Expansion and contraction joints in Rigid Pavements.

Hi,

I have studied about the expansion and contraction joints. In the rigid pavements, like the cement concrete pavements, the cement slab is laid on the sub-grade. The concrete changes its volume with the change in the temperature.

If the natural temperature of the concrete is low i.e. concrete is laid down in the season of winter, then the chances are there that concrete will undergo expansion in the summer season.

Expansion joint

Similarly, if the concrete is laid in the summer season then natural temperature of the concrete is already high, so the concrete will contract in the season of the winter.

Whether the concrete is going to expand or shrink, one has to provide the expansion or the contraction joints respectively.

• Spacing of the expansion joints: The spacing of the expansion joint can be determined as below:

            (expansion) e = co-efficient of thermal expansion * Ls * (t2-t1)

we provide width of the joints double then 'e', 50% allowance is provided for the filler material. 

• Spacing of the contraction joints: The contraction of the concrete is opposed by the frictional force between the sub-grade and the concrete.

This frictional force should always be less than the ultimate strength of the concrete which resists the tensile forces developed in it due the contraction force and the frictional force.

Contraction joints on rigid pavements

Frictional force is dependent on the surface area of the concrete(L*B), and the resisting force depends upon the (h*B) of the concrete, so we can get the minimum spacing required if we equate the two forces.

References: 

Thanks for visit!

Highway Development in India

Hi,

India had a network of roads in the ancient times. 

The road development in India can be discussed by taking different phases of the history at one time.

Ancient Times:

The excavation of the Mohn-Jodaro and Harappa civilization shows the traces of the roads in the ancient Indian times, in a period f 35th to 25th B.C. 

The Aryan Period and Road Construction:

There are various scriptures available, which script about the road development in India in the Aryan period. "Arthashastra" written by Kautilya (Chanakya), the prime minister of the Chandra Gupta Mourya, discusses the rules laid down for the depth of the road construction for different purposes in the 4th century.

There were punishments for obstruction of roads.  The emperor Ashoka has improved the quality of the roads in India for the travelers, in his ruling period i.e. fifth century A.D.


Best Books for GATE, SSC, PSU preparations:

Mughal period and Road construction: 

The Mughal and Pathans improved the quality of the roads in India. Sher Shah Suri is still remembered for the construction of the Grand Trunk Road(GT Road) from Bangladesh-India to Kabul in Afghanistan.

19th Century and Road Construction in India:

After the fall of the Mughal Empire in India in 19th century the Britishers participated in the road construction for the military and administrative purposes. 

The work was carried out by the British Military Engineers. Railway was introduced later but the existing roads were metaled and bridges were provided. The governor general of India i.e. Lord Dalhousie in the mid of 19th century introduced the PWD(Public works department), which still runs the various public works in India. 

Later after the introduction of the railways in India the attention was shifted to the railways construction and only the feeder roads and railways got the prime importance afterwards.

Jayakar committee: 
The committee was formed by the both chambers of the Indian Legislature in the year 1927 to examine the roads in the India and ways of their development. The number of vehicles on the Indian roads increased after the first world war, so it was felt necessary to develop a good network of the roads in India.

Indian Road development committee was formed in the year 1927, with M.R.Jayakar as its chairman. The committee submitted its report in the year 1928, and made some important recommendations:

The road development in India should be considered a national interest, because it is out of control of the local bodies. 

1. An extra tax should be put on the petrol consumers to develop a road development fund, called the Central Road Fund.
2. A semi-official body should be formed to pool technical ideas, knowledge from the various parts of the country and to act as an advisory body on various aspects of roads. 
3. A research organisation should be organised to carry out the research  and development work.

As a result of these recommendations a central Road Fund was formed by the year 1929, a semi-official body called Indian Roads Congress was formed in 1934 and the Central Roads Research Institute was started in 1950.

• Central Road Fund (1929):

Central Road Fund was formed in the year 1929, extra money 2.64 paisa per liter of the petrol, was charged from all the ptrol buyer in the country. This fund was kept separate for the use in the road development in India.

 About 20% of the fund was kept to be used for the expenses of the administrative meetings and the research work of the highways of the national importance in the country. The rest of the 80% of the funds were distributed among the provinces at that time, according to their road users, for the development of the roads by the state governments.

• Indian Roads Congress (1934):

A semi-government organisation named, Indian Roads Congress was formed in the year December 1934, and was registered in the year 1937 under the registration act.

 The main function of the IRC was to act as a forum for the regular pooling of the technical knowledge and know how, from the various parts of the country. IRC performed the various plannings, and also it has become the most important agency to provide the standards and the specifications for the road construction in the country.

• Motor vehicle act(1939):

The increased numbers of vehicle on the Indian roads demanded for the rules and regulations. The motor vehicle act was passed in 1939, which laid down the rules for the road users and also for the identity of the vehicles. It is still running in the country in almost same way as it was at that time.

• Central Road Research Institute(1951):

A series of laboratories, known as the Central Science and Industrial Research Center situated at Delhi, contains the research center for the research work of the road construction in India, it is known as the Central Road Research Institute

The main function of the CRRI is to do the research work for the road construction and to provide the consultation services for the state government also.

• First 20-years road plan(Nagpur Road Plan-1943 to 1963):

The first twenty years road network plan was prepared in the meeting of the Chief Engineers from the various parts of the country at the Nagpur, in 1943, which is also known as the Nagpur road plan.

It was the first ever major planning which contributed a lot for the development of the roads in the country. It classified the Indian roads according to their location and purpose, and also it laid down a target for a density of road network of 16 km per 100 sq. Km in the country at the end of the 20 years road network in the year 1963.

After the starting of the 5 years plans in the year 1951, the first two 5 years plans also contributed to the target set by the first 20 years plan of the Nagpur so the density of 16 km per 100 sq. Km was achieved in the year 1961, 2 years earlier to the target year.

A typical hill road (Ghaghas to Shimla- Himachal Pradesh) - in 2013

• Second 20-years road plan(Bombay Road Plan- 1961 to 1981):

As the earlier target was achieved before the planned year, so a need to set a new target arises  and another 20 years road plan was laid down at the meeting of the various authorities from different states at Bombay. The road density target was doubled this time.  

Ref: 

Thanks for visit!

Functions and Testing of Various pavement components/layers(Overview)

Hello There!

Functions of various components of Pavement:

There are four pavement layers:

1.     Sub-grade

2.     Sub-base

3.     Base

4.     Surface course

Functions of each layer are described as below:

·         Sub-Grade :

·         Functions: The load is transferred by the sub-grade effectively to the earth mass. However the locally available earth is used to construct the sub-grade but it becomes necessary that the sub-grade should be of required strength.

·         Testing: This makes it necessary to check the strength characteristics of the sub-grade by using the various methods. Here is the list of the tests that are employed to check the strength of the sub-grade:

a.  California bearing ratio test.

b.  California resistance value test.

c.  Tri-axial shear test.

d.  Plate load test.

California bearing ratio test is a kind of penetration test, in which we get the value of the California bearing ratio of the given soil sample. The test can also be performed in the field to take the in-situ measurements. 

The value is used to design the thickness of the flexible pavements by using some empirical charts.This test is also used to calculate CBR value for the other layers too. 

California resistance value is got by using the Hveem stabilometer. This test is used in empirical methods of the flexible design methods, based on the soil strength.

Tri-axial shear test: This test gives the value of the shear strength of the soil, but it is not done, because the values obtained from this test are used only in a very few theoritical methods of flexible pavement design.

Plate Load Test:    In this test we make use of the plates of some larger diameter. In this test we get the values of the elastic modulus of sub-grade. These values are used in the methods of flexible pavement designs like that in Mcleaod method and in method of layer system approach for analysis by Burmister. 

The modulus of sub-grade reaction is also calculated for the rigid pavement analysis by the Westergaard's approach.

·         Sub-base and base course: 

Base course and sub-base course is used in the flexible pavement to disperse the upcoming loads to large area through a finite thickness, so as to increase the load bearing capacity of the pavement. The material used is the broken stones, or gravels, or bound or unbound aggregates. 

Sometimes the bricks can also be used as the sub-base and base materials. Generally the sub-base layers have the inferior quality of aggregates, than that used in the base course.  

Generally smaller aggregates are used because the larger gravels or aggregates have the tendency to sink to the lose sub-grade soil under the heavy loading.

The function of the sub-base or the base layer in case of the rigid pavement is to -

1.  Check the pumping action.

2.   Protecting the sub-surface against the frost action.

The basic purpose of the sub-base and base layer is to transfer the load through a dispersed/larger area to the sub-grade. So it must of sufficient strength to do its job. These layers are evaluated using a suitable strength or stability tests like the plate load test, California bearing ratio test, and the Hveem stabilometer test, where each test has its own significance and importance. 

Wearing course:   Top most layer serves as the smooth riding surface for the traffic, and it wears all the abrading forces. The top most layer is constructed with the superior quality of aggregates because it has to wear the maximum intensity of loads. 

·         It has to be water proof to stop the water penetration to the lower layers, so in case of flexible pavements the bituminous concrete is used and it is well compacted, and in rigid pavements the cement concrete is used and is well compacted so that no water penetration takes place. 

·         There is no direct test to check the stability of the surface course but the bituminous concrete used in the flexible pavement is checked for its suitability. Marshall stability test is used to determine the optimum content of the bitumen to be used in the aggregate mix, based on the stability density, VMA and VFB of the given grading of the aggregate mixture.

Thanks for visit!

Modes of Transportation

Modes of Transportation:
If you think of, there are three basic modes of transportation, by water, by air third by  land.  The land has provided us the scope of  Roadways and railways, air has provided the airways and the water has provided the scope of the waterways. The roadways include all type of the roads, National highways, state highways, Major district roads, Village roads, etc. It includes all the feeder roads.  Railways is generally used for the long travels, but the Metro railways are used for the short travels. The waterways are used by the cargo ships, or other boats, on the oceans, rivers, seas, canals or rivers wherever possible. The airways are used by the aircrafts and the helicopters. 
So the major modes of the transportation are : (1) Waterways (2) Railways (3) Roadways/Highways (4) Airways
The transportation by the airways is the fastest among the four and by waterways it is slowest.  Travel by air also provides more comfort.  The transportation by the waterways is possible between the two ports, or along a river and canals where the facilities for landing are available.
Transportation through the railways is advantageous for the long journey to transport the goods and passengers between different stations. The roads can act as the feeder system, to cater the traffic from various near and far places. The energy required to haul a unit load through a unit distance is only a fraction of that required for the haulage through the roadways. So we should make the use of the railways as much as possible. 
The transportation by the water is the slowest among the four modes but it needs the minimum energy to haul a unit load through a unit distance.
The transportation by road is the mode which can provide us the maximum flexibility with the routes, type of vehicles, lanes, and times. We can use a two wheeler or four wheeler, what ever suits the situation. It is the mode of transportation which provides the door to door service, and is required by all the other three modes of transportation. 
Everyone need to use a roadway  to reach the Airport, Harbour or the Railway station more often. So this mode also acts as a feeder system to all the other three modes of transportation. 
The branch of the Engineering which deals with the design, construction and maintenance of the highways is known as the Highway Engineering. 

Secret to be a good Engineer

I have seen that the students who are consistence with their studies, who are determined to get their goal, to understand everything, and who are determined to do something meaningful in their life are the ones who become good Engineers. They are good with the Analysis, Design and construction.
They get the success in their professional life. So start studying in a meaningful way from  the time of your study. I have realized it now, I hope you don't get late to realize it. 

Types of Pavements: Highway Engineering

The pavement is the structure which takes up all the traffic loads coming on the road. According to their behavior they can classified in these major categories:
(1) Flexible pavements: These are the pavements which have very less flexural strength. They transfer the load coming over them directly to the lower layers through grain to grain contact. So the load transfer largely depends upon the type of the grains/aggregates that are used in the construction of the pavement.  If the aggregates are well compact/ well graded then their grain to grain contact will be good and they can transfer the load to a wider area. The flexible pavement has the following layers:
(a) Wearing course
(b) Sub base course
(c) Base course
(d) Sub grade
The stress intensity is maximum at the top layer of the pavement and it decreases with depth. Due to ability of the pavement to transfer the loads to lower layers in the truncated form, the layer concept has been introduced for its construction. The pavements is made of layers of different materials. The top layer is made of superior material, because it has to face the largest stresses, and the lower layers are constructed with with inferior materials.  So the wearing course is made of the superior quality material and sub-grade can be constructed of the locally available earth too. The materials like bituminous concrete, is best to use as the surface course and the others like water bound macadam, and other crushed aggregates, gravels can be used for the base and sub base courses. The flexible pavements are designed with the help of the empirical design charts or some equations taking into account the various design factors. Some semi-empirical and theory methods are also available for the design of the flexible pavements.

(2) Rigid Pavements: These kind of pavement possess a high flexural strength and can transfer the loads coming over it to the lower layers with the slab action of the various layers. The reason behind the flexural strength is the kind of material used in its construction. The various materials like plain cement concrete, reinforced cement concrete or the pre-stressed concrete are the good materials to be used as the rigid pavement materials. There is no need to construct the sub-base course or the base course but for the precautionary purpose the base is generally provided. A good base course of course aggregates makes it more stable, and is more economical in the long run. The base course is more important when the sub grade is formed of the finer material. The rigid pavements are analysed and designed by using the elastic theory, in which the surface layer is considered as the elastic layer, which is supported by another elastic plate called the subgrade. The rigid pavement will not deform like the flexible pavements if the undulating surface is present at the base.

(3) Semi Rigid Pavement: These pavements are constructed with the materials like the pozzolana  concretes,the lime-fly ash-aggregate mix, or lean cement concrete and thus have sufficient flexure strength. They possess the flexural strength in between those of the rigid pavement and that of the flexible pavements. They are designed as the flexible pavements but with some correction factors applied to it, or they are designed by some other methods. These materials don't have the good resistant against the impact and the abrasion loads so the surface course is constructed with the flexible pavement materials.

GATE 2013 for Civil Engineering Online exam held on 20th January -Solution are required

I appeared first time in the GATE exam and it was a nice experience. It was all online, so there was no paper wastage. It is a good way to save the paper and the environment around us. 

The exam duration was 3 hours, and it carried about 62 or 63 questions.  Questions carried different marks with it. 

For Civil Engineering aspirants, I wanted to make an answer key but it is hard to remember the questions now. I remember some of the questions. I have confidence over some questions which I have attempted rightly. 

If you remember the questions, then please write in the comment box and I can discuss the answer that I know with you. I hope that I may help you this way.