Frequently Asked Questions
Frequently Asked Questions
What makes concrete harden?
What is plastic shrinkage cracking?
What causes plastic shrinkage cracking?
Ways to minimize plastic shrinkage cracking?
- Erect a temporary wind break, sunshade, or fog spray to keep the surface from drying out too fast
- Dampen the subgrade, formwork, and reinforcement
- After the initial float or trowel, use a spray on evaporation retardant, such as Confilm, to minimize surface evaporation
- Start curing the concrete as soon as possible with a liquid membrane or cover with wet burlap
- Use synthetic fibers to help resist PSC
- If PSC does occur during finishing, the finisher may be able to close them by refinishing the surface
How does hot weather impact concrete placement?
- Increased water demand which may lead to higher water/cement ratios and lower strengths
- Accelerated slump loss and loss of entrained air
- Faster set time
- Increase potential for plastic shrinkage cracking (see Plastic Shrinkage Cracking) and other types of cracking
- Decreased strengths if concrete is exposed to continuous high temperatures without proper curing techniques
Coping with hot weather placement of concrete?
- Use a set retarder or order concrete containing some percentage of fly ash to slow set time
- Avoid pouring concrete during the hottest times of the day
- Make sure to properly cure the concrete
- Make sure you have enough manpower and equipment to place the concrete without any delays
- Take care to schedule the trucks properly and make sure the job site is accessible so trucks can unload and leave faster
- Do the precautions set out in Plastic Shrinkage Cracking, including setting up windbreaks or sunshades and the use of surface evaporation retardant or fibers
What impact does cold weather have on concrete?
How to protect concrete from freezing?
- When placing concrete in cold temperatures, make sure that you order concrete with heated water and/or aggregates so that the temperature of the concrete delivered is at least 50 degrees
- Use an accelerator, such as calcium chloride, or non-calcium chloride if reinforcing steel is used. This will speed up set time so the concrete achieves 500 psi at a faster pace. Use concrete with higher percentages of Portland cement
- Pour the concrete at a lower slump to speed up set time
- Use of insulation on the finished concrete is a must to maintain concrete temperature and to protect against freezing
- Use insulated blankets or plastic covered with straw to insulate the concrete
About Ernst Concrete
The people at Ernst really know concrete. After all, we have been mixing and delivering concrete since 1946 when Pete Ernst started a gravel and ready mix concrete business in Houston, Ohio.
Today, Ernst Concrete is a fourth-generation, family-owned business and you can still count on the same good old-fashioned personal service from the experienced staff at Ernst.