Power Float

**Power Float**

Although this picture is incredibly clustered with material, the power float in the picture was being used in a different area where the slab had just been recently poured. A power float is a machine that finishes concrete. The machine essentially has 3 or 4 trowels that spin around to smooth the concrete. As a result, a power float drastically speeds up the time to finish concrete. When using a power float, you want to make sure that the concrete has hardened enough to walk on. Bringing a heavy machine on concrete that is still wet would be disastrous.

To finish concrete, there are a few steps that take place. First, the concrete needs to be poured. Once poured inside your form, take a screed to level the concrete. This is called striking the concrete because of the "striking" motion one makes when pulling up the concrete and then leveling it with the 2x4.

Next, you use a hand float or a bull float(larger float on a pole so you can push longer distances). This is a "rough grade" for the concrete to become level. As you do this, water will come up because the mix is settling and the more dense mix is going to the bottom. **before you start finishing any concrete, you want to make sure to use a vibrator to "mix up" the concrete. The aggregate in the mix will tend to settle towards the bottom, thus, not creating an evenly distributed mix. The concrete will not be as strong as the specs called for as a result of the aggregate settling to the bottom.

**Bull Float**

Once you have bull floated the concrete, use the power float to finish the concrete. This is the "fine grade" on your slab. This makes the concrete especially smooth, taking out all the bumps and extrusions of the concrete. The opening picture for this blog post is a power float. Power floats come in 3 different types that I know of. 1)walk behind 2)ride-on 3)remote control. The pictures below are of each one, respectively. Once you are done with your finish float, the concrete is ready to go!

Remote control trowel taken from - http://famrichard.us/id16.html

Ride on power trowel photo taken from - http://cm.baumpub.com/news/507/multiquip-provides-versatile-ride-on-trowel

Bull float photo from - http://www.saltcreek.menard.k12.il.us/courtside_at_the_creek.htm

K- Joists

This engineered steel K-joist will eventually support a metal roofing deck. Most K-joists that you see are level and straight. Below is an example of what typical k-joists look like.

These joists, in the first photo, happen to be curved to fit the shape of the roof. K-joists in general are engineered, and can support heavy loads. They take the place of a stick built wood joist system.

The joists also have other applications other than just support. If you notice, they have a distinct shape within the two main beams, a triangle. This is so that conduit and other material can be run through the beams in the ceilings.

These joists do not necessarily just come in one shape. Engineered joists come in all shapes and sizes. Some of joists have places to set HVAC units, ducts, water supply/returns, and any other material that would need to be run in the ceiling area. Below is an example of HVAC ducts run within the joists. I apologize for the blurriness.

A detail of a K joist looks as such. The top and bottom beam of the joists are called the chord, and the middle area is called the web. - where the triangles take place. This photo is from class lectures.

It is also important to know how the joist is connect to the wall. In this case, the weight of the joist bears on a steel plate that sits on top of the bond beam, which is the top course of CMU that is filled with grout to strengthen it. The photo below shows the attachment of joist to wall.

Mastic Duct Sealant

Above is an HVAC duct. The day I visited the day site the HVAC subs were behind and had to stay late because the ducts were not sealed yet. The mastic duct sealant helps to provide a stoppage against leaking in the ductwork, it is NOT to hold the ductwork together. That needs to be done with hangers, bolts, and screws.

The mastic sealant is a flexible sealant that takes the shape of the material which you are applying it to. According the the Green Building Library, most of the energy loss in a house comes from your HVAC ducts. The loss can equate to 20 to 60% of the air leakage in a home. So ensuring that your home or office properly sealed is very important to reduce your heating and cooling bills. Also, the mastic sealant is being used in commercial work, but is making its way into residential applications as well.

The sealant actually never hardens, so it can withstand the expansion and contraction of materials. The material also acts as a barrier to moisture.

There are other ways to seal ductwork as well. Tape, such as a mesh tape. The tape is similar to drywall tape but is has a different width and is also reinforced with fiberglass. In order to make the best seal on ductwork, use both the tape and mastic sealant. This will ensure a tight seal.

Areas which should be sealed are: around the air-handler, transition or different connections, where a solid connection meets a flexible connection- there is obvious movement from a flexible to a rigid connection, and in building cavities.

For more information on mastic and mesh tape sealants for HVAC usage, visithttp://oikos.com/library/ducts/index.html

More photo's below of different sealant areas.

Control Joints

Control joints are important when dealing with concrete. Throughout the year, concrete will swell and contract depending on temperature. When the weather warms, concrete tends to expand; when the weather cools, concrete tends to contract. Control joints help to keep the concrete from cracking in areas where you don't want cracking.

In order to keep the cracking contained, a joint must be run through the concrete before it dries. Below is a picture of someone "rolling" a control joint in the wet concrete. The second photo is someone using a saw to cut the joint out. Both are acceptable ways of producing the joint.

Marking the line to roll is important. You want to keep the line as straight as possible so that when the concrete dries, it conforms to code. You also want something that looks asthetically pleasing. If your joint was not uniform, it would not serve its purpose for containing the break in the concrete, because as some point or another, concrete will crack.

This photo does a good job at visually explaining the importance of a control joint. If you notice, the crack is not wide, and it follows alongside the control joint. If the joint was not there, the crack could have gone any which way, and caused an eye-sore on the slab. It is important that you do not try to alleviate or stop cracks, but you want to make sure that the crack is controlled.

The last three photos are taken from these websites respectively:

1)https://fp.auburn.edu/heinmic/PerviousConcrete/images/JointCut.jpg

2)http://www.shutterstock.com/pic-19734637/stock-photo-man-cutting-control-groove-in-concrete-slab.html

3)https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhdm0axTCrDYyYpknx0oNKSYioCA9GVWeIZGWD-bO7RL5mvqDEg46lZWTI8KkhvyAUFdNVThTyySm0A6ZdU9CxICqU4bIy3PziIa0L8NMb0CZVUhhyphenhyphenoryoTaLWBcLRfFkMdxjJyoMaLtK0/s1600/2010-06-30+09+53+41.jpg

Lintels

This pre-cast lintel, shown in brown, is a structural support member used to distribute load coming from above. In this case, a stained glass window will be put above the lintel in the half-round area. Lintels distribute the load from above around the opening.

Because we are dealing with CMU, arching action is one property that can be found within these units. I would assume there is a purpose of the half round above the window in dealing with the load above. If you roughly draw a line from each end of the lintel, to the top of the half-round window, it roughly makes a 45 degree angle. The half-round would act as the 45 degrees necessary to spread the load out over the lintel. Arching action allows walls to carry and deflect more load than if AA didn't take place. Below is a digram to help further illustrate the role of arching action. The slides are taken from class lectures.

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Buffing CMU

A man above is buffing CMU walls to get the coarse feeling off of the block. This is taken in one of the classrooms. The reason the block is being smoothed out is because it will be painted at a later date. Not only does the block need to be smooth for paint, but also for children who are using the rooms. It would be easy for a child to run along the wall and cut up his or her hands on the block.

Notice the man has all his PP&E on. It is important for whoever is operating the buffer to wear a mask and a face shield. Chips from the CMU could fly up and potentially damage your eyesight. Also, small dust particles fill the surrounding area, and it is important that you don't breathe the toxic particles in.

Temporary Bracing

The orange steel tube is connected at both the slab and the masonry wall. This temporary bracing provides support for the wall until completion as well as ensuring the the wall remains plumb. When the wall is at a hight okay for the bracing to be put up, typically specified on the specs, bracing will be inserted into the mortar and also on the slab. The bracing on the mortar fits around a block, as noted in the picture below.

From there, the rod is attached to the wall bracing with a bolt and pin. The bracing has different holes where the bolt can go in depending on the height of the wall. This gives flexibility if you have to bolt the rod on the slab closer or further away from the wall because of conduit or other material coming out from the slab. Next the rod is attached to the slab in a similar fashion to the wall.

Although this picture doesn't show it, normally the rod allows you adjust its length so that you can get the wall plum. This allows one to fine-tune the rods length so that the wall is as close to plum as possible. It is so important that the adjustments are made because you are dealing with small units of measurement to correct a walls level. Again, the rod is attached to the ground with a bolt and pin. The bracing is held firm in place by a bolt that was shot into the concrete and then screwed tight to ensure it won't move.