Long-term compressive strength and some other properties of controlled low strength materials made with pozzolanic cement and Class C fly ash.

Controlled low strength material (CLSM) is a flowable mixture that can be used as a backfill material in place of compacted soils. CLSM (or flowable fill) require no tamping or compaction to achieve its compressive strength and typically has a load carrying capacity much higher than that of compacted soils, but can be proportioned to allow future excavation. In this study, several different CLSM mixtures containing Class C fly ash (FA) obtained from Soma Thermal Power Plant in Turkey, crushed limestone sand (CLS), and a minimal amount of pozzolanic cement (PZC) were produced. The mass of PZC was kept constant for all mixtures at 5% of FA by mass. The mechanical and physical properties of CLSM mixtures such as unconfined compressive strength, water absorption by capillarity and EP toxicity were investigated by a series of laboratory tests. CLSM mixtures with low PZC contents and high Class C FA and CLS contents can be produced with excellent flowability and low unconfined compressive strengths in the range of 1.16-2.80 MPa at 365-days age when re-excavation at later ages might be needed. The results presented here show a new field of application for Soma FA in CLSM mixtures, resulting in great advantages in waste minimization, as well as, conservation of resources and environment.