Thx for posting about your experiences with this project. I've been researching doing something like this and it's good to hear about problems too. I agree with others-- it looks like a good start. 
I've read that anything with cement needs like a month in water to leech completely. I've read of people using dilute acids to speed the process. Also, there is a reinforced concrete (fiberglass fiber mixed in) that might be more durable and easier to build up. You can also mix up your own batch of concrete to avoid the rocks in pre-mixed concretes. (just use cement and sand). Anyway, just some ideas I've read about...
Any updates on this?
I've read that anything with cement needs like a month in water to leech completely. I've read of people using dilute acids to speed the process. Also, there is a reinforced concrete (fiberglass fiber mixed in) that might be more durable and easier to build up. You can also mix up your own batch of concrete to avoid the rocks in pre-mixed concretes. (just use cement and sand). Anyway, just some ideas I've read about...
Any updates on this?
