| Few experimental research have been done about the early age mechanicalproperties of concrete at home and abroad, especially with the influences ofadmixture. Therefore, here is a research on the effect of the different blending amountof high efficiency water reducer and early-strength water-reducing agent on thedeveloping rules with age of the cube compressive strength, the indirect tensilestrength and the direct tensile strength of C25 concrete, and finite element analysison tensile strength was done at the same time. It provides a basis of concretestructure or checking computations and the control of cracks during construction.As results of compressive tests for 7 groups of cubic specimens in 4 ages, aformula for computing the cubic compressive strength of concrete in different agesunder standard curing conditions was fitted, which coincides not only with theordinary concrete but also with the concrete with addictives for its suitability.The tensile strength of concrete is usually obtained by splitting test, which is anindirect method. The paper designs the experimental apparatus for concrete of thedirect tension, which resolves the difficulty of ensuring that the load is truly axial, atthe same time, the making of the specimens is easy and cheap. The method in thispaper which is used to measuring the direct tensile strength is suggested to furtherapplication.The splitting tensile method for the tensile strength of concrete is usually usedin structural applications, so there is great importance in the investigating the relationbetween the direct tensile strength and the splitting strength, which have beenobtained in this paper on the base of tests.Concrete is anisotropic,non-linear,brittle and time-dependent, its mechanismproperties is very complex, and performance index is very disperse. Therefore, finiteelement analysis based on the parameter of the experimental data, compared with theresults of experiment, will compensate the deficiency of experimental observation.
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