1
CNST252- Construction Materials
Hydrometer Analysis
Group 9
Will Priest Abdul Malik Rahmanzai, Brandon Rojas-Carrera, Peh Reh
Due date: 9/25/25
2
Experiment Summary: The objective of the hydrometer analysis experiment was to
identify the significance of performing the analysis, perform experimentations of particle size
distribution of fine-grained soils. As well as identify the standard used to measure the particle
size distribution of the sample, analyze the data obtained from the experiment and draw a full
gradation curve of the sample soil.
The materials used for this lab were: 50g of soil, dispersing agent, 2 1000-cc graduated cylinders,
small flask, hydrometer, thermometer, scale, distilled water, a mixer, and No. 12 rubber stopper.
The standard used in this experiment was ASTM D422, which is a standard test method for
determining the particle-size distribution of soils. In this standard test method, a soil hydrometer
test was conducted to analyze soil particle distribution (using 152H hydrometer). A 50 g soil
sample was prepared and mixed with a dispersing solution made of sodium hexametaphosphate
dissolved in distilled water. The dispersing solution prevents soil particles from clumping
together, ensuring accurate sedimentation results.
A reference hydrometer reading was taken using only the dispersing solution to establish
zero and meniscus corrections. The soil with the dispersing agent was then blended thoroughly
using a mixer and transferred into a 1000-cc graduated cylinder. Distilled water was added to
bring the solution to volume, and the cylinder was sealed and inverted multiple times to ensure
uniform mixing.
After mixing, the hydrometer was inserted into the cylinder with the soil, and readings
were recorded at specific time intervals (0.5, 1, 2, 5, 15, 30, 60 minutes, and 24 hours). Between
measurements, the hydrometer was returned to the reference cylinder to maintain calibration.
These readings provide data on the rate of soil particle settling, allowing calculation of particle
size distribution in the soil sample.
3
Results:
4
5
6
Sample Calculations:
Rcp = R + Ct – Fz ===> Rcp = (54+.85) - 6 ===> Rcp = 48.85
Rcl = R + fm ===> Rcl = 54 + 1 ===> Rcl = 55
PF = [(Rcp*a)/Ws]*100 ===> PF = [(48.85*1)/50]*100 ===> PF = 97.7%
D (Grain Diameter, mm) = K*(L/T)0.5 ===> D = 0.01317 *(8.1/.5)0.5 ===> D = 0.0530
Analysis and Discussion:
7
a) Yes, our results obtained were in the required range as shown in the results above.
b) Some sources of error that could have happened were the hydrometer not being properly
cleaned or not reading the hydrometer correctly.
c) These potential errors could have affected our data and skewed our results.
d) The graph shown is a gradation curve and it shows the particle size based off the percent
finer. So, our graph shows that as the particle gets larger, the percentage finer gets closer
to 100%.
Conclusions:
a. The objective of the hydrometer analysis experiment was to identify the significance of
performing the analysis, perform experimentations of particle size distribution of finegrained soils. As well as identify the standard used to measure the particle size
distribution of the sample, analyze the data obtained from the experiment and draw a full
gradation curve of the sample soil.
b. The method of this lab was to use the hydrometer to measure how much of the particle
was settling based on the density of the solution and using that to calculate the particles
size. The specific standard method that was used during this lab was ASTM D422.
c. These readings provide data on the rate of soil particle settling, allowing calculation of
particle size distribution in the soil sample.
d. Some of the main limitations of this experiment were giving the soil enough time to
settle. Based off of the first 6-7 readings the soil didn’t settle much. So, by giving it
enough time to settle it gives you more accurate readings.