Sudy On The Effect Of Super Absorbent Polymer On Shrinkage Of Alkali Activated Slag Cement Mortar

Alkali activated slag cement(AAS)is a kind of green,environmental protection cementitious material which is made of alkali metal compound.The utility model of AAS has the advantages of high strength and good durability and teh development and application has broad prospects.However,the shrinkage of alkali slag cement is an important factor which restricts its application and development.At present,a lot of research is to develop the corresponding expansive agent,shrinkage reducing agent to deal with the problems in the shrinkage of alkali slag cement and achieved certain results,but they can not promote a wide range of use due to poor results.The results show that the addition of super absorbent plomer(SAP)can effectively reduce the shrinkage of concrete.However,there are few reports about the effect of SAP on shrinkage of alkali activated slag concrete.In this paper,the effect of SAP on the fluidity,compressive strength,autogenous shrinkage and drying shrinkage of alkali activated slag cement mortar(AASM)was studied.Results show:The fluidity and strength of alkali activated slag cement mortar are related to the water absorption of SAP.Under the conditions of this study,the liquidity of alkali slag cement mortar decreased at pre-water SAP less than 20 times and the alkali slag cement mortar fluidity is improved when the pre-absorption degree of SAP more than 20 times.The introduction of SAP will lead to a decrease in the strength of mortar alkali slag cement and reduce the increase with the increase of additional water cement ratio.In comparison,the effect of SAP addition on the alkali slag cement mortar with water glass as the alkali component is slightly lower than that of NaOH alkali componentSAP can greatly reduce the self shrinkage of AASM and the effect of NaOH and 1.5 modulus of water glass as activator of AASM is different.The effect of self shrinkage is better when the water binder ratio is high.The autogenous shrinkage decreased by over 50% when the additional water binder ratio was 0.09.When the NaOH as activator,AASM self shrinkage decreased significantly with the increase of the content of alkali and the autogenous shrinkage of AASM is reduced by 80% with alkali content was 6%.When the 1.5 modulus of water glass as activator,alkali content of 4% AASM autogenous shrinkage decreased significantly.The autogenous shrinkage of AASM decreases with the increase of the modulus of water glass.SAP has little effect on the drying shrinkage of AASM.The effect of SAP was smaller than that of AASM when the content of alkali and the modulus of water glass were used as variables.SAP will have a slight negative influence on dry shrinkage of AASM when the total water binder ratio or the additional water quantity is higher.SAP can change the pore structure of AAS and it could increase the total porosity and increase the number of capillary pores and gel pores.But SAP by internal curing effect can replenish the water of hydration reaction and drying effect and reduce water hole negative pressure and widen the aperture.This is why shrinkage is reduced.A certain amount of hydration products were filled in the closed pores left behind by SAP and the dense hydration products were favorable to block the connectivity of the pores.SAP the hydration exothermic rate increased but the exothermic peak without delay or advance when NaOH is used as the alkali slag cement activator.However,the ASS exothermic peak was delayed when the 1.5 modulus of water glass was used as the activator.The total heat release rate of the above two groups was higher than that of the baseline group but both were less than the total water binder ratio.SAP can improve the hydration degree of AAS at 28 d.