Minnesota’s weather and temperature fluctuations can be very tough on the surface of exterior concrete. We’ve produced a guide, located below, on the best practices for placing concrete in our area, as well as other considerations to make. Remember, we’ve been working with concrete in Minnesota since 1936, and we are here to help you!
Make sure your using the best mix for your application. There are certain materials one is required to have on hand, and we’ve made a checklist of those materials and put that down below.
Several years ago, Minnesota experienced an unusually high number of jobs with surface defect issues. In an attempt to understand what caused the surface defects, Marshall cored and tested dozens of jobs with surface defects. In almost every case, the concrete below the top surface of the slab was of high quality and could be expected to provide years of durable service.
However, the surfaces of the core samples told a different story. The surfaces showed at least one of the following:
We suggest following these practices to avoid those problems:
All driveways in Minnesota should be cured as soon as the last finishing operation is completed.
Few topics cause more confusion for users of concrete than curing and sealing. We want everyone using our products to understand these vital steps in the concrete construction process.
Concrete is a mixture of cement, sand, coarse aggregate, water and admixtures. When the cement comes in contact with water, a chemical reaction called hydration occurs. It is this chemical reaction that changes concrete from a fluid to an inflexible, strong, stone-like substance.
Cement hydration is a long term process. After 28 days, 95% of the hydration is completed, so the concrete has gained most of the compressive strength that it will achieve. However, for hydration to continue for 28 days, two conditions must be maintained:
If either of these conditions is not maintained, hydration will stop, and concrete will stop gaining strength at that time. Curing is maintaining sufficient moisture and temperature for hydration.
Sealing is applying surface protection on cured concrete. Sealing should occur 28 days after the concrete is placed. For exterior applications, especially areas exposed to road chemicals, sealing should be repeated every 3-4 years with high quality sealers. We have a full line of curing and sealing products available to protect your project.
Chemical cures – spray on chemicals – water based or solvent based.
We realize that our products are used for a variety of projects including sidewalks, decorative paths, pools, etc. Here are some additional practices to keep in mind when working with concrete in general no matter what the projects is.
Popouts – deleterious material in aggregate absorbs moisture, freezes during the winter, expanding and “popping” off the top surface. A small crater remains in the surface, and the remnants of the soft, deleterious material are still in the crater. Common issue with gravel mixes. Once the soft aggregate has popped, no further damage will be done to the slab.
Mortar Flaking – the surface layer of paste peels off the slab, leaving a sound piece of aggregate exposed. this is a Common problem with granite mixes if the curing was ineffective. Usually limited to areas immediately above a submerged piece of non-porous, flat aggregate. Damage often limited to a few spots where aggregates were close to the surface.
Scaling – top surface peels off the slab. Typically not an aggregate problem. Caused by too much water in the mix, lack of curing or water added to the surface and troweled back in while finishing. Slab must be carefully assessed to determine if the problem is limited to the surface or if the entire slab is compromised.