Study On Structure And Properties Of Super High Strength Concrete Composite Material

Reactive Powder Concrete is a kind of inorganic non-metal composite material with low density,high toughness,high strength and other characteristics.In this paper,the structure and properties of ultra high strength reactive powder concrete(RPC)are studied,and the main achievements are as follows:Fine aggregate is the main component of RPC,which accounts for 30-50%of the total volume of RPC concrete.Not only the properties of fine aggregate have great influence on the RPC,but also the particle size has a great influence on the performance of RPC.As the partical size of fine quartz sand aggregate increased,flexural strength and compressive strength of RPC concrete with 12mm steel fiber were gradually increased.Flexural strength and compressive strength of the examples with the fine quartz sand aggregate whose particle size ranges from 0.6mm to 1.18mm reached maxium.The compressive strength of the examples was stable to 330MPa,flexural strength reached 73MPa.Use white corundum and fine ceramic beads aggregate to replace quartz sand aggregate(0.6-1.18mm)by volume.The compressive strength of RPC examples using fine ceramic beads reached 3 95MPa and the flexural strength reached 8 5 MPa.However,the compressive strength of RPC examples using white fused corundum can reached 410MPa and the flexural strength reached 97MPa.Fine ceramic beads and white corundum aggregate can significantly enhance the performance of reactive powder concrete,fused corundum and fine ceramic beads with high strength,high hardness,high elastic modulus in RPC matrix were relatively dense,the increase of strength was more obvious,compared with fine ceramic beads aggregate,the role of corundum aggregate were more significant.The RPC samples with different water cement ratio used autoclaved curing at 200? for a long time to simulate the storage environment of nuclear waste.The mechanical properties of RPC,such as ultrasonic speed,expansion shrinkage,dynamic elastic modulus and compressive strength,were studied under different curing time.The rule of nucleation and growth of hydration phase during long time autoclaved curing was also studied.When the curing time increased,In the initial stage of autoclaved curing,the quality of RPC specimens increased slowly with the increase of curing time,after 18 cycles of autoclaved curing,the quality of samples remained basically stable;the samples were expanded after a little shrinkage,the dynamic modulus of elasticity micro-expansion and its mechanism of reactive powder concrete under long term hydrothermal conditions increased rapidly at the initial stage of autoclave curing,and then in a steady status after the hydration reaction of 96 hours,the strength of the samples remains stable.With the increase of curing time,the hydration reaction makes the quality of the sample increase,and the dynamic elastic modulus and strength are also stable.It shows that the micro expansion of the RPC specimen under the long time autoclave has no damage to the sample microstructure.The study of RPC matrix was carried out.In the condition of low water cement ratio,first the examples cured for 24h at 90 degrees centigrade,then the examples autoclaved curing of 24h observed dicalcium silicate(2CaO·SiO2),calcium silicate(3CaO·SiO2)and accompanied by calcium silicate hydrate(C-S-H gel).With the increase of curing time,the hydration reaction was carrying on,at the curing time of 480h,the diffraction peak of RPC matrix C-S-H gel decreased significantly;in SEM images,the RPC matrix was very dense,showing only few small internal micropore,which was a crystalline state of hydration products formed in the micropore.The micromorphology appeared the formation of TOB phase under the condition of long time curing,this is the important reason for the improvement of the mechanical properties of reactive powder concrete under long-term curing.The protective performance of the RPC was studied.The RPC target has excellent protective effect against the bullets,and the composite protection effect of the target plate is good,so that the bullet is not easy to penetrate the target plate.The damage of the jet to the RPC target plate was characterized by the depth of the jet hole and the damage to the target plate.The density of RPC was about 1/3 of armored steel.Therefore,protective performance of RPC target plate was superior to that of the armor steel target plate with the same quality,which reflected the superior performance of RPC as protective material,the RPC materials met the requirements of construction in the protective facilities.Scanning electron microscopic showed that the RPC matrix attacked by metal jet perforation was dense.The layer structure caused by the shock wave was found in the perforation,at the same time,copper and iron appeared after melting of copper plated steel fiber at the bottom of jet perforation.The high strength concrete target plate put up an outstanding resistance to the high temperature and shock wave of the metal jet propellant cover.