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Created: 2024/07/10 19:23

Experiment no. 03

Experiment name: Determination of specific gravity and absorption capacity of fine and coarse aggregate

Objective

The objective of this experiment is to determine the specific gravity and absorption capacity of fine and coarse aggregates.

Significance

Understanding the specific gravity is necessary:

1. To convert aggregate weight into solid volume
2. To calculate the compacting factor, influencing workability assessments.
3. For various construction applications such as water filtration systems, slope stabilization, and railway bedding.

Absorption capacity is essential:

1. To determine the change in aggregate weight due to water absorption.
2. To calculate the percentage of free moisture on aggregate particles.
3. To ensure the correct water-cement ratio.

Apparatus

1. Balance
2. Pycnometer
3. Wire basket
4. Water tank
5. Absorbent cloth
6. Oven
7. Thermometer

Data sheet

Calculation

For fine aggregate

Here,

• Mass of OD sample in air, $A=500\text{[PARSE ERROR: Undefined("Command("space")")]}gm$
• Mass of pycnometer filled w/ water, $B=1258\text{[PARSE ERROR: Undefined("Command("space")")]}gm$
• Mass of pycnometer filled w/ sample & water, $C=1571\text{[PARSE ERROR: Undefined("Command("space")")]}gm$
• Mass of SSD sample, $S=502\text{[PARSE ERROR: Undefined("Command("space")")]}gm$

Therefore,

(OD) Bulk specific gravity, $$\frac{A}{B+S-C}=\frac{500}{1258+502-1571}=2.65$$

(SSD) Bulk specific gravity, $$\frac{S}{B+S-C}=\frac{502}{1258+502-1571}=2.66$$

Apparent specific gravity, $$\frac{A}{B+A-C}=\frac{500}{1258+500-1571}=2.67$$

Absorption capacity, $$\frac{S-A}{A}\times 100=\frac{502-500}{500}\times 100=0.40\mathrm{\%}$$

For coarse aggregate

Here,

• Mass of OD sample, $A=2952\text{[PARSE ERROR: Undefined("Command("space")")]}gm$
• Mass of SSD sample, $B=2978\text{[PARSE ERROR: Undefined("Command("space")")]}gm$
• Mass of SSD sample in water, $C=1920\text{[PARSE ERROR: Undefined("Command("space")")]}gm$

Therefore,

(OD) Bulk specific gravity, $$\frac{A}{B-C}=\frac{2952}{2978-1920}=2.79$$

(SSD) Bulk specific gravity, $$\frac{B}{B-C}=\frac{2978}{2978-1920}=2.81$$

Apparent specific gravity, $$\frac{A}{A-C}=\frac{2952}{2950-1920}=2.86$$

Absorption capacity, $$\frac{B-A}{A}\times 100=\frac{2978-2952}{2952}\times 100=0.88\mathrm{\%}$$

Result

For both fine aggregate and coarse aggregate, the determined value of apparent specific gravity was 2.67 and 2.86, bulk specific gravity (OD) was 2.65 and 2.79. bulk specific gravity (SSD) was 2.66 and 2.81, and absorption capacity was 0.40% and 0.88% respectively.

Discussion

In this experiment, the apparent specific gravity, bulk specific gravity (OD), bulk specific gravity (SSD), and absorption capacity for both fine and coarse aggregates were determined. They were 2.67, 2.65, 2.66, and 0.40% for fine aggregate respectively, while 2.86, 2.79, 2.81, and 0.88% for coarse aggregate respectively.

For fine aggregates, the values indicate that it has a relatively low absorption capacity, suggesting it has lower porosity and will absorb less water. This is beneficial in concrete mix design as it reduces the variability in water content, leading to a more consistent mix.

However, the coarse aggregate has a higher absorption capacity compared to the fine aggregate. This higher absorption capacity indicates a higher porosity which could potentially impact the water-cement ratio and the workability of the concrete mix.