What is Underwater Antiwash Concrete?

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Although underwater concreting has been in use for a long time, development of the technique has mainly proceeded in the areas of concrete placing method and improvements to the construction machinery. The prepacked concrete method, tremie method, concrete pump method, and others are now the representative underwater concreting methods. With all these concreting methods, the essential aim of technological development has been to improve how the concrete is placed and to minimize contact between the water and mortar so as to prevent the concrete from segregating under water.

On the other hand, antiwashout underwater concrete is quite different in concept from the methods mentioned above; the developmenta1aim in this case was improved performance of the fresh concrete. That is, the viscosity of the concrete was increased and its resistance to segregation under the washing action of water was enhanced by mixing an antiwashout admixture with the concrete. The effect of this is not only to greatly improve the reliability of Concrete placed underwater, but it also has remarkable effects on environmental preservation in the construction area. In addition, the earlier tremie and concrete pump placing methods can be adopted for construction.

The specific advantages of antiwashout underwater concrete include the following:

• Compared with ordinary concrete, antiwashout underwater concrete is highly resistant to the washing action of water, and rarely separates even when dropped under water

• Its yield value is small and viscosity high, so the concrete components never segregate and it displays high fluidity.

• As a result of the high fluidity, filling property and self-leveling ability are improved.

• Almost no bleeding occurs.

These qualities are taken full advantage of in work which would be difficult to handle using conventional underwater concrete. This includes work where high reliability is required, work in flowing water, work where water turbidity is restricted due to environmental considerations, and work where construction stretches over a considerable area and good flatness is necessary. On the other hand, however, handling is more difficult than with ordinary concrete, and in order to produce concrete of the required quality and a structure of the required performance, careful consideration of mix proportion, mixing, transport, and placing, etc. is necessary when antiwashout underwater concrete is used.

In particular, when producing the underwater antiwash concrete it is necessary to mix it for longer than ordinary concrete in a mixer large enough to uniformly disperse the antiwashout admixture. Also, when using concrete pumps for placement, it is necessary to design a pumping plan with care as regards pumping equipment, pumping distance, etc., because the pumping resistance is increased by the higher viscosity.

The Era of Flexible Concrete?

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 Looks like the brittle concrete has been tamed at last!
A team of researchers at the University of Michigan has developed a concrete material that bends like rubber, cracks very little, heals itself with no manual intervention, and is almost as good as new concrete upon recovery, with its stiffness and strength intact.
The research team led by Professor Victor C. Li more here , Professor of Civil and Environmental Engineering
at the University of Michigan, has achieved this by designing the new material with tiny crack widths. This ensures that any damage caused due to overloading and subsequent tensile strain manifests itself as small cracks that are autogenously healed.
Here’s how the self-healing mechanism works. The extra dry cement that is exposed on the surface of the crack reacts with water and carbon dioxide to form calcium carbonate, a strong and resilient compound that brings back the material to its original state. But this works only if the crack width is tiny, a factor that is taken care of by the nature of the material itself. The new material is an improvement over the bendable engineering cement composite (ECC) that Li and his team have been developing for the past decade and a half. The research team discovered that the brittleness of concrete could be altered by limiting the crack width to 150 microns, preferably 50 microns to enable full healing. The average crack width in the ECC was found to be 60 microns, half the width of human hair.
While traditional concrete is brittle and rigid, prone to failure and breakage under strain, the flexible ECC is held together with reinforcing fibers. So while traditional concrete fractures under a tensile strain of 0.1%, experiments revealed that the ECC is able to withstand a tensile strain of up to 5%. That makes it an astounding 500 times more durable than concrete.
The flexible ECC has several obvious advantages over traditional concrete as a construction material.

Stronger Structures
Presently, concrete structures are reinforced with steel reinforcement (aka “rebar”) to minimize concrete cracking, as well as provide tensile strength for bending moments for structural beams and columns. While ECC cannot replace rebar for structural tensile strength, it can reduce the need for rebar to limit concrete cracking. In addition, ECC has the added benefit of self-healing these cracks, thereby reducing the risk of water and de-icing salts penetrating into the structure, causing corrosion of reinforcement steel that might be present.

Decreased Costs
While ECC is three times as expensive as traditional concrete, these costs are outweighed in the long run since the structure would not require extensive repair and maintenance. Li claims that ECC could help do away with repair and rebuilding processes for about an additional five to ten years. It could also eliminate the need to monitor seismic stresses on structures.

Reduced Environmental Impacts
Use of the ECC is also expected to reduce the energy and carbon footprints of infrastructure, thereby reducing the detrimental effects of construction on the natural environment.

Quieter Structures
In 2006, a bridge over Interstate 94 in Michigan was built with a similar self-healing concrete, which was reinforced with toothed metal slats that allowed concrete to expand and contract without bending. However, this structure turned out to be a noisy affair as vehicles rattled over the metal slats. In contrast, ECC is a silent material.

The research certainly bodes well for the construction industry. In addition to the obvious applications in buildings and infrastructure, self-healing concrete could also very well be the solution to potholes and cracks on roads and bridges, and leaky walls. Flexible ECC is also being considered for use in irrigation channels in Montana.
However, the one crucial factor that could put a wrench in the works is that the self-healing process is almost entirely dependent on the availability of water. Under laboratory conditions, ECC was found to require about one to five cycles of wetting and drying in order to self-heal. Extrapolating this finding to large structures such as bridges, it can be concluded that the ability for the material to self-heal is likely to be seasonal in nature. This leads one to question whether the new material would be suitable for commercial use in dry arid lands, and under all climatic conditions. And, would the alternate freeze-thaw cycles during our cold winters, complicated by use of de-icing salts, affect ECC’s material properties? These are some of the questions that should be addressed.
All said and done, should ECC prove to be a success in terms of industrial and commercial use, we are likely to see safer, smarter and more durable structures being erected.

How to Choose the Best Structural Engineering Colleges

Narrowing Down the Selection

For prospective structural engineering students, choosing an institution of higher learning can be a complex task. Many factors come into play, such as the reputation of the college, specialties offered, cost and availability of financial aid, location, career placement, and potential alumni support are just some of those factors. And while there are more than a few top engineering colleges with structural engineering degree programs worth mentioning, the following selection appears to figure fairly prominently in many ratings systems and discussion forums:

Pennsylvania State University

Harrisburg, Pennsylvania, USA.
Diverse B.S., M.Eng., M.S., and Ph.D. degrees with emphasis in several technical disciplines such as: Civil Systems; Construction; Environmental & Water Resources; Geotechnical and Materials Engineering; Structures; and Transportation. One of the most comprehensive engineering programs in the world.
Web sites: Civil And Environmental Engineering-Structural Engineering: http://www.engr.psu.edu/CE/Divisions/structure/structure.htm

University of Illinois at Urbana

601 E. John Street Champaign, IL 61820-5711 USA.
Ranks in the top five U.S. engineering colleges and in the top three engineering programs in the world. Deep, well established programs and research centers.
Web site: Civil And Environmental Engineering-Structural Engineering: http://cee.illinois.edu/StrucEng

Western Michigan University

1903 W Michigan Ave, Kalamazoo MI 49008-5200 USA
Undergraduate degree program designed to prepare for work immediately in many civil engineering careers, including structural and geotechnical engineering. Also offers graduate course work leading to a M.S. degree in Civil Engineering including structural engineering specializations.
Web site: Civil and Construction Engineering: http://www.wmich.edu/cce/about.php

University of California- San Diego

Voigt Drive, La Jolla, CA 92093 USA
UCSD's Structural Engineering Department offers B.S., M.S., and Ph.D. degrees. One of the consistently top-ranked public U.S. universities, diverse engineering and science programs including structural engineering.
Web site: UCSD Structural Engineering Department: http://structures.ucsd.edu/

The University of Sheffield

Sir Frederick Mappin Building, Mappin Street, Sheffield, S1 3JD UK
One of the most active civil engineering programs in the UK. Consistently top-ranked university world wide, diverse civil engineering and science programs including structural engineering.
Web site: Civil and Structural Engineering Department: http://www.euroeducation.net/euro/sheffield_university_stuctural_engineering.htm

University of Toronto

35 St. George Street, Toronto, ON M5S 1A4 CA
One of Canada's largest, top ranked universities, with a well established civil engineering program and structural engineering specialties.
Web site: Department of Civil and Mineral Engineering: http://www.civil.engineering.utoronto.ca/Page13.aspx

Central Michigan University

Mount Pleasant, MI 48859 USA
Good structural engineering programs, notable for the specialized B.S. degree in Vehicle Engineering Design Technology.
Web site: Department of Engineering and Technology: http://www.cmich.edu/Admissions/Academic_Programs/Science_and_Technology/Vehicle_Engineering_Design_Tech.htm

Making The Best Choice

There are no standard formulas to determine which institution suits an individual’s educational needs for pursuing an advanced civil engineering or structural engineering degree. While preferred lists and ranking systems can narrow down some choices, there is no substitute for asking questions, visiting websites, reviewing curriculum offerings, faculty, and staff. If an actual site visit cannot be arranged, the websites of many colleges offer virtual online tours of campus and housing facilities for critical review. Members of alumni associations are also typically available to answer email or telephone inquiries. When making a choice of this nature, it really pays to do the homework!

The Need of Low Cost Software for Structural Engineering Design

       Tedious hand calculations and slide rules for structural engineering design and analysis has given way to a plethora of low cost or even free structural engineering design software. A few example links are listed for convenience.

The Evolution of Structural Engineering Design Software

It wasn’t too long ago that structural engineering design calculations were performed on paper, with support from that ancient device called the slide rule. Static models ruled, and dynamic response models were limited at best. When mainframe computers were commercially available, software programming advances were developed primarily to speed up the computational processes. Electronic calculators arrived and also began to make significant contributions, and the writing was on the wall for the venerable slide rule. Then, in the early 1960’s, a newer modeling process called finite element analysis became encoded into NASTRAN software, and in the mid 1970’s started to become widely available on mainframe computers. This analysis complemented the more traditional static and dynamic models also being incorporated at the time into structural engineering software. Structural engineering students began to obtain access to unprecedented engineering design software, but only at the price of school tuition. Structural engineers could utilize these engineering programs if their employers had the resources to obtain the expensive computers, software, and technical expertise to install and maintain them.
The development of the personal computer drove another round of developmental structural engineering software, and as the pc became more and more capable the software evolved as well. Today, incredibly powerful (compared to the last century) engineering analysis software is available at little or no cost to the user. While not as capable as commercial versions, free structural engineering design software modules can take on formerly unprecedented analysis and design tasks using personal computers no larger than the “ancient” desk top electronic calculators of the 1960’s.

Sources of Low Cost or Free Structural Engineering Design Software

Following are a few of the many freely available programs that can be utilized for structural engineering design and analysis. By no means a comprehensive list, and no claims, representations, warranties, or guarantees for fitness of use are made here; the usual admonitions re viruses, personal information disclosure, etc. when downloading programs from the internet do apply. “Free” may apply for a limited time, or to trial and evaluation versions only:

• http://yakpol.net/ Combination shareware and freeware spreadsheets.
• http://www.seaoc.org/software.html Various freeware download listing maintained by The Structural Engineers Association Of California.
• http://www.grapesoftware.mb.ca/index.html Evaluation copy is free, continued use requires payment.
• http://www.elpla.com/elpla_en/download.htm Trial versions only, geotechnical analysis and design.
• http://www.fabsec.co.uk/free_fbeam.asp Beam analysis, trial versions.
• http://frame3dd.sourceforge.net/ Open source structural analysis software for static and dynamic analysis of 2D and 3D frames and trusses.
• http://www.ecf.utoronto.ca/~bentz/mhome.shtml Reinforced concrete panel analysis.
• http://opensees.berkeley.edu/index.php Software framework for developing applications to simulate the performance of structural and geotechnical systems subjected to earthquakes. Requires registration.
• http://www.lisa-fet.com/index.htm Free trial version, low cost full version finite analysis software.

What is Porous Pavements?

What is Porous Pavements?

Porous pavements, both asphalt and concrete have been around for years.  In most areas they haven’t really caught on.  Now, with the large focus on environmental issues and green building, are they worth looking at again?
Pavement design
Traditional pavement design
Typically when pavement mixes are designed, they include different sizes of aggregate.  They use a wide range from fine sand to coarse stone.  The largest size depends on the expected use of the material.  Then it is all bound together with binder or cement.  With asphalt pavement that top layer will go on a water proof layer then a base.  Concrete pavement may go on a base or directly on the ground.
This results in an impenetrable surface that blocks rain water from getting into ground water systems and increases runoff.
Porous pavement design
Porous pavement or pervious pavement is designed using medium and large sized aggregate without any smaller fines such as sand.  It is then held together using with cement or binder.  The lack of fines in the mix creates relatively large pore space in the pavement.  This large pore space allows water to pass through.
The top layer is placed either directly on the ground or on other porous base layers to allow water to drain completely through the system into the ground.
Pros and Cons
Here are some pros and cons as well as a few notes on them.
Pros
Increased water quality – Oils, heavy metals and other contaminates on the pavements are not carried downstream and into stormwater drainage systems.  Also, water is filtered as it passes through the pavement.
Lower initial construction costs – Construction costs may be lower because porous pavements lower the amount of stormwater drainage facilities that a site will need.  Fewer and smaller inlets, detention ponds and storm drain pipes means lower construction costs.
Lower long term costs – less maintenance needed for storm drain and filtration systems.
Fewer fees – Storm water impact fees may be lower since porous pavements are proven to reduce runoff.
Less runoff – Less runoff means less potential flooding and lower peak flows.
Increased safety – Since water drains through the pavement there is a lower chance of hydroplaning and an increase in traction.
LEED Points – It can indirectly help gain LEED Points.  It can contribute in the areas of Stormwater Design, Heat Island Effect, Water Efficient Landscaping, Recycled Content, and Regional Materials.  There may be other ways that using it can help LEED certification.
Cons
Higher initial construction cost – Yes, I know I listed construction cost as a pro also.  The cost of constructing the pavement itself tends to be higher than regular pavement.
Soil restrictions – The soil below the pavement must drain at least as well as the pavement.
Clogging – The pores in the pavement may clog.  Suppliers and other proponents say that regular cleaning and maintenance will nearly eliminate clogging.
Pavement strength – Porous pavements are structurally weaker than standard pavements.   That generally results in them being used only for low traffic roads and parking lots.  Extra care must be taken when designing a pavement for high traffic or heavy traffic.
New/Untested technology – That’s not entirely accurate.  The technology has been tested since at least 1971.  However, most contractors don’t have experience with it.  Proper training, clear instructions, material testing, and site investigations should be done to ensure that the pavement meets all applicable standards during construction.
Contamination – Pavement surfaces usually have a lot of contaminates on them.  Porous pavements can filter contaminants, but no system is 100%.  Since water drains directly into ground soil it is possible that it will take the contaminants with it.
Conclusions
There is a lot of potential for porous pavements in future projects.  Each project would have to be investigated independently to determine any cost or environmental savings that might be gained by using porous pavements.  However, the potential positives do seem to outweigh the potential negatives.  It would certainly be worth your time to investigate it and present your findings to your client.
What are your thoughts on Porous and Pervious Pavements?

Tips on Interviewing

Tips on Interviewing

Whether you are interviewing for a full time job or an internship the basics are the same.  Here’s a few notes, tips and things to keep in mind for interviews.
BEFORE THE INTERVIEW
Everybody Has The Internet
Clear off anything that you posted on the internet that you wouldn’t want the interviewer to see.  Many companies regularly do a Google search before an interview.
Dress The Way The Boss Would
Guys, you should wear a suit and tie.  If it’s a hot environment or in the summer you can probably get away without a coat, but wear the tie.  Ladies, dress equivalently.  The civil engineering world is fairly conservative.  Dress professionally and at least one level higher than you think the job would generally require.
Prepare Answers for Questions
I’m planning an entire post on interview questions.  But have answers to typical questions ready.  Know a few strengths, at least one weakness, some goals, how you’ve handled difficult work situations in the past, etc.
DURING THE INTERVIEW
Qualifications
The interviewer knows that you are probably qualified or they wouldn’t take the time to interview you.  So during the interview, when they ask you about your qualifications, give them examples of specific things you have done in the past.
The Interview is Not About You.  It’s About How You Can Help the Company.
The interviewer wants to find out how you can help them.  The questions they ask will be geared toward this.  Tell them about your accomplishments and how you can use your accomplishments and skills to help them.
Part Of It Is A Personality Test
Whether or not they give you a written test interviewers will try to find out if you will fit in with the team.  The civil engineering field is very team oriented.  Engineers aren’t stereotypically know for there interpersonal skills.  Being able to work well with people is very important.  That is true for your coworkers as well as internal and external clients.
Ask When You’ll Here From Them
When the interview is winding down ask when you can expect to hear from them or when you should call them.  This will set your expectation.  Some places will take months to get back to you.  Some, just a few days.
Don’t Lie
Just like on your resume, don’t lie.  Tell the truth.  If you don’t know the answer then say so.  If the answers looks negative on you, then say what you’ve learned from the experience.
AFTER THE INTERVIEW
Say Thank You
Send a thank you note, or call the interviewer and thank them.   Not a text message or email.  Write the note by hand, or call them.  As old as this advice is it is amazing how few people do this and how effective it is.
Follow Up
If you say you’ll follow up with them at a certain time, then do it.
That’s a few key points.  What are some that you’ve run into that others should know?

Certifications and Licenses (LEED AP)

Certifications and Licenses (LEED AP)


LEED AP

What it is – LEED AP stands for Leadership in Energy and Environmental Design Accredited Professional. Basically, having the LEED AP credential shows that you have specific knowledge and experience using environmentally friendly designs, processes, etcetera.

Who governs it – The LEEP AP is run by the Green Building Certification Institute (GBCI).

Requirements – Professional experience working on a LEED project
- Pass the LEED AP exams

Who needs it – Anyone working in the construction industry from design all the way through maintenance. Especially if you are working in an area with a very strong environmental focus or environmental needs.

Why you should get it – The environment is a hot topic right now. Having the experience and knowledge to work on environmentally friendly projects is an asset. The LEED AP credential shows that you have both the experience and knowledge to build environmentally friendly constructions.

Why you should not get it – Like most certifications there is no real negative to having LEED AP. However, the credential is focused mainly on building design, construction and maintenance. Outside of buildings there isn’t the same demand for LEED AP. That is changing, though.

When you should get it – Once you start working on LEED projects you are eligible. If you plan on staying in the industry it adds one more proof of qualification to put on the resume.

Other notes – GBCI is in the process of changing from a general LEED AP credential to LEED AP with a specialization. Check out their website for more information on the new specializations.