Exploration on the occurrence state of fluorine in cement hydration products mixed with high fluorine alkali free liquid accelerator

If there was abundant fluorine in shotcrete, it might leach out and pollute the soil or migrate to corrode the reinforcement.Therefore, this research mainly investigated the basic properties of high-fluorine alkali free liquid accelerator (HF-AFA) and its occurrence forms in cement hydration products.The macro-test results showed that with the increase of HF-AFA dosage, it appeared excellent coagulation promoting property. However, when the HF-AFA dosage exceeded 7.0%, the 1d compressive strength of mortar was lower than 7.0 MPa. In addition, by measuring the early hydration heat of cement, C 3 A, C 3 S, C 2 S and C 4 AF pastes with and without HF-AFA, and combining XRD and SEM micro-analysis, the occurrence forms of fluorine in different clinker minerals were obtained.The final analysis results indicated that fluorine mainly existed in the form of CaF 2 , CaAlF 5 and Ca 2 AlF 7 crystals in C 3 A and C 3 S minerals, while only little CaF 2 crystals appeared in C 2 S and C 4 AF minerals.