How should I categorize products . Labor and concrete. We don't make money on concrete, we just pass along the cost from the contractors (i.e. pump truck or mud).

if you are just passing along the cost of concrete, then billable expense is the easiest way to do that. Requires the plus or higher version

Labor, if you have employees, you are already paying the expense of labor.  I you hire contractors, then those are vendors and you will issue them a 1099 at year end, usually I post the contractor payments to an expense account I create called non-employee compensation.  I use that title simple because that is what it is called on the income tax form an it makes it easy to transfer from the P&L