Activation energy of lime cement containing pozzolanic materials

Abstract The impact of locally pozzolanic materials on the activation energy of lime cement, with Grade 32.5, was assessed in the fresh and hardened phases of paste and mortar, respectively. The activation energy is used to represent the relationship between the strength gain of concrete over time and temperature sensitivity. Two proportions of mixed pozzolanic materials, metakaolin (MK) and silica fume (SF), were used as a replacement for cement weight. The first was 5% (MK) and 7% (SF); while the second was 10% (MK) and 15% (SF) as a high replacement level. The activation energy of cement was calculated, as per the ASTM C1074 approach, at 5, 20, and 35°C temperatures. The results showed that the rate of strength development ( k -value) increased in mixes containing pozzolanic material at all temperatures. The activation energy ( E a ) increased in all mixes containing pozzolana but decreased with a high replacement level of pozzolana, because of the filler effect during the hydration progress due to the high surface area of these materials, resulting in loss of strength. The results concluded that using the strength development rate ( k -value), calculated from ASTM C1074, to estimate the concrete strength at any age is valuable and it is very close to the actual values.