Research On The Alternate Bay Construction Of Mass Concrete Foundation Slab

With the extensive use of mass concrete,how to effectively control the generation of concrete cracks under the condition of no deformation joints or few deformation joints,it is always the key and difficult point in the engineering field?Starting from a project cases,this paper introduces the basic principle and relevant requirements of concrete crack control by the alternate bay construction;Studies the concrete mix proportion under the given low hydration heat requirements;And carries out the on-site temperature monitoring for the alternate bay construction of mass concrete foundation floor;At the same time,with the aid of the finite element method,combined with the analysis of concrete internal temperature,deformation,constraint conditions and age The relationship between the ambient temperature and the measured results is compared.The main research contents and conclusions are as follows:1? Summarize the basic requirements of the relevant codes for the construction of mass concrete,introduce the basic principle of the alternate bay construction for the control of concrete cracks.2?Combined with regional resources,starting from the raw materials of concrete,composite mineral admixtures(fly ash and slag)are used to replace part of cement in order to seek the concrete mix proportion that can effectively reduce the hydration heat of concrete and meet the requirements of anti-cracking performance,so as to control the cracking of mass concrete foundation slab.3 ? During the construction of mass concrete foundation slab,calculate the maximum bin block size according to the empirical formula,and the deformation and internal temperature of concrete were monitored,and the monitoring results showed that:Concrete shrinkage deformation increases with age and then tends to be stable.The stronger the external constraint condition is,the larger the constraint deformation of the second casting block is.Under the given external constraints,the location of the second casting block with greater constraint is deformed relatively large,but the temperature difference is relatively low.Therefore,the internal and external temperature difference and boundary constraints are the key factors leadingto the cracking of mass concrete.4 ? Finite element method was adopted to simulate and analyze the internal temperature field of mass concrete foundation slab under different constraints.The results are as follows:(1)The temperature of the first casting block reached a peak on about the second day after the completion of casting,then began to decrease,and reached a plateau on the sixth day.The temperature variation trend and law of the second casting block is basically the same as that of the first casting block,but the temperature difference is greater than that of the first casting block.The temperature difference between inside and outside of the joint surface of new and old concrete of adjacent bin block is large.(2)The stronger the circumferential constraints are,the greater the temperature difference will be.The temperature difference between the new and old concrete joint surface decreases with the increase of constraint conditions and increases with the increase of size.(3)Finite element simulation analysis of temperature and the measured temperature has carried on the comparison of the two trends and law basic same,but there exist certain differences in values,mainly chooses the concrete thermal parameters and the concrete differences between the actual thermal performance,the actual environment temperature change can not fully reflected in the numerical simulation analysis,test point location deviation and error caused by factors such as test system.The research results in this paper can provide basis and reference for the construction of bulk concrete hopper method.