What is porous concrete?

Porous concrete is concrete which is designed to trap water and allow it to percolate through the concrete to the ground below. There are a number of advantages to porous concrete which have caused it to become a popular option for things like sidewalks, driveways, and parking lots. It is especially popular with ecologically sound construction companies, since it helps to manage water runoff in a sustainable way. Many so-called “green” builders promote the use of porous concrete in their projects.

There are a number of alternate names for porous concrete including permeable concrete, porous pavement, and pervious concrete. All of the names basically mean the same thing; porous concrete is a form of concrete which is permeable, rather than solid. Porous concrete is made by mixing large aggregate material with mortar, creating lots of voids in the cast concrete. When water lands on the concrete, it trickles through the voids and into the ground below.

For people who are concerned about the environment, porous concrete is attractive because it traps water, rather than allowing it to drain uselessly into the ocean. Porous concrete can help route storm runoff and rain directly into the soil where it can nourish gardens and trickle down into the water table. It also comes in a range of colors, and it can be made with recycled materials including recycled concrete rubble. This flexibility and potential for recycling makes it an ecologically friendly and aesthetically pleasing building material.

From the point of view of a contractor, porous concrete has some distinct water management advantages. Instead of allowing water to pool, porous concrete sucks up water and wicks it away. This prolongs the life of the concrete, and it also makes it safer for people driving, walking, and biking on the concrete, since they do not have to contend with pools of water. While extremely wet conditions will eventually overwhelm the absorption capacity of porous concrete, it is still a better drainage choice than tightly packed concretes.

Because porous concrete does have a lot of empty space, it is not suitable for all building applications. There are specific requirements for structural concrete, for example, to ensure that it will be safe and sound, and porous concrete may not always meet these specifications. It can be used safely for pathways, concrete patios, driveways, sidewalks, and so forth. Some companies also cast bricks and tiles in porous concrete for people who want to build their own tiled walkways.

Construction firms bag orders worth Rs 3,810 cr from July 1-15

Domestic construction firms inked contracts worth just Rs 3,810 crore in the first 15 days of July, over 72 per cent lower than the order intake in the preceding fortnight, as per data compiled by IDFC Securities.

Construction firms' order intake stood at Rs 13,730 crore between June 16 and June 30, out of which Larsen & Toubro accounted for contracts with a cumulative value of Rs 5,500 crore.

The brokerage firm said of the total order intake in the first fortnight of the current month, the lion's share went to Pratibha Industries , which bagged two orders worth Rs 1,249 crore from the Delhi Jal Board along with joint venture partner Mosinzhstroi Open Joint Stock Company.

Under the contracts, Pratibha will design, construct and lay interceptor sewers along three major drains in the national capital.


Meanwhile, Pune-based wind turbine maker Suzlon Energy received a Rs 650 crore order for supplying 100-MW turbines to Orient Green Power.

Furthermore, KNR Constructions bagged orders worth Rs 580 crore from Sadbhav Engineering for two road projects, while NCC garnered orders worth Rs 820 crore for various projects from the Rail Vikas Nigam and Bangalore Development Authority, among others.

During the fortnight, French power equipment-maker Alstom bagged contracts worth over Rs 270 crore for setting up three hydro-power projects in India.

The first contract was from Shiga Energy for the 97-MW Tashiding hydroelectric project in Sikkim. The second was with NSL Tidong Power Generation for the Tidong I hydro-electric project, consisting of two 50-MW units, in Kinnaur district of Himachal Pradesh.

The third contract is from Haridwar Infrastructure for the Dikchu hydro-electric project on the river Dikchu, in Sikkim, for a 96-MW plant.

Types of Construction Contracts

While construction contracts serve as a means of pricing construction, they also structure the allocation of risk to the various parties involved. The owner has the sole power to decide what type of contract should be used for a specific facility to be constructed and to set forth the terms in a contractual agreement. It is important to understand the risks of the contractors associated with different types of construction contracts.

Lump Sum Contract

In a lump sum contract, the owner has essentially assigned all the risk to the contractor, who in turn can be expected to ask for a higher markup in order to take care of unforeseen contingencies. Beside the fixed lump sum price, other commitments are often made by the contractor in the form of submittals such as a specific schedule, the management reporting system or a quality control program. If the actual cost of the project is underestimated, the underestimated cost will reduce the contractor’s profit by that amount. An overestimate has an opposite effect, but may reduce the chance of being a low bidder for the project.

Unit Price Contract

In a unit price contract, the risk of inaccurate estimation of uncertain quantities for some key tasks has been removed from the contractor. However, some contractors may submit an “unbalanced bid” when it discovers large discrepancies between its estimates and the owner’s estimates of these quantities. Depending on the confidence of the contractor on its own estimates and its propensity on risk, a contractor can slightly raise the unit prices on the underestimated tasks while lowering the unit prices on other tasks. If the contractor is correct in its assessment, it can increase its profit substantially since the payment is made on the actual quantities of tasks; and if the reverse is true, it can lose on this basis. Furthermore, the owner may disqualify a contractor if the bid appears to be heavily unbalanced. To the extent that an underestimate or overestimate is caused by changes in the quantities of work, neither error will effect the contractor’s profit beyond the markup in the unit prices.

Cost Plus Fixed Percentage Contract

For certain types of construction involving new technology or extremely pressing needs, the owner is sometimes forced to assume all risks of cost overruns. The contractor will receive the actual direct job cost plus a fixed percentage, and have little incentive to reduce job cost. Furthermore, if there are pressing needs to complete the project, overtime payments to workers are common and will further increase the job cost. Unless there are compelling reasons, such as the urgency in the construction of military installations, the owner should not use this type of contract.

Cost Plus Fixed Fee Contract

Under this type of contract, the contractor will receive the actual direct job cost plus a fixed fee, and will have some incentive to complete the job quickly since its fee is fixed regardless of the duration of the project. However, the owner still assumes the risks of direct job cost overrun while the contractor may risk the erosion of its profits if the project is dragged on beyond the expected time.

Cost Plus Variable Percentage Contract

For this type of contract, the contractor agrees to a penalty if the actual cost exceeds the estimated job cost, or a reward if the actual cost is below the estimated job cost. In return for taking the risk on its own estimate, the contractor is allowed a variable percentage of the direct job-cost for its fee. Furthermore, the project duration is usually specified and the contractor must abide by the deadline for completion. This type of contract allocates considerable risk for cost overruns to the owner, but also provides incentives to contractors to reduce costs as much as possible.

Target Estimate Contract

This is another form of contract which specifies a penalty or reward to a contractor, depending on whether the actual cost is greater than or less than the contractor’s estimated direct job cost. Usually, the percentages of savings or overrun to be shared by the owner and the contractor are predetermined and the project duration is specified in the contract. Bonuses or penalties may be stipulated for different project completion dates.

Guaranteed Maximum Cost Contract

When the project scope is well defined, an owner may choose to ask the contractor to take all the risks, both in terms of actual project cost and project time. Any work change orders from the owner must be extremely minor if at all, since performance specifications are provided to the owner at the outset of construction. The owner and the contractor agree to a project cost guaranteed by the contractor as maximum. There may be or may not be additional provisions to share any savings if any in the contract. This type of contract is particularly suitable for turnkey operation.

Larsen & Toubro to Double Orders From Outside India on Gulf Construction

Larsen & Toubro Ltd. (LT), India’s biggest builder of power networks and refineries, expects to double overseas orders in three years as a new structure helps it challenge South Korean builders for projects in the Middle East.

Contracts from overseas will rise to 25 percent of total orders in the period as the company divides operations into nine units to improve management focus, Chief Financial Officer Y.M. Deosthalee said in a July 4 interview at the company’s Mumbai head office. Foreign deals now account for less than 10 percent of orders, he said.

“Our international strategy has not panned out the way it should have,” he said. That is one reason for the new management setup as “this business has to grow,” he said.

The company will focus its overseas push on the Gulf, as rising oil prices and economic development spur investment in refineries and infrastructure. Countries in the region plan to spend almost $1 trillion on construction over five years, Deloitte Corporate Finance Ltd. said in November.

“Larsen has the wherewithal to win orders overseas,” said Rupesh Kumar, a Mumbai-based analyst with KR Choksey Shares & Securities Pvt. “But, the going won’t be easy for them as they are facing some formidable competitors.”

The company gained 0.8 percent to 1,806.6 rupees at the 3.30 p.m. close of trading in Mumbai. The shares have dropped 8.7 percent this year, matching the decline in the benchmark Sensitive Index of the Bombay Stock Exchange.

Larsen plans to promote work it has done in India, including building four airports, to win overseas contracts, Deosthalee said. India’s lower wages may also help Larsen challenge South Korean builders, including Hyundai Engineering & Construction Co., the nation’s biggest, which got 38 percent of sales in the Middle East last year.

‘Tough Job’

“It’s a very tough job to compete against them, but we have some advantages,” Deosthalee said. “Our entire design and engineering team is sitting in India,” which pares costs, he said.

Larsen last month announced 13.7 billion rupee ($310 million) of transmission and power distribution orders from the Middle East, including installing a 225 kilometer-long power line for a Saudi Arabian railway and building five substations for Abu Dhabi Ports Co.

Nine Units

The builder expects its total orderbook to rise as much as 20 percent by March 31 from 1.3 trillion rupees at the end of the last fiscal year, it said earlier this year. The company in January unveiled the new management set-up centered on nine units, focused on areas including construction, shipbuilding, electrical parts, information technology and financial services.

Aside from the Middle East, Larsen is also looking to win business in other South Asian countries and in Africa, Deosthalee said. It has opened an office in South Africa to win contracts there to build electricity transmission lines, he said.

The company also makes heavy-engineering equipment, including parts for fertilizer plants and refineries, which are sold worldwide.

Construction slump may force Britain back into recession

A weak performance by the construction industry in May could force the economy back into recession, say leading economists.

A 0.4% rise in activity last month was far below the estimates of most economic commentators, and follows a 12.4% plunge the previous month. The weak figures for May left the sector down 2.7% year-on-year.

The Office for National Statistics said the sector was dragged down by a 5.9% fall in private industrial work, which offset rises in public housing starts and new infrastructure projects.

Alan Clarke of Scotia Capital warned the economy could be slipping back into recession. "For some time we have seen significant risks that GDP growth will be around zero in [the second quarter]. The incoming monthly data for May have reassured our expectations of near zero growth. In fact, it is looking more and more likely that we might see another negative quarter for GDP growth," he said.

He joined several other economists in saying that figures this month showing a slowdown in manufacturing and severe pressure on the services sector, combined with the poor construction figures, could push the economy into reverse when official second-quarter GDP figures were published on 26 July.

Services sector data for May is due next week and is expected to reflect huge falls in consumer confidence over recent months. Several retailers have issued dire warnings of significant falls in turnover. John Lewis, which had proved immune to the retail slowdown until recently, said on Friday morning that year-on-year sales fell 3.4% to the week ending 2 July.

The figures are expected to put further pressure on the Treasury to explain how the economy will grow over the next few months and avoid slipping back into a second recession in three years.

The chancellor, George Osborne, has faced calls for tax cuts and a boost to spending to jolt the economy back into life after a sharp fall in consumer confidence this year. It takes two consecutive quarters of decline before an economy is considered to be in recession.

The National Institute of Economic and Social Research said on Friday that Britain was suffering a depression that would last longer than that of the 1930s.

The respected thinktank revealed its latest estimate for GDP growth in the three months to June at just 0.1%.
Construction industry expert Tom MacLennan, of accountants RSM Tenon, said the outlook for many building firms was bleak. "Looking at balance sheets, nearly 37,000 construction companies – almost a quarter of the sector – are at high risk of insolvency. By contrast, only 20,800 firms – 13% of the industry – have very healthy cashflow," he said

"Construction companies face a nasty combination of circumstances – materials are costly, the government has cut back on capital spending on infrastructure, and UK businesses remains chastened by the pre-crash building boom.

"Worse, when the industry hears bad news such as today's figures, these problems are amplified; negative publicity can push suppliers to ask for quicker payment terms, causing less working capital being available.

So, the question is whether a resurgent economy can increase demand for building, and save the sector from a downward spiral. As construction accounts for 6% of the UK's GDP, let's hope so," he added

Builders setting up prefabrication units to cut costs

Real estate developers are setting up prefabrication plants to speed up construction and cut project costs as an acute shortage of labour and a rise in raw material prices threaten to wipe out the industry's already wafer-thin margins.

Between 2009 and 2011, labour costs have risen 50% while prices of raw materials-steel, cement and bricks-have grown 25%, but developers are betting on the use of prefabs, which promise to save a third in construction time and 10-15% in costs over the long run. "This (labour shortage) is impacting delivery of projects and escalating costs," says Godrej group chairman Adi Godrej.

According toresearch firm PropEquity, nearly half of the 930,000 under-construction residential units scheduled for delivery between 2011 and 2013 are likely to be delayed by up to 18 months. In the current market, where margins are thin and customer sentiment is low, developers cannot afford project delays. "To improve the situation, we need to bring in more technology like prefab structures," says Godrej.

Prefab technology, now adopted by a number of developers in the south like Janapriya, Supertech, Brigade group and Trigunaas Build-Tech, involves making concrete walls and slabs at a manufacturing facility, transporting them to the construction site and then installing them.

India's construction industry is projected to face a labour shortage of 18-28% if the country grows at a medium rate, according to a recent World Bank report. Moreover, the success of the government's flagship job scheme, the NREGS, has reduced labour supply in large cities.

Janapriya Projects, which was facing labour shortages for quite some time, decided to use prefabricated walls in its latest project, the Lake Front township in Hyderabad. As a result, the project is now almost four months ahead compared to the construction time using the earlier method. "Earlier, we were unable to meet timelines and costs were spiraling due to high labour costs," says K Kranti Kiran Reddy, executive director at Janapriya. In October, it signed a technology deal with Finland-based Elematic for setting up a prefabrication unit, which now produces 5,000 sq ft of wall area a day. "We are using 60% less labour in the Lake Front project now."

Though companies building low-cost housing have been using the technology successfully, now developers like Janapriya are using prefabs to develop affordable and mid-income housing.

"It makes more sense to use prefabricated structures for large developments," says Harleen Oberoi, executive director, project management at Cushman & Wakefield.

Noida-based developer Supertech is investing Rs 200 crore to set up a pre-fab plant in Greater Noida and has raised Rs 50 crore debt from ICICI Bank . "We plan to use pre-fabricated walls and slabs for our mid-income and affordable homes projects," says Supertech managing director RK Arora.

"The reduced construction cost will help us keep our selling price low. Otherwise it is difficult to compete in this price range," says Arora. He and his team had visited a construction site in Malaysia last year to see how the prefab technology works. "Only five people working at the site: one man on the crane, two helping him load the prefabs and two to install them on the building."

Says Trigunaas Built-Tech project manager Bima Rajesh: "We are importing prefab moulds from Malaysia and Germany for our low-income housing projects. Now we are setting up a plant so that we can tap the growing market for affordable housing." Using prefabs, three floors can be built in 45 days as compared to a year taken by the conventional method, says Rajesh. Malaysian firm Plastek Industrial System is partnering Trigunaas in building the plant, which will cost Rs 200 crore,

Bangalore-based Brigade group is currently negotiating with a Singapore-based prefab company to design and manage a plant for it. "We are looking to set up a captive production plant (at a cost of Rs 15 crore) for affordable homes in Bangalore ," says Kailash Advani, CEO, BCV Developers, a subsidiary of Brigade Group.

Research Invitation for graduates in civil engineering by UK

Engineers at the University of Liverpool (UK) are looking for students from India to join an international research team investigating the development of environmental-friendly materials for use in construction industries around the world.

Researchers at the University's Centre for Engineering Sustainability are exploring the use of recycled demolition waste in construction materials, as well as how recycled glass could be used in ultra high-strength concrete pavement flags that are resistant to accidental damage caused by vehicles. The team, which comprises postgraduate students from all over the world, is also aiming to replace cement in concrete construction products with waste materials of high silicon dioxide content.

India has long been recognised as one of the most active in developing innovative solutions to the challenges faced in construction and materials engineering. Marios Soutsos, from the University's School of Engineering, travelled to India in May this year to talk to students about his research and he is now inviting postgraduate applicants to work with his team at Liverpool in September.

Soutsos said: "The Indian Institute of Technology and the Institute of Chemical Technology in Mumbai, as well as the American Concrete Institute in India are examples of some of the big organisations that have driven forward rapid developments in the country's construction industry. The research skills of graduates from universities in India have contributed to some of the most successful construction projects in the country , such as the Bandra Worli Sealink and the JJ Hospital Flyover. We are looking to work with graduates from India who are interested in pursuing research in sustainable materials."

Postgraduate research degrees at the university run for three years and to apply for the same, students should have a class 2.1 engineering degree or better. Individual consideration is given to mature engineers with significant experience with professional qualifications. A good standard of English is also required at ELTS 6.0. Alternatively, students should successfully complete the appropriate pre-sessional English language course.

NCC bags fresh orders of Rs 815 cr

Construction firm NCC on Monday said it has secured fresh orders worth Rs 815 crore to be executed over a period of upto 36 months.

In a communique to the Bombay Stock Exchange (BSE), the Hyderabad-based firm said it has bagged a Rs 215 crore order from Rail Vikas Nigam, Bhubneswar.

The project would be completed over 36 months, NCC said but did not divulge other details.

The company has also received an order worth Rs 159 crore from the City and Industrial Development Corporation of Maharshtra for construction of an elevated road. The project would be completed over 24 months, it said but did not mention when it bagged the order.

NCC has also got a Rs 119 work from Bangalore Development Authority for construction of flyover and underpass roads. The work would be completed in 15 months.

"Some more orders have been received from various clients totaling to Rs 322 crore," it said.

The company had earlier said that its orderbook, as on April 1, stood at Rs 16,180 crore. During April and May, it secured Rs 716 crore fresh orders.

NCC hopes its consolidated turnover to go up by 15 per cent this fiscal to Rs 7,200 crore over the last fiscal.

Is China's bridge really the the world's longest bridge?

China's latest engineering marvel, the Qingdao bridge, has been hailed as the world's longest bridge over water. But the claim has ruffled feathers in America, previous owners of the title.

The bridge is over 26 miles long and carries its eight lanes of traffic over the Qingdao bay. Motorists will be able to travel from downtown Qingdao to the Huangdao city centre in about 20 minutes, saving themselves a 40-minute journey around the bay's edge.

The fact that it crosses over the bay means that it has been entered into the Guinness World Records as the longest bridge over water, which according to the Guinness World Records team means it is "2.53 miles longer than the former record holder, the Lake Pontchartrain Causeway in Louisiana".

However the general manager of the Causeway in Louisiana is not going to relinquish this title without a fight and said that the Chinese bridge team were "a bunch of wannabees".




Causeway General Manager Carlton Dufrechou said his bridge, built in the 1950s and traversing the Lake Pontchartrain in a straight 24-mile line, deserves to hold on to the title.

'We're proud of that record and we think we still hold that' - Carlton Dufrechou, Causeway Commission

Dufrechou told Channel 4 News that while he agreed the Qingdao bridge is a "magnificent bridge", he believes the 54-year-old Causeway bridge still holds the record by eight miles.

Terminology appears to be at the heart of the dispute. Dufrechou maintains that because the Qingdao bridge is curved, it is using part of that curvature over the water to add to its length of 26 miles.

If you were to measure the distance from the start of the bridge to the end of the bridge as the crow flies, it would only measure a distance of 16 miles over the water, he argues. His bridge by comparison is a straight 24 miles from end to end over the water (you can see the Causeway on the map below).

View Larger Map

However the Guinness World Records has come down on the side of the Chinese. Its editor-in-chief Craig Glenday says their title, for the Longest Bridge over Water, "recognises an incredible feat of engineering." and explains how they award it:

"It is calculated by the actual length of the bridge and not the size of the body of water it covers or the distance between two land masses that it spans."

Defrechou seemed undeterred by the Guinness World Records response. "I understand that measurement," he said, "but we believe the open span over the water is the proper measurement - we're proud of that record and we think we still hold that."

Chinese bridge-building has been making waves recently with the sheer speed and scale of its construction.

'The west is competing with China with doing projects in its own back yard' - Alistair Lenczner, Foster + Partners

Alistair Lenczner, partner at Foster and Partners who were behind the Millau Viaduct in France, explained what a force Chinese construction has become.

"You have to be impressed the rate and the magnitude of the projects they're doing," he told Channel 4 News. "It's probably unprecedented in terms of the volume of infrastructure in such a short number of years."
Previously, Lenczner said, western consultants would be invited to Chinese construction projects, while their own engineers stood by and watched and learned. Now they have developed their own industry and have become world leaders, exporting their skills.

"The tide has turned - the west is competing with China with doing projects in its own back yard."
Lenczner knows how well the Chinese have progressed. Among its several world records, the Millau bridge also held the record for the highest road bridge deck in the world. Now he says the Chinese have broken that record "a dozen times over".

But Lenczner points out that in terms of records the real holy grail for the bridge designer is the "longest span" record - that is to say, the part of length of the bridge between any supporting columns.

Both the Qingdao bridge and the Louisiana Causeway may have length on their side, but they have a lot of columns beneath them, creating very small spans. The owner of the longest bridge span title is in Japan.

List of Theory and Practical subject for 7th semester GEU civil engineering

Theory  

TCE 701  Design of Steel Structures  

TCE 702  Environmental Engineering II 

TCE 703  Water Resources Engineering I 

 TCE 704  Earthquake Resistant Design of  Buildings 

   

Labs  

PCE 701  Environmental Engineering Lab. II 

PCE 702  Structural Detailing Lab. II 

PCE 703  Practical Training & Seminar 

CEP 701  Project ( Stage - I ) 

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7th sem.doc