DIFFUSIVITY OF CHLORIDES FROM SEAWATER INTO HIGH-STRENGTH LIGHTWEIGHTCONCRETE

As part of a more comprehensive research program on high-strength ligh t-weight concrete (50 to 100 MPa), test results on the diffusivity of chlorides from natural seawater are presented. The chloride diffusivit y of the various concrete mixes was very low, with effective diffusion coefficients typically varying from 2.7 to 5.6 x 10(-9) cm2/sec. Of t he various material parameters included in the test program, it was th e presence of silica fume that had the most dominating effect on the d iffusivity. Nine percent replacement of the cement by silica fume redu ced the chloride diffusivity by a factor of about 5, while an increasi ng content of the total amount of cementitious materials from 440 to 6 60 kg/m3 decreased the diffusivity by a factor of about 2. Five differ ent types of lightweight aggregate with increasing particle densities from 1.07 to 1.44 g/cm3 were used. The difference of the concretes wit h the least dense aggregate was about two times higher than those obta ined with the most dense aggregate. Type of fine aggregate and maximum aggregate size had only a minor effect on the chloride diffusivity. T he impact of the obtained chloride diffusivity on service life is also discussed.