From the pictures of the lower section of cement, it looks as no forms were used, hand mixed with a couple variations of aggregate, along the line of 3/8-3/4 gravel. Doesn't take long for moss to grow on concrete especially in remote areas, but your moss looks pretty thick with a few layers of build up. The rail isn't modern, scrap piece someone picked up. New rails are wider and more of a wider rounded rectangle shape. If you chip of some concrete the aggregate will be consistent throughout with a modern truck pour, wide spread with a hand pour, if no aggregate present could just be a sand Portland slurry mix, more of a thin set consistency. Tough to say without being able to visual inspect. Looks intentional more so then emptying out the wheel barrow of waste from a project.