Properties Of Precast Prestressed Slab-on-Ground Based On PP-Fiber Reinforced Alkali-Activated Composite

Infrastructures with higher performance requirements,such as precision instrument factory,logistics,warehousing,large commercial complex,etc.,need to use high mechanical performance of concrete floor,to enable them to bear the repeated and long-term effects of loads,as well as the effects of temperature difference stress and concrete shrinkage within the designed service life.Slab should not appear bending,cracking or even local broken,to ensure the service life of the floor.The precast prestressing fiber reinforced caustic concrete floor is a new type of structure using new materials:The alkali activated concrete surface layer with characteristics of fast hardening and early strength is adopted,and the toughness of concrete is enhanced by adding PP fiber,and the water-quenched slag replaces 50%natural sand to make the material more environmental friendly;The parts are made of post-tensioned prestressed concrete,which can balance and resist the surface tension caused by external action effect,enhance the structural rigidity and control the deflection;The assembly type is adopted to facilitate quick repair and construction of the floor.Through the mixture ratio design,mixing and curing method research,the adaptation tests such as expansion degree,3D compression resistance and 3D folding resistance of fiber alkali activated concrete were completed.The test results show that when the fiber content does not exceed 1.92kg/m~3 and water quench slag replaces 50%natural sand,the alkali activated mortar can basically meet the requirements of fluidity and mechanical properties.The finite element analysis method was used to analyze the common concrete floor board,the prestressing concrete floor board(parts)before assembly and the prestressing concrete floor board after assembly(the post fiber alkali-activated concrete surface layer).The influences of load position,plate thickness and the ratio of the length and width of the plate to the mechanical properties of the floor plate are obtained,and the comparison of whether there is pre-stress,whether there is surface layer,different surface layer structure and layer material combination,and different working conditions of soft foundation is completed,and the bearing capacity of each working condition is quantitatively analyzed.The main research results include:first,when the load is concentrated in the plate Angle or the plate edge,it is unfavorable.The total thickness of the board is 200mm,which can give consideration to economic and structural performance.The length-width ratio of 2:1 plate boundary is between the one-way plate and the two-way plate,which is favorable;Second,applying prestress can reduce the deflection value by 60%,and increasing the surface layer can reduce it by 13%.The combination of surface layer and post-tensioned prestressed structure layer with fiber alkali excitation can effectively reduce the possibility of slab cracking.Third,when the position of the soft foundation is under the load,the deflection deformation is close to two times of that of the non-soft foundation,otherwise,the increase amplitude is small;Fourth,the ability of the floor plate to resist local weak foundation after assembly is further improved.When the load acts on the middle,edge and angle of the floor plate,the load displacement curve shows a three-stage formula with gradually increasing slope,a two-stage formula with a larger slope and a straight line with a significantly lower ultimate bearing capacity than the first two.Beam on elastic foundation method is used to analyze the ground floor under static and dynamic load.It is found that the maximum tensile stress of a single slab is less than5%different from that obtained by the semi-infinite beam on elastic foundation method.The maximum tensile stress of the assembly plate obtained by using dynamics(v=30km/h)of infinite length beam on elastic foundation method is slightly smaller than that of the single plate under static load,which verifies the effectiveness of the classical elastic calculation theory in the design and calculation of prestressed floor.