Page 175 - Handbook of Thermal Analysis of Construction Materials

158 Chapter 4 - Introduction to Concrete Admixtures

The strength of a cement, mortar, or concrete containing a Ca-
formate may depend on the cement composition. Geber [53] found that the
early and later strengths in mortar depended on the C A/SO ratio of the
3
3
cement. The compressive strength increase over the control at C A/SO
3 3
ratios (at 1 day and 2% Ca formate) of 2.44, 3.32, 4.34, 5.00, and 7.22 were
3, -14, 25, 88, and 70% respectively. It is suggested that to derive the
effectiveness of formate, C A/SO ratios higher than 4 should be preferred.
3
3
Generally, Ca formate increases the early strength of concrete. In
Fig. 8, the results on the effect of 2% and 4% Ca formate indicate that the
strengths are increased in the first 24 hours. [54] At lower dosages, the
strength development may not be very significant. In combination with
sodium nitrite, Ca formate accelerates the early strength development in
cement to a significant extent. In comparison with the reference specimen
without an admixture, the combination admixture increases strengths by
125, 70, 47, and 23% at 18 hrs, 1 day, 3 days, and 7 days, respectively. [55]

Figure 8. Influence of calcium formate on early strength of concrete.