1. What is Bulk Specific Gravity SSD?

Definition: The ratio of the mass of a unit volume of aggregate in the saturated surface-dry (SSD) condition to the mass of an equal volume of water.

Purpose: Used in concrete mix design to calculate volume relationships between aggregates and cement paste.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( SG_{SSD} \) — Bulk specific gravity in SSD condition (unitless)
• \( m_{SSD} \) — Mass of aggregate in SSD condition (kg)
• \( V \) — Volume of aggregate (m³)
• \( \rho_{water} \) — Density of water (typically 1000 kg/m³)

Explanation: The mass of SSD aggregate is divided by the mass of an equal volume of water to determine the specific gravity.

3. Importance of Bulk Specific Gravity SSD

Details: This property is essential for:

• Calculating concrete mix proportions
• Determining aggregate quality
• Assessing absorption capacity
• Volume-to-weight conversions

4. Using the Calculator

Tips:

• Measure mass after surface drying (SSD condition)
• Use pycnometer or volumetric flask for accurate volume measurement
• Standard water density is 1000 kg/m³ at 4°C

5. Frequently Asked Questions (FAQ)

Q1: What is SSD condition?
A: Saturated Surface Dry means the aggregate is fully saturated but with no free water on the surface.

Q2: How does this differ from apparent specific gravity?
A: Apparent specific gravity uses only the solid volume (excluding pores), while bulk SSD includes water in the pores.

Q3: What's a typical SG_SSD value for aggregates?
A: Normal range is 2.4-2.9 for most mineral aggregates, depending on mineral composition.

Q4: Why is water density important?
A: Specific gravity is defined relative to water density, so accurate water density ensures correct calculations.

Q5: How temperature affects the calculation?
A: Both water density and aggregate volume change with temperature, so measurements should be at standard temperature (usually 23±2°C).