Experimental Study On The Mechanical Properties And Impact Resistance Of The Active Powder Concrete

Reactive Powder Concrete(RPC)is a kind of high strength concrete,with the excellent mechanical properties and durability.The curing methods for RPC have been the focus in the field of civil engineering materials.The research process of high strength RPC is generally different from that of ordinary cement materials cured at room temperature.Usually,high temperature curing method is used to prepare the high strength RPC.However,in actual construction,the high performance of RPC is difficult to play,as the components usually can not be cured by heat and the special curing methods.Therefore,considering the practicability and economy of the project,it is the key to develop RPC in the field of structural engineering application by the conventional natural curing method.Additionally,the impact loads caused by landslides,collapses and rockfalls pose a serious threat to the safety of concrete structures.To ensure the safety performance of concrete structure and the safety of life and property,it is significant to study the impact resistance of RPC structures under impact load for earthquake prevention and disaster reduction.In this study,we made a detailed selection of RPC materials,and then through the flexural and compressive tests to explore the appropriate mix ratio,and finally the impact test and its related anti-impact mechanism are explored and discussed.The main contents and achievements of this study are as follows:(1)Based on the existing research foundation in our laboratory,the effects of steel fiber,water-binder ratio and water reducer on the basic mechanical properties of RPC under room temperature curing conditions for 3,7?28 and 54 days were studied in this paper.(2)RPC slabs were made with the optimum mix ratio with the best mechanical prope rties(water-binder ratio:0.16,steel fiber content:3.0%,liquid polycarboxylic acid water reducer content:2.0%,fly ash content:20%,silica fume content:25%).The impact resi stance of RPC concrete slabs were studied by drop weight impact test,and the RC slab s were used as control group.The results showed that the impact duration,of RPC plate obviously prolonged;the impact velocity and the impulse increased;the peak value of impact acceleration,average impact force and maximum impact force all reduced comp ared with the RC plate.Additionally,the dynamic reaction amplitude of the four corner s and the maximum strain of RPC plate were obviously larger than that of RC plate.When analyzing the failure degree of concrete slab,we found that there was only a sm all impact pit in the front contact impact site of RPC board,without penetrating failure like the RC board.Moreover,the number of cracks on the back of RPC plate was les s than that of RC plate,and the crack width was obviously smaller than that of RC pl ate.All these results showed that the impact resistance of RPC material is obviously hi gher than that of concrete slab made of RC at room temperature.(3)The impact resistance of RPC slabs is further analyzed by changing the steel fiber content only,and the other mixture ratio of other components of RPC material remains same.The results showed that the steel fiber content made great influence on the impact resistance of RPC slab under room temperature conditions.With the increase of steel fiber volume fraction,the impact resistance of RPC boards was gradually enhanced.(4)The anti-cracking effect and toughening effect of steel fiber on RPC was further analyzed from the point of view of fracture mechanics,and the related mechanism of impact resistance of steel fiber reinforced RPC plate was further analyzed.The results showed that the addition of steel fiber reduces the brittleness of concrete matrix.The concrete matrix can continue to bear impact load after cracking as its excellentductility,thus delaying the development of cracks.Moreover,the distributing density of the steel fiber on the impact surface of the RPC plate increased with the increase of the steel fiber content.As a result,the energy dissipation coefficient of the corresponding matrix of the RPC plate decreases gradually,and enhanced the impact toughness of the RPC plate.