Step 4: Cure the Concrete

Don’t stop reading yet or you will miss one very important point. You need to “cure” the concrete. If the concrete isn’t kept moist for a few days it may crack. The problem is that the surface will dry out while the bottom is still wet causing tension which basically tears the concrete apart. There are several ways to cure concrete. The easiest is to simply spray it very lightly with a hose. You can cover it with a wet cloth such as burlap (don’t let the burlap dry out). Or you can use chemical curing agents such as Sakrete Cure `N Seal. The question of how long to do this and how often is a tough one because it depends on temperature, humidity and air flow. The hotter and dryer and windier it is the more you will have to re apply water.

Bob Schmidt
Product Manager
Sakrete of North America
<p>Thank you for this instructable. I learned not to play with it too much as this what my problem was last time. I am going to have a go at this project again.</p>
At times, I like the &quot;exposed aggregate look&quot;. But how and when to do this is &quot; touchy&quot; no?
Thank you for your series in making concrete projects. Every now and then someone wants to make a casting project with a concrete and a mold. Sometimes the &quot;top&quot; of the final project will be the shape of the mold (flipped over after curing) and sometimes the top will be the top surface of the dried concrete. Do you have recommendations for making smooth surfaces when casting flat or curved concrete? The projects I'm thinking of would be smooth enough to apply wax for a perfect shine.
As you well know concrete mixes are usually very porous once they set and that is mainly due to the gravel aggregate in the mix. The top of the mold area can easily be floated or troweled to a somewhat smooth surface but the bottom of the mold is much harder to control. The aggregate will fall to the bottom of the mold. My suggestion would be to allow for the top of the molded concrete to be the top of the project piece as it is the only side you can consistently control the surface of. If it is necessary for the bottom to be used as the top of the project, you may want to look into using an additional resurfacing material which dosen't contain the large aggregate such as the Sakrete Top N Bond Concrete Patcher. The&nbsp;patcher can be used once the concrete piece is set enough so that it is undisturbed when applying the Top N Bond.&nbsp;Hope this helps..<em>The Sakrete Team</em>

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Bio: Sakrete is the pro's choice for concrete, mortar and stucco mixes along with maintenance and repair products for concrete and asphalt. Contractors and do-it-yourselfers ... More »
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