Study On The Adaptability Of Polycarboxylate Water Reducer In UHPC

The adaptability of cement and polycarboxylate superplasticizer is an important factor affecting the performance of UHPC.When the adaptability of superplasticizer and cement is poor,the fresh cement paste may have the problems of poor fluidity,bleeding,segregation,high loss rate of fluidity and large shrinkage crack caused by concrete hardening,etc.In order to study the adaptability factors of fresh cement and polycarboxylic acid water reducer in UHPC slurry performance,this paper tests the net slurry fluidity of 12 different types,manufacturers and batches of cement and 9 different polycarboxylic acid water reducer with low water binder ratio and high water reducer ratio,and tests the initial net slurry fluidity and the net slurry fluidity after 60min The adaptability and influence of fresh cement and polycarboxylate water reducer are further analyzed from the type,chemical composition,fineness and strength grade of cement.The results show that the adaptability of each water reducing agent to S11 cement is poor,and among the 9 water reducing agents,SP2 water reducing agent has the best adaptability to S11 cement,and SP5 water reducing agent has the worst adaptability to S11 cement.Nine kinds of water reducing agents have good adaptability to S12 cement paste,among which SP2 water reducing agent has the best adaptability and SP5 water reducing agent has the worst adaptability.The test results of 9 kinds of water reducing agents on 10 kinds of ordinary portland cement and Portland cement are quite different.The adaptability of SP2,SP9 water reducing agents and ordinary portland cement is better,among which SP2water reducing agent and S8 cement are the best,and SP5 water reducing agent and ordinary portland cement are the worst,Among them,SP5water reducer has the worst adaptability to S6 cement,while SP6 water reducer has a negative loss rate of 60 min fluidity of S1 to S10 cement due to its super slump retention performance.The adaptability between cement and polycarboxylate water reducer has an important relationship with the type of cement.Among them,sulphoaluminate cement has the worst adaptability to water reducer,white portland cement has the best adaptability to water reducer,while ordinary portland cement and Portland cement have the general adaptability to water reducer,and there are great differences between different cements.Among them,the adaptability of sulphoaluminate cement and SP2 water reducer is the best,and the adaptability of SP5water reducer is the worst;the adaptability of white portland cement and SP2 water reducer is the best,and the adaptability of SP5 water reducer is the worst;among 10 kinds of ordinary portland cement and Portland cement,S8 and S9 cement show better fluidity,of which S8 cement has the best fluidity,while S6 and S7 cement have the poor fluidity In particular,the fluidity of S7 cement is the worst;in terms of the fluidity of cement,S6 and S8 cement have a large loss rate of fluidity in 60minutes,of which S6 cement has a maximum loss rate of fluidity of3.42%.The lower the Al₂O₃content in cement,the smaller the loss rate of fluidity of corresponding Portland cement in 60 minutes,and the better the adaptability of cement and water reducer.Among the 10 kinds of Portland cement s1-s10,the lowest Al₂O₃content is S3,S4,S10 cement,and their 60 min fluidity loss rate is also the lowest among the 10 kinds of cement,while the highest Al₂O₃content is S11 sulphoaluminate cement,which has the worst adaptability with various water reducing agents.In a certain range of alkali content in cement,the alkali content has little relationship with the fluidity of the initial cement paste,but when the alkali content exceeds this range,the higher the alkali content in the cement paste,the lower the initial fluidity of the cement paste,The fluidity of cement is obviously poor.In the range of 0.491 to 0.746 of 10kinds of ordinary portland cement and Portland cement,the relationship between the alkali content and the initial fluidity of cement is not significant,but when the alkali content exceeds this range,the initial fluidity of concrete paste is significantly reduced.When the main chemical components of cement are similar,the higher the fineness of cement is,the greater the loss rate of cement fluidity is.When the water cement ratio is 0.20 and the water reducing agent is 1%,the average loss rate of 60 minute fluidity is 0.42%and0.43%,respectively.When the percentage of cement fluidity is reduced to1.11%,the average loss rate of 60 minute fluidity is rapidly reduced To1.40%.The research on compressive strength of cement shows that the influence of cement strength grade on the fluidity of cement paste is very limited,and cement strength grade is not an important factor for the adaptability of cement and water reducer.