Implementation of the use of hydration stabilizer admixtures at a ready-mix concrete plant

Waste generated during concrete production is approximately 3 % of the total volume of concrete produced in a ready-mixed concrete plant. The economic and environmental costs of such waste are high, which means that more solutions are required to eliminate this problem. This paper presents a case study that focuses on the implementation of a process for reusing the adhered and leftover concrete using a hydration stabilizer admixture (HSA) in a ready-mix concrete (RMC) plant and it aims to present the operational procedures and the results obtained during this implementation. The methodology adopted was based on preliminary laboratory studies followed by real-scale tests in order to evaluate the technical and financial feasibility of implementing the process under real RMC conditions focusing on the impact of using HSA on setting time and compressive strength of concrete. In sequence, the results of 1500 tests carried out for reuse leftover concrete and adhered concrete with an HSA admixture were presented and analyzed showing that the characteristic compressive strength of the reference concrete was similar to that of stabilized concrete.. This study contributes to the advance of knowledge in the area of ​​RMC concrete waste reuse, since it proves that the use of HSA is feasible as long as parameterized in previous laboratory tests considering the influence of temperature and the setting time for concrete stabilization. The study also concludes that the use of an HSA does not negatively affect the compressive strength of concrete. Finally, in the case studied, the method of reusing concrete with an HSA is economically advantageous for RMC since the revenue generated by the reuse of reused raw materials is higher than the cost of the HSA used in the stabilization of the concrete leftovers and the adhered concrete.