06/01/2026
Why Driller’s Gel (Bentonite) is a Concrete Liability—And What We Use Instead 🛠️🔥
As a concrete pumping business owner, our biggest priorities are two things: protecting our customers' concrete work and preventing our operators from running into avoidable line plugs.
A lot of guys swear by Bentonite (also known as Driller's Gel) because it’s cheap. You buy one 50 lb bag, throw a couple of large handfuls into a 5-gallon bucket of water, and that single bag lasts you a month or more. It sounds like a great cost-effective shortcut. But here is why we personally don't use it, and why our operators prefer a different method:
🛑 The Bentonite Liability Problem:
Bentonite is engineered to absorb water and swell to a massive size—and it never hardens. If your operator primes out and leaves a puddle of Bentonite on the job site, all it takes is for a finisher to step in that puddle, walk into the forms, and drop that gel right where the pour is happening. Once the slab is poured over it, that trapped Bentonite will expand and refuse to dry, potentially causing cracks and other deformations of the concrete as it cures. If you do use Bentonite, you better have your crew walking the line with heavy-duty contractor bags to catch every drop of that prime before it contaminates the forms.
🪨 The Plugging Problem:
Even putting liability aside, in our 45+ years of experience running our own pumping company, we’ve found that Bentonite more consistently plugs up or causes plugging over using mortar clay/fire clay.
🧱 What about Portland Cement?
Arguably the best lubrication you can get, but it's a brutal timing game. Portland cement gets wet, it's cement and it will harden. If you prime your lines and the ready-mix truck doesn't show up for another hour, you effectively just put cement down your hose that will harden. You can't let it wait. If you use Portland, you have to pop your reducers and prime only when you physically see that cement truck coming down the road towards you.
🏆 Our Safer, More Effective Solution:
We only allow our operators to prime with Mortar Clay (also known as Fire Clay). Any brand works just fine, but the specific one we use in this video is by HC Muddox. It comes in a brown 50 lb paper bag stamped "A Superior Clay Product" and you can find mortar clay easily at Home Depot or most local hardware and specialty concrete supply stores.
Yes, it costs more. We buy it by the pallet, it costs us about $12 a bag, and we use about half a bag per 5-gallon bucket mix (blended to a sloppy pancake batter consistency). But that $6 of material is cheap insurance. Mortar clay takes a long time to dry, stays more of a clay consistency, won't harden like Portland, and won't damage or dissolve structural concrete if it gets into the footings. It removes the opportunity for an employee to make a costly mistake on a customer's job site.
How we set up the rig in this video:
This procedure is specifically for S-Tube and Rock Valve line pumps (not boom pumps or ball valves, which usually prime right in the hopper because manufacturer manuals are written with big boom pumps in mind).
1️⃣ We run an extra-long reduction layout on our lines. The longer the reduction, the less likely you are to have a plug.
2️⃣ Using a chopped-up traffic safety cone as a rugged, unbreakable truck funnel, our operator executes a double-tap lubrication split: he pours a little less than half the bucket down the reducer into the hopper, and the rest straight down into the 2.5-inch hose line.
Regionally, every mix is different. Down in Florida, you might get a beautiful smooth river mix where a handful of dirt or plain water does the trick. But up here in Northern California, the ready-mix plants use manufactured crushed rock. It’s bony, it’s a little bit spicy, and a very effective prime is very important to prevent a plug.
Every method is valid if it gets your job done, but after 45 years in the dirt, fire clay is the safest, most consistent way we’ve found to protect our backs, our equipment, and our business liability.
Watch the video to see our operator walk through the whole setup from start to finish!
📞 Got questions about a difficult mix design or your pump layout? Give us a call at 1-800-585-1206. We always have line pump technicians on call ready to help you handle your situation.
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