Frequently Asked Questions and How-To’s

What is ready mixed concrete?

Ready-mixed concrete is a combination of Portland cement, rock, sand, and water. Also, concrete may contain some admixtures including mineral and chemical. These admixtures improve the properties of concrete.

How far apart should I place my contraction joints?

Spragues’ Ready mix recommends that you place your contraction joints no more than 2 times in feet the thickness in inches of the slab. (4” slab 8’ joint spacing) These joints must be a minimum of ¼ the depth of the slab. (1” on 4” slab) Also, it is recommended that you attempt to design panels that are as square as possible. (Avoid exceeding 1.25 times square) For more information see CIP 6.

How should I cure my concrete?

Spragues’ Ready Mix recommends that you cure your concrete with a liquid membrane curing compound. The curing process should begin immediately after final finishing. (Colored concrete may require curing compound that is approved for application) For more information see CIP 11.

How should I prepare my sub-grade?

The sub-grade should be well compacted, uniform in depth, and well draining. Also, a fill of granular nature such as sand, rock or crushed base and dampen this base before placing concrete.

Should I use fibers in my concrete?

Spragues’ Ready Mix recommends the use of fibers for reducing the possibility of plastic shrinkage cracks. Fibers are used only as secondary reinforcement. For more information see CIP 24.

How can I avoid concrete cracks?

There are many different types of concrete cracks. Proper joint layout is critical in flatwork. Pouring concrete with a low-slump is also very important. Cracks can also be caused from external restraint. (Pouring a footing and slab concurrently) Cracks can occur in between two immovable obstructions. If felt or foam is not used between a house and a block wall it is likely that a crack will develop. Crazing cracks (web cracking) often will develop when concrete is poured with a high slump and/or bleed water or water was introduced to the surface of the drying concrete before final set. For more information see CIP 3.

How should I prepare for hot weather?

Concrete will set-up much quicker in hot weather. Ask our dispatchers to add a set retarder to your load. Make sure you have enough people on site to place the concrete quickly. It is recommended that the sub-grade is dampened before placement begins. For more information see CIP 12.

How should I prepare for cold weather?

In Southern California our temperatures rarely drop below 40 degrees. Nevertheless, we recommend that when the mercury drops you use a set accelerator in your mixes. Also, pouring your concrete with a low slump will help increase your set times. When concrete is poured on a cold sub-grade set times also tend to be increased.

What do I need to know about colored concrete?

Extra care must be taken when placing colored concrete. It is important that the slump remains consistent throughout each load. Also, as with any concrete, you never want to introduce water to the drying surface.

How do I avoid discoloration of my slab?

It is important not to over use a steel trowel while finishing. This has an effect that “burns” the surface of the concrete and seals in moisture. (Trapped) Also, you do not want to introduce any steel onto the wet concrete until after all of the bleed water has disappeared. Avoid using calcium chloride for flatwork. For more information see CIP 23. 

How can I repair discoloration?

Discoloration is difficult to fix. However, the earlier you treat the surface the more effective it will be. Scrub white vinegar onto the dampened slab and hose off the surface before the vinegar dries. Vinegar is slightly acidic and will often open up the pores of the concrete and allow it to breath. Discoloration caused by calcium chloride will not be affected by this procedure.  

What Is Pervious Concrete?

Pervious concrete is concrete manufactured with zero fine aggregate. It allows water to pass through the concrete which eliminates storm water run-off. Pervious concrete pavement is a unique and effective means to address important environmental issues and support sustainable growth. By capturing stormwater and allowing it to seep into the ground, porous concrete is instrumental in recharging groundwater, reducing stormwater runoff, and meeting EPA stormwater regulations.