You want a mix of compost and sand or pete and sand (not pete moss). I have seen various places in GA that sell a mix, just can't find it right now.

I don't know where you have been reading but I have good news for you. You don't need to aerate and you don't need to topdress. And more good news, even though it does not apply if you are not using sand - sand and clay makes sandy clay, not concrete. Concrete must have cement in it to harden. More good news - sand and clay don't even make good adobe. Sand really is an impurity that opens up the soil. People who claim to have clay who add sand and find it hardens up, those people did not have clay. They had excess magnesium salts with not enough calcium and should have gotten a soil test before top dressing.

Before you go out and spend any money on aerating or shopping for (unneeded) top dressing, try this. Spray your lawn with shampoo. Yes, find a cheap bottle of clear shampoo and spray the lawn at a rate between 3 ounces and 20 ounces per 1,000 square feet. Follow that up with 1 inch of irrigation as measured by cat food or tuna cans. In two weeks repeat that process and see if your soil has not improved beyond your imagination. When the soil is right it will feel soft underfoot when it has just been watered or rained upon. As it dries out the soil will harden at the surface. I describe it as being just like a sponge - soft when wet and hard when dry.

Aerating will bring up weed seeds that have been buried for years. Of course it also brings up plugs of soil which you have to deal with for several weeks until they all become crushed back into the soil. The soap is used by anyone (even professionals) who wants to improve the penetration of moisture into the soil. Shampoo is a poor man's version of a product called Cascade (not the dish washing detergent). It releases the surface tension of the water and allows water to drain deep below the soil surface. Apply as often as you want to. Test the ability of your soil to accept a screwdriver stuck into it. Do that before and after you spray the shampoo and irrigate.

If you have not already memorized the Bermuda Bible, find it online and memorize it. It has saved many bermuda owners a lot of time, money, energy, and hassle. It was written by a (now retired) sod farm owner who goes by the handle, texas-weed on the lawn forums.

Just because I'm in a mood.
I'm going to be kind and just say this sort of thing is a pet peeve of mine. When I thought I had clay soil (turns out I do not) I found advice saying adding sand will improve clay soil and I also found advice saying adding sand to clay makes concrete. So I did a lot of research. Neither is true. Yes, some clays contain elements when hydrated will chemically react to create Roman Cement. Some clays contain elements that after being kiln fired (I think it was 900 degrees C.) will form cement (Modern Roman cement invented in the 18th century) when later hydrated. Most clay soils have neither more than traces of these elements nor been heated to 900 C. Sand is an aggregate, it does not chemically react in the cement process (unless your talking "pumice sand") People giving out this bogus crap don't seem to even know that sand and "cement" makes mortar not concrete. Do you know there are reports that claim to show that Coca Cola contains minute traces of cocain? Have you ever let your kid drink a Coke? Why are you giving your kids OPIATES? Call chidren services on yourselves. Rant Off. (this was not addressed to the OP or the contributor)

Pet peeve of mine too, but I was more calm.

Cocaine is not an opiate by the way, but your point is well made.

Cocaine is not an opiate.

I think I'll go have a Coke.....or 2......or 3.

Thanks dchall, I got carried away, if I recall it's a timulant. But my point STILL stands--even if my analoy was incorrect. Now I've started another misconception -(

Jeez can't a guy have a brain fart or two without the world watching?

LOL @ grass.

I don't think the argument is that sand + clay literally equals concrete -- just that it produces concrete-like soil if not mixed in the right proportions, which appears to be true.

Linda Chalker-Scott, a horticulture professor at Washington State University has a nice writeup on this.

Chalker-Scott is a loose cannon in the universe of horticulture professors, and that is the nicest thing I've ever said about her. She invents myths and then debunks them. Too often her support for the debunking is unsupported anywhere else but in her mind.

I find it interesting that she had a revelation about the use of mulch that we have been discussing on the GardenWeb forums since at least 2004. I wonder when she wrote that article? Could it be that our discussions were inadvertently based on a discovery she already had?

Rager,

Like several MistaScott, I thought you were using "concrete" as a metaphor for really hard soil. Which seems appropriate for some sandy clay soils, like mine.

How did you resolve your issue? Did you core aerate and topdress with a sand peat mixture? if so, did the lawn come back lush and green?

In some locations, my Saint Augustine is perpetually yellow and thin. i suspect there is not enough permeability to facilitate deep rooting. If I run the sprinkler too long the water goes into the street. So, I run the sprinkler more frequently, and the stressed lawn develops fungal problems. These patches oscillate between severe dryness and mold issues, because the clay soil is impermeable to water, and fails to retain moisture. That area of the lawn is like a hydroponics operation.

I have attempted the baby shampoo approach, using an Ortho Spreader, a cup of beer, some milk and J&J Baby Shampoo (Laurel Sulfate). I figured I could feed bacteria, combat the fungal issues, and break down the clay in one fell swoop. Let's see if the shampoo hype is more than just hype.

Ultimately, I have littel faith. I suspect i will need to import viable soil to amend these patches of hardened clay. I will need to core these spots and topdress with a soil to prevent the clay from rendering the cores impermeable. The holes will trap water and fertilizer becoming the Normandy beach of my grass invasion.

Any advice on what soil mixture to use on compacted Houston clay? And no . . . I'm not really invading Normandy.