What is SSD condition of aggregates?

SSD – Saturated, Surface Dry. The condition in which the aggregate has been soaked in water and has absorbed water into its pore spaces. The excess, free surface moisture has been removed so that the particles are still saturated, but the surface of the particle is essentially dry.

What is meant by SSD condition of aggregate?

SSD stands for saturated surface-dry and it describes a condition that a concrete surface must be brought to when a cement product is to be applied to it. The surface is SSD when the substrate is saturated with water, filling the voids in the substrate’s aggregate, but the outer surface is devoid of free water.

Why is the SSD condition of aggregates the best choice especially in the proportioning of materials of a concrete mix design?

The SSD state is the best choice as a reference state for the following reasons: It represents the “equilibrium moisture” state of the aggregate in concrete; that is, the aggregate will neither absorb water nor give up water to the paste.

How is SSD weight calculated?

Simply stated, it is the unit weight of a saturated material divided by the unit weight of water and is computed as follows: Gs(ssd) = (1 + Absorption) x Gs(dry).

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Why aggregates are considered as SSD condition in mix design?

Saturated surface dry (SSD) is defined as the condition of an aggregate in which the surfaces of the particles are “dry” (i.e., surface adsorption would no longer take place), but the inter-particle voids are saturated with water.

Which type of aggregate is good for concrete?

Gravel or broken stone aggregates with rough and non-glassy texture are the best aggregates because they create a good bond with the cement paste. Aggregates need to be hard, strong, chemically inert, and non-porous. Organic substances and dirt coating compromise the strength and durability of concrete.

How does one know when the SSD has been reached in a sand sample?

VI. ASTM C128 – Specific Gravity and Absorption of Fine Aggregate How does one know when SSD has been reached in a sand sample? Condition Using the cone test, tapping the sample 25x in place then removing the cone from the sample, the sample should slump slightly which will conclude that it has reached SSD.

What are the four conditions of moisture in aggregate?

There are four moisture states: Oven-dry (OD); all moisture removed. Air-dry (AD); surface moisture removed, internal pores partially full. Saturated-surface-dry (SSD); surface moisture removed, all internal pores full.

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