Figure 2 Relationship between (%) strength retained and sulphate attack rating for Portland and blastfurnace slag cement concretes (100mm cubes) after storage in sodium (I) and magnesium (E) sulphate solutions for 5 years

SR CEMENT COMPN. DEPTH SOLN I SOLN E SOLN SOLN E

NUMBER OPC SLAG (mm) (w.27d) (w.27d) E (a.1d) (a.28d) 1 850 1-6 9.83 N.D. N.D. N.D.

Ingress of Sulphate Ions

The results of the sulphate ion ingress at different depth ranges for the concrete specimens containing blends of the high C3A OPC and the high and low alumina slags after 5 years storage in sulphate solutions are given in Table 4. The relationship between the % sulphate ingress and the depth of sample for the range of high C3A OPC/high Al2O3 slag blended cements (air-cured for 28 days) clearly shows that the least ingress of sulphate occurred with the specimens containing 80% slag whereas the highest levels of sulphate penetrated the plain OPC concretes. The air-cured specimens had consistently been shown to have the least amount of sulphate penetrating the concrete (see Figure 3) with ‘A.28 days’ the least, ‘A.1 day’ the next and the water-cured specimens providing the highest sulphate ingress.