I did quite a bit of testing of track bed materials, and found that the most durable "concrete" mix was type S brick laying mortar mixed 50-50 with fine gray trap, and then use acrylic bonding additive as the only liquid. Regular concrete breaks apart any time it is less then 2 inches thick. Type N mortar is also too soft and breaks up easily. Type S mortar all by itself breaks apart - it needs something to cling to. The mix I came up with is pretty tough. You can hold a foot-long inch-thick section of this track bed by one end in mid air and even with rocks still stuck to the bottom, does not break apart.

The entire layout is raised up off the ground by 2 feet using a base of packed clay/sand mix. A layer of landscape cloth covers that, then a layer of gray trap (crushed basalt). The "ground level" track beds are then a layer of landscape rock with a ribbon of 1-inch thick "concrete" poured over that. The idea behind the rock under the concrete is to allow drainage.

I created a jig for applying the mortar. It was suggested that I add a vibrator of some sort, so I hacked up an old back massager. It vibrated the jig nicely, but the mortar still required mechanical mixing in the form of a push paddle I devised a short time after this test.

The "ground level" track beds are a concrete ribbon poured on top of rock. The track beds on the mountains are the same concrete mix poured directly onto the foam.

"Concrete mix"
• Type S mortar - found at home improvement stores (e.g. Home Depot, Lowes, etc)
• Gray trap (bluish-gray basalt) - found at landscape supply stores that sell rock, gravel, dirt, etc
• Acrylic bonding additive - found where concrete mix is sold (e.g. home improvement stores)
• Iron oxide pigments for coloring, mix of yellow oxide and red oxide - found on eBay, normally sold for use in ceramics but is the same pigment used in premixed concrete coloring additive

The Logging Loop that goes up and down around the mountains was finished in 2016, and the remaining loops finished in 2017.

The flexible track I used had screw tabs molded into the ties every few inches. I screwed the track down every 6 to 12 inches (closer on curves), screwing right into the concrete.

I used crushed granite for ballast since it was the most realistic thing I could find readily available. There are two things that will make fine ballast disappear quickly: A leaf blower, and heavy rain. I was starting to experiment with clear acrylic when a fellow modeler turned me on to Mulch-Lock. It is made for keeping mulch in place, but works pretty well on ballast, too. It is a form of acrylic that is easily sprayed on using the pump sprayer the product comes in. You can buy it on Amazon or at some home improvement stores. The ballast doesn't go anywhere when hit with rain or the leaf blower after locked down with Mulch-Lock.

Once the layout is finished, you really don't see the concrete very much. The concrete was colored to blend right in with the natural rock.