Removing/working around badly applied reef cement?

[danb87]

Hi guys, first timer here and trying to stick together my first aquascape - using AF Stone fix currently.
I basically had a bit of a nightmare and either didn't leave two pieces to cure long enough, or didn't use enough cement, but basically the stuff came apart when I went back to it the next day. Now I've got a resulting grey, cementy mess and I'm worried if I try and work in that same area again, I'm going to have issues adhering the pieces together on top of the already dried cement.
Anyone have any ideas how to work around this? I've already chipped away and sanded the residual cement as much as I could, is there anything else I could do or should I just carry on over the top of it?
I was also thinking of getting some air duster/compressed air to blow away some little bits of rubbled cement that are stuck into the crevices, would using that be safe for my rock (this is all out of the water at the moment)
Attached some pictures of the mess I've made - thanks in advance.

 

[Timfish]

If the left over material is stuck to the rock as well as you indicate cement should be fine cement other rocks to it. Persoanlly I preffer to drill my rock ao it can be dissambled when upgrading or moving. Don't forget to use some live rock for beneficial sponges and microbial stuff.

Establishing a Healthy Microbiome in a New Aquarium Using Live Rock

About this article This article describes an experiment documenting the effects of live rock in a newly established aquarium. While I’ve tried to tell the story as briefly as I can, it’s the story of a month-long study of replicated tanks, with analysis of both water chemistry and the microbial...

www.reef2reef.com

 

[danb87]

If the left over material is stuck to the rock as well as you indicate cement should be fine cement other rocks to it. Persoanlly I preffer to drill my rock ao it can be dissambled when upgrading or moving. Don't forget to use some live rock for beneficial sponges and microbial stuff.

Establishing a Healthy Microbiome in a New Aquarium Using Live Rock

About this article This article describes an experiment documenting the effects of live rock in a newly established aquarium. While I’ve tried to tell the story as briefly as I can, it’s the story of a month-long study of replicated tanks, with analysis of both water chemistry and the microbial...

www.reef2reef.com

Thanks for the feedback - I'll continue with trying to cement over the top of what I've got and hope I do it a bit more securely this time.
As for Live rock, good advice I'll look to get some once I actually get my tank (still in transit) to put in my sump. Thank you!