The purpose of this form is to estimate the necessary
replacement level of normal weight aggregates by their pre-wetted
lightweight counterpart to compensate for chemical shrinkage and avoid significant autogeneous shrinkage of a
high-performance (low w/c ratio) concrete.
Even in higher w/c ratio concretes, this form will calculate
the LWA/water needed to compensate for the chemical shrinkage so that all pores
in the cement paste remain water-filled during hydration. Autogenous shrinkage
is not typically an issue with w/c > 0.45 concretes. For these higher w/c
ratio concretes, it may be more efficient and practical to supply curing
water via conventional external curing methods.
For details, see the following papers:
Bentz, D.P., and Snyder, K.A., Protected Paste Volume in Concrete:
Extension to Internal Curing Using Saturated Lightweight Aggregates,
Cement and Concrete Research, Vol. 29, 1863-1867, 1999.
Bentz, D.P., Lura, P., and Roberts, J., A Methodology for Mixture Proportioning for Internal Curing, Concrete International, Vol. 27, No. 2, February 2005, pp. 35-40. pdf version