| Popis: |
Coarse aggregate has a large influence on drying shrinkage which is one of the major causes of cracking in concrete structures. The stiffer an aggregate, the lower is the drying shinkage of concrete. Since it is not possible to alter the stiffness characteristic of an aggregate, a practical method of minimizing cracking of concrete when high-absorption or low-modulus aggregates must be used can be the application of a shrinkage-compensating cement in combination with these aggregates of marginal quality. Data are presented showing that the use of high-absorption aggregates in combination with a Type K shrinkage-compensating cement produced concretes whose net contraction due to drying was equal to or lower than the drying shrinkage of a portland cement concrete made with a low-absorption aggregate. The shrinkage-compensating cement concretes developed higher strength than the corresponding portland cement concretes. High-absorption or low-modulus aggregates when used in appropriately proportioned shrinkage-compensating concretes can meet even the most rigid shrinkage limitations specified to minimize cracking and deflections in concrete structures. |
