Research And Preparation On Early Strength Fiber Mortar

At present,cement mortar used in engineering has many defects,for example low tensile strength,brittleness,poor impact resistance,easy to crack.These prevent the development of cement mortar to the direction of high performance and limit the scope of its application in the field of construction engineering.So this paper puts forward a kind of early strength fiber mortar.In the case of fly ash replacing 50%cement mortar,the early strength fiber mortar 3 days flexural strength can reach more than 4 MPa and compressive strength can reach more than 20 MPa.At the same time,it has good crack resistance,good construction workability,good ductility,and its performance is stable.It aso has certain social economic benefits.Raw materials are used in this paper with 32.5 slag portland cement,CA-50 aluminate cement,river sand,polypropylene fiber and fly ash,early strength agent,water reducing agent.In order to achieve early strength mortar purpose,firstly,the type and dosage of additives are optimized to determine the best combination of additives according to the initial fluidity and strength of mortar.On this basis the author analyzes different fiber content and fly ash content on cement mortar different performance,optimizing the best mixing quantity of the two,make its strength to the expected goal.Main test steps as follows:first of all,the author mixes mortar mixture evenly,and tests the initial fluidity of mixture,according to "the fluidity of cement mortar test method"(GBT2419-2005);Then,the author made 40mm x 40mm x 160mm of block,into the box standard curing,curing to the provisions of age;Finally,according to "cement mortar strength test method(ISO act)",the author tests the test block of 3d,7d strength,28d.The experimental results showed that the best mix ratio of sulfamic acid salt water reducing agent and naphthalene series high efficient water reducing agent is 1:5.The optimum adding amount is 0.6%.When aluminate cement content is 5%,the 3 days strength of cement mortar is biggest.When triethanolamine content is 0.02%,anhydrous sodium sulfate content is 0.4%,the cement mortar for 3 days,7 days strength are the largest and the final setting time is the shortest;When the water binder ratio is 0.34,the sand binder ratio is 1.5 and the fly ash content is 50%,Mortar block 3 day flexural and compressive strength can reach 4.6MPa,27.1MPa.The long-term mechanical properties show that strength of the block 120 days without fly ash is already close to block.Performance of early strength fiber cement mortar include flexural strength test,splitting tensile strength test,the elastic modulus experiment,crack resistance,wear resistance test.Experimental results show that when the water binder ratio is 0.34,the sand binder ratio is 1.5 and the fly ash content is 50%,the flexural strength of the specimen at 28th day and 60th day increase by 15.89%and 15.38%respectively than plain cement mortar specimen,the splitting tensile strength also increase by 52.38%and 57.14%respectively.The elastic modulus reduces by 7.01%and 7.01%respectively than the ordinary cement mortar with 0.2%and 0.4%fiber content.Fly ash has a certain degree of crack resistance effect and the fiber added to prevent the crack effectively.Fly ash reduces the wear resistance of the specimens and the fiber can improve the wear resistance properties.