Research And Application Of Ultra High Early Strength Sulphoaluminate Cement-based Materials

As the development of society and economy,the required for existing engineering and new engineering is becoming higher and higher.Ordinary concrete can't already meet the special requirements the material of the major project.Such as railway,viaduct,military engineering and major infrastructure projects,the important part of special proects require material with high mechanical properties of short cycle,and easy to construction.According to this situation,this paper relying on reconstruction and extension projects of ji-qing freeway prepared ultra high early strength sulphoaluminate cement-based materials,which choose the Sulphoaluminate cement(SAC)and self-developed special composite admixture.It is an environmentally friendly low-energy material,with good fluidity,suitable setting time,high early strength,anti-frozen strong,resistance to sulphate attack and other characteristics.The material is suitable for the maintenance of highway,bridge and other projects which has special requirements for the material.Which can provide reference for the research and application of SAC in the field of special cementitious materials.This paper first prepared a SAC special composite admixture.Based on the research and experiment of the accelerating mechanism of calcium formate,lithium carbonateand aluminum sulfate in the hydration reaction of sulphoaluminate cement,which prepared a new composite early strength agent for SAC,referred to as ICCH.It can significantly increased the early strength,and steady development of long term strength.In order to retard the setting time of cement,and ensure sufficient operating time,the use of boric acid,cellulose ether and other developed a cement composite retarder(BS),BS can be stable and effective delay of SAC setting time.The ultra high early strength sulphoaluminate cement-based materials were prepared by poly carboxylic acid water reducing agent and self-developed special composite admixture ICCH and BS.There are cement paste,mortar and concrete.The initial fluidity of the cement paste is greater than 200 mm,the initial setting time is about 20 min,the compressive strength reached 46.64 MPa at 4h and final strength is more than 70 MPa.The mortar have good fluidity and maintain the working time of about 30 min,2h compressive strength of more than 30 MPa,4h compressive strength of 43.7MPa,1d compressive strength of more than 50 MPa,and the long term strength of steady growth.Concrete to maintain the working time of more than 40 min,4h compressive strength of more than 40 MPa,7d compressive strength of not less than 50 MPa,flexural strength after 4h are not less than 6.5MPa.The early characteristics and durability of ultra high early strength sulphoaluminate cement-based materials were studied.The test showed that the material had good early crack resistance and the volume stability,it was able to bind well with the portland cement and its own material,and the Self-adhesive bond strength after 1d no less than 6MPa.The materials has good frost resistance and resistance to sulphate attack.It is in the 250 freeze-thaw cycles,the compressive strength remained above 40 MPa.It is immersed in saturated sodium sulfate solution for 90 days,the compressive strength is more than 40 MPa and the flexural strength is more than 10 MPa.Preparation of ultra high early strength sulphoaluminate cement concrete which it has been industrialized production.It was used in advance for bridge repair and reinforcement projects in August and November of 2016 in Gansu,which greatly shortened the construction period and achieved good results.