Ready-Mix Concrete Facts

• Over-vibration can cause honeycomb instead or 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, non 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.
• Partially set concrete can be revibrated without harm provided the vibrator would enter the concrete of its own weight and restore the concrete to a plastic state.
• A vibrator setting 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, dust less, by 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
• Water Spray (keep slab continuously damp)
• Waterproof Curing Paper
• Damp Burlap
• Plastic Sheets
• Damp Earth, Straw, Sand & Hay
• Ponding for 7 days

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

• 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
  • Dusting
  • Cracking
  • Repairs
• You can affect setting times in cold weather (Retard)

Slab ThicknessLess Than 3/4″ AggregateLarger Than 3/4″ Aggregate

Note: Depth of the control joints in the slab should be 1/4 to 1/3 thickness of the slab.

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 Retarders and Accelerators

1. Joints are simple good looking Pre-Planned Cracks
2. There are two basic joints to remember;
   • Contraction Joints… Tooled or saw cut into slab to direct crack
   • Expansion Joints… These isolate the slab from other structures
3. Joints should be carefully designed and properly constructed.
4. For further information, contact us