I assume I would need some kind of frame around it so the cement couldn't fall through the bottom or push out the front. How would I go about patching this step? With what?

 

No, I don't think you need a form though one on the front face might help if you've never worked with mortar before. I would use mortar or a crack filling cement mix. Start in the morning. Make a thick mix, not soupy. I would keep packing it in until you filled the cavity. Trowel it off flush with the surface. You can leave the mortar high if you want. Final finishing will come later in the day. Now let it sit for 6-12 hours.

At about 6 hours brush the surface with a wire brush. If the mortar comes off in dry crumbles continue brushing to give the mortar a uniform brushed texture. This will give you good traction when walking on it and will get rid of the shiny white mortar look of a patch job. If the mortar sticks to the wire brush or gums up then wait an hour or two and try again. If you had high spots in your mortaring just work them down with the wire brush.

 

SO what do I need besides the trowel, water, and mortar or crack filling cement mix? I know cement mix requires water and gravel. Are you thinking of a fully pre-mixed solution where I just add water?

 

That's all you should need.

 

brand make model crack filling cement and trowel you recommend?

 

Any brand of prebagged "mortar mix". But you won't be able to match the existing aggregate. (The exposed gravel look) unless you can find some matching gravel to work into the surface.

 

So the only difference between cement and mortar is the presence of absence of gravel? I do want gravel in it.

 

Cement mix does have gravel but will not bond as well and is not as durable when it's not at least 2" thick. Any thinner and it breaks easily. Mortar mix is stickier and bonds better. That's why I said use mortar mix but work a little gravel into the surface if you want a similar look and texture. As it sets up you can brush it a little like Dane said to expose the aggregate.

 

Could I get prebag mortar mix, add gravel to the mix on the whole and use that?

 

If I was doing the job I would probably use a bonding agent such as SBR on the cracked part and use a mix of concreting sand and Portland cement to fill in the gap.

 

No matter what you do the repair will not match so I would focus on doing a proper repair and worry less about being able to see stones in the repair. One thing that will help the appearance is to do the wire brushing 6-12 hours after installing the mortar. This will knock down the smooth "white" appearance of fresh mortar and give it a rough, dull look that will blend in a bit better.

 

I have a 1.5 by 2.5 inch piece long enough to cut into five pieces. I'll nail four together to make once piece 5 x 3 inches, which fits perfectly under the step. I will keep one piece for finishing the cement. I will nail another piece about 1/2 inch thick and 7 inches wide to it to cover the front of the step. I think nails about 3 inches long and 1/8th thick would work. What is the best nail for the job so I know what to get?

 

What are you nailing together? Are you making forms or are you covering the steps in wood?

 

Just a form for underneath and in front of the concrete step in this thread that i plan to patch this Sunday.