how to make a complete cycle

Question

I am on a project of LCA of 1000kg concrete production

i entered the value of inputs(like cement, sand, gravel, water) to make to a fixed amount of concrete

now at the end of life of concrete, we can recycle gravel from the concrete.

NOW I DONT KNOW HOW TO MAKE A RECYCLING PROCESS FOR CONCRETE AND TO CONNECT THE OUTPUT(i.e gravel) OF RECYCLING PROCESS TO THE MAIN PROCESS OF MAKING THE CONCRETE, thus making a complete cycle

Answer 1

You can create a concrete recycling process that receives input from the use phase, and let it feed back to the production. Used concrete would be waste after the use phase. And then you calculate the use of concrete as main product.

What you need to observe is that the process you start the calculation from, i.e. that delivers the quantitative reference of the product system, is really the last process in your life cycle, anything that uses an output product of this last process is not considered unless it (as in the concrete example) feeds into the processes that in turn deliver to the last process, directly or indirectly. I hope this is somehow clear. Thank you!