Viscosity Determination

Question 1

Define the term viscosity

Answer 1

This is the the measure of a fluid’s internal resistance to flow

Question 2

State the objective of determining viscosity of bitumen using Brookfield thermosel apparatus.

Answer 2

To measure the apparent viscosity of bitumen using Brookfield thermosel apparatus

Question 3

What’s the difference between apparent viscosity and kinematic viscosity?

Answer 3

Apparent viscosity is a measure of the fluid’s internal resistance to flow, which may change depending on the applied force (especially for non-Newtonian fluids),
while
kinematic viscosity indicates a fluid’s resistance to flow under the force of gravity, taking into account its density.

Question 4

How do we calculate for the viscosity of the material

Answer 4

Obtain the ratio of the shear stress to the shear strain

Question 5

How can dynamic viscosity also be described?

Answer 5

It can be described as the ratio of shear stress to shear rate for a Newtonian or non Newtonian liquid

Question 6

State the difference between Newtonian or non Newtonian liquid

Answer 6

Newtonian liquid is a one that has its shear rate proportional to the shear stress
While
Non Newtonian liquid is one where the ratio between shear stress and shear rate is not constant

Question 7

Dynamic viscosity is also called ______

Answer 7

Apparent viscosity

Question 8

What are the SI units for viscosity

Answer 8

Pascal seconds (Pa x s)

Question 9

True or false doesn’t bitumen exhibit both Newtonian and non Newtonian behaviour?

Answer 9

False it does depending on the shear rate and temperature

Question 10

Differentiate between shear rate and shear stress

Answer 10

Shear rate measures the speed at which a fluid layer deforms,
while
Shear stress measures the force per unit area required to cause that deformation

Hint:

In simpler terms, shear rate is the “how fast” of the flow, and shear stress is the “how much force” is needed for that flow.

Question 11

What is the main equipment used for this test?

Answer 11

The Brookfield thermosel high temperature viscosity unit

Question 12

State any other equipment for this test

Answer 12

Spindles for the The Brookfield thermosel viscometer
Thermosel system
Heating oven
Balance

Question 13

What are the components of the thermosel system?

Answer 13

Thermo container
Temperature controller
Sample chamber
Extraction tool

Question 14

How do we select the appropriate spindle and speed that will be used to match the expected viscosity of the material ?

Answer 14

We use values from table 3.8-2 and 3.8-3 (CML)

Question 15

How does a Brookfield thermosel viscometer work ?

Answer 15

A Brookfield viscometer works by measuring the torque required to rotate a spindle in a fluid at a known speed. The resistance of the fluid against the spindle creates a torque that’s proportional to the fluid’s viscosity. This torque value is then converted to a viscosity reading in centipoise (cP) or millipascal-seconds (mPa·s).

In simple terms : imagine stirring honey versus water with a spoon. The honey creates more resistance (higher viscosity), requiring more effort (torque) to maintain the same stirring speed. This is precisely what the Brookfield viscometer measures, but with precision instrumentation.