In addition to conventional external curing methods, there shall be a substitution in 0.43 wc ratio or lower concrete mixtures of lightweight aggregate sand (LWAS) for natural and/or for manufactured normalweight sand.  The lightweight aggregate sand (LWAS) substitution is to be on an equal volumetric basis and in accordance with the following:

LWAS shall be expanded shale meeting the following standards and criteria:

• “ASTM C330 Standard Specifications for Lightweight Aggregates for Structural Concrete.”

• “ASTM C33 Standard Specifications for Concrete Aggregates” (under revision).

• “ASTM C109C, 109M Standard Test Method for Compressive Strength of Hydraulic Mortars.”   LWAS shall be capable of meeting 100% of the control strength.

• “ASTM C128 Standard Test Method for Density, Relative Density (Specific Gravity), and Absorption of Fine Aggregate.”  LWAS shall be capable of having an absorption of 15% at 24 hours and a minimum of 10% in 30 minutes

PRECONDITIONING OF LWAS
LWAS shall be pre-saturated by either sprinkling or soaking to ensure a saturated surface dry condition when tested in accordance with “ASTM C70 Standard Test Method for Surface Moisture in Fine Aggregate,” when introduced into the mixture batching sequence

BATCHING
Introduce SSD LWAS into the mixer drum first, along with the mixing water, or at least a sufficient quantity of it to be sure that it remains SSD as drier materials are sequentially batched after the introduction of the LWAS

SAND REPLACEMENT
Depending on the characteristics desired, a general volume replacement of
15%-25% of natural/manufactured sand by LWAS will yield desired benefits.  For confirmation of desired results, a 3-Point Curve of varying amounts of LWAS is recommended.