Abstract: A concrete wall system includes first and second opposing wall panels and a plurality of spacers disposed between the first and second wall panels. A plurality of reinforcing bars is placed between the first and second wall panels and supported by the spacers, and a concrete core is disposed between the first and second wall panels such that the spacers and the reinforcing bars are embedded in the concrete core. Each one of the spacers has a cup-like body defining a closed first end and an open second end with a flange formed on the second end. The spacer bodies are tapered so that the spacers are stackable.