| High belite cement would be applied in hydraulic structures concrete for its lowhydration heat in the future,comparing with Portland cement. It had the advantage oftemperature control in hydraulic structures concrete. In order to solve the problem oflow early compressive strength for standard size specimens, temperature control,mechanical properties, volume stability and durability of high belite cement hydraulicstructures concrete with different sizes were systematically studied based on sizeeffect of concrete. Crack extension of concrete and stability against sliding ofconcrete-rock were concerned with safe operation of hydraulic structures. Therefore,it was important to research the fracture properties of high belite cement concrete andanti-shear performance of rock-high belite cement.Standard specimen with size Ф200mm×100mm and different size specimenswith size Ф1000mm×500mm, Ф2000mm×1000mm, Ф4000mm×2000mm were madein the laboratory and in site of Qingzhou Renhe reservoir. Temperature control andautogenous volume deformation of various size high belite cement concrete andPortland cement concrete were studied. Mechanical properties and durability of highbelite cement concrete with different sizes, parts and ages were compared with that ofPortland cement concrete by drilling core specimens. The fracture properties of highbelite cement concrete and Portland cement concrete was measured by three-pointbending beam test. Anti-shear parameters of rock-high belite cement concrete androck-Portland cement concrete was tested by flat stacking method in site of LinquTangshuiya reservoir.Microstructure of concrete was characterized by mercuryintrusion porosimeter (MIP).The results showed that comparing with Portland cement concrete, high belitecement concrete was of large ultimate tension, high tensile strength, good autogenousvolume stability and large cracking index, which had the advantage of resistance tocrack of concrete. High belite cement concrete significantly saved the amount ofcooling water in temperature control. The fraction of pores whose diameter wasbetween20nm and100nm in high belite cement concrete was higher than that ofPortland cement concrete,while the fraction of pores whose diameter was more than200nm in high belite cement concrete was lower than that of Portland cement concrete.As a result, mechanical properties including compressive strength,tensile strength,ultimate tension,tensile elastic modulus and durability including resistance to freezingand thawing, impermeability,corrosion resistance of high belite cement concrete werebetter than those of Portland cement concrete with the same size and locations.Mechanical properties and durability of high belite cement concrete specimenshave obvious size effect. Compressive strength of high belite cement concretespecimens with different sizes was higher than that of standard specimens at7d.Performance of concrete with various sizes and locations was quite different. The fraction of pores whose diameter was between20nm and100nm in the middle ofconcrete which was the middle location from the center to the edge of specimens wasthe highest,while the fraction of pores whose diameter was more than200nm was thelowest. Therefore, compressive strength, tensile strength, ultimate tension and tensileelastic modulus of the middle of concrete were largest. Durability including resistanceto freezing and thawing, impermeability and corrosion resistance of concrete with sizeФ4000mm×2000mm was less than that of standard specimen. Autogenous volumedeformation of concrete was of significant size effect. With the increasing of concretespecimens size, autogenous volume deformation of concrete enlarged because that thefraction of pores whose diameter was less than20nm in concrete increased andnegative pressure increased in capillary of concrete. Based on it, size effect theory onautogenous volume deformation of concrete was founded. The magnitude ofautogenous volume shrinking deformation of high Belite cement concrete was lessthan that of Portland cement concrete because that the fraction of pores whosediameter was less than20nm in high belite cement concrete was lower than that ofPortland cement concrete.Initial fracture toughness and unstable fracture toughness of high belite cementconcrete were as1.17times and1.24times as those of Portland cement concreterespectively. Anti-shear friction coefficient of rock-high belite cement concrete (1.204)was much more than that of rock-Portland cement concrete (0.790). Anti-cut frictioncoefficient of rock-high belite cement concrete was as almost two times as that ofrock-Portland cement concrete. It would be benefical to stability against sliding ofconcrete on rock for hydraulic structures concrete.Mechanical properties, durability, volume stability and temperature control ofhigh belite cement concrete were better than those of Portland cement concrete. Theproblem on application of high belite cement concrete in engineerings had beenresolved because that compressive strength of high belite cement concrete with largesize was higher than that of standard size specimens at7d. High belite cement whichimproved anti-shear performance of rock-concrete and fracture toughness of concreteprovided an effective solution to crack extension of concrete and stability againstsliding of concrete on rock for hydraulic structures concrete. Size effect theory onautogenous volume deformation of concrete offered a theoretical basis for crackprevention of hydraulic structures concrete. |
