If for any reason you can’t get at least 40 bricks to make your outdoor pizza oven, then there are alternatives to consider. If you make most of your brick pizza oven out of concrete cinder blocks, you will still have something that works. Of course, you still need to monitor the oven so that none of these cinder blocks crack or pop. We used concrete blocks in our fire pit for a while (a simple drum on top of blocks for airflow) but they didn't last long. They all cracked in the end. You'd be better off getting kiln-fired red bricks or fire bricks for your outdoor DIY pizza oven.