Two curing mediums containing 5% H2SO4 and 2.5% Na2SO4 each are used as
aggressive environments. In order to understand what really happens when concrete
is ‘cast-in-situ’; where concrete is introduced to the service area during its initial
age, specimens for H2SO4 were placed into the aggressive curing environment
immediately after removal from moulds. However, specimens for Na2SO4 as well
as water absorption test were given one month treatment in ordinary water at
23 C and 80 ± 5% RH before subjection to the aggressive medium and coring
respectively. In fact, in the case of specimens for Na2SO4, 72 h air drying at
20 ± 3 C and 80 ± 5% RH was entertained before immersion into the diluted curing
medium.