Study On The Hydration Characteristics In Cementitious Materials Mixed With Calcium Silicon Slag

The chemical composition of the calcium silicate slag is similar to the cement,and the main mineral composition is?-C₂S.This article mainly evaluates the activity of calcium silicon slag as to the mixed cement materials,the content ofcalcium silicon slag and water/cement ratio are taken as the parameters,The hydration characteristics of the calcium silicon slag as cementitious material are studied from the view of non-evaporable water content,meanwhile,it is studied calcium silicon slag-cement mixed gelling material of hydration products from the XRD,TG-DSC and SEM analysis.,and quantitative analysis of the hydration products.The following conclusions are obtained:?1?The various oxides content of calcium silicon slag are less different from other active minerals.the mass fraction of calcium silicon slag in various literatures and in this paper are greater than 1.2.The compressive strength was measured by replacing cement in the same amount,and the strength index of the cementitious materials with each dosage was greater than 1.XRD and SEM of pure calcium silicate slag hydrated for 28 days showed that rhomboid CaCO₃ is found in the hydration products,so the calcium silicate slag was evaluated to have certain gel activity.?2?The hydration reaction degree of the cementitious materials mixed with calcium silicon slag are over 59.09%.The water-cement ratio is a great influence on the degree of hydration in the mixed cementitious materials.When the hydration is to be 56d,the hydration reaction degree of W3CS1 is more than W3CS0.Calcium silicon slag makes the hydration reaction rate reduction slow down.W1CS0 and W1CS1 hydration reaction rate in the early hydration are all above 1.4/d,The hydration reaction rate decreases with the increase of the age.The hydration reaction rate has been reduced to 0.1/d at 7d.?3?According to the XRD analysis,with the decrease of cement content,the diffraction peak intensity of C₃S and C₂S changes to different degrees.The addition of calcium silicon slag don't affect the variety of hydration products.The main hydration products are Ca?OH?₂and CaCO₃,and the diffraction peak intensity decreases with the growth of calcium silicon slag content.The intensity of Ca?OH?₂ and CaCO₃ diffraction peaks of CS0-CS4 increased with the growth of water-binder ratio,while the intensity of Ca?OH?₂ and CaCO₃ diffraction peaks of CS5-CS6 don't change significantly.?4?We can learn from TG-DSC results in calcium silicon slag-cement mixed gelling materials that there are mass loss and endothermic peak between 450?⁵00?and650?⁷00?,which represents the Ca?OH?₂ and CaCO₃'s decomposition.The influence degree of CS1-CS3 in DSC curves are low.but the TG curves have different degrees of decrease.It illustrates that the decomposition of Ca?OH?₂ volume is decreasing,and the hydration products Ca?OH?₂ content of mixed cement materials is lower.Except for the mixed cementing materials with a content of 30%,other mixed cementing materials Ca?OH?₂ all tend to a certain stable content.?5?According to the study on the micro-morphology of the cementitious materials mixed with calcium silicon slag-cement,at the early stage of hydration,the fineness of calcium silicon slag was smaller than cement particles,which could play the role of micro-aggregate filling,and the number of pores is significantly reduced,while the flocculent C-S-H gel appeared in the system.With the increase of age,unhydrated cement particles can still be observed in all mixed cementing materials,CS0 has formed a blocky cementing system,while with the increase of the content of calcium silicon slag,the hydration reaction occurs in C₂S,and divergent flocculent cementing products appear in the morphology of hydration products,especially in CS6.