KEC Hurricane Irene

An unexpected visitor, Tropical Storm Irene, made its way through the project site this past weekend.  The storm dropped a lot of rain and heavy wind, brought down many trees, and knocked out power to half of Connecticut as well as much more damage from North Carolina to Vermont.  The site weathered the storm amazingly well due to careful preparation.  Materials were secured and stored.

stormwater detention was modified to accommodate additional capacity

existing structures were braced and reinforced

The timber frame erection was rescheduled to start after the storm so as to not take any chances.  The storm hit between Saturday night and Sunday.  The site did not lose power.  Amazingly the large slab on grade pour scheduled for Monday morning was unaffected.

A few trees and limbs came down around the site but that was the extent of the damage.

  Many subcontractor offices were closed for several days due to power outages which has slowed some of the paperwork traffic and even some of the fabrication process.  For example, the steel shop in Hartford lost power and was not able to finish fabricating our steel as planned.  The timber frame installers are from Vermont and their home town was cut off by flooded rivers and washed out roads so they could not make it back to the site until late on Tuesday.  However, the overall impact was minimized due to good team preparedness.

KEC Polished Concrete Floors

This project has a polished concrete slab as the floor finish in many of the rooms including the classrooms and hallways.  Since the polished concrete slab is the finished flooring, it can not be patched later so it is very more important to make sure the work is fully coordinated prior to placing the slabs.  It is also important to pre-plan the slab pour with the structural engineer and the concrete subcontractors along with the subcontractors that have work installed below the slab.  When concrete cures it is subject to many many variables and therefore no two concrete pours are quite the same.  Concrete is also subject to cracking due to many many variables.  While it is impossible to prevent slab cracks, there are lots of ways to minimize and control cracks.  Polished concrete floors look really great when they are done right, but even the best slabs will crack, that is a nature of the product and part of the look.

Polished concrete floors are a sustainable floor option for the following reasons:

1. A concrete slab is a required element for almost all construction projects and polishing the slab as the finished floor does not require the harvest, manufacture, and transport of additional materials such as wood flooring, carpet, or vinyl tiles. 
2. There is no finished flooring like carpet, wood, or vinyl on the slab that will need to be replaced in 5 to 10 years.  So you are avoiding the manufacturing and transportation of the new material and removal to a landfill of the existing material.
3. The polished slab is a smooth hard surface that does not trap dust or allergens like a carpet can so a polished concrete floor provides less opportunities for these indoor air quality issues to build up.
4. The reflective nature of polished concrete can assist with added ambient lighting which can reduce the amount of artificial illumination needed. This will help to maximize the natural and artificial lighting and imrpove energy efficiency.
5. Use of passive solar design benefits from exposed concrete slabs which help retain the internal temperature of the building. Using thermal mass as a design element will moderate the daily temperature fluctuations, and reduce the load on HVAC systems.
6. The mix design for this slab on grade includes Ground Granulated Blast Furnace Slag (GGBFS).  This is a by-product of energy plants that used to be sent to landfills but is now used in concrete mixes to supplement the cement.  This increases the amount of recycled content in the concrete mix, diverts materials from landfills, and reduces the amount of cement and therefore embodied energy in the concrete mix.

Source International Polished Concrete Institute

Below is a mock-up that was prepared for the KEC showing the look of this polished slab.  This slab was first ground down to expose the aggregate in the concrete mix.  The surface is then polished using a multi-step polishing process to give it a glossy finished look.

Here is a sample video demonstration of the concrete grinding and polishing process.  Note this demonstration was not performed at the KEC or by the company doing the KEC, it is simply for reference of the typical process.

KEC Week 19

This month MEP coordination continues and we have been using Building Information Modeling (BIM) for some of the more complicated spaces.

[perspective looking at building from the North]

[interior view of the attic mechanical space over the kitchen from the service hatch]

Onsite the underslab electrical and plumbing in the basement was completed.  A vapor barrier is installed to prevent moisture from working its way up from the ground through the slab and into the building.  Without the moisture barrier below the slab, moisture can come up through the slab and start deteriorating building materials such as wood framing and sheetrock and can also lead to mold growth.  The moisture barrier has been added to ensure good indoor air quality in the building.

[basement slab pour]

After the concrete slab is poured it must be properly cured.  There are several methods for properly curing a slab.  Curing compounds can be added to mix designs to help accelerate project schedules, however most agree that a "wet cured" slab is a better quality job.  To wet cure a curing paper is spread over the entire slab and it is kept wet for typically 7 days depending on the structural engineer's requirements for the project.  While this is happening, not much other work can happen on the slabs which is why some projects try to use a curing agent to allow work to continue on the slabs right away.  Again most would agree a wet cured slab is a better job and this is what we have done for this project.

[wet curing the basement slab]

At the North and West wings, activity has focused on underslab plumbing, underslab ductwork, and underslab electrical.  You have to install the deepest work first and then work your way up.  All work needs to be carefully coordinated so that the piping does not conflict with other piping and to also make sure it comes up from below the slab in the walls and not in the middle of a corridor or room where it doesn't belong.

 [underslab supply air duct]

 [underslab earth duct]

 [these underslab supply ducts will supply conditioned air to the corridor spaces through floor grills]

[here is a row of the floor gills in the corridor before being backfilled]

 [here is the row of floor grills after being backfilled]

 [forming the greenhouse stem walls]

 Slab prep is underway in anticipation of pouring the slab on grade for the West Classroom Wing and starting the timber frame installation next week.

  [underground electrical piping in lab areas]

 

[vapor barrier being installed under slab in lab areas]

The mason started the CMU block stairwell walls and elevator shaft and the framer has started in the East Residential wing.

[temp stair tower for access to basement]

[staging at the stair tower and elevator shaft]

[stair tower and first floor framing sill plate]

The timber pedestrian bridge will start next week.  Steep slope erosion control as well as disturbance limits and silt fence are installed to minimize impacts of construction on adjacent wetlands areas.

Geothermal well drilling is complete and they will focus next on the horizontal piping between the wells and the vault just outside the basement mechanical room.

[geothermal well field]