Repairing Your Cement

Tips for Trouble-Free Concrete Mold Casting

Home improvement stores sell concrete molds for making your own paver stones and decorative walkways. Using the mold seems simple: follow the directions on the mold and the concrete mix, pour the mix into the mold, and wait for it to set. But problems can arise if you have no experience working with concrete or concrete in molds. If you know the common problems ahead of time, you can fix the issues as you go along rather than needing to scrap the molded piece and start over.

Here are a few of the common problems and tips for how to avoid disaster.

Chunky Concrete

When you prepare the concrete mix, the resulting texture should be close to brownie batter, thick but spreadable. It should not resemble chunky brownie batter. Chunks in your concrete mix indicates that you either didn't mix the concrete well enough or didn't use enough water. If you pour the concrete into the mold without fixing the chunks, your paver might crumble when it comes out of the mold or the final project can have more texture than you planned.

You can fix this problem with better prep work. Make sure you're mixing the concrete in a large enough container to allow for proper and thorough mixing. You also want to use a power mixer not your hand. There are mixer attachments available that fit onto the end of your drill for easy stirring.

As far as the right amount of water to use, this is where the problem becomes trickier. If you have no experience, it's hard not to follow the package directions completely. If you mix using a drill and there are still significant chunks, you need a bit more water. But you will need to estimate the amount based on texture and too much water can also cause the molded concrete to fail.

If you simply can't get the mixture right, call a concrete contractor to make some paver stones for you.

Surface Dents 

An incorrect amount of water can also cause the final project to have numerous surface dents or pitting. But the dents can also be caused by too much air remaining inside the mix, which can be caused when the mold isn't properly vibrated before the concrete is left alone to set up.

Ideally, a mold should be vibrated using a mechanical instrument created just for leveling out concrete. But a do-it-yourself homeowner usually doesn't have access to such equipment. Instead, you will need to settle on shaking the mold firmly back and forth above the spot where the mold will sit while the concrete cures. You can also take a hammer and firmly bang the exterior edges of the mold to knock out any air bubbles sticking to the outside edges. For assistance, talk to a professional like Pyramid Concrete & Consulting Ltd.


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