Slab ridges in Sections - why are the ridge lines not visible?

[amgam]

I have what seems like a very basic problem, see screenshots attached. The slab ridges in sections seem to not exist. The lines just aren't there. Any way to fix this? 

[Erika Epstein]

In Attributes settings of your composites you set the pens for each material, including the end lines. However as you show in your 2nd picture, like materials from different slabs will read as one contiguous material. To rectify that, you would need to create a second version of the composite with one having for example concrete 1 and the other concrete 2.