One way to dispose of unused concrete is to have the ready-mix company that delivered the concrete remove the excess or use a reclaimer to separate any mixed concrete for future use. For used or old concrete blocks, call a local green contractor who accepts donations, and arrange for him to pick up the used blocks.
Another option for disposing of concrete is to check the yellow pages for listings under Concrete Recycling. Many companies listed there make a profit by breaking up hardened concrete and selling it. If the concrete is excess from a completed project, allow it to harden in pieces easy to handle when hauling them to the recycling company. If it is used block, and the block is heavy or large, find out if the company is able to transport the concrete to avoid damaging a personal vehicle.
A recycling center is the best option for used concrete blocks that are damaged or incomplete. A local green contractor is the best option for used blocks that are whole or have minor damage that is easily patched. If any of these options fail, call the local city or county dump. Ask if the facility accepts old concrete; if so, discuss any applicable disposal fees. This is typically the most expensive option for disposal.