LEGO Technic 42112 Concrete Mixer Truck [Review]

The Summer 2020 LEGO Technic wave has had a surprisingly high level of controversy surrounding it. The 42113 Bell-Boeing V-22 Osprey got cancelled, and the 42114 6×6 Volvo Articulated Hauler can’t move without being paired with a smart device. That just leaves the 42112 Technic Concrete Mixer Truck to try and put a positive spin on things. This 1163 piece set will be available in North America starting September 1st, and is available now in the UK from the LEGO Shop Online (US $119.99 | CAN $159.99 | UK £89.99). Technic fans have been asking for a concrete mixer for ages… Can this offering satisfy that demand? Or will this set finish off the season’s offerings with some cement shoes?

The box and contents

The packaging for this set is pretty standard for the Technic line. The primary model is clearly displayed on the front, with some out of focus construction yard graphics in the background. The back of the box shows the mixer from other angles and highlights the action features. There are no alternate builds or “hook this up to motors for more fun” teasers to be found. This set is only focused on the primary model. That’s not a bad thing, as that primary model is plenty nifty.

Inside the box are nine bags, grouped into four building sections. There’s an unnumbered bag containing the tires, a flier for LEGOLAND, a sticker sheet, and two instruction books. Also loose in the box are the key new parts for the set: the two halves of the mixer barrel.

The parts

Before we get to that mixer barrel, it’s worth noting that this set also has a wealth of hard to find Technic elements in dark blue. In particular, the flat panel was only in this color in 2013’s 41999 4×4 Crawler Exclusive Edition. and other elements haven’t been seen since the 2018 42083 Bugatti Chiron or as far back as 2005 Bionicle sets.

But who cares about that, when we could be focusing on this glorious mixer barrel? This brand new mold comes in two halves, with the interior featuring an Archimedes’ screw. Depending on the direction of rotation it will either pull things deeper into the barrel or send them spiraling towards the exit. The logo is printed on both halves, with the center of the “C” amusingly surrounding the injection molding dimple. I’d normally be grumpy about that printing, but this is a fairly large piece (each half is 6.5 x 13 x 26 studs). Applying stickers neatly onto such a large curved surfaces would have resulted in some very sloppy looking mixers. It certainly would have sucked for me, anyway.

The build

The first set of bags focus on building the core of the truck. The gearing is interesting and straightforward enough to be understandable to a relative Technic novice like myself. I learned a bit building the proportional steering in the front, and the differential gearing at the rear connects up to an axle that that drives pistons in a small engine block.

It may be simple gearing in that engine, but it’s still satisfying to watch. Sadly, we’ll see that this cool feature ends up being integrated into the final build in what may be the dumbest way possible.

The rest of the first instruction book covers the second group of bags. By the end, all of the core functionality will be in place. In a departure from most other LEGO sets I’ve built, the tires will also be in place. It felt kind of odd not having them be the final step in the build.

There are three modes that can be swapped by moving a switch on the side of the chassis. We’ll go over that in a bit, but for now here’s a look at how moving that switch engages one of two gears, or leaves things in neutral. It may be simple stuff to more experienced builders, but I can’t help but imagine how many other newbies will be inspired by seeing this in action, and end up including something similar in their own creations.

The mixer barrel’s mounting bracket is also built out in this section. It will connect to a large Technic turntable, which in turn is hooked up to the gearing described above.

The second instruction book covers sections three and four of the build. Any fears that this will end up a hybrid between a Technic and City set are soon left behind. Although the complex building is complete, there are very few standard LEGO System parts in the remainder of the build.

The barrel’s rotation is smoothed by these angle-mounted rollers. The white element in the center is a new clutch, previously seen only in the high end Volvo hauler and 42100 Liebherr R 9800 Excavator.

Stickers are applied on each side of the chassis to help explain functionality. The three-position switch lets you choose between how the mixer’s barrel will rotate. It can be set to turn along with the wheels, left in neutral, or turned via the crank on the opposite side. The stickers there tell how the direction you turn the crank will impact the contents of the barrel. Turn things clockwise and things stay in the barrel. Counterclockwise rotation moves them out.  (Amusingly, when in gear, pushing the mixer backwards will also send the concrete flying. Play feature or bug? You decide!)

The cab of the truck has some big pluses and minuses. On the positive side, the dark blue color looks great, and is a nice accent to the grey interior.  The negative? Instead of a center console, the engine is exposed between the seats. Sure, that means you can see those pistons moving, but it’s a real departure from the realism shown in the rest of the set. I mean, where are the cup holders supposed to go? The front of the cab also has some more stickers detailing the lower fender and the license plate. The identifier “CM 42112” on the plate calls back to the set name and number.

Behind the cab, there’s a brick-built water tank. You know it’s a water tank, as there’s a huge sticker applied to it with “Water” pointing at an illustrated valve cover. The tank itself looks good, but there’s a lot of gap between it and the cab itself. This is one part of the overall build that looks very unfinished to me.

Another questionable choice in this area is the selection of parts used for the steering. The yellow Technic rod can be rotated to turn the front four wheels, and functionally it works just fine. But why yellow? There’s no need to call attention to this action feature, and the same axle comes in grey. That color would have blended in a lot better.

The final part of section three is attaching the mixer barrel. I’m looking forward to seeing how that barrel gets used by builders. The logos may end up making inclusion in custom creations a bit trickier, but I’m sure people will find a way around that. And now we can start hoping that LEGO will make use of this mold in other sets, possibly in other colors and sans-decorations.

And at last it’s time for section four! This step is pretty unusual for LEGO sets – it’s just a single bag with 100 1×1 beams in dark blue-grey to serve as the concrete. Dumping them into the mixer completes the building experience. And now you can go on to imagine building something else with what you just built. That may mean taking this bad boy to a growing Technic construction site, or ripping it apart and using the pieces somewhere else. That’s pretty meta, when you stop and think about it. (Okay, I got a little desperate here. Give me a break…I needed to write a paragraph about 100 1×1 beams.)

The finished model

One of the best things about this model is how LEGO didn’t lean into a standard yellow “construction” color scheme. The primary dark blue plays well with the white, blue and orange accents. As mentioned earlier, the “C” logo is printed on the mixer barrel, but the rest of the printing is sticker based.  The ones along the front and side of the cabs have a few necessary gaps due the edges of the panels, but it’s not a big distraction. You really don’t even need to apply them if you’d rather keep those dark blue parts optimized for reuse…the truck would still look sharp without them.

As discussed above, the only real problem with the look is when you look at it directly from the side. The gap between the cab/water tank and mixer barrel does feel like there are pieces missing. Some additional detailing there could have unified the model a bit. But from just about every other angle this truck looks good.

A nice bonus is that the doors on the cab open and close. It’s a small touch, but the functionality is good and it adds a nice touch of realism to the cab. It’s not enough to explain that exposed engine, but every little bit helps.

At the rear, there’s a funnel to direct the concrete as it leaves the barrel. It’s mounted on a pivot that lets it swing up and out of the way, or to direct the flow where you want it.

There’s no easy way to motorize the mixer, but you can just replace that hand-crank with a Technic motor if you’re feeling sassy. So I did.

Firing up that motor gives you the ultimate “mixer in action” experience. I was happy to see just how well that interior screw will move those 100 1×1 beams out of the mixer, down the chute, and across a  work surface. My motor was just a touch overpowered for this application, and this image shows things in more or less real time. I think I found most of those beams. Maybe.

Conclusion and recommendation

At just over 10 cents per piece, this set is not a great value as a parts pack, particularly for an unlicensed set. (And it should be noted that over 350 of the 1163 parts are Technic pins. A necessary evil, sure, but it may be a factor for non-Technic builders when determining value.) There are also a few places where the build could have been enhanced by a few more panels or additional detailing.  And they really should have put a cover on that engine. But that’s pretty much it in terms of negatives for this set.

Overall it looks great, it works great, it has a great selection of parts. It’s real-world accurate and the play features are all top notch. It’s fun. This set changed me from being a casual Technic fan to someone who is making room in their LEGO budget for a lot more from this theme. So…yeah. Recommended.

Now I just need to figure out how to re-purpose that mixer barrel.

42112 Technic Concrete Mixer Truck is available now in the UK and will be available in North America starting September 1st from the LEGO Shop Online (US $119.99 | CAN $159.99 | UK £89.99), and is available for pre-order from It may also be available via third-party sellers on eBay and elsewhere.

The LEGO Group sent The Brothers Brick an early copy of this set for review. Providing TBB with products for review guarantees neither coverage nor positive reviews.

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3 comments on “LEGO Technic 42112 Concrete Mixer Truck [Review]

  1. Defiant

    Great review. It would be nice if clicking pictures in the article would open them in a separate window, or a hovering window that could be easily closed.

  2. Russell Chapman

    Note that the PDF building instructions on the Lego web site are wrong for this model – they show a completely different crankshaft arrangement. I never use the printed books, so I assumed my parts were wrong, until I saw this review.
    I assume they updated the set to include the red half beams instead of 4 x orange beams, but never updated the instructions. There are other small differences as well.

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