29 September 2009

Solving the Slump

We are fortunate to have International Geotechnical Laboratories (Aka Michael Karantinidis, PE) on our side when it comes to quality assurance/ quality control. Concrete is typically tested on the day it's poured and there are two site tests and one laboratory test.

Some of the tools of the trade.

Chris conducts the slump test. Concrete is poured into a cone shaped metal shell (12" in height)and slowly lifted to measure the slump of the concrete. The concrete is poured in a numerical value and we typically ask for a 4" - 5" slump. Anything more than a 5" slump is referred to as soup. The more water, the more diluted the concrete mix. More water = more microscopic cavities = potential cracks.

Concrete is placed (In three layers) in plastic cylinders and left to cure (In a curing box) for two days at the site. Then it's transported to the testing lab where on the 7th day, it will go through a compression test and loads (Close to the 4000 psi) will compress it. If concrete is compressed on the 7th day, you want to have a result where it fails (Cracks) at 2,800 psi. On the 28th, you're aiming for the ideal and designed amount (4,000 psi in our case).

Also, another site test involves weighing the concrete, taking it's temperature and testing the amount of water for every cubic foot.

Time Cures All Ills and Concrete

Curing, in Construction vernacular, is when concrete transforms from the liquid state to a solid state (7 days = 70% strength and 28 days = 100% strength). We began prepping for the next phase (Foundation walls) the day after we poured the footing. Although the concrete had not completely cured, the surface was solid enough that one or two can walk on. Remember, concrete is an excellent material under compression. The guys tied the vertical and horizontal rebar grid (Spacing 12" x 12"), placed the bond breaker barrier (So out foundation wall doesn't attach itself to the neighbors) and then...

erected the form work. The form is the layer (Made out of plywood and steel angles) that one creates the negative space, and where the concrete will be pumped into to create the positive space. Notice how the forms are braced so the weight of the concrete does not blow them out (Diagonal wood members and horizontal 2" x 4" members along the form edge).

The guys are relaxing before the storm, aka the 12 yard concrete truck (12 yards = 11 actual yards because there is hard shell of concrete inside the drum). Notice more diagonal bracing and a platform where the guys can manage the pumps hose (The hose is in sections and lying on top of the form, clamped at every section). As the concrete is pumped to the farthest distance, a section of pumps hose is removed (And cleaned) and concrete is pumped to a closer section of the form.

Concrete goes into the pump..

and out of the hose and into the form. In this image, Jose is standing on the hose pump while Cigaro and Lucio are vibrating the concrete mix. The concrete vibrator is used to make sure that the concrete surrounds itself around the rebar and prevents honeycombing (Small pockets of cavities).

21 September 2009

Somethings Afoot(ing)

Ok, so the foot metaphor is corny, but it could've been worse. The parging of the neighbors lower building foundation was complete and now the bond breaker is ready for install.

It didn't take too long for ReBar Construction (Our foundation subcontractor) to produce a section of 103's form work and lay the rebar (Steel reinforcing bars). A footing, for those not familiar to the term, is a part of the foundation wall. It's the lowest point of the building where all the building loads (Building walls, floors, furniture and people) funnel their way down and spread into the undisturbed (And compact) soil. In this image, the rebars are tied into a grid (12" x 12") and lifted about 1/3 of the footings depth (18").

There was very little time to waste, because as soon as the guys completed the form work and rebar placement, six cubic yards of 4000 psi concrete was delivered. The concrete was dumped into the excavators bucket and ...

lowered below and poured into the form work. Notice how the concrete gets under and over the rebar grid. FYI, concrete (Without reinforcement) is excellent under compression, but reinforced concrete is great in compression and tension.

Finally the vertical rebars were placed and vibrated into the footing. These two layers of vertical rods will be tied with longer vertical rebars (And horizontal) that will be encapsulated by the buildings concrete foundation wall. They will eventually rise and meet the buildings masonry walls. Tomorrow we parge the neighbors upper masonry wall and prepare (Remove dirt and debris) the site for more footing and foundation work.

17 September 2009

Sigh of Relief

Our Engineer Harry Melos stopped by to inspect the neighbors foundation (With my foundation sub - Kim) and it turns out their buildings footing is as low as where our footing will be. Although the neighboring buildings cellar is 6' -8" below grade (And 1'-6" above grade), the foundation wall continues well below the slab grade and rests on a footing that is 4'-6' lower.

14 September 2009

Let the Probing Begin

When we dug out our first section this morning, it appeared that the masonry foundation was a composite (Masonry and stone) at different elevations below grade. Stone foundations are typically unpredictable and a concern.

So with a few primative hand tools, we removed a few of the loose stone, only to...

Uncover another layer of masonry. This discovery was analogous to a treasure trove. What seemed like a long and arduous process is now standard protocol.

09 September 2009


Today we are continuing securing the sidewalk, so we can work on the foundation.
This image shows the sidewalk in front of our site.

This image show the work happening behind the blue fence. The excavator is removing dirt so that the lagging can be installed.

The steel was anchored into the earth yesterday and today the lagging (wood) is placed between the vertical steel members, and then backfilled with the dirt.

08 September 2009

shoring up the sidewalk

Today the steel was errected to shore the sidewalk. Since our building does not have a front yard or setback, the foundation contractor needed to keep the sidewalk in its place, while we get ready to dig further and work on the foundations. The steel was placed 25'-35' deep.

04 September 2009

four feet

Thursday they started removing the top 4' of dirt. It is starting to really look like a construction site!

01 September 2009

Kyrie Eleison

We are thankful for Father John, of The Cathedral of St. Constantine and Helen, for stopping by this morning to bless our site(s). It is common in the Greek Orthodox tradition/ faith to bless a site prior/ during development, as is the blessing of a home.
After clearing my throat, I served as the cantor (Although Father John may not agree), during this ceremony, and lead the choir.