Influence Of Mineral Admixtures On The Mechanical Strength And Permeability Of Concrete

Mineral admixtures are important for modern concrete in improving its strength and durability properties.The determination of both the type and replacement ratio of mineral admixtures and rapid measurement of concrete’s permeability are essential to assure concrete’s construction quality and durability.In this thesis,experiments are carried out to study the effects of fly ash,slag,limestone powders and fly ash/slag on the compressive flexural strength of concrete and mortar specimens up to the age of 28 days.Rapid chloride migration test and electrical resistivity measurements are performed to study the effects of ly ash,slag,limestone powders and fly ash/slag on the chloride permeability and resistivity of concrete specimens.In addition,the correlation between electrical resistivity and chloride migration coefficients at 28 days age is analyzed,and the effect of mineral admixtures on the evolution of strength and resistivity is studied..The results of this thesis indicate that: 1)for concrete specimens of 28 days age under standard curing,the use of slag increseas its compressive strength,and the use of fly ash and limestone power decreases it compressive strength.2)Using fly ash increases concrete’s chloride permeability at early age but decreases it chloride permeability at long term;using slag decreases concrete’s chloride permeability while using limestone power increases concrete’s chloride permeability.3)Using fly ash and slag as mineral admixtures could increase the long term compressive strength and electrical resistivity of concrete.4)Electrical resistivity method can quantitatively characterize chloride penetration resistance of concrete.The research results in this thesis can provide references for the mixture design of concrete with mineral admixtues,and provide experimental support for the practical application of the electrical resistivity method to evaluate the permeability of concrete.