I figured I moved by hand about 15,000 lb. of concrete and crushed rock. Both loading into the back of the truck and then unload from the truck to the construction site. Oof.

Gathering the raw materials that nobody else wanted.
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Batter boards and string lines kept me on track. I didn't put down a gravel base
but things were pretty firm.
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The center of the wall is packed tight with smaller concrete chunks and filled
with 5/8"- crushed rock. The crushed rock packs very tight and firm. This was
done on each course which left a pretty flat top.
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Took a break here or there to get some planting in so it could start growing.
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The stacked concrete wall is now up to full height. It's very strong, too. I can run
and jump and stomp on it all day long and it doesn't budge.
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About a year later the rest of the landscaping is settling in.
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Outside the wall is the "public" area and inside is the semi-private more showy
planting area. It is a mix of rhodies, vine maples, and perenials.
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FYI: I laid down about 5 ft of a course per hour. This included picking each partiular piece, doing any chipping or shaping, setting in place and then fililng and packing that 5 ft section.

That didn't include gathering the raw materials, the initial digging down to the bearing level, or any string line layout or measurements.

My only complaint? I would NOT hide that wall with all that great landscaping! Just kidding, it looks like a garden that has been there for many years, the wall fits in perfectly. I may have to keep my eyes open for concrete rubble and cart some home myself. Thanks for sharing.

I'd have much preferred stone or a monolithic cast-in-place concrete wall but it was simply not in the budget. I'm sure a lot of people here know how that goes.

As it is I'm pretty happy. My wife was REALLY skeptical when I broached the idea: "yeah, I'd like to build a wall in the front yard out of left over concrete chunks . . . oh, and rip out most of the lawn too!" But now she really likes it.

I've seen other brocken concrete walls, some in the neighborhood, and they're not as neat and tidy. The trick is to keep each course nice, flat, and level. This takes a fair amount of work. This was my process:

1. Dig down to a level base. If I were to do this again, I'd over excavate slightly and lay down a bed of crushed rock 3-4" deep. But get the whole wall foot print nice and level.

2. Lay the first course with the flat side up. Most broken concrete has a flat top surface and the more lumpy bottom surface. Put the bottom surface down. Make sure chat the flat tops of each chunk are level with each other. Dig out or add a touch of crushed rock as needed.

3. Pack the internal voids of the first course with smaller concrete pieces and fill with more crushed rock. Compact the crushed rock. This should give you a very flat, smooth, compacted layer.

4. Start the second course. This time put the flat side of the concrete chunks face down. Since the bottom course should be flat and level and the second course is built with the flat side down construction should go quickly . . it's just flat side-to-flat side. Again, fill voids with concrete chunks and crushed rock and compact. Overlap joints.

5. Now the works starts on the 3rd course since the lumpy side is facing up on the second row. Build the 3rd course with the lumpy side down. This means that you'll need to shape the top of the second course and the bottom of the 3rd course (shaping the lumpy sides). Use a concrete chisel and 3-5 lb. mallet and chip off high points, protruding aggregate stones and such. You can also skim some crushed rock on the top surface and wedge smaller pieces of stones or concrete to stabilize each piece. The goal is to get the top of the 3rd course to have all the flat sides of the concrete facing up AND pretty level. Again, pack voids with smaller concrete chunks and crushed rock and compact.

6. The 4th course is like the second course. . . flat side down and should be built up reasonably quick. From this point forward you alternate every two layers with flat sides facing each layer. If there are any bends in the wall, weave the corners together. And make sure joins overlap. If you can, try to get longer concrete chunks to span both sides of the wall.

Other Tips:
Tools - concrete chisel, 3-5 lb. one-handed mallet, and 8-10 lb. sledge hammer, 48" level, string for string lines, batter boards, shovel, wheelbarrow

Shaping - It goes reasonably quick as the concrete chips off easily with the chisel and 3-5 lb. mallet. Breaking bigger pieces down is with the sledge hammer. Support the larger piece to break so the break line is off the ground. Strike along the breakline with the sledge hammer, just march it across. Most chunks should be brocken within 3-6 whacks and break reasonably straight.

Even Courses - Try to get the same thickness of concrete chunks for the entire course. This will help keep things level

Thickness - My wall is 21" thick and has two layers, or "wythes" (as seen in photos) for each course. I figure 21" is about as tight as you can reasonably get and still be stable. You might go tighter but it probably means working with smaller concrete chunks.

Battered Wall - I didn't batter this wall and just built straight up. Perhaps not as stable as a battered wall but it's rock solid at this height.

The wall has been up for a little while now and I still look at it coming and going. I can't wait for the rest of the landscaping to settle in and the vine maples to leaf out more. After doing the wall it has me looking around the yard for other places to use the broken concrete. Other use I can see:

1. We have a slight slope around the base of a tree in the back yard. Use a similar technique and build a small, maybe 2-course high planting bed that dies into the slope for some flowers or plants and such.

2. Use the broken concrete as pavers. My aunt built a sunken court yard at her place with broken concrete chunks for pavers. It looks great.

3. Set the concrete chunks on edge to create a border for planting beds. Like this

I have some nice, large, Vine Maples you can have free. They have nice rootballs and are transplantable. I live in Maple Valley and can be reached at botann@aol.com.
Bring your own shovel and truck, I will help dig.

I'd like to take you up on that. Just need to figure out the schedule and a good place for the vine maples. I've transplanted the ones I have from my aunt's propery on the south side of Tiger Mountain. So Maple Valley is just around the corner from her place. Doing this I've learned I need to watch the size of the trees. 8-10 ft including the root ball is about as big as I "should" go. And transplanted before leaves are out or after they drop in fall seems to have worked out best for me. I'll drop you an e-mail.

Material Sources / Costs
As for anyone else. The material is "almost" free. My aunt has used tons of it to build hundreds of feet of retaining walls on her farm. She keeps in contact with an excavator and basically pays for his fuel costs (~$80 / load) to have an entire full dump truck of the concrete dropped off. My aunt would let me take as much as I wanted, no cost. Watch on craigslist, too. Sometimes people will post "broken concrete free, u-haul" or something like that. I also picked up 2 - 3 pick-up truck loads from a lady who was an acquaintence of one of the people working at a local nursery. She had a broken patio she wanted to get rid of. I got the material for free and probably saved her $300 in dump fees for the tonnage.

New Concrete Project
As it is, I'm planning a new backyard patio design that uses the concrete as regular retaining wall cut into a small bank in my back yard. The trick to getting to look good is to keep the joints tight. I think I've also figured out how to use the Lowes / Home Depot low-voltage lighting system I have to have in-set lighting into the retaining wall.

I threw some stuff together in the 3D design software we use in our firm and did some sun/shade studies to determine the optimal location of the recessed seating area to maximize spring/summer shade. Otherwise, the existing patio just gets baked in the sun in the late afternoon.
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One concern I would have is that concrete will make the surrounding soil more alkaline/less acid. If your rhododendrons turn a little yellow, you know it is needs to be acidified. The easiest way to do that is to go to Starbucks and get the coffee grounds that they would throw out, and put that on the soil. You can easily test the PH with a kit, but if you see yellow rodies you know it's needs acid. Your grass should be very happy with the Ph that the concrete provides.

The other way to handle that, is just to use plants that like more alkaline soil around the walls

Debby