Making Use ​of the Useless

Peeter Paaver, University of Tartu

Description

The durability of mortars and concrete with a high volume of Ordinary Portland Cement (OPC) substituted by a fly ash calcium sulfoaluminate binder Authors Dr. Peeter Paaver - Estonia - University of tartu Abstract The durability of mortars and concrete with a high volume of Ordinary Portland Cement (OPC) substituted by a fly ash calcium sulfoaluminate binder is investigated in this study. The utilization of circulating fluidized bed combustion (CFBC) boilers imposes limitations on the recycling of fly ash due to its low combustion temperature. This low temperature inhibits the formation of reactive calcium silicate minerals and diminishes the cementation properties of the ash. Previous research (Paaver et al., 2020, 2022) conducted by our team demonstrated that the mechanical activation of sulfur and calcium-rich CFBC fly ash results in the formation of a calcium sulfoaluminate (CSA) type active binder. This binder allows for high-volume OPC replacement, with a reduction in strength of less than 10%. In this contribution, we examine the durability of mortars and concrete produced with activated CFBC CSA and OPC. Specifically, we assess their resistance to freezing cycles, heat, leaching, and flexural strength. Our findings indicate that standard freezing-thawing tests did not have a significant impact on the test specimens. Surprisingly, heating cycles increased the compressive strength of some test mixtures. We conclude that the properties of mechanically activated fly ash CSA mortars and concrete are comparable to standard CEM1-42.5R OPC applications. These findings suggest the potential for their use as a complete or partial substitute for Portlandite cement and as a composite mix for lightweight blocks.

 
May 14th, 1:30 PM May 14th, 2:00 PM

Making Use ​of the Useless

Grand Rapids, Michigan

The durability of mortars and concrete with a high volume of Ordinary Portland Cement (OPC) substituted by a fly ash calcium sulfoaluminate binder Authors Dr. Peeter Paaver - Estonia - University of tartu Abstract The durability of mortars and concrete with a high volume of Ordinary Portland Cement (OPC) substituted by a fly ash calcium sulfoaluminate binder is investigated in this study. The utilization of circulating fluidized bed combustion (CFBC) boilers imposes limitations on the recycling of fly ash due to its low combustion temperature. This low temperature inhibits the formation of reactive calcium silicate minerals and diminishes the cementation properties of the ash. Previous research (Paaver et al., 2020, 2022) conducted by our team demonstrated that the mechanical activation of sulfur and calcium-rich CFBC fly ash results in the formation of a calcium sulfoaluminate (CSA) type active binder. This binder allows for high-volume OPC replacement, with a reduction in strength of less than 10%. In this contribution, we examine the durability of mortars and concrete produced with activated CFBC CSA and OPC. Specifically, we assess their resistance to freezing cycles, heat, leaching, and flexural strength. Our findings indicate that standard freezing-thawing tests did not have a significant impact on the test specimens. Surprisingly, heating cycles increased the compressive strength of some test mixtures. We conclude that the properties of mechanically activated fly ash CSA mortars and concrete are comparable to standard CEM1-42.5R OPC applications. These findings suggest the potential for their use as a complete or partial substitute for Portlandite cement and as a composite mix for lightweight blocks.