Normal and Controlled Low-Strength Material Concrete with High Volume of Fly Ash and Glass Waste
Mohit Agarwal and Enrique del Rey Castillo
Appears on pages(s):
controlled low-strength material (CLSM); fly ash concrete; glass sand; glass waste; sustainability; sustainable concrete
The use of industrial waste in concrete and controlled low-strength mixtures (CLSM) along with the experimental analysis of the fresh and hardened properties was investigated in this research. Four waste materials were used to design 17 mixtures. Fly ash and glass powder were investigated at high rates of replacement for cement, from 60 to 90%. This information is scarce in published literature and can help practitioners and concrete batchers in developing mixtures with a high level of replacement. Additionally, natural sand was substituted by glass sand which, in combination with fly ash and glass powder as cement replacement, provides an entirely new body of knowledge of concrete mixtures that use limited newly produced materials. Adequate strength and flowability was achieved with the use of recycled waste materials for both normal concrete and CLSM.
All normal concrete mixtures except one, which had a 90% fly ash replacement, achieved a 28-day compressive strength of at least 29 MPa. Concrete with this compressive strength has multiple applications that represent a significant portion of the concrete produced. Using these mixtures has the potential to significantly reduce the amount of virgin products, especially cement that has a significant carbon footprint. All CLSM mixtures except two had a compressive strength of less than 2 MPa, therefore meeting the walkability and excavability requirements as set out in American Concrete Institute (ACI) guidelines and codes. Finally, an equation was proposed to predict the 28-day compressive strength of concrete with high volumes of fly ash replacement (>60%). As far as the authors are aware, there is no method to calculate the compressive strength of this type of concrete. This equation represents a significant contribution not only to the research body but also to practitioners and concrete batchers.