Concrete Forms

These men are taking down forming for a site-cast concrete wall. What you see happening is the man in the neon green safety vest hammering out pins within the metal clamps. These pins and clamps keep the wood form from coming apart. In between the horizontal 2x4 members, is a rebar tie that helps to strengthen the concrete after poured. The ties put somewhat of a camber in the wall so that when the rest of the load is built on top of the CC wall, it will settle level.

Also, the pieces of lumber that are coming off the wall at a 45 degree angle are support members to keep the wall plumb. Plumb is level but vertically. They also are used to support the wall when the concrete is poured in the form. If the forms weren't properly supported, then the forms could potentially break and concrete would go everywhere and cleanup would be a mess.

Waterproofing

This photo was taken from my commercial site during the beginning phase of the school. The black material that has been sprayed on the CMU is waterproofing. Waterproofing can either be sprayed or rolled on; it just depends on the limitations around the site.

This waterproofing application actually is not a good job. You can see towards the upper right hand corner of the picture that there are voids within the WP coat. This can cause water to get into the concrete and if exposure is prolonged, then the integrity of the concrete can be jeopardized. Also, the FD wall is not necessarily smooth. The WP coat will again have a hard time of sealing the area due to the inconsistency of where it was applied.

-- So make sure that your surface area is 1)clean 2)smooth 3) ready for the WP coat to be applied. This will make sure that your WP will hold up to its intended use.

New Way to Fix Concrete Cracks?

I ran across this article today...http://www.msnbc.msn.com/id/40201539/ns/technology_and_science-green_innovation/ It states that a certain bacteria can "fix" concrete cracks by emitting a glue like substance. Apparently, the bacteria has been trained to "swim" down concrete cracks in buildings. Once the bacteria has reached the bottom of the crack, it emits calcium carbonate and some sort of bacterial glue. The bacteria is found in soil particles and has been nicknamed "bacteriafacillia."

The researchers have found that this new method of healing concrete cracks is really useful in earthquake prone zones where there is no other alternative to fix buildings with too many cracks in the concrete.

The bacteria will only emit the glue like substance when it comes in contact with concrete. When the bacteria has reached the end of the crack, it releases three types of substances.

"This clumping activates the concrete repair process and the cells differentiate into three types: cells which produce calcium carbonate crystals, cells which become filamentous —acting as reinforcing fibers — and thirdly cells that produce a glue that acts as a binding agent and fills the gap."

What are your thoughts on the this chemical bacteria? If it does seem to work, this agent could help all types of building structures. Prolonging the life of concrete will help many buildings last long and therefor avoid being torn down. It would also alleviate costly demolition expenses. It seems like a win/win situation - - if it works!

Metwood Truss and Garage

The photo above shows a boom operator hoisting a metwood truss into place on a concrete basement wall. The truss is held by a high strength rope that can hold heavy objects. The truss was picked up from the delivery truck and then moved to the slab. Laborers were in the basement with a 2x4 to help steady the truss to set it into place.

Once the truss is set, W-pans are set on top of the trusses to pour the concrete on. The pans over various depths so that the the concrete will be structurally sound throughout. The pans are shaped so that they can tie into each other on each end. The right side will clamp into the left so that the pans will act as one unit.

Rigid Vs. Moment

On this exterior frame, the horizontal I beams are connected with bolts to a flange in the metal column. The difference between a rigid and moment connection is a bolt to weld connection, respectively. A rigid connection is made so that movement is allowed. The bolt from the beam to column allows for rotation of the beam when the building moves. A moment connection welds part of the beam to the column so that there isn't any movement. The contractor will "call out" why type of connections are to be made on the plans for each connection.

This is another photo, although harder to tell, of a rigid connection. This I-beam is used as a header over a door opening. A hole is drilled through the flange on beam, and a bolt is inserted through into the CMU. A washer and nut are then used to lock the beam into place.

If you notice, the beam doesn't sit flush with the CMU wall. This is because there needs to be a gap so that when there is movement(in most cases it is dealing with the heating and cooling of materials which causes expanding and contracting). If the beam were to sit flush with the CMU, it would put pressure on the interrior wall when the beam expanded in hotter temperatures. This could cause damage, most likely cracking, with the interrior wall.

Wall to Contrete

Have you ever wondered how you tie a wall into concrete? The wall cannot just sit on top of the concrete, it has to somehow be nailed into the concrete. How does this process happen? Hammering a nail into the concrete will end up going no where, and you can't screw in the nail; the concrete is too hard.

In order to nail a wall system into the concrete you can use a ramset(looks like a dewalt pistol) that fires a .22 caliber bullet into a nail which gives the nail enough power to drive through the concrete. I was able to experience this process this past weekend. We were putting up a cage that would hold propane tanks into an already existing old brick wall. Although this method didn't work, due to the inconsistency with the brick in the wall, it was awesome watching the process. Below is a photo of what a ramset looks like, as well as the nails that it uses.

You can use ramsets on wood and metal framing. Thus, this method works on both residential and commercial projects.

Ramset photos were taken form left to right- 1) http://www.nextag.com/RAMSET-ITW-Ramset-2-510293463/prices-html

2)http://www.getprice.com.au/Ramset-Powder-Actuated-Fastener-JOB-MASTER-GAS-Gun-Gpnc_503--46910865.htm

Pouring a Slab

This is a close up photo of a recently poured slab for a garage on our residential site. In order for your slab to be correctly constructed, a few proper steps must take place. The earth which you are pouring your slab should be tamped, or compacted, so that your sand and gravel bed has a flat surface to sit on. Next, gravel is brought on site and leveled out in the area that the concrete will be poured. The gravel is normally 4" thick. After the gravel has been spread out, a moisture retardant is laid on top. The moisture retardant keeps water from the soil coming up into the slab. If moisture has prolonged exposure to the concrete, it can cause serious problems with the integrity of your slab.

This photo shows the gravel bed, moisture barrier(in yellow) and wire mesh(rebar) in preparation for a slab pour. Once all the components have been properly put into place, a chalk line is used to mark the height of where the concrete is to be poured. In this photo, the chalk line is just above the waterproofed lumber. You can see the chalk line the best in-between the two CMU blocks.

If a slab is being poured where an opening is, such as a garage, there needs to be a mechanism set up so that the concrete doesn't leave the area that it is supposed to. Every time I have seen this done, a piece of lumber is screwed into a metal form. The lumber acts as a barrier to keep the concrete from flowing out of the intended area. On the back of the form, there is a place where you can drive a stake into the ground in order to hold the form in place. Below is a photo that better explains what the form looks like.