C	-	ASTM D4402
Dynamic Shear @ 70°C, G*/sin d, kPa	1.00	-	-	-	-
After RTFO	-	-	-	-	-
Dynamic Shear @ 70°C, G*/sin d, kPa	2.20	-	-	-	-
Mass Loss, %	-	1%	-	1%	-
After PAV @ 100°C	-	-	-	-	-
Dynamic Shear @ 28°C, G*·sin d, kPa	-	5000	-	-	-
Creep Stiffness @ -12°C, S, MPa	-	300	-	-	-
Creep Stiffness @ -12°C, M-value	0.300	-	-	-	-

Problems Caused due to Lateral Deflection of Tall Buildings - wind load

Wind loading on a high-rise building can have a dominant influence on its structural arrangements and design. Lateral deflection due to wind load actions on tall buildings has become a major concern for the designers of today’s high-rise buildings and it is one of the key important factor that must be considered in the structural design of a tall building.

In contrast to vertical loads, lateral load effects, such as the forces exerted by wind on buildings are quite variable and increase rapidly with increase in height. Further, such lateral forces tend both to snap(shear)  and push over (bending) the tall buildings. Excessive or uncontrolled lateral deflection may cause extensive structural, non structural, constructional damages and discomfort to building occupants leading both extensive economic and social damages. It may cause cracking of partitions and external cladding, misalignment of mechanical systems and doors, and possible permanent deformations.

Lateral defections must be limited to prevent second-order P-Delata effects due to gravity loading being of a such a magnitude to precipitate collapse. Further, it must be limited or maintained at a sufficiently low level to allow the proper functioning of non structural components , to avoid distress in the structure, to prevent excessive cracking and consequent loss of stiffness, to avoid any redistribution of load to non-load-bearing components and to prevent dynamic motions becoming large enough to cause discomfort to occupants, to prevent delicate work being undertaken, or effect sensitive equipment.

In recent years the subject of tall building motion and its reduction has received considerable attention. With present trends towards taller, lighter, and more flexible structures, the importance of study and research on this topic is ever-increasing. Of particular interest are methods to reduce the lateral deflection due to wind load actions.

 Reasons for Tall Buildings

Ancient tall buildings and structures are primarily solid structures serving as monuments rather than space enclosures. By contrast, contemporary tall buildings and structures are human habitats, conceived in response to rapid urbanization and population growth.

There are various reasons for construction of tall buildings. The growth in modern tall building construction has been largely for commercial and residential purpose.   However, ego and competition still play a part in determining a building’s height. In addition, various other social and economic factors, such as increase in land value in urban areas and high density of population have lead to a great increase in the number of tall buildings all over the world. Further, the business and tourist community , with its increasing mobility, has fuelled a need for more frequently high-rise , city centre hotel accommodation. The high cost of land, the desire to avoid continuous urban sprawl, and the need to preserve important agricultural production have all contributed to the increasing number of tall buildings.

 Early Tall Building Versus Modern Tall Buildings

As mentioned in the previous section, ancient tall buildings are primarily solid structures rather than space enclosures. By contrast modern tall buildings are human habitats. The difference in the usage of buildings, from solid monumental structures to space enclosures, in itself has not changed the basic stability and strength requirements; the structural issues are still the same, the materials and methods are different.

In the design of early monuments, consideration of spatial interaction between structural sub systems was relatively unimportant, because their massiveness provided for strength and stability. Comparatively, with evolution of radically new structural systems the size and density of structural elements of modern tall building are strikingly less and continue to be diminish motivated by real-estate market, aesthetic aspects and innovative and challenging structural solutions powered by the immense analytical backup provided by computers. Early tall buildings are either prismatic, square or round. The modern tall buildings are better designed and takes more varied and irregular external architectural shapes. 

In recent decades there have been great advances in the design and construction of tall buildings throughout the world, and in the associated development of analytical techniques. The progress in reinforced concrete was slow and intermittent. The inherent advantages of the concrete which could be readily formed to simultaneously satisfy both aesthetic and load –carrying requirements, were not fully appreciated until the end of World War I. Since then significant developments in reinforced concrete occurred. Rather than bringing significant increases in height, these modern developments comprised new structural systems, improved material qualities and services and better design and construction techniques.

The constant search for more efficient solutions led to the innovative designs and new structural form of recent years. The taller and more slender a building, the more important the structural factors become, and more necessary it is to choose an appropriate structural form or system.

This chapter provides a comprehensive literature review on the research subject. It describes various important aspects that is related to the research subject and must be considered in executing the research. Further, apart from a general outline of the structural systems for concrete buildings, special attention is devoted to the structural systems those are studied under this research. These structural systems are described in detail.

Structural Concept of tall building

With regard to lateral loading, a high-rise building is essentially a vertical cantilever beam from the earth. This is the key idea in conceptualizing the structural system for a narrow tall building. This conceptualized cantilever may comprise one or more individually acting vertical cantilevers, such as shear walls or cores, each bending about its own axis and acting in unison only through the horizontal in-plan rigidity of the floor slab. Alternatively the cantilever may comprise a number of columns or walls that are mobilized to act compositely , to some degree, as the chords of a single  massive cantilever, by vertically shear resistant connections such as bracing or beams.

The laterally directed forces due to wind load actions tends to snap the building and push the building over. Hence, the building must have a system to resist both the shear and bending. In resisting the shear forces, the building must not break by shearing off and must not strain beyond the limit of elastic recovery. Also the system resisting the bending must ensure that the building is not overturned and is not broken by premature failure of columns. In addition its bending deflections should not exceed the limit of elastic recovery.

On the other hand when the structure resists to bending and shear, this may set the building in motion, creating an other engineering problem; motion perception or vibrations. As mentioned earlier, excessive or uncontrolled dynamic motions will cause discomfort to the building occupants and extensive socioeconomic damages.  

Different types of wind load on buildings

Fire protection for Buildings

Fire protection is one basic need in a building today, it can be given the first priority in a hospital due to what extinct the damage could cause, simply saying it’s a killing machine.
Fire eats every thing in its path.

Fire Detectors and alarms

Detection of a potentially dangerous rise in air temperature or pressure or the presence of smoke is required at the earliest possible moment to start an alarm . Evacuation of the hospital complex building and manual or automatic contact with the fire brigade monitoring switchboard should take place before people are at risk. Means of detection can be combined with security surveillance.

Hospital needs to have the following diction methods in order to prevent a devastating fire.

Hazard Detectors

Hazard Detectors give an early warning of the risk of a fire or explosion.

Temperature Rise: A local rise in temperature leads to the melting of a fusible link in a wire holding open a valve on a fuel pipe to a burner, thermal expansion of a fluid-filled bellows or capillary tube or movement of a bimetallic strip to make an alarm circuit.

Flammable vapour detector: Gas, oil petrol, or chemical vapour diffusion through a membranes is detected.

Diffusion: Butane and propane vapour diffusion through a membrane is detected.

Explosion: Rise of local atmospheric pressure above a set value, or at a fast rate, is detected.

Ionization smoke detector 

ionization smoke detectors contain a radioactive source of around 1 microcurie, typically americium- 241, which bombards room air within the detector with alpha particles ( ionization).  Electrical current consumption is 50 micro ampere. The presence of smoke reduces the flow of alpha ions; the electric current decreases and at a pre-set value an alarm is activated.


visible smoke detector

 A source of light is directed at a receiving photocell. Smoke obscures or scatters the light and an alarm is triggered.

Laser beam 

A laser beam is refracted by heat or smoke away from its target photocell and an alarm is initiated. A continuous or pulsed infrared beam can be transmitted up to 100 m and can be computer – controlled to scan the protected area. It can also serve as an intruder alarm.


Closed-circuit television 

Manned security monitoring also as fire and smoke detection. Infrared imaging cameras reveal overheating of buried pipes and cables and can detect heat sources unseen by visual techniques.



Fire alarms are a statutory requirement. Audible bells, sirens, klaxons, hooters and buzzers are arranged so that they produce a distinctive warning. A visual alarm should also be provided throughout a building. Breakable glass call points are located 1.4 m above floor level within 30 m of any part of the premises.

Fire protection concept 

Although fires in buildings can be avoided, they nevertheless occur. Some of the reason for this is human error, arson, faulty electrical equipment, poor maintenance of heating equipment, and natural causes, such as lightning. Consequently building should be desingned to minimize the probability of a fire and to protect life and to limit property damage if a fire should occour, the minimum steps that are to be followed are as follows:

- limit potential fore loads, with respect to both combustibility and ability to generate smock and toxic gases.
- Provide means for prompt detection of fires, with warning to occupants who may be affected and notification of the presence of fire to fire fighter.
- Communication of instruction to occupants as to procedures to adopt for safety, such as to staying in place, proceeding to a designated refuge area, or evacuating the building.
- Provide mean for early extiguishment of any fire that many occur, primarily by automatic sprinklers but also by trained fire fighter.
- Make available also for fire fighting an adequate water supply, appropriate chemicals, adequate- size piping, conveniently located valves on the piping, hose, pumps, and other equipment necessary.
- Prevent spread of fire from building to building, either through adequate separation or by enclosure of the building with incombustible materials.
- Partition the interior of the building with fire barriers, or divisions, to continue a fire to a limited space.
- Enclose with protective materials structural components that may be damaged by fire (fore proofing)
- Provide refuge areas for occupants and safe evacuation routes to outdoors.
- Provide means for removal of heat and smoke from the building as rapidly as possible without exposing to these hazards, with the air-conditioning system, if one is present, assisting the removal by venting the building and by pressurizing smoke proof towers, elevator shafts, and other exits.
- For large buildings like this Hospital, install standby equipment for operation in emergencies of electrical system and elevators.

 Oshkosh; Fire truck

Common Engineering Terms used

If your an engineer, you must be able to know all the common engineering terms. following are few common ones.


Stress terms
Stress is the internal distribution of forces within a body that balances and reacts to the loads applied to it. It is a complicated tensor quantity that can be broken down into simpler elements for engineering purposes;

• Compressive stress (or compression) is the stress state when the material tends to compact (volume decrease). A simple case of compression is the uniaxial compression induced by the action of opposite, pushing forces. Most materials can carry compressive stress, even the granules such as sands. 
• Tensile stress is a loading that tends to produce stretching on a material by the application of axially directed pulling forces. Materials can withstand some tensile loading, but if enough force is applied, they will eventually break into two parts. Steel is an example of a material with high tensile strength. 
• Shear stress is caused when a force is applied to produce a sliding failure of a material along a plane that is parallel to the direction of the applied force e.g. when cutting paper with scissors. 

Strength terms

• Compressive strength is a limit state of compressive stress that leads to compressive failure in the manner of ductile failure (infinite theoretically yield) or in the manner of brittle failure (rupture as the result of crack propagation, or sliding among a weak plane - see shear strength).
• Tensile strength is a limit state of tensile stress that leads to tensile failure in the manner of ductile failure (yield as the first stage of failure, some hardening in the second stage and break after a possible "neck" formation) or in the manner of brittle failure (sudden breaking in two or more pieces with a low stress state).

Strain - Deformation terms

• Deformation of the material is the change in geometry when stress is applied (in the form of force loading, gravitational field, acceleration, thermal expansion, etc.). Deformation is expressed by the displacement field of the material.
• Strain or reduced deformation is a mathematical term to express the trend of the deformation change among the material field. For uniaxial loadings - displacements of a specimen (for example a bar element) it is expressed as the quotient of the displacement and the length of the specimen. For 3D displacement fields it is expressed as derivates of displacement functions in terms of a second order tensor (with 6 independent elements).
• Deflection is a term to describe the magnitude to which a construction or structural element bends under a load.

Stress - strain relations

• Elasticity is the ability of a material to return to its previous shape after stress is released. In some materials, the relation between applied stress and the resulting strain is directly proportional (up to a certain limit), and a graph representing those two quantities is a straight line. Hooke's law describes such relationships and is valuable in the study of springs. (see Solid mechanics). In other materials, the relation is not linear. In steel, the most common material for making springs, most of the elastic range is linear, though the relation becomes non-linear at the extreme end, just before the material begins to deform plastically.
• Plasticity is the property of materials to deform permanently after force is applied and released. Most solid materials behave elastically when relatively low amounts of force are applied, and plastically under higher amounts of force.

Design terms

• Ultimate strength is an attribute directly related to a material, rather than just specific specimen of the material, and as such is quoted force per unit of cross section area (N / m2). For example, Ultimate Tensile Strength (UTS) of mild steel is 470MegaN / m2. It is useful to remember that 1Pa = 1N / m2.
• Factor of safety is a design constraint that an engineered component or structure must achieve. FS = UTS / R, where FS: the Factor of Safety, R: The acting force (or stress) and UTS: the Ultimate force (or stress). For example to achieve a factor of safety of 4, the allowable stress in a mild steel component can be worked out as R = UTS / FS = 117.5MPa.

laboratory test on expansive soils- Swell Test

The most important laboratory test on expansive soils is the swell test. The standard one-dimensional consolidation test apparatus can be used. A standard consolidometer can accommodate a remolded or undisturbed sample from 2 to 4.25 in. diameter and from 0.75 to 1.25 in. thickness. Porous stones are provided at each end of the specimen for drainage or saturation. The assembly is placed on the platform scale table and the load is applied by a yoke actuated by a screw jack. The load imposed on the sample is measured by the scale beam, and a dial gage is provided to measure the vertical movement.

The advantage of such arrangement is that it is possible to hold the upper loading bar at a constant volume and allow the measurement of the maximum uplift pressure of the soil without a volume change. This requires a constant load adjustment by an operator. An advanced scheme is an automatic load increment device that measures swelling pressure without allowing volume change to take place.

The consolidometer can also be used to measure the amount of expansion under various loading conditions. Since swelling pressure can be evaluated by loading the swelled sample to its original volume, it is simple to convert the platform-scale consolidometer into a single-lever consolidation apparatus. Such a modified con- solidometer can be made locally at low cost. The average soil laboratory should have a train of such apparatuses to speed up the testing procedure.

It is important for the geotechnical engineer not to confuse “swell” with “rebound.” All clays will rebound upon load removal, but not all clays possess swelling potential. The use of graduated cylinders to measure the swelling potential of clay upon saturation is not a standard test. Such a test has been abandoned and should not be repeated.