Effect Of Metakaolin-CaCO₃ Auxiliary Cementing Material On The Properties Of White Reactive Powder Concrete

White reactive powder concrete（WRPC）has a broad application prospect in structural decoration integration engineering.However,auxiliary cementing materials suitable for WRPC are scarce.Metakaolin and limestone are among the few auxiliary cementing materials that can meet the requirements of WRPC whiteness and physicochemical properties.It is of great significance to study Metakaolin-Limestone auxiliary cementing material（MKL）with large amount to replace cement clinker for developing low carbon ecological white Portland cement（WPC）and WRPC.The effects of MKL on rheological properties,mechanical properties,alkali resistance and partial durability of WPC and WRPC were studied by isothermal calorimeter,XRD,SEM and TG-DSC.The results show that:（1）Adding MKL will increase the water consumption for standard consistency of WPC and prolong its setting time,but the effect is small when the dosage is less than15%.The influence of MKL on the initial setting time of cement is greater than the final setting time.Proper amount of MKL substituted cement can enhance WPC,and the strength decreases when the substituted cement content is more than 30%,and the strength performance is the best when the substituted cement content is 30%.（2）The addition of MKL can promote the hydration of cement,and partial substitution of WPC can significantly reduce the content of Ca（OH）₂of hydration products of WPC,while the quantity of hydration products such as C-S-H and AFt remains basically stable,indicating that the addition of MKL to WPC can produce a good pozzolanic effect.（3）Using MKL instead of 30%WPC as auxiliary cementing material,quartz powder and quartz sand as fine aggregate,adding polycarboxylic acid water-reducing agent,silica fume and other components,the self-compacting WRPC with compressive strength of 107.4MPa at 28d without adding fiber was prepared.（4）The fluidity of WRPC decreased with the increase of MKL content.It has little effect on fluidity when the dosage is below 15%.Because the fine particles of metakaolin and its cation exchange ability can weaken the reducing effect of water reducer,the plastic viscosity,yield stress and shear stress of WRPC increase obviously with the increase of MKL content.（5）The addition of MKL can greatly improve the phenomenon of alkaline flooding in WRPC products.When the dosage reaches the maximum 75%,WRPC products can be considered as approximately non-alkaline flooding.（6）MKL partially replaces cement to prepare WRPC.When the dosage is less than 45%,the strength of WRPC decreases little.Adding MKL can greatly improve the chloride penetration resistance,toughness,impact resistance and wear resistance of WRPC.