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Civil Engineering Information

Plastic Roads

The disposal of plastic is a major problem everywhere in today’s scenario. The plastic we use mainly consists of low-density polythene and non-biodegradable. The burning of these plastic wastes causes environmental pollution. Laboratory experiments conducted on bituminous materials proved that waste plastic enhances the property of the mix. The improvement in the property of bituminous mixes provides a solution for disposal of plastic in a useful way. Since bottles, containers, plastic strips used in packing are increasing day by day. As a result, the amount of waste plastics is also increasing. This leads to various environmental pollution. These wastes produced today will remain in the environment for many years leading to various environmental concerns. Therefore it is very necessary to utilize the wastes effectively using modern techniques in each field.

Many by-products are produced in making plastic bags. The wastes consisting of carrying bags, cups, and other utilized plastics can be used as a coating on aggregate and coated aggregates can be used for road construction. The mix polymer coated aggregate and modified bitumen have shown greater strength. The roads which are constructed using plastic wastes, which are known as plastic roads are found to perform better compared to those constructed with conventional bitumen. The Indian Center for Plastics in the Environment (ICPE) has been promoting the use of plastic waste in construction of asphalt roads.

There are two kinds of plastic roads:
1) The plastic road is constructed with modular, hollow and prefabricated road elements which are made from consumer waste plastics.

2) Plastic roads consist of an asphalt mix with plastic waste incorporated with asphalt mixture.

Advantage of Plastic Roads:
In hot climates, road surfaces with neat bitumen can cause bleeding, may develop cracks in cold climates and possess fewer load bearing capacity. This can cause serious damage because of the higher axle load of vehicles in present condition due to rapid infrastructure development. The useful life of the bituminous layer decreased to 7 to 8 years from an average life of 5 to 6 years. The use of plastic waste materials with bitumen mixes enhances the pavement performance. The cost of construction of the road is also low. In this way we can protect the environment to some extent.

Laboratory Experiment Result:
The penetration value of the bitumen mixes decreases with increase in the percentage of polymer. It is because the addition of polymer increases the hardness of bitumen. The ductility of the bitumen mixes also decreases due to addition of polymer. The decrease of value of ductility is due to interlocking of polymer molecules with bitumen. Flash and fire point of the bitumen mixes increase with increase in the amount of polymer. That is why plastic road surfaces are less affected by fire hazards. It also shows that the bitumen blend has better resistance towards water. It is also due to the binding property of polymer bitumen mix. The Marshall Stability Value is high.The softening point also increases due to increase in addition of plastic to the bitumen. Higher is the amount of plastic added, higher is the softening point value. It is due to the chemical nature of polymer added. The increase in the value of softening points results in less bleeding during summer. Since bleeding accounts for increased friction between the tyre of a moving vehicle and road surface, and on the other hand it accounts for slippery conditions in rainy periods. These two adverse conditions can be overcome by polymer bitumen blend.

Significance of Plastic Roads:
I. The total material cost of the project is reduced almost by 8%.

II. The modified bitumen with plastic gives better results as compared to ordinary bitumen.

III. The optimum content of plastic with bitumen should be 5% to 10%.

IV. Since plastic has a property of absorbing sound, the use of plastic roads will help in reducing sound pollution caused by heavy traffic.

V. The bitumen mixed with polymer, as a road construction material improves the quality and performance of the road.

VI.There is no effective radiation of UV Rays.

VII. Zero maintenance cost.

VIII.It will give employment for unskilled laborers.

Plastic Roads in Use:
Many countries like Australia, Indonesia, United Kingdom, USA, South Africa, and Vietnam have used the technology which can incorporate plastic waste into asphalt mix. In India, the technology for plastic roads was developed by a man named Prof. RajagopalanVasudevan. He is a Professor of Chemistry at Thiagarajar College of Engineering, Madurai. He is known as the plastic man of India. He developed the technique for reuse of plastic waste to construct better, more durable and cost effective roads. Chennai is the first city in India to implement this technology. In November 2015, the Central Government of India made it mandatory for all road developers in the country to use waste plastic, along with bituminous mixes for construction of roads. This is an initiative which falls in line with the Government’s Swachh Bharat Mission which aims to address India’s garbage crisis. A survey done in December 2019, India has built a total 21,000 miles of roads using plastic waste. There are total 33,700 km of plastic roadways in the country. It is said that almost one million plastic bags are used every one km of road.

plastic road india
Fig:Plastic Road in India

The use of waste plastics on the road helps us to provide a better place for burying the plastic waste. It will end the disposal problem of plastics. At the same time, better roads are also constructed. This technique will also help us to avoid the general disposal technique of waste plastics namely land-filling and incineration which have certain burdens on ecology.

What are various Types of Cement?

Cement is a construction material which is used as a binder. It binds other construction material aggregate and sand together. Cement exhibits different properties if we change the chemical composition.  Earlier the different types of cement was found by only varying the relative proportion of the oxide composition.As time advances, new materials like additives to the clinker at the time of grinding, use of new raw materials resulted in production of new variety of cement.The various types of cements as per Indian Standards are-


Bar Bending Schedule


Bar bending schedule is a means to calculate the exact quantity of reinforcements required in a structure. It is helpful for any concrete work to know exact amount of cement, aggregate or sand required for a structure. It is referred to as BBS in short form. It involves calculating development length, diameter of bars to be used, stirrups, cutting length, crank length, and many more. It is a process of cutting and bending reinforcement bars into desired shape and size as per structural drawing. These drawings are handed by structural engineers for various structural elements like footing, column, beam, slab, etc. and then handed over to contractors for the execution of the work at site by the labors. The contractor must understand in depth before portraying it to the labors. BBS is necessary to the contractor as it is important in bidding for tenders. All these works play an important role without which work can’t proceed.

Geotechnical Investigation of a Construction Site

Geotechnical Investigation of a Construction Site
A civil engineer needs to understand the soil behavior of the construction site and to find the satisfactory solution to the soil problem. The knowledge of subsoil conditions at a site is a prerequisite for safe and economical design of sub-structural elements. A well planned and properly executed site investigation programme will provide information about the stratigraphy and physical properties of the soil at the site including ground water table and its fluctuations. The process of investigation are as follows:

Sub-surface Investigation:
Preliminary Exploration which is study of geology of the site and the reconnaissance.Detailed investigation follows the preliminary investigation and from this we come to know about the nature, sequence and thickness of soil layers and lateral variations, sequence and position of ground water table.

As a part of geotechnical investigation,we need to construct boreholes.There are different methods used for boring.e.g. Auger Boring,Wash Boring,Percussion Boring, Rotary Boring etc. The suitability of any particular method of boring depends mainly on the nature of soil,the position of water table,the ease and accuracy with which changes in soil and ground water conditions can be determined.

Soil Sample:
Generally it can be classified as
(i) Disturbed Sample: Disturbed Sample are those where natural soil structure gets modified or disturbed during sampling procedure.
(ii) Undisturbed sample: Here original soil structure is preserved and also soil properties have not undergone any alteration or modification.

For all practical purpose, undisturbed soil sample is suitable for all laboratory tests including shear strength and consolidation tests.

Types of soil samples Required for Laboratory Tests

Type of Test Type of sample required
Natural water content Undisturbed
Density Undisturbed /Representative
Specific Gravity Undisturbed / Representative
Grain size distribution Undisturbed
Atterberg’s Limit Undisturbed
Coefficient of permeability Undisturbed
Consolidation parameters Undisturbed
Shear strength parameters Undisturbed

Field Tests:
The field tests commonly used in sub-surface investigation are:

(i) Vane Shear Test
(ii) Plate Load Tests
(iii) Standard Penetration Test(SPT)
(iv) Cone Penetration Test
(v) Pressure Meter Test
(vi) Geophysical Methods

Number and Deposition of Trial Pits and Borings
The purpose of soil exploration is to provide the designer with complete information about the subsoil layers at the site. The number and spacing of boreholes or trial pits depend upon extent of site, uniformity of strata, nature of structure and loading diagram.

As per IS:1892-1979 recommendations,for a compact building site covering an area of about 0.4 hectare,one bore hole or trial pit in the center and one at each corner will be sufficient.For larger areas,it may be useful to perform sounding test /cone penetration tests at a spacing of 50m to 100 m by dividing the area in a grid pattern.

Borehole Logs:
After the soil investigation has been completed and the results of laboratory tests become available, the ground conditions discovered in each boreholes are summarized in the form of a chart called borehole log. A borehole log contains following data-

(i) The soil profile with elevations of different strata
(ii) Ground water table
(iii) Termination level of borehole
(iv) The depth or range of depth at which samples are taken
(v) Depths at which in-situ tests were performed
(vi) Type of soil sample
(vii) Results of important laboratory tests
(viii) N-values at the measured elevations

A sample of borehole log is shown below
Sample Borehole log
Sample Borehole log


Site Investigation Report:
A site investigation report is the conclusion of the investigation, exploration and testing programme. The report is addressed to the client. Although individual reports may be given in the form of content and presentation, a typical report contains:

(i) Introduction
(ii) Borehole logs
(iii) Field and laboratory tests results
(iv) Analysis of data
(v) Recommendation
(vi) Reference

Explain briefly various types of Estimates

Before undertaking a construction project it is necessary to know the expected cost and it is worked out by estimation. It is a computation of the quantities required and expenditure likely to be in the construction of the work.

The following are the different types of estimates:

1. Preliminary or Approximate Estimate:
This estimate is prepared to decide the financial aspects,policy and to give the idea of the cost of the proposal to the competent sanctioning authority.The calculation for approximate estimate is done in many ways. There are three types of approximate estimate