Mechanical Properties And Microstructure Of Green Ultrahigh-performance Concrete With Ceramic Tile Particles

Ultrahigh-performance concrete(UHPC),as a cementitious material with excellent performance,has attracted widespread attention in worldwide.Quartz sand is an important component of UHPC,and it mainly comes from quartzite ores.Quartz sand is much more expensive than river sand,and its mining is not conducive to the nature.River sand can also be used as fine aggregate of UHPC,but the properties of UHPC with river sand is inferior that with quartz sand.Moreover,there is an enormous shortage of river sand in the world at present,and there is a serious impact on the nature because of the excessive excavation of river sand.Fine aggregate has become one of the urgent problems of UHPC.In addition,millions of tons of ceramic wastes are produced in China every year,which is difficult to dispose of,and it is easy to contaminate soil and water sources when occupying land.In order to solve these two problems,this paper used ceramic tile waste particles,instead of quartz sand,to prepare green UHPC.The flow-spread test,compressive and flexural strength test,packing dense model,Scanning electronic microscopy analysis(SEM),Mercury intrusion porosimetry analysis(MIP)were conducted to analyze the effect of ceramic particles on the workability,basic mechanical properties,packing density and microstructure of UHPC.In addition,the environmental impact and cost of UHPC with ceramic tile particles were also quantitatively analyzed by material sustainability indicators.Results indicated that due to the multi-angular shape and water absorption of the ceramic particles,the flow-spread degree of the fresh UHPC reduced,but its consistency and mixing time increased.The flow-spread degree decreased linearly as the content of ceramic particles increased,and also decreased linearly as the actual water-binder ratio or actual water content decreased.As the content of ceramic particles increased,the packing density of UHPC increased and the microstructure was denser.As the curing age prolonged,the hydration degree of cement gradually increased,and the compressive strength and flexural strength gradually increased.The development trend of the flexural strength to compressive strength ratio was more familiar to that of the flexural strength,indicating that compared to the compressive strength,the ceramic particles have a greater effect on the flexural strength.When UHPC with ceramic tile particles is subjected to flexure,it will be destroyed in three stages.The failure mode is brittle failure.The effect of ceramic tile particles on the fracture energy of UHPC was not significant,and the effect was within ±7%.When 100% ceramic tile particles were introduced,the fracture energy of UHPC increased slightly;Ceramic tile particle improved the particle size distribution of UHPC,but the ceramic particle had no significant effect on the overall packing density of the mixture.In general,as more ceramic tile particles were introduced,the compacting degree of UHPC increased,and the packing density also increased.As the curing age prolonged,the amount of pores and cracks decreased in UHPC with ceramic tile particles,and the pore diameter and crack width also decreased.The thickness of the Interfacial transition zone(ITZ)in UHPC decreased with the ceramic particle increasing.Compared with the control group,the ITZ thicknesses of UHPC with 100% ceramic particles decreased maximally in 7 days and 28 days,which were61.9% and 85.4%,respectively.This is due to that with ceramic tile particles increased,the amount of fine particles was more,which means that the reduction of large particles weakens the wall effect,and fine particles can fill in ITZ effectively.The critical pore radius of UHPC decreased with the increasing of ceramic particles.The filling effect of ceramic particles can improve the pore structure of UHPC.The porosity of UHPC mixed with ceramic particles and quartz sand is within 10% in 7 days and 28 days.With ceramic particles increased,the total porosity of UHPC decreased,and its compacting degree increased and corresponding compressive strength intensity also increased.The pores in UHPC were mainly mesopores and gel pores.The refining effect of ceramic tile particles on the pores was proved by the conversion of mesopores to gel pores.The maximum refining effect of 100% ceramic particles is about 17% in 28 days;There was no impact of UHPC with ceramic tile particles on the nature,and no significant improvement on the energy saving and the reduction of greenhouse gas.However,if the UHPC with ceramic tile particles can be produced and used in large amounts,as far as Jiangxi is concerned every year,45 million square meters of ceramic tile wastes can be utilized to prevent ceramic waste from occupying the land and polluting water sources and soil.Ceramic tile particle,which is instead of quartz sand to prepare UHPC,is beneficial to cost-controlling.When 100% ceramic tile particles were introduced,the production cost was reduced by 13.42%.After mass production or industrialization of UHPC with ceramic tile particles,the cost can be further reduced.