Ready-Mix Concrete Facts

• Over-vibration can cause honeycomb instead of eliminating it as intended
• Inadequate vibration is sure to result in honeycomb, particularly with low slump concrete.
• High slump concrete can not stand as much vibration as low slump: very wet concrete, none at all. 
• Over-vibration will cause loss of entrained air-as much as 50% loss in 30 seconds.
• Moving concrete around in the form by using the vibrator will result in sand streaks and rock pockets.
• Cold joints may result even though each lift is vibrated unless the vibrator penetrates just into the lower lift.
• A vibrator set at a flat angle has little effect, if any, on the concrete immediately below. 

Why curing is so important:

• Improper curing can cut the designed strength by 50%
• It will crack less, be stronger, more durable and have a better wear resistance surface
• It will have fewer pores where water can enter and freeze
• It will promote less crazing and spalling of the concrete

Methods of Curing:

• Membrane Curing Compounds
• Waterproof Curing Paper
• Damp Burlap
• Plastic Sheets
• Damp Earth, Straw, Sand & Hay

Cure concrete longer when the temperature is below 70 degrees because concrete strengths develop more slowly at lower temperatures.

NOTE: All concrete should be poured at least 4″ thick.

• You increase the slump about one inch
• You cut the compressive strength by as much as 250 psi
• You waste the effect of 1/4 bag of cement
• Your increase the possibility of seepage through the concrete by up to 50%
• You increase the shrinkage potential about 10-15%
• You decrease the freeze-thaw resistance by 20%
• You lower the quality of concrete in many other ways
  • Less wear resistance
  • Cracking
  • Repairs
• You can affect setting times in cold weather

Note: Depth of the control joints in the slab should be ¼ the thickness of the slab, not less than 1 inch.

One of the most important steps in the process of placing color conditioned concrete is the curing process. Curing is defined as the maintaining of  a satisfactory moisture content and temperature in concrete for a definite period of time (preferably 7 days), in order to develop the desired properties (strength, durability, water tightness) in concrete. It will also allow the color to develop to its full potential and be uniform in appearance. If there is no curing done, or if it is done incorrectly, you can be guaranteed that discoloration will arise as well as potential for efflorescence and you will have a call back to the job. 

The setting of concrete is a physical-chemical reaction. Generally, this chemical reaction is altered by approximately 1/3 for each 10 degree F change. 

As an example of the relationship between temperature and setting times, concrete, at 70 degrees F sets in about 6 hours. Assuming that both the concrete and ambient temperatures are the same, here’s when you can expect concrete to reach initial set at other temperatures.

Contact Us for information on Stabilizers and Accelerators

1. Joints are pre-planned cracks
2. There are two basic joints to remember;
   • Control Joints… Tooled or saw cut into slab to control crack locations
   • Expansion / Isolation Joints… These isolate the slab from other structures
3. Joints should be carefully designed and properly constructed.
4. Timing is key, depending on the type of cut they should be run within 12 hours of finish.
5. Entrant corners require careful joint placement, avoid L shaped slabs.  Concrete prefers to be placed in squares. 
6. For further information, contact us