油酸改性超细水泥对注浆材料性能的影响OA

In the repair of concrete micro-cracks,ultrafine cement(UPC)faces the problems of poor slurry fluidity,high porosity and susceptibility to dissolution under low water-cement ratio.In this study,the surface modification of UPC with oleic acid was proposed to simultaneously improve its injectability and hydrophobicity.Oleic acid modified UPC with oleic acid content of 0%～0.3%(mass fraction)was prepared by ball milling method.The rheological properties,compressive strength,heat of hydration,hydrophobic properties and interfacial bond strength of the modified UPC paste were systematically evaluated,and the modification mechanism was revealed by FTIR,SEM,TG,LF-NMR.The results show that appropriate amount of oleic acid(0.1%)modification can reduce the viscosity of grouting material and improve the rheological properties.At the same time,at this dosage,the inhibition effect on cement hydration is small,the strength of the slurry is not much affected,and the autogenous shrinkage of the slurry is significantly reduced.Oleic acid is involved in the surface modification of cement particles,and the contact angle of hardened slurry increases from 48.6° to 126.4°.However,an excessive amount of oleic acid(>0.2%)severely inhibits the hydration reaction,reduces the 28 d compressive strength from 54.95 MPa to 23.08 MPa,and increases the autogenous shrinkage and porosity.In this paper,the study investigates the action mechanism and dosage threshold of oleic acid in UPC,which provides support for the development of high-performance microfracture anti-seepage repair materials.