  In this paper the kinetics of the pozzolanic reaction between lime (calcium
hydroxide) and sugar cane straw ash with 20 and 30% of clay burned at 800 and
1000 C is studied. A simple experimental technique where the conductivity is
the experimental variable was used. A calibration curve was established for
correlating the conductivity with the concentration of calcium hydroxide (CH).
We elaborated a mathematical model that allows us to describe the process in
kinetic - diffusive or kinetic regimen. The fitting of the model by
computerized methods lets us determine the parameters that characterize the
process: i.e. the diffusion coefficient and reaction rate constant. The
pozzolanic activity is evaluated according to the obtained values of the
reaction rate constant. The results show that sugar cane straw ash (SCSA) has a
good pozzolanic activity comparable to that of the rice husk ask (RHA).
