Properties And Microstructure Of PB-g-PSG Cement Modifier Modified Cement Mortars

In this paper,the polybutadiene grafted polystyrene and epoxy propyl methacrylate emulsion（PB-g-PSG）with mass ratio of 50/50/0,50/49/1,50/47/3 and 50/45/5 were synthesized,and the product was confirmed by FTIR,then Tween-80 was added into PB-gPSG emulsion to prepare PB-g-PSG cement modifier,and the content of Tween-80 in PB-g-PSG emulsion solid mass was 2%,4% and 6%,respectively.PB-g-PSG cement modifier was used to modified cement mortar,and studying the GMA,twain-80,and the cement modification agent on the influence of physical properties of the modified cement mortar（fluidity,water retention and water absorption rate）and mechanical properties（compressive strength,flexural strength）,at the same time.The microstructure of modified cement mortar was observed by SEM.The action mechanism of tween-80 on PB-g-PSG emulsion was analyzed.The experimental results show that the relationship between tween-80 and cement modifier and the fluidity of modified cement mortar is an increasing function.GMA had no effect on fluidity.They also show an increasing function relationship with the water retention rate,and their maximum value is 93%（mass fraction）.The relationship between Tween-80 and the compressive strength of modified cement mortar is firstly increased and then decreased;The relationship between the modifier and the compressive strength is a decreasing function.The compressive strength of pure cement mortar is generally higher than that of modified mortar.The relationship between the flexural strength and GMA is an increasing function.The relationship between Twain-80 and the flexural strength of modified cement mortar is firstly increased and then decreased.The relationship between the bending strength of the cement modifier and the modified cement mortar is firstly increased and then decreased.The flexural strength of reference mortar is lower than that of modified mortar.When the dosage of cement modifier is 10%,the maximum value is 9.52 MPa.The relationship between the flexural strength of modified cement mortar and GMA is an increasing function.The relationship between Tween-80 and the mass of absorbed water of modified cement mortar is firstly a decreasing function and then an increasing function.The relation between modifier and mass of absorbed water is decreasing function.The mass of absorbed water of pure cement mortar is generally higher than that of modified mortar.The relationship between GMA and mass of absorbed water is a decreasing function.FTIR and DSC analysis showed that both cement modifier and GMA had effects on the hydration of cement and the structure of modified cement mortar.The cement modifier enhanced the hydration of cement,while GMA reduced the content of Ca（OH）₂.SEM photos showed that the cement modifier has adhesion and bridging effect on cement hydrate,and the two have formed an interpenetrating network structure.The hexagonal sheet crystal structure of calcium hydroxide is observed.The structure of modified cement mortar is denser with GMA,and it has been proved that the chemical reaction between GMA and Ca²⁺ can improve the properties of cement mortar.The hydrophilic action of Tween-80 resulted in the formation of a thick layer of hydration on the surface of the latex particles,which separated the latex particles from each other to avoid the occurrence of condensation,so that,the PB-g-PSG emulsion can be stable.