The Preparation And Engineering Application Of Self-leveling 160 Reactive Powder Concrete

Reactive Powder Concrete（RPC）is an ultra-high performance concrete with ultra-high mechanical properties,excellent durability,good ecological effect,long-term economic benefits and broad application prospects.At present,RPC research focuses on mechanical properties and durability,ignoring the improvement of working performance.How to make RPC have ultra-high strength while being able to self-flow and compact,it is a key problem to be solved.The following main conclusions are based on the research of RPC at home and abroad which combined with the application in a certain bridge steel deck pavement engineering and studied the preparation technology,mechanical properties and durability of self-leveling RPC by choosing high quality raw materials.（1）With the increase of water-binder ratio from 0.14 to 0.20,the working performance of RPC mixture was improved,the compressive strength first increased and then decreased,and the flexural strength presented a decreasing trend,indicating that RPC water-binder ratio was not as low as possible.The water-binder ratio should be between 0.16 and 0.18.With the increase of the mortar ratio from 0.7 to 1.5,the working performance of RPC mixture decreased,and the strength first increased and then decreased.The mortar ratio had a great influence on RPC homogeneity,and the mortar ratio should be controlled between 0.9 and 1.1.When the silica fume content increased from 0%to 45%,the working performance of RPC mixture decreased,and the strength first increased and then decreased.When the silica fume content exceeded 25%,the effect on strength was not obvious,but it would affect the working performance of RPC,thus the silica fume content should be between 20%and25%.As the volume content of steel brazing dimension increased from 1.2%to 2.4%,the working performance of RPC mixture decreased and the strength growth slowed down,indicating that there was a saturated content of steel brazing dimension,and the content of steel brazing dimension should not exceed 2.2%.（2）The optimum mix ratio of RPC after experiment optimization is:cement:silica fume:ultrafine fly ash=1:0.20:0.25,water-binder ratio is 0.16,sand-rubber ratio is 1.1,water-reducing agent dosage 2%,the steel brazing volume is 2%,the initial slump is 270 mm,the slump expansion is 685 mm,the slump is 255 mm after 1h,the slump expansion is 585 mm and the compressive strength is 166.7 MPa,The flexural strength is 28.2 MPa,which meets the requirements of the design goal.（3）The effect of curing system on the self-leveling RPC strength:steam curing>hot water curing>standard curing>natural curing.SEM indicated that RPC cement paste of steam curing and hot water curing is more dense than standard curing and natural curing,mercury intrusion tests indicated that the RPC porosity of steam curing and hot water curing is much lower than standard curing and natural curing.（4）The ratio of the axial compressive strength and cubic compressive strength of self-leveling RPC prism was higher than ordinary concrete,and the average value reached 0.88.The ratio of flexural tensile strength and cubic compressive strength of self-leveling RPC prism reached 1/6,and its toughness was much higher than ordinary concrete.The average value of the static elastic modulus test of self-leveling RPC was 48.7 GPa,and the relationship between elastic modulus and axial compressive strength were fitted by matlab:E_C=4070(f_cp)^1/2.（5）Self-leveling RPC has excellent permeability and frost resistance.When the electrical flux was lower than the design index 40 C,and after 600 freeze-thaw cycles,the specimens did not break.Among them,hot water curing and steam curing were conducive to improving the RPC microstructure and improving the permeability and frost resistance.（6）In engineering application,RPC always has the outstanding problem of steel fiber agglomeration.It is found that it is easy to agglomerate when steel bit dimension is put into mixer at one time.By setting a vibrating screen type dispersion device at the steel brazing dimension inlet,the phenomenon of steel brazing dimension clustering can be effectively reduced when the steel brazing dimension is evenly dispersed into RPC dry mixture.