Removing a BIG Rock: Dexpan to the Rescue!

I wanted to build a lean-to shed of the back of my carport as a place to keep my Kubota tractor, (A.K.A. Big Orange). However, my first obstacle was a big one, specifically a BIG rock. This rock had to go, but it was too big to be dug out without risking damaging the garage foundation and dynamite was not an option.

Ever find yourself between a rock and a hard place? That was my situation when I was getting ready to build the tractor shed. Thank goodness there is such a thing as expansive demolition grout!  There several makers of this kind of product.  I chose Dexpan because I could order it through Home Depot and get it in a small 11 pound container – just enough for my project – and it cost around $40 per container.  This stuff can generate up to 18,000 pounds of force per square inch.  There’s just one catch: you have to drill some holes in the rock. So that’s what I did first.

Dexpan Expansive Demolition Grout

I rented a very big rotary hammer from Home Depot with a couple of 1.5” masonry bits – an extra one in case one broke, which one did.  Progress was quite slow, so patience is a must.   It typically took about 10 minutes per hole and I drilled about 10 in the top, roughly 12 inches apart, and a few along the base of the rock.  The holes were about 14 to 16 inches deep from the top of the rock to make sure they were well below grade.  By the way, the rock measured about 5 feet long by 3 feet wide and stood about a foot above ground.   I also used my grinder and a diamond blade to score the rock about an inch deep across the top and all the way around the base to help weaken it.

Holes in the top are about 12″ apart

After drilling the holes, I used an air compressor and a tube to blow the excess rock dust out of the holes. Then it was time for the Dexpan to work its magic.

I’m just giving a summary of the instructions here, but you should read the full instructions before using this product.

Dexpan is available in three temperature ranges so make sure you get the right kind for your weather.  I used Dexpan II – the 50 to 77 degree F version, since this was done in the fall.   The instructions say to mix 0.4 gallons of cold water with one 11-pound bag of Dexpan in a bucket.  It should be mixed to a slurry that is easily poured.  A drill with a paddle mixer works well for this.  The Dexpan slurry should be poured within 15 minutes after mixing.  One 11-pound bag will fill 9 lineal feet of 1.5” diameter holes, so keep this in mind when figuring out how much you need.

A drill with a paddle mixer works well for mixing Dexpan

The instructions warn that forceful blowouts from the holes may occur so do not look directly into the holes after they’ve been filled with Dexpan. Also, be sure to thoroughly rinse the Dexpan from your bucket and tools after pouring the slurry.

After the holes are filled, the 24-hour wait begins.  The video includes a time lapse showing what this amazing product can do.

Now, this didn’t really get rid of the whole rock but it did break up what was above the ground so that I could get on with building the tractor shed.

Picture Gallery

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