How Sidewalks Could Become the Future of Power Generation

        So it's been quite awhile since I've posted here but I thought this article would be a great one to post.  Today on CNN.com's technology section I came across an article entitled "Green Sidewalk Makes Electricity - One Step at a Time".  These small tile slabs which create electricity will be installed at a mall near the 2012 Olympic Games Site in London.
        A 25 year old English engineer invented the recycled paving slabs called "PaveGen".  These small green slabs convert kinetic energy from people walking over them into electricity.  The slabs are designed to compress five millimeters when stepped on creating electricity which can be stored for up to three days.  One step produces enough energy to power a single LED for 30 seconds.  This may not sound like a lot but with hundreds  to thousands of compressions per day, this electricity could add up.
        I see this invention as likely being very costly at this point in time but as the technology is improved upon and becomes cheaper, the sky is the limit for these paving slabs.  They are 100% green and likely just as nearly efficient.  Imagine large slabs being installed on highways where hundreds of cars pass per hour.

10 Year Look Ahead at the Construction Industry

          Over the past two semesters as part of the BC 2014 & 2024 courses, I have been visiting multiple construction sites and making observations about the construction practices being employed on these sites.  I have then posted back on these observations here on this blog.  There are many new things I have learned by visiting these sites and in turn I have received a good idea about the direction the construction industry is heading in over the next decade.

          At the beginning of the semester as part of our first assignment we were asked to make a prediction of what changes would occur in the construction industry and then apply these predictions to our site observations. Over the past fourteen weeks I have come to the conclusion that my prediction of the construction industry heading in a technologically advanced direction, was correct.  Technology has allowed us to become more green and sustainable, saving time and labor in areas that otherwise causing inefficiencies.

          On just about every site I visited I noticed workers and contractors holding cameras and taking pictures of the work being done.  This observation fell under my prediction that in the near future, all work done on sites would be digitally documented in order to keep accurate records of what work was performed and how it was performed.  Although structural drawings may show one thing, contractors may not always perform the work exactly how it is drawn.  It is not rare for contractors to make small changes to plans if they happen to run into problems.  By taking pictures of the site and making digital reports, these reports can then be referenced in the future if need be.  This leads me to believe that it is very possible that in ten years, tablet PC's can be used to fully document the work which is performed on job sites and allow for up to date changes to be made to drawings directly from the job site.

          To prove that the industry is heading in the sustainable direction, I took a look at some of the Virginia Tech construction sites.  I noticed that by using precast concrete panels on many of these sites, the contractor was able to reduce the amount of Hokie Stone used; which requires a lot of labor to install; and at the same time provide quality work.  Precast panels also ensure that the components were made to the best quality possible.  Off site manufactured components are made in factories where concrete can be mixed and poured in controlled environment's increasing the quality of the concrete and overall craftsman ship.  Problems with concrete often arise when it is either too humid, cold/hot, or if it is raining out.  Precast and modular units used in construction will also allow buildings to be erected quicker because less on site labor will be involved meaning labor costs and overalls of the project will go down.  Just one precast panel, used on the Undergraduate Admissions and Visitors Building, can be installed in just under 20 minutes and provide a large square footage of exterior veneer to a structure.

          In the future, as the economy beings to rebound and construction beings to pick up, resources such as alloys and plastics will begin to become scarce.  With this scarcity in resources, it will become important for the materials being used in construction to be of partially recycled materials.  By using recycled materials, the cost of products will remain low.  Energy sources will also begin to become scarce, and for this reason it will be important to create more energy efficient buildings.  This can be done by using more energy efficient construction methods, such as precast and modular units, as well as better insulated structures.

          Over the course of the semester there has been one overlying theme that I could not avoid mentioning.  I have noticed a theme of preventing water infiltration into structures.  There are few things which can deteriorate a structure quicker than water.  Water helps mold to grow, weaken wood, and cause metal to rust.  To help us understand the problems associated with water infiltration, every lecture in class seemed in some way to incorporate some way to prevent water infiltration which in my opinion was very important.  The importance of flashing and weep holes when using veneer walls is one method I have noticed being employed on the sites around the Virginia Tech campus because the buildings all have the Hokie Stone veneer.  I also found the spray on tar, and plastic and vinyl sheathing used on the foundation walls of the bank to be a great way to prevent water infiltration.

           The past two semesters have given me great insight into how the construction industry works and the direction it is heading in.  By visiting real construction sites in person and not just reading a text book, I have learned a lot and received great insight into the technological and sustainable direction the construction industry is heading in.

Commercial Site Visit: Undergraduate Admissions and Visitors Center Building Observations

          I took a walk around the Undergraduate Admissions Building job site and wanted to take some detailed notes on some of the materials and methods used to erect the exterior walls of the building.  The first place I started at was the mock-up sectional wall next to the site trailer.  This wall is required by the university on all new buildings constructed in order to get certain building certifications and show that the structures are up to code.
          The Undergraduate Admissions Building is a steel framed structure using 6" studs and top and bottom tracks.  The studs are screwed together with sheet metal screws.

Here shown is a double stud wall which is enclosing a stairwell.

Because stairwells must be fire rated for a certain time, a double stud wall is being constructed with a 6" gap between them for extra sheathing and a space for conduit to be run.  This double wall will act as a fire wall.

          Over the studs a sheathing of 5/8" Extended Exposure GWB was placed and covered with stucco.  This was later followed by two 1 1/2" layers of foam core for insulation and then a plastic corrugated material to allow water trapped behind the Hokie Stone veneer to drain.  Finally the Hokie stone veneer was placed as the exterior faciad.

          It is imporant to note that the veneer provided no structural support for the structure, however it is tied back into the structure at certain intervals.  This allows for the Hokie Stone to move as needed and be self supporting.

This a a cut view of the exterior wall as described above.

Betweeen the GWB and Foam Core layers it is imporant to place flashing to prevent water from running all the way down behind the wall.  The flashing is usually placed at each floor and is held to the foam core using a caulking material (the yellowish material) as seen in the photo.

Commercial Site Visit: Signs of A Poor Concrete Pour

          When pouring concrete it is very important to vibrate the mix as it is poured into the forms to release air pockets and force the concrete to completely settle.  At the bank being constructed close to my home in NJ, I noticed a few areas around the foundation wall were the concrete had not been properly and cracks had already started to develop after only a week.  The first spot was where the brick ledge cut out was near one of the column step downs.

Photo of poorly vibrated concrete.  Lower ledge is a brick ledge for a brick facia to be placed on.

This photo shows a comparison between properly and improperly vibrated concrete.

As you can see the concrete under the baseplate is not level at all.

         This concrete is a large liability because over time there is a good chance this concrete could fail due to freezing and thawing of any water which is able to work its way into this crack.  This crack in the concrete was formed by air bubbles in the concrete mix before it cured.  It is a possibility that this foundation wall could fail inspection because of this crack in the concrete.  This area would be very hard to patch as well because fresh concrete cannon be used to patch this area because it will not adhere properly and the section cannot be replaced because the foundation has to be continuous in order to maintain strength.

          The concrete under the base plate does not need to be perfectly level because the area will be filled with grout after the baseplate's are leveled.

Commercial Site Visit - Bank Site: Structural Columns and Steel Base Plates

          After applying the spray on tar and vinyl sheathing to the foundation wall and backfilling the site over the past few days, it came time to level the base plates.  As I mentioned in one of my earlier posts, the steel baseplates being used on this job are 1'-4" and 1'-2" sized plates with 10" anchor bolts with a 4" thread embedded into the concrete foundation wall.  The large 4" threaded area of the anchor bolt allows for the baseplates to be adjusted easily to ensure that they are perfectly level.  Back about two weeks ago when the concrete was first poured, the baseplates were not level.  Instead they were simply attached to the four anchor bolts and left unleveled until the concrete had cured and the anchor bolts had set into the concrete properly.

Shows baseplate after forms were removed.  Plate has not been leveled.

         Now that the concrete has had a substantial amount of time to cure, it came time to level the baseplate's and seal them.  The baseplates are leveled by adjusting the nuts along the threaded anchor bolts.  You may look at the baseplate above and say to yourself, "Won't there be a gap underneath the plate, meaning that an entire column is resting on only four bolts?" and the answer to this question is no.  After the baseplate has been properly leveled using the bolts, the gap under the plate is then sealed with grout.

Photo of leveled baseplate with a small gap underneath.

Baseplate which has been leveled and sealed with grout.

          I did some research about the grout used when sealing a baseplate and realized one very important thing about the grout used, as water evaporates out of concrete or grout, the concrete/grout will shrink.  For this reason it is important to use a non-shrink grout.

Commercial Site Visit - Bank: Foundation Backfill

          I have been curious about the progress being made on the bank being built near my home back in New Jersey since I came back to school after Thanksgiving Break so I asked my father if he would mind stopping by the site to take some photos for me yesterday.  I must say he did a great job getting some very good photos of the site.
          Over the past week a spray on tar water proofing has been applied to the foundation wall.  This spray on tar will keep water from seeping into the concrete and through any cracks that develop over time.

(Click on photo to see larger view)

Above you can see the sprayed on tar with a vinyl and plastic covering over.

          The vinyl covering which is applied over the sprayed on tar water proofing is corrugated.  This 

sheathing allows for water which is trapped against the building to flow away from the foundation.  This is a material I have never seen before but it looks like it works very well.
          Waterproofing the foundation is extremely important because there are few things that can ruin a structure quicker than water.  If the concrete foundation is exposed to water for to long cracks can develop from the freezing and thawing of ice.  As water trapped against the concrete seeps into the small pores and beings to freeze, extreme amounts of pressure are put on the surrounding concrete causing cracks.  This is the same reason potholes often form in roadways.

Above is a section of the vinyl and plastic sheathing.  The corrugated plastic

provides channels for the water to drain.

           Once the hole foundation was waterproofed the site was backfilled and bracing was place on the interior of the foundation wall in order to provide support as the concrete is still not to full strength and the weight of the dirt could cause a collapse.

Picture of backfill and bracing.

Commercial Site Visit: Form Removal

         This afternoon; Friday 12/3/10; I returned to the dining hall construction site to see if the forms had been removed from the curing concrete and sure enough they had been and a new set of forms had been constructed. The concrete had been poured into the last forms on Wednesday, 11/1/10.  The concrete was given 48 hours to cure before the forms were removed.  As these forms were removed, a new set of forms were erected in order to start a new segment of the wall.

This is a photo taken before the forms were removed.

Here is a photo after the forms had been removed.  As you can see plywood

has been used to brace the corner of the walls to provide support as the new forms

are put up and the weight of the concrete is added to the new forms.

          It is important to brace the corner of the wall because as the weight of the concrete is added to the right wall, the pressure will increase on the left wall.  Because the fresh concrete is still curing it is not at full strength, and the added pressure could cause a failure.

           I also have noticed that there is a darker color to the fresh concrete which could be because it is not fully cure and the water is still evaporating out to the surface.

          Once again as you can see, a tarp has been draped over the top of the plywood forms to protect them from any rain which could delay a concrete pour.