If you’re building raised beds on concrete, they are effectively containers. They’ll need to be around 400mm high so you can grow a variety of vegetables in them. Make sure you fill the containers with a good quality (preferably organic) garden mix. The soil in containers will not have the usual bacteria and fungi in it that you get from the earth, so it would be good to add trichoderma to your containers. You can buy Dalton’s Bio-fungicide powder which contains trichoderma at Bunnings stores. Only add this once a year. We would also recommend giving your plants a regular liquid seaweed feed. Lastly, after each crop grown in containers, it’s important to add compost and sheep pellets (which are slow-release) to nourish the soil and raise the level back up to the top.