Thursday, December 26, 2019

Finding Grade

Finding Grade

In a majority of Civil contracts Floor Flatness (FF) and Floor Levelness (FL) will be specified. Expectations by client/owner typically require contractors to sponsor a certified test which meet ASTM E1155 or ACI 302.1. For additional information regarding FF/FL please refer to ARCHBOX article titled FF and FL Numbers - Floor Flatness and Levelness


Contractors Red Flag: Equipment must have current calibration. Conduct test prior to early entry joint saw cutting; typically 4 to 6 hours after concrete placement.

Have you ever heard some say "Money is made on the Green"? Well, in concrete work it's all about the grade.

Large Flat Work (No Slope):Most experienced concrete contractors utilize a rotating laser with sensor mounted on grade rod. Grading is
typically conducted by two labors screeding concrete with light-
weight magnesium or aluminum bar. This technique would be acceptable if FF/FL is 50 or less. The crew operating walk behind and ride-on trowel machines can clean up most grade imperfections with float pans.

Higher FF/FL numbers require laser equipment similar to the picture shown above right called Samero. Laser guided machines will product tolerances of 1/16" per 10 feet, eliminating need for manual screeding shown above left.

Large Flat Work (Slope): Sites requiring drainage to trenches, catch basins or sumps use pre-established grading devices such as pipes or flat bars. Both are sufficient but flat bar screeding lowers concrete void as shown below. In most cases a shake of the bull float can fill flat bar void.

A #4 rebar driver is used to drive #4 rebar into subgrade. Note, if using vapor barrier tape or mastic will be required to seal penetration. In most cases 4' OC is sufficient.
#4 Rebar Driver

Application: Flat bar can be used in conjunction with spin screed pipes or manual screed bars. Flat bars unlike pipes are flexible enough to be utilized in radius forming; i.e. tanks.
"This system kicks ass! Worked really well." 
Christiaan Long Totem Construction LLC 
Baton Rouge, LA

Thursday, December 19, 2019

Crack Injection

Cracks in concrete are typically caused by subgrade failure. Some will say pour consolidation or inadequate curing methods. Either way you have two simple choices. You can break it out, replace with new concrete or apply a resin/hardener mix called Epoxy. A product I have used with great success is Crack Bond LR-321 by Adhesive Technologies.
Crack-Kit is for the small job, 8 to 10 LF based on 8" thick concrete. For the larger projects look at purchasing the 16 oz tubes, individual ports, nozzles and Miracle Bond past.

Crack Injection Video

Keys to Success: 

  1. Clean surface
  2. PPE; i.e. safety glasses, gloves, ear plugs, dust mask and knee pads
  3. The RIGHT tools
    • Hepa Filter Vac
    • Grinder
    • Battery Caulk Gun
    • Wire Brush
    • Compressed Air
  4. Time - refer to Miracle Bond (Paste) tds for cure time
Allow three days for scope of work
Day One: Prep and Paste
Day Two: Inject and cap ports
Day Three: Break off ports and grind surface smooth

Monday, December 16, 2019

Introducing Keycup™ Now at CS&E

Stacks Image 9
Keycup™ is the easy way to create keyed joints with waterstop.
Keycup™ is a multi-function, reusable concrete accessory that is used to securely hold waterstop in place while simultaneously creating a keyed construction joint. Typical applications include:

  • Slab on grade
  • Wall joints
  • Lumber replacement
  • Labor saver