Using perforated cenospheres to improve the engineering performance of limestone-calcined clay-cement (LC3) high performance concrete: Autogenous shrinkage, strength, and microstructure

Limestone-calcined clay-cement (LC3) is a novel ternary cementitious material. Cenospheres (CS) are a type of fly ash with a smooth surface and hollow center. The chemical etching of the CS creates perforated CS (PCS) with pores through with water can be transported to achieve internal curing of LC3. In this study, experiments were performed to determine the effect of PCS on the performance of LC3 high-performance concrete. The dosage of PCS was 4% and 8%, and the dosage of CS was 8%. The autogenous shrinkage of samples with 4% and 8% PCS was reduced by 31.1% and 61.8%, respectively. This means PCS reduces the autogenous shrinkage of LC3. The strength of the sample with 4% PCS increased by 7.01 and 12.06 MPa compared with the control sample at 7 and 28 days of age, respectively, due to the internal curing of PCS and its volcanic ash This achieves the dual impact of low shrinkage and high strength. Furthermore, the experimental X-ray diffraction and Fourier transform infrared spectroscopy results showed that PCS can undergo pozzolanic reactions with calcium hydroxide. In addition, the heat of hydration and thermogravimetric analysis experiments showed that the internal curing of PCS promotes the hydration of LC3. Scanning electron microscopy images showed that the sample with 8% PCS had a high-quality dense bond between the PCS and matrix. Therefore, PCS can be used as a reactive internal curing material and the microscopic reaction of PCS can improve the macroscopic properties of concrete.