Effects of Coal Metakaolin on the Mechanical Properties and Microstructure of High-belite Sulphoaluminate Cement

The effects of coal metakaolin on the mechanical properties of high-belite sulphoaluminate cement under compressive loading were investigated.The composition and microstructure of hydration products at different hydration times were analyzed by X-ray diffraction and scanning electronic microscopy.The hydration process of blended cement was studied via electrochemical impedance spectroscopy.In particular,replacing a part of cement with CMK(10%,20%,and 30%)was found to promote the hydration process,to refine the pore size,and to improve the compressive strength of the composite.The best compressive strength of the cement was achieved at a CMK content of 30%after 28 days hydration,being improved by 20.13 MPa,or1.44 times relative to that of undoped specimens.Furthermore,the compressive strength is shown to correlate with the impedance parameter R_(CCP),which allows the latter to be used for nondestructive assessment of the compressive strength of blended cement materials.