Concrete

1. Zenithal prime the base of the model. For most models, this won't do a lot as the base will be relatively flat, but it does build up some gradiation and variations in tone.
2. Basecoat the concrete areas with a thinned down Brown Gray . This should be done in a few layers. You don't need (or necessarily even want) a perfectly smooth coat of color here -- variations in grey will sell the textured concrete look.
3. Use an AK Panel Liner like Grey and Blue Camouflage to line any cracks and crevices. Clean up any overage with some white spirits and dab it with a paper towel. A little overage is fine as concrete isn't clean.
4. Use a mix of Nuln Oil and Agrax Earthshade in heavily damaged areas of the concrete to define the texture.
5. Use Streaking Grime on areas of the concrete up against curbs or other areas you want to add some interest. Use a brush with white spirits to spread it around, and then dab the edges with a paper towel.
6. Add a few edge highlights or stippled highlights with Rainy Gray along the most prominent edges, cracks, etc.

Manhole Cover

1. Basecoat the manhole cover with a thinned mix of Red Leather , Black Leather , and Black . Apply a few coats until you reach the desired color.
2. Use a very thinned Mars Orange to apply some rust to the manhole cover if desired.
3. Use a mix of Birch tinted with a bit of SMC05 - Taurus Emerald or Turquoise Blue and highlight the edges of the manhole cover. You can also highlight the raised textured areas. Last, thin this a bit and provide some dings and scratches along the edges of the manhole cover.
4. If desired, use some Slimy Grime Light along the edges/crevice of the cover for a small look of algae.

Bricks

1. Basecoat the bricks with a thinned Red Leather .
2. Edge highlight and provide texture on the bricks with a mix of Moonray Flesh and Red Leather .
3. Dot the corners, add textures/scratches, and some texturized edge highlights with pure Moonray Flesh .
4. Tone down the edge highlights and dings with a thinned glaze of Red Leather .