An experimental study for the application of nano concrete to reduce roughness coefficient

Tayebeh Sanghchulie1, Shervin Faghihirad2, Yousef Khalaj Amir-Husseini3

1,2,3Water Research Institute, Ministry of Energy, IRAN

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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 coatedby 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 coatedby 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 nano-particles.

  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.

  1. 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.

(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. Hydraulicboundary 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 showthe laboratory flume used in this experimental study.

Figure 1: Laboratory Hydraulic Flume

  1. 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 / Flow Rate of Hydraulic Tests (lit/s) / Type of Concrete / Coating Position / Measured Parameters / Notes
1 / 20 / Regular Concrete / Floor / Flow velocity and water surface level / 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.
40
80
100
2 / 20 / Concrete with Silicate Nano-Particles / Floor / Flow velocity and water surface level
40
80
100
  1. 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).

Diagram2: Comparison of Roughness coefficients Diagram1: Comparison of Roughness coefficients

Diagram 4: 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 reductionsare 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 revealthat 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.

References

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