Research On Effect Of Micro-nano Pozzolan On Early-age Cracking Of Cement Concrete

Compared to asphalt pavement,cement concrete pavement has a high loading capacity,making its wide application in airports,ports,and mining areas where heavy loads are popular.Cement concrete shrinks in the early age,which leads to cracking when such shrinkage is restrained.Early-age cracking weakens the loading capacity of cement concrete slab and its durability.It is always a hotspot in the research on how to control the early-age cracking in cement concrete pavement.In this study,micro-nano pozzolan was added to cement concrete,its influence to early-age cracking in cement concrete was studied,the cause of the influence was analyzed.Through the comparison of early-age cracking in Portland cement concrete and micro-nano pozzolan cement concrete,the influence of micro-nano pozzolan to early-age cracking in cement concrete was investigated,it was found that adding micro-nano pozzolan can significantly reduce early-age cracking.At the same time,the primary properties of micro-nano pozzolan materials was obtained,including the particle size,density,mineral composition and content of each component.How micro-nano pozzolan influence the early-age cracking was explored in macro,the mechanic properties,temperature and humidity of micro-nano pozzolan cement concrete and Portland cement concrete was tested,found that the incorporation of micro-nano pozzolan decreased the early strength,temperature and humidity of cement concrete;the reasons how micro-nano pozzolan influence the early-age cracking of cement concrete was analyzed through micro perspective,the influence of micro-nano pozzolan to cement concrete early-age cracking was researched by SEM and X-ray technique,it was discovered that micro-nano pozzolan can slow the early hydration process of cement concrete,thus decreased the inside temperature and humidity gradient of cement concrete,compared with ordinary cement concrete,micro-nano pozzolan cement concrete has a more compact microstructure and better durability.In order to analyze the influence of micro-nano pozzolan to cement concrete early-age cracking,clarify the influence mechanism of index such as tensile modulus and strength etc.to early-age cracking of micro-nano pozzolan cement concrete,micromechanical model of composite materials was established to simulate the early-age cracking of cement concrete basing on microstructure image of cement concrete obtained by CT scanning,then,the material para meters of the model were changed to investigate the influence of various factors on the early-age cracking of cement concrete,it was found that the influence of modulus of cement mortar on early-age cracking was greater than that of mortar modulus,the ad dition of micro-nano pozzolan retarded the early-age hydration process of cement concrete,the modulus increased more slowly,thus slowing the development of internal damage and cracking.