Harbor Freight Cement Mixer - Pizza Oven Construction - Tools - February 2024

After excavation, the first step of building my backyard pizza oven is framing and pouring a solid foundation for the oven to sit-on.  This foundation is going to be a 5.5" thick, reinforced concrete slab.  I've been probing for the boundaries of the in-ground drywell in our backyard (post with photos here) and have to decide on final location in the coming weeks.  

Once that location is set, I can begin excavation.  Then, my brain will switch to construction material ordering - starting with bags of concrete/cement and concrete block for the foundation.

The first consideration in that process is how I'll go about making/mixing the concrete.  One of the recommendations from the builder community on the Forno Bravo forums is to buy a 3.5 cubic foot cement mixer from Harbor Freight.  I went over to the local HF store this past weekend and sized the machine up.  Here, below is a photo of the cement mixer below:

Here's the product page - shows the specs and the price:  $249.99.  I haven't bought anything from Harbor Freight, but I understand that there's plenty of opportunities for coupons and/or sales.  So...if this is the right answer, I'll have to watch a bit more closely to see if the price goes down.  $250 for a device that I can use at my leisure.  But...have to assemble it myself.  I also have something - a cement mixer - that I can use a second time (more to come about that) and dispose of with a secondary market sale (via Facebook marketplace).  I figure, I could sell this thing all-day-long for $100 after I use it.  Making the net cost about $150.00.

Why does having this mixer available for 2 different pours matter?  Because, building the oven requires (at least) two pours.  Likely three.  The first is the slab.  Second is to fill the cores.  (I suppose I could use fast-setting concrete that doesn't require mixing - treating the cores a lot like a sonotube where you pour in concrete and add water on-top.). The third is for the hearth.  Once the block foundation is done, I need to frame-up and pour the hearth on top.  That means....a second concrete mixing-need.  

The labor involved in this HF mixer is first in the assembly.  From the reviews, it sounds like a couple of hours of work to put it together.  Then, it holds about 120 to 150 lbs of bags of concrete.  That means, picking up, tearing and pouring the mix.  At 40 bags of 60# mix, that's 20 'loads'.   I think I'd like to try to build a CHUTE that carries the material out of the drum down to the framed slab.  There's a DIY Concrete mixer chute video on YouTube that shows how something could be fabricated from dimensional lumber.  

Seems like a viable option.  

But...there is another way.  Something that is a bit more 'automatic' when it comes to the mixing:  the mudmixer.  It is a machine that still requires the same lifiting/filling of the bags of concrete, but does the rest automatically - and includes an auger - to push the finish mix out.  

I priced one from the local equiement rental place.  Below is the estimate.  $109 for the day.  Adding taxes, it comes to about $125.  So...basically HALF the cost of the HF mixer.  There's no assembly required, but I have to go pick the rental up (need a pickup, I think) and drop it off.  They (according to their publicly-listed hours) are open M-F, so a 'one-day rental' means...that I could pick the machine up on a Friday and not have to have it returned until Monday morning.  

Knowing that there are two pours required, this option means that I'd have to pickup/use/return the machine one weekend.  Wait until the slab cures a couple of weeks.  Then do it again.  

The upside is that the rental makes the process a little easier - not batches, but instead constant flow.    The labor is in picking up/cleaning/returning the machine instead of assembly.    It also would, I think, make the job go quicker.  

The downside is that there's a time-crunch.  I *have* to complete the pour according to the rental schedule, not my own.  Also, I have to do it 2x vs. using my own machine twice.  

The labor to pick-up and pour the bags into either machine is the same.  The rental is 'set-it-and-forget-it', while the HF drum requires water calibration every few bags.

On cost, assuming resale value of $100, the HF mixer wins.

On acquisition effort, let's call it a draw:  pickup/returning mixer 2x vs. assembly of HF mixer.

On labor-effort, the mudmixer rental wins.  

Feels like a push overall with a little lean towards the flexibility of owning the machine that the HF drum mixer allows.  

In terms of order-of-operations on the pizza oven, here's what I need to do:

1.  Select location

2.  Begin excavation

3.  Plan for materials and order

4.  Decide on mixer

5.  Get goin'.