An experimental study for the application of nano concrete to reduce roughness
coefficient
Tayebeh Sanghchulie1, Shervin Faghihirad2, Yousef Khalaj Amir-Husseini3
1,2,3
Water Research Institute, Ministry of Energy, IRAN
1
T.sangchouli@gmail.com,2Faghihirads@cardiff.ac.uk,3yousefkhalaj@yahoo.com
Abstract
Roughness coefficient and calculating it are fundamental issues in hydraulic engineering. Also, analyzing
the correct evaluation of flow rate and interaction with other hydraulic parameters such as velocity, shape
and type of section, and flow pattern, is one of the most important problems in fluid mechanics. The
possibility of minimizing roughness on designing of hydraulic structures and irrigation networks in order
to increase velocity and then the flow rate at different sections, are subjects which have been noted by
researches and industrial entrepreneurs since years ago. In this experimental research, the effects of using
silicate nano-particles in the floor coating of the channels have been studied in a hydraulic laboratory
flume. Adding Nano-Silicate to the concrete mixture will cause the active SiO2 to mix with the free
calcium hydroxide available in the micro holes of the concrete and produce unsolved calcium silicate, and
eventually cause the structure of the cement to become more dense and become less penetrable causing
the concrete to be more resistant. By using this product, we can produce smooth and homogenous
surfaces in the upper surface that can increase the flow rate and velocity of fluid in channels, clarifiers
and crests of dams. In this research, a hydraulic flume with a rectangular section with a length of 10m,
height of 0.6m and width of .55m was used for experimental studies to investigate the effect of silicate
nano-particles. In the first step, the floor of this hydraulic flume was coated by a regular concrete and at
five different flow rates (20, 40, 80, 100 lit/s) flow velocity and water surface level were measured at
points in different sections and different locations (Figure 1). In the next step of this experimental study,
the channel floor was coated by using concrete containing silicate nano-particles and then the all tests
were repeated in same conditions. The results of the flow hydraulics tests at different flow rates show a
decrease from 16 to 38% of the calculated roughness coefficient in the concrete containing silicate nanoparticles.
1. Introduction
It appears that one of the most important applications of Nano technology in civil engineering is the use
of nano-particles in the production of cement and concrete. In this research, it has been tried to study the
possibility of using these material in hydraulic structure and irrigation networks. Since using silicate nano
particles in concrete has many advantages, the following applications can be considered:




Tunnel surface coatings, due to high solidity and increase in pressure, density, and flexibility
resistance
Resistance to leaks
Increase of adhesion and resistance in reinforced concrete
Decrease of abrasion in surfaces containing nano-silicate concrete
SiO2 is in mixture of a regular concrete and the results of studying concrete at nano scale is that using
silicate nano-particles one can increase the density of particles and decrease micro holes. This causes
raise density and the nano-structures will improve the mechanical qualities of the concrete.
2. Hydraulic Tests
For studying the role of silicate nano-particles in the reduction of roughness, the flow velocity was chosen
as a hydraulic parameter and a series of hydraulic tests were carry out in a hydraulic flume with a
rectangular section and the following specifications. To calculate the roughness coefficient, the Manning
relationship (Equation 1) was used.
n = 1/V R2/3 √S
(1)
In this equation (n) is the roughness equation, (v) flow velocity, (R) hydraulic radius, and (S) the slope of
the energy line. Laboratory flume specifications: Length of 10m, Rectangular section with a height of
0.6m and width of 0.55m. Floor material: regular concrete in the first stage tests, and concrete containing
silicate nano-particles for the second stage tests. Hydraulic boundary conditions: Upstream of the flume
using a hydraulic valve to regulate the inlet flow rate, and downstream of the flume using a gate to
regulate the water surface level. Figure 1 show the laboratory flume used in this experimental study.
Figure 1: Laboratory Hydraulic Flume
3. Scenarios of Hydraulic Tests
All tests were done in two series with five different flow rates. Table 1 shows the attitudes related to the
hydraulic tests.
Table 1: The attitudes for the scenarios
Stage
1
2
Flow Rate of
Hydraulic Tests
(lit/s)
20
40
80
100
20
40
80
100
Type of
Concrete
Coating
Position
Measured
Parameters
Regular
Concrete
Floor
Flow velocity and
water surface level
Concrete with
Silicate
NanoParticles
Floor
Flow velocity and
water surface level
Notes
Acoustic Doppler Velocimeter
(ADV) has been used to measure
velocity and the Ultrasonic
Levelmeter Probe (Ultra 3000
model) has been used to measure
water surface level.
4. Test Results
Diagrams 1 to 4 show the calculated roughness coefficients for the four different discharges of 20, 40, 80,
and 100lit/s in two experimental modes (regular concrete and nano concrete coatings).
Roughness coefficient
Roughness Coefficient
Q=40 lit/S
0.016
0.014
0.012
0.010
0.008
0.006
0.004
0.002
0.000
Control
One
Two
Three
Section Name
Four
Q=20 lit/s
0.035
0.030
0.025
0.020
0.015
0.010
0.005
0.000
Results of first stage,
uncoated nano
Results of first stage
with coated nano
Control One
Output
Q=80 lit/s
Three
Four
Output
Roughness Coefficient
Roughness Coefficient
Two
Four Output
Diagram1: Comparison of Roughness coefficients
Q=100 lit/s
0.014
0.012
0.010
0.008
0.006
0.004
0.002
0.000
One
Three
Section Name
Diagram2: Comparison of Roughness coefficients
Control
Two
0.009
0.008
0.007
0.006
0.005
0.004
0.003
0.002
0.001
0.000
Results of first stage,
uncoated nano
Results of first stage with
coated nano
Control
Section Name
Diagram 4: Comparison of Roughness coefficients
One
Two
Three
Four
Output
Section Name
Diagram 3: Comparison of Roughness coefficients
Those diagrams show the reduction of roughness coefficient when silicate nano-particles are used as
coating on the floor of the flume. The average percent of these reductions are as follows:
Discharge 20lit/s:
38.61%, Discharge 40lit/s:
33.45%,
Discharge 80lit/s:
16.76% and Discharge 100lit/s:
23.43%
The overall averages reveal that the silicate nano-particles can decline the roughness coefficient up to
28.06%.
According to the preliminary laboratory results of this research, a suggestion for use of this type of
material can be presented. By using this type of coating, the flow velocity can be increased and
sedimentation decreased in canals and water facilities.
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