Preparation And Investigation On The RPC Cover Plate

Reactive Powder Concrete (RPC) is a kind of new cement-based compositematerial with ultra-high strength, high toughness and excellent durability, it has agood prospect of engineering application. Currently, RPC is mainly used for thepreparation of the cover plate in the country. This paper based on the basic preparationprinciple of RPC, and combined with the actual situation of raw materials in Hubeiprovince. Based on the traditional preparation of RPC, choosing ordinary river sandas fine aggregate, whose particle size range was from0.15mm to0.60mm. As10%cement was replaced by fly ash, the volume fraction was2%and water-binder ratiowas0.23, a kind of ultra-high strength concrete was prepared with the compressivestrength was181.9MPa and the flexural strength was34.6MPa after90℃steamcuring (48h), whose flowability was better, it provided a theoretical reference forreducing the production expenses of RPC cover plate in the local.Two curing systems were used in this paper (standard curing and thermal curing),based on the most closely packed theory of particle, firstly, the effect of the particlesize distribution composition and type of the aggregate on the performance of RPCwere studied. And then, the effect of superplasticizer, silica fume, cement partlyreplaced by fly ash, steel fibers, water-binder ratio, sand-cement ratio and otherfactors on the performance of RPC were studied. Also, the micro-structure of RPCwas analyzed by XRD and SEM method. The results showed that:(1) Basing on theinitial proportion of RPC, the optimal proportion of RPC was attained by experimentsof contents of different components changed and considering the factors of workableperformance, strength, economy etc.(2) In the preparation process of RPC, we couldchoose ordinary river sand (particle size range is from0.15mm to0.60mm) to replaceof the same particle size range of quartz sand as fine aggregate through optimizingparticle size distribution. We also should choose the325mesh of quartz powder asmicro-aggregate and use steam curing method. Moreover, the suitable thermal curingtime was two days.(3) It could improve the workable performance and strength ofRPC when cement was replaced by part fly ash. As water-binder ratio was0.25and10%cement was replaced by fly ash, the compressive strength was139.6MPa andthe flexural strength was19.9MPa.(4) Steel fibers could significantly increase the toughness of RPC. As water-binder ratio was0.25and the volume content of steel fiberwas2%, the compressive strength was181.9MPa and the flexural strength was34.6MPa.(5) The RPC that was prepared by the optimal proportion could get a gooddimensional stability and durability under steam curing. The shrinkage in120d ofRPC was300～350×10-6, electric flux in6h was less than10C and carbonation depthin56d was less than1mm.(6) It showed that the content of Ca(OH)2in the RPC gelwas very low by XRD and SEM tests, Ca(OH)2was bad to improve the strength ofRPC. However, there was a lot of cement clinker（C2S、C3S）did not participate inhydration. Using thermal curing system and10%cement was replaced by fly ashwere all conducive to reduce the content of C2S, C3S, and Ca(OH)2in the RPC, whichcould promote the process of hydration and improve the dense of hydration product.