Study On Early Age Crack Of High Pier Concrete And Experiment

With the rapid development of transportation, a large number of hollow piers are applied toroads, railways and bridges. These high piers are big and their heat conductivity is poor. In theearly age of concrete pouring, the temperature and humidity inside and outside concrete arechanging because of the influence of hydration heat and external environment. Various parts ofthe structure are in different states, which lead to different degree of deformation. In this way, itcan produce considerable stress, when these volume deformations are under a constraint, it cancause cracks. As mass concrete, high pier's early cracks are mainly belongs to temperaturecracks and desiccation cracks.Based on the factors which result in high pier's early cracking, the paper makes finite elementanalysis and experimental research. The main contents are as follows:(1) Under the heat conduction finite element method, hollow high piers'hydration heattemperature field and thermal stress are analyzed in ANSYS. And get temperature variationscurve, temperature distribution nephogram, temperature stresses changing curves, temperaturestress nephogram of key parts.(2) Analyses the affection of ash and water reducing agent on the hydration heat, under theoptimum proportion experiment which aims at reducing he hydration heat of cement. The bestprogram are obtained that double mix with 20% fly ash and 1.5% water reducing agent(3) Design mortar's early anti-crack experiment, and study crack-resistance and othermechanical properties based on different ages & different mix proportion. From the experimental,analyses high pier's early cracking under the influence of admixtures. The mix proportion of20% fly ash,10% slag and 1.2% water reducing agent can minimize the creation of cracks.(4) Make the micro-analysis to cement hydration process and observe the hydrationproducts, analyses the early-age cracking forming from the microscopic point of view.