Durability of Flyash Based Geopolymer Concrete

This paper by SOURADEEP GUPTA (National University of Singapore) is aimed at discussing properties of geopolymer concrete, how these differ from properties of ordinary Portland cement, durability properties of fly ash based geopolymer concrete and its advantage when used as a construction material as well. Also some focus has been made on relevant issues that need to be solved and research needs to make it a better construction material.

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What are Green Buildings?

By
Er. Kaushal Kishore ,
Materials Engineer, Roorkee

INTRODUCTION:
A green building is that building which is constructed at a well planed location with proper design and sustainable materials. Fitted and painted with eco friendly materials. The building should gives to its occupants healthy and comfortable environment in all climates. It remains cool in summer, warm in winter, inside fully protected from rain, gives natural pollution free air and light through doors, windows and ventilators without any artificial means. For particular requirements it has solar, wind power and eco friendly electrical, mechanical etc. devices.

A green building should have all safety devices. It should be provided with potable water, having proper drainage, severage and rainwater harvesting system. The building should be surrounded with trees, plants and grass to provide natural greenery. Can the above building be possible when day by day the population in India is increasing at a very fast rate? The facts may be found from the following table.

Table: 1 Human population per sq.km of country area:

Country

Year

1947

2009

2049

India

121

350

581

China

132

141

U.S.A.

34

49

With the increase in the population the house demand will also increase. For India it is of the top concern as by the year 2049 having the same country area 581 persons sharing recourses of one sq. Km. area against China 141 and USA only 49. From the present day crowd, it can be well imagine what will be the crowd condition of India in 2049. A drastic action is needed otherwise it will be too late to cope with this situation. There will be more slumps. By 2011 India will have 9.31 crore slump dwellers in which 31.63 lakhs people will be living in slumps in Delhi alone.

Some builders have a novel way to attract the client for the apartments they are going to build or already build. They gives big advertisement in green colour showing apartment surrounded by tall green trees. When you go to such site you will not found the trees of your dream. The other misleading advertisement is that the apartment has 70% open lush green area. The facts will be known when you calculate the actual open area for one house you will be going to live. See the following table:

Table 2: Actual open area shared by number of people:

Storey of building

Total houses

Covered area sq.ft.

Ground open area sq.ft.

Persons living in total apartment

1

24

36000

25200

96

5

120

180000

25200

480

10

240

360000

25200

960

15

360

540000

25200

1440

From the above table it can be seen that in a single storey apartment of 24 houses for 96 persons the open area is 25200 sq.ft., whereas for a 15 storey apartment of 360 houses for 1440 persons the open area is again same only 25200 sq.ft. Accordingly if a builder claim that his 15 storey apartment has 70% open area of covered area then the open area should be 378000 sq.ft. and not 25200 sq.ft.

Suppose per house there is one car, then a single storey apartment will have 24 cars and a 15 storey apartment will have 360 cars. In a 15 storey apartment where is the open space will be left for trees. To maintain our natural environment there must be one tree for each house. Accordingly in a 15 storey apartment having 360 houses there should be 360 tall trees. Have we such greenery in any of the apartment in our cities. How then they may be called green houses and claiming 70% lush green open area. The fact is we are living in congested places where we can never feel comfortable and enjoy the life of natural environment.

URBAN HEAT ISLAND MITIGATION
Urban areas have been found to have air temperature 20C to 50C warmer than the surrounding country side. This phenomenon known as the URBAN HEAT ISLAND EFFECT. There are number of ways one can fight the urban heat island at home and around the city.

1. Planting Trees: Trees are one of our most important allies in the fight against the urban heat island effect. Air temperatures directly under trees can be as much as 100C cooler than temperature over unshaded blacktop. Trees can be sited stragically to shade roofs, pavement, walls, and other surfaces, keeping them cooler and reducing energy bills. Trees also provided a cooling effect through evapotranspiration. Other vegetation, including grass etc. also provides cooling effects, though not usually as significant as trees.

2. Green Roofs: Green roofs are roofs planted with grasses, flowers, or other vegetation. Like trees planted at ground level, the vegetation shades the surface, keeping it cooler. Reducing the urban heat island effect, isn’t the only benefit of green roofs- they can also be used to grow fresh local products in the city, and they significantly reduce storm water run off as well. Local birds will be attracted on the roof greenery and make their nest upon it.

3. Permeable Pavement: Many types of permeable pavement reduces the urban heat island effect in one or more ways. For example, many grid or block pavers incorporate grass or other ground covers, which help shade the surface of the pavement and increase local evapotranspiration. Porous pavements often have much lower total mass than asphalt or concrete, reducing the amount of heat they absorb and many permeable pavements are lighter colored than traditional pavement as well.

4. Building Walls: The walls of building should be painted with solar reflective paints.

5. Roofs: The roof of house remain expose to direct sun rays most of the day time. The traditional methods of keeping roof surface cool are lime terracing, mud phuska and brick bat coba treatment. These methods are not only time consuming, costly but also increases the dead load on roof. The new and very convenient method is to paint the roof surface white with solar reflective paint/coating.
Solar reflective coating is an acrylic based coating which provides weather proofing and heat insulation to the exposed roof. This can be used for coating RB, RCC roof top surface, asbestos cement roofing sheets, galvanized zinc sheets as well as aluminium sheets. With such coating temperature may be lower upto 100C thus giving cooling comfort to the occupants of house and also reduces the load on Air Conditioner.

We are thankful to Sir Kaushal Kishore for publishing his unpublished research paper here on the website. This would be of great use to all the civil engineers who work are looking for information regarding Green Buildings .

Seismic Disaster Mitigation

An approach on how to counter the damages caused by the earthquake in high risk areas of Pakistan.

Abstract
An applied study on different types of construction techniques in order to make a structure complaint and be able to withstand lateral forces lateral forces.

Magnitude and intensity of Seismic Waves depends upon the Earth quake, which in turn depends upon the origin of depth.

Click here to download the file

We are thankful to Sir Zeeshan Ahmad for sharing his research with us.

The fate of Landfills in the context of saving our environment

1 Introduction:
Municipal Landfills are the final resting and hiding place for all of our garbage. Landfills cost millions of euros to build and tens of euros to maintain. They often leak, spilling toxic fluids that contaminate groundwater. Paper can take well over 160 times longer to decompose in a landfill. They fill up after only about 7 years, but must be maintained for 30 years. They are a massive polluter to groundwater and are a leading contributor to global warming. But still we are maintaining them. Where else can we put all those wastages?

1.1 Background:
Today municipal solid waste is an accumulating problem with increased urbanisation. About ten million people live in Dhaka city, the capital of Bangladesh. Estimates for solid waste generated in Dhaka city varies from 3,000 to 3,500 tons per day. The wastes are highly diverse in nature and encompass a variety of materials including household refuse, mining, industrial by-products and street sweepings. The disposal of solid waste produced in Dhaka city is calculated to require 110 hectares of land per year. With further increase in population, the amount of solid waste will also increase proportionately. It is expected that by the year 2015, the total waste created in Dhaka city will be about 8,000 tons per day, requiring about 292 hectares of land for disposal. Bangladesh, a land-scarce country, does not have such physical space (Sinha et. al., 1997). As long as the population to grow the need for more disposal sites will grow. The indiscriminate disposal of solid waste in landfills causes serious environmental hazards and health risks. Flies, cockroaches and rodents thrive in landfills, and they are the known sources of many diseases. Uncontrolled wastes in landfills also clog the urban drainage system, cause frequent floods and contaminate drinking water sources. Thus, the growing problem of solid waste dumping in landfills is posing increasing threats to the health and well being of the residents.

1.2 Problems associated with landfills
1.2.1 Drinking water contamination:

Leachate is water that gets badly contaminated by contacting waste ( Quasim S.R.et. al.,1994),. Municipal landfill sites produce leachate when rain, surface or ground water enters into the landfill site. Leachate contains a wide range of toxic substances arising from the decomposition of waste, and causes contamination of domestic groundwater sources and deterioration of water ecosystems through oxygen depletion (eutrophication) of watercourses. Leaking landfills pollutes drinking water wells with cancer-causing chemicals such as toluene or vinyl chloride and have harmed many communities.

Sources of leachate are generated in the municipal waste dumping sites in large cities. Also considerable amounts of industrial leachates are generated from industrial sources. In Dhaka city, and all other big cities of the country, municipal wastes are dumped in low-lying landfills. Municipal leachates are rich in chlorinated hydrocarbon solvents (CHS), which are very toxic and carcinogenic. Recent investigations have found remarkable quality deterioration under landfill leachates and identified a number of CHS in groundwater from the industrial areas (Bernard B et. al. 1973). It is very likely that the same contaminants may also be present in groundwater in other large cities and industrial zones of Bangladesh. The picture is also the same in the developed countries of the world. In a recent study of 163 municipal waste landfills in the U.S.A, there was evidence of contamination rate for ground water quality at 146 of them (NORTHWEST, 2010). That’s a 90% contamination rate for ground water beneath municipal solid wasteland fills. Once ground water is polluted it is almost impossible to clean it up.

1.2.2 Global Warming:
Biodegradable garbage rotting in a landfill produces methane gas—a ‘greenhouse gas’ that contributes to global warming. Methane is 21 times more potent in its greenhouse effect than carbon dioxide (from car exhaust), and landfills are the largest man-made source of methane (37% globally).

1.3 How landfills are constructed and why they fail?There are three critical elements in a secure landfill: a bottom liner, a leachate collection system, and a cover (ZERO WASTE AMERICA, 2010) as described below:

section of landfill
Figure: Section of a Landfill. Source: (GETSTUFF, 2010)

What is a bottom liner?
It may be one or more layers of clay or a synthetic flexible membrane (or a combination of these). The liner effectively creates a bathtub in the ground. If the bottom liner fails, wastes will migrate directly into the environment. There are three types of liners: clay, plastic, and composite.

What is wrong with a clay liner?Natural clay is often fractured and cracked. A mechanism called diffusion will move organic chemicals like benzene through a three-foot thick clay landfill liner in approximately five years. Some chemicals can degrade clay.

What is wrong with a plastic liner?
The very best landfill liners today are made of a tough plastic film called high-density polyethylene (HDPE). A number of household chemicals will degrade HDPE, permeating it (passing though it), making it lose its strength, softening it, or making it become brittle and crack.

What is wrong with composite liners?
A Composite liner is a single liner made of two parts, a plastic liner and compacted soil (usually clay soil). Reports show that all plastic liners (also called Flexible Membrane Liners, or FMLs) will have some leaks. It is important to realize that all materials used as liners are at least slightly permeable to liquids or gases and a certain amount of permeation through liners should be expected. Additional leakage results from defects such as cracks, holes, and faulty seams. Studies show that a 10-acre landfill will have a leak rate somewhere between 0.2 and 10 gallons per day.

What is a leachate collection system?
Leachate is water that gets badly contaminated by contacting wastes. It seeps to the bottom of a landfill and is collected by a system of pipes. The bottom of the landfill is sloped; pipes laid along the bottom capture contaminated water and other fluid (leachate) as they accumulate. The pumped leachate is treated at a wastewater treatment plant. If leachate collection pipes clog up and leachate remains in the landfill, fluids can build up in the bathtub. The resulting liquid pressure becomes the main force driving waste out the bottom of the landfill when the bottom liner fails.

What are some of the problems with leachate collection systems?
Leachate collection systems can clog up in less than a decade. They fail in several known ways:
1. They clog up from silt or mud;
2. They can clog up because of growth of microorganisms in the pipes;
3. They can clog up because of a chemical reaction leading to the precipitation of minerals in the pipes; or
4. The pipes become weakened by chemical attack (acids, solvents, oxidizing agents, or corrosion) and may then be crushed by the tons of garbage piled on them.

1.4 What can we do to reduce pressure on landfills?
Landfills are outdated technologies that do not have a place in the 21st century. However, vested interests are still promoting them as safe waste management solutions. No matter what technologies are available, we can all help by reducing the amount of waste that we generate. The main motivations for waste reduction are frequently related to the high cost and scarcity of sites for landfills. The places that currently do not have significant disposal pressures can still benefit from encouraging waste reduction.

1.4.1 Key concepts in municipal waste reduction
1.4.1.1 CLEANER TECHNOLOGY

Industries should use processes that make the least possible waste. This is called using Cleaner Technology. It is always best to avoid creating waste in the first place. To avoid creating waste we should (Ljiljana R., 2000 ;Maksimovic C. et. al., 2001; Sinha et. al., 1997):
• Buy only what we need and can use
• Avoid extra packaging
• Separate wastes such as paper, tins and bottles for recycling or re-use.
Industries should be encouraged to:
• Check that machinery is working properly
• Use less raw materials
• Recover and recycle waste wherever possible
• Reduce toxicity of the waste
• Use only necessary packaging
• Train staff to avoid mistakes that cause waste, such as spilling of oil or chemicals.

1.4.1.2 REUSE
We should:
• Consider reusable products
• Maintain and repair durable products
• Reuse bags, containers, and other items
• Borrow, rent, or share items used infrequently
• Sell or donate goods instead of throwing them out.

1.4.1.3 RECOVER AND RECYCLE
Anything that can be used again should be taken out of the waste. This is called recycling or Resource recovery. We can take useful items out of our waste and use them again, for example:
• old engine oil and car batteries can be taken back to the garage for recycling
• tins, bottles and paper can be taken to recycling bins
• vegetable peels can be made into compost

And also we should:
• Choose recyclable products and containers and recycle them
• Select products made from recycled materials.

Any improvements in waste management standards will always cost more. The person or industry that makes the waste must pay these costs. It is only fair that the waste generator or polluter should pay the cost of waste management and not the community. This is known as the polluter pays principle. After all it is the community that suffers if waste is not properly managed. Increased disposal and clean up costs will also encourage the waste generator to use cleaner technology and to reduce the waste generation as much as possible.

1.5 Conclusion
There is no debate that all landfills eventually contaminate our environment. It is expected that in future, municipal solid waste management practices will greatly emphasize in resource recovery, and solid waste reduction. Modern techniques with energy recovery will play an important role in waste reduction and energy conservation. So alternatives to land filling would have environmental effects which include: resources for the future, jobs from discards, more open space and natural habitat, less contamination of drinking water and soil improvement to assist agriculture in fertile soil.

References:
1. Bernard B, Charles H. P., DeBell and Richardson (1973), “Solid waste Disposal, vol-1, incineration and landfill”, 1st edition, Michigan, USA
2. GETSTUFF (2010), “How Landfills Work”, [On Line] http://science.howstuffworks.com/landfill6.htm [15th May, 10]
3. Maksimovic C., Jose A.T.G. (2001), “Frontiers in urban Water Management, Deadlock or Hope” 2nd edition, IWA publishing, London, UK
4. NORTHWEST INDIANA (2010), “Landfills in Northwest Indiana”, [On Line] http://www.iun.edu/~environw/landfills.heml [2nd March, 10]
5. Ljiljana R., (2000), “Reliability of Landfill Technology”, 1st edition, Uitgeverij Eburon, Delft, The Nethelands
Quasim S. R., Walter C.(1994), “Sanitary landfill leachate, generation control, treatment”, 1st edition, Technomic Publishing Company, USA
6. Sinha and Enayetullah, 1997, “Waste as resource.” Article in The Bangladesh Observer, Dhaka, November 21, 2001.
7. ZERO WASTE AMERICA (2010), “The basics of landfills: How they are constructed and why they fail”, [On Line] http://www.zerowasteamerica.org/BasicsOfLandfills.htm [12th March, 10]

Terms
Groundwater: Water that infiltrates into the Earth and is stored in usable amounts in the soil and rock below the Earth’s surface; water within the zone of saturation.

Leachate: A liquid that results from water collecting contaminants as it trickles through wastes, or soil containing agricultural pesticides or fertilizers

Percolate: To drain or seep through a porous and permeable substance; to filter such as a liquid passing through a porous body (water through soil to the aquifer)

Residue: Something that remains after a part is taken away

We are thankful to Barua R. (Public Works Department (PWD),Bangladesh) and Naz N.N. (Local Government Engineering Department(LGED), Bangladesh) for sharing this information with us on engineeringcivil.com. We hope this would be of great significance to civil engineers.

Design of Substructure Bridge with Different Codes and Analysis the Data for Settlement and Bearing Capacity Manually and by Using Plaxiz 3D Program of Finite Elements

Abstract
This paper discussed the design of substructure of bridge subjected to load of train with using two codes, the first code is AASHTO code and the second is the Chinese Code. This study focuses on the substructure of the bridge design and the design manually with the two codes.

By the design of the Bridge using the codes above, we found that Chinese Code is more safely that the number of reinforcement bars more in the pile cap and pile.

Settlement of the bridge also is calculated by using the data collected from the project site, the vertical ultimate bearing capacity of pile group and the dynamic action of the train loads, by this study it can be concluded all the above are safe values.

Another analysis by using the three-dimensional Plaxis program of finite elements and many parameters calculated, the value of the maximum vertical displacement was near from the calculated value which gives another checking for the design and maintain the safe conditions for the Bridge.

1. Introduction
Many of codes used in the world for design the bridges and many of countries have special codes for design depending on the specialty of that country and the nature, environmental conditions, effect of earth quakes etc. In the United States Bridge Engineers use AASHTO’s standard Specification for Highway Bridges and, in similar fashion or trends, German bridge engineer utilize the DIN standard and British use the BS 5400 code. In general, countries like German and United Kingdom which have developed and maintained major highway systems for a great many years possess their own national bridge standards. The AASHTO Standard Specification, however, have been accepted by many countries as the general code by which bridges should be designed.

In this paper, the design of a bridge by using two codes the AASHTO and Chinese codes. The AASHTO Code for design bridges named “American Association of State Highway and Transportation
Officials.”

In China there are many codes for design about 81 codes for design for all the majors in the civil engineering with serial numbers of standard, the code used for this study is (The Chinese National Standard (CNS, 2002)) [4], Building Foundation Design Code (GB50007-2002). The Chinese Codes for design bridges focusing on the rail-way design like:

- Fundamental Code for Design on Railway Bridge and Culvert (TB10002.1-2005).
- Code for Design of Steel Structure of Railway Bridge (TB10002.2-2005).
- Code for Design on Reinforced and Pre-stressed Concrete Structure of Railway Bridge and Culvert (TB10002.3-2005).
- Code for Design on Concrete and Block Masonry Structure of Railway Bridge and Culvert (TB10002.4-2005).
- Code for Design on Subsoil and Foundation of Railway Bridge and Culvert (TB10002.5-2005).
- Standard for Constructional Quality Acceptance of Railway Bridge and Culvert Engineering
(TB10415-2003).

2. Research Significance
This paper is to make a comparison between two or more codes in different countries to show the differences and similarities and advantages and disadvantages also for checking the design by the analysis and find the suitability of using the structure according to the design.
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