Abstract: The well-separated aggregates and the hardened cement paste are obtained from the waste concrete, which is through a process of crushing and separating of the waste concrete by using self-developed waste concrete recycling equipment. The experiment shows that this self-developed recycling equipment is effective, the obtained size of hardened cement paste is smaller than 0.15mm which is easy to fine grinding. The ground hardened cement paste is used as an admixture in cement and concrete respectively to be tested, and the properties are tested as well. The test results show that the hardened cement paste possesses activity, and its pozzolanic activity index is greater than 65%. Performance indexes such as water requirement of normal consistency, setting time and soundness all meet the requirements of cement performances. The hardened cement paste can be used as cement blending material and the concrete admixture.