Properties of Normal- and High-Strength Concrete Containing Metakaolin
Appears on pages(s):
high strength concrete; hot water curing; metakaolin;
normal strength concrete; permeability
Mechanical properties and chloride permeability of normal and high strength concrete containing a mineral admixture called metakaolin are presented in this paper. The target 28 day strengths for normal and high strength concrete were 34 and 68 Mpa respectively. The major independent variables were: (i) addition of metakaolin at 5 and 9 percent as cement replacement; (ii) type of cement, ASTM Type I and III; (iii) type of curing, moist and hot water cure; and (iv) age at testing varying from 1 to 90 days. Fresh concrete was tested for slump, air content, unit weight, and concrete temperature, and the hardened concrete was tested to obtain compressive strength, modulus of elasticity, modulus of rupture, and permeability. The results indicate that metakaolin improves the compressive strength by as much as 25 percent. It is possible to obtain a one day strength of 24 MPa using metakaolin and only 305 kg/m3 of Type I cement. The one day strength can be increased to 31 MPa using Type III cement. Hot water curing can increase one day strength to as much as 54 MPa. Modulus of elasticity is slightly higher for concrete containing metakaolin. Metakaolin has very little influence on modulus of rupture. Control concretes had a low chloride ion permeability, and metakaolin decreased the permeability even further.