Study On Shrinkage Of Polymer Modified Cement Mortar

The traditional front mortar has large shrinkage and more cracks,compared to the ordinary front mortar,polymer modified cement mortar has the unique superiority,the addition of polymer could obviously reduce the brittleness of mortar,and the flexibility improved obviously.The effects of water binder ratio,redispersible latex powder,fly ash,shrinkage reducing agent and polypropylene fiber on the autogenous shrinkage,drying shrinkage and mechanical properties of mortar were studied by orthogonal test in this paper,the optimal mix proportion was selected,a kind of high performance front mortar was maked according to the optimal mix proportion,and its mechanical properties and shrinkage were tested.Firstly,the effects of water binder ratio,redispersible latex powder,fly ash,shrinkage reducing agent and polypropylene fiber on the autogenous shrinkage of mortar were studied.,the results showed that the autogenous shrinkage of mortar decreased with the increase of water binder ratio,fly ash content,shrinkage reducing agent content and polypropylene fiber content,the autogenous shrinkage of mortar decreased first and then increased with the increase of redispersible latex powder,Range analysis showed that the biggest influence on the autogenous shrinkage of mortar was redispersible latex powder and shrinkage reducing agent,the optimal mix proportion of autogenous shrinkage was A1B2C4D4E4 that the water cement ratio was 0.40,the content of redispersible latex powder was 2.5%,the content of fly ash was50%,the content of shrinkage reducing agent was 1.2%,the content of polypropylene fiber was 0.5%.Secondly,the effects of water binder ratio,redispersible latex powder,fly ash,shrinkage reducing agent and polypropylene fiber on the drying shrinkage of mortar were studied.,the results showed that the drying shrinkage of mortar increased with water binder ratio increasing,the drying shrinkage of mortar decreased with the increase of redispersible latex powder content,fly ash content,shrinkage reducing agent content and polypropylene fiber content,the inhibition effect of low content of fiber on the drying shrinkage of mortar was not obvious.Range analysis showed that the biggest influence on the drying shrinkage of mortar was fly ash and redispersible latex powder,the optimal mix proportion of drying shrinkage is A4B4C4D4E4 that the water cement ratio was 0.25,the content of redispersible latex powder was 10%,the content of fly ash was50%,the content of shrinkage reducing agent was 1.2%,the content of polypropylene fiber was 0.5%.Thirdly,the effects of water binder ratio,redispersible latex powder,fly ash,shrinkage reducing agent and polypropylene fiber on mechanical properties of mortar were studied.The results showed that the compressive strength and flexural strength decreased with the increase of water binder ratio,the compressive strength and flexural strength increased first and then decreased with the increase of the content of redispersible latex powder,the compressive strength and flexural strength increase with the increase of fly ash content,the compressive strength and flexural strength decreased first and then increased with the increase of shrinkage reducing agent content and polypropylene fiber content.Ratio of bending-compressive strength increased with the increase of water binder ratio and redispersible latex powder content,ratio of bending-compressive strength increased first and then decreased with the increase of polypropylene fiber content,the effect of fly ash content and shrinkage reducing agent content on the ratio of bending-compressive strength was not obvious.The optimal mix proportion of ratio of bending-compressive strength is A1B4C4D4E3 that the water cement ratio was 0.40,the content of redispersible latex powder was 10%,the content of fly ash was50%,the content of shrinkage reducing agent was 1.2%,the content of polypropylene fiber was 0.3%.Finally,after comprehensive analysis,the optimal mix proportion was A2B4C3D4E3 that the water cement ratio was 0.35,the content of redispersible latex powder was 10%,the content of fly ash was30%,the content of shrinkage reducing agent was 1.2%,the content of polypropylene fiber was 0.3%.The front mortar that made according to the optimal mix proportion was lower than the ordinary mortar in compressive strength and flexural strength,but the ratio of bending-compressive strength and drying shrinkage were improved greatly,the comprehensive performance was better than the ordinary front mortar,poor toughness and large shrinkage of ordinary front mortar were improved.