Experimental Research On Crack Control Of Mass Concrete Slab And Finite Element Analysis For Thermal Stress

With the continuous development of modernized construction,more and more mass concrete structures have been applied to the engineering practice.But cracks of concrete structure have obsessed the engineering workers for a long time.The damage and collapse of construction starts from occurring the crack in structures. Otherwise,the growth of cracks of structures is the initial stage of building's damage as a result that the bearing capacity and durability of constructions are weakened, such as the leakage of roofs,the shedding of surfaces of concrete,the rebar corrosion in the concrete,the aggravation of freeze-thaw cycles,the concrete carbonation and soon.At present,in order to control the development of mass concrete cracks,many measuers and skills are took in the engineering projects,that reduces the temperture difference to the utmost level to make the concrete in the good condition.Such as adding the ice chippings in mixed concrete,cooling with moving recycling water, insulating heat by atomizing water,although those measures can greatly control the crack development,but greatly increase the project costs.Therefore,there is a need for balancing the method and cost as a whole in mass crack control projects.Based on the concrete test,the main work of this paper is follow as:1).Based on experience and measures of temperature control and crack prevention of mass concrete,this paper presents the formation cause and mechanism of cracking,and the basic theory and calculation method of temperature-field and thermal stress.Built upon variatbnal principles,the paper educes basic formulas of finite element methods in unsteady temperature-fie Id of concrete structures.Followed the concrete constitutive relationship of elastic-plastic body,the writer deduces the formula of finite element method of thermal stress in concrete. 2).Using the model test method,the paper discusses the improved materials effecting on physical and mechanical properties of concrete by adding into heterogeneous and diverse mixed quantities.In order to depress the hydration heat, the concrete is added into the fly-ash and silica fume.To reduce water consumption and to improve workability of concrete,the Emulsified asphalt is doped.The polypropylene fiber is added to strengthen the anti-crack performance and to enhance the capability of ultimate tensile of materials.3).The model of mass concrete slab is built by SAP2000 finite element analysis software.In this model,the temperature field and thermal stress of concrete slab are compared and analyzed between added-in and added-not materials.In addition,the different boundary conditions and dimensional parameters of the models are analyzed to find out its effects on thermal stress distribution in concrete baseplate.4).In order to control temperature and thermal stress in mass concrete slab,the paper mentions different measures,such as raw material selected,special materials added in concrete,mix proportion optimized and hydration heat reduced.Besides,this paper discusses the ways and means,for example,minished constraints degree, reinforced local structure and real-time monitored temperature of mass concrete structures,allround to keep cooling rate of concrete,enhance construction quality, decrease shrinkage of concrete.This work can offer a reference to the mass concrete design and construction.