1. Strength grade of cement W/C Strength formula of the concrete Factors of aggregate Curing condition Testing condition §4.4.6 Influencing factors

2. Testing conditions Influencefactors of concrete strength strength Operation Experimental instrument instrument Surfacetexture Shapes Dimensions

3. Two kinds of effects hoop effect size effect Testing conditions

4. hoop effect  When the concrete specimen is suffered by the axis compression.  The traverse deformation of compression panel is smaller than that of the concrete.  Thus the contacting surface between specimen and compression panel is influenced by the centric constraint.  It is effective in the range of √3a/2  Improve the concrete strength  After the damage of the specimen a complete pyramid is formed upper and below.

5. flash

6. Aggregate Dmax （ mm ） Size of specimen （ mm ） hoop effect strength Conversion coefficient ≤60≤40≤31.5200150100 feebleness low feebleness low strong high 1.051.00 0.95 0.95 Size of specimen ≮ 3Dmax size effect Tab.4.4.3 Effects of size to concrete strength Effects of size to concrete strength are listed in Tab.4.4.3