Table 8 shows the average modulus of elasticity of the test mixtures at different ages.
Same as the results of strength measurements, the elastic modulus of recycled concrete
mixtures are 20 to 30 percent lower than that of crushed limestone mixtures. The effects of
mixing variables on the development of the modulus of elasticity were also found not much
different from the result of strength tests. Again, for a given aggregate type used, applied
cement content appears to be the most governing factor for the development of stiffness or
modulus of elasticity. The ratio of elastic modulus of high cement (8%) to low cement (4%)
mixtures reaches over 2.0 at the early ages, while it generally ranges from 1.3 to 1.7 for the
mixtures aged more than 7 days.