Hydration Mechanism And Strength Of Marble Powder Cement

Marble is widely distributed all over the world,with the rapid development of the construction industry,marble in the production,processing process will produce a large amount of waste,the use of stacking or landfill treatment is waste of land resources and pollution of the environment.For this reason,it is used as a mineral filler in cement,so that marble powder can be rationally used and can reduce the cost of building materials for engineering construction.In this paper,marble powder and cement are mixed externally and internally to study the properties of composite cementitious materials,and the hydration process and early properties under the composite system are explored.The main research contents and results of this paper are as follows:（1）The mechanical properties of the marble powder-cement system were tested.The results showed that the compressive strength of cement slurry decreased at all ages when mixed with marble powder,and the compressive strength of cement slurry was still lower than that of the control group without marble powder at 28 days,and the loss of strength of marble powder below 15%was relatively small for the early stage of cement slurry,while the loss of strength loss of more than 15%of marble powder for the later stage of cement slurry was relatively large.With the increase of marble powder,the strength loss of cement slurry in the early stage is relatively large,but the strength loss in the later stage of cement slurry is small.Under the same age conditions,the higher the content of marble powder,the smaller the compressive strength value of the cement slurry in the early stage.（2）The changes of its hydration products were studied by XRD and simultaneous thermal analysis.X-ray diffraction analysis test showed that the diffraction peaks of the hydration products calcium alum（AFt）and Ca（OH）₂ appeared in the hydration products calcium alum（AFt）and Ca（OH）₂ in the hydrostatic 1,7 and 28d diffraction patterns of the internal and external doped dali powder slurries,and no new characteristic peaks were observed in the XRD pattern after the incorporation of marble powder,and the synchronous thermal analysis test showed that with the increase of marble powder content,the weight loss peak area of Ca（OH）₂ in the cement slurry was significantly reduced compared with the pure cement slurry.However,when the amount of marble powder is higher,the peak area of Ca CO₃ weight loss also increases.（3）Low-field NMR technology was used to study the early hydration reaction process after external and internal doping of marble powder,and it was found that the early hydration of the external and internal doped marble powder-cement system was divided into two stages,the hydration degree and glue-to-air ratio of the marble powder-cement system were relatively flat at the beginning stage,and the difference between the hydration degree and the glue-to-air ratio of the marble powder-cement system gradually increased after entering the acceleration stage.Under the same hydration time,the signal intensity of T₂ increases with the increase of marble powder content,which delays the transformation of evaporable water to non-evaporable water in marble powder cement slurry,and it is concluded through the Power model that with the increase of marble powder content,the compressive strength of the externally mixed marble powder cement slurry gradually increases,and the glue-to-air ratio also increases,and the two are linearly related.