07_Kolar_K_i_inni_Influence_of_separation_agents_on_quality_of_concrete_surface.pdf

XXIV

awariebudowlane

Doc. Ing. K AREL K OLÁŘ , CSc., karel.kolar@fsv.cvut.cz

Faculty of Civil Engineering, CTU in Prague

Doc. Ing. T OMÁŠ K LEČKA , CSc., klecka@vc.cvut.cz

Doc. Ing. J IŘÍ K OLÍSKO , Ph.D., kolisko@vc.cvut.cz

Klokner Institute, CTU in Prague

Ing. P AVEL R EITERMAN , pavel.reiterman@fsv.cvut.cz

Doc. Ing. J AN V ODIČKA , CSc., jan.vodička@fsv.cvut.cz

Faculty of Civil Engineering, CTU in Prague

INFLUENCE OF SEPARATION AGENTS ON QUALITY

OF CONCRETE SURFACE

WPŁYW Ś RODKÓW SEPARUJ Ą CYCH NA JAKO ŚĆ POWIERZCHNI BETONU

Abstract Application of new type of unique Confocal Laser Scanning Microscope system, that presents a new

generation optical system for identification and description of esthetical imperfections of fair-face concrete are

presented in contribution. System enables 3D observation and high-precision 3D measurement in real time.

The influence of mixture composition, separation demoulding agents and technology procedures are observed..

Streszczenie W artykule przedstawiono moŜliwość zastosowania nowego rodzaju mikroskopu Confocal Laser

Scanning Microscope do identyfikacji i opis jakościowego powierzchni betonu. System pozwala na 3D obserwa-

cję i duŜą precyzję pomiaru w rzeczywistym czasie. Analizowano wpływ składu mieszanki betonowej oraz

środków separacyjnych na jakość powierzchni betonu.

1. Introduction

The concrete is the most used building material at the moment and this trend is going to

continue for a long time in future. The production of fair-face concrete components that are

used more or less successfully as a final surface of not only transport constructions (bridges,

retaining walls, piers, etc.) but also at public and house-building constructions is growing up

and is applied more often.

Fair-face and architectonic concretes are extremely technologically difficult elements

because of high requirements on final esthetic view and because of many factors that

influence production and result. Very important role in building up of top surface layer of

concrete plays application of separation agents on formwork surfaces [1],[2]. Methodology

and some results of 3D microscopic observation and measurements of concrete surface treated

by different separation agents are presented in this contribution.

XXIVKonferencjaNaukowoTechniczna

SzczecinMiędzyzdroje,2629maja2009

Materiałowe aspekty awarii, uszkodze ń i napraw

2. Perspective methodology of measurements

Some opportunity of objective and quantifiable evaluation of concrete surface is offered by

a confocal laser scanning microscope LEXT OLM 3000 we use for different types of

observations and measurements. Confocal laser scannig microscopy is a representative of new

generation of optical systems with the high accuracy, 3D projection and measuring. It offers

new possibilities for development and control of various materials and components. It is

especially useful for new applications in micro- and nano-technological branches that put

heavy demands on nonstandard ways of nondestructive noncontact measurement and control

of materials, miniature components, very fine connections and also on control of roughness of

surfaces with submicron accuracy.

The basic principle of confocal laser scannig microscope is that it does not create a picture

as the whole but point after point – by scanning. With the help of scanning optical sections are

scanned in the plane X-Y and due to the accurate defined feed of the objective in axis Z also

single optical sections.

It allows also 3D observation and highly accurate 3D measurement in a real time. Owing to

an excellent resolution 0,12 mm and an range of magnification 120´–14 400´ the LEXT is

assigned directly to research workers that work between limits of common optical micro-

scopes and scanning electron microscopes (SEM). Apart of a situation in SEM any sample can

be put directly on the microscope table without pre-preparation. Confocal microskop

is suitable ideally for ultra-detailed observation of surfaces and measurements that are

necessary during production of micro-devices, such as MEMS (Micro Electro Mechanical

System), during development of new materials and also at contemporary compact devices

during a spatially more compacted surface installation.

In construction industry it is used for measuring of real distances, volumes, areas and

projections, measuring of roughness of surfaces, measuring of profiles, analysis of particles,

control of materials, coatings and many other functions directly in 3D projection. Abilities of

such system can be utilized very well also during analysis of faults and defects (such as

cracks, porosity, etc.) and it also exceeds a frame of conventional microscopy significantly by

the fact it presents a very efficient 3D projection tool with high accuracy of measuring.

Z tm

Measured length L

Fig. 1: Middle height Z tm of elements of contour curve in measured length L

In the experimental program desribed below the scanned area of concrete surface was

divided to partial rectangles size 1000x1024

464

m by ten axes. The gained values characterize

the structure of surface in sections along the single axes. For analysis of roughness of a

Kolá ř K. i inni: Influence of separation agents on quality of concrete surface

microscopic area 15 characteristics are described altogether, but for evaluation of a surface

just three were chosen because quality and structure of the surface is manifested the most at

these chosen quantities. It is middle height Z tm (fig. 1), maximal height of a profile R t (fig. 2)

and arithmetical middle height R a (fig 3).

Zp max

R t

Measured length L

Zv min

Fig. 2: Maximal height R t of a profile of curve. It is sum of maximal height of apex Zp and minimal depth

of a saddle Zv of contour curve in measured length L

R a

Measured length L

Fig. 3: Arithmetical middle height (roughness) R a . Middle value from absolute value Z(x) in measured length L

3. Experimental program

Further important aspect in evaluation of concrete surface was examination of a possibility

to evaluate not only roughness of the surface but also its variety of color. The microscope does

not contain differentiating software that would carry out such a color evaluation.

Consequently there was examined the way coloring of the surface is projected to its

roughness. To examine this relationship a sample of concrete surface was chosen that showed

regular marbling. Observation of surface was performed on the boundary of a light and a dark

concrete surface. Screen of controlling PC is presented on Figure 4. Illustration of numerical

outlet of microscope in the area of the boundary of color is given in Table 1.

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Materiałowe aspekty awarii, uszkodze ń i napraw

Table 1. Illustration of numerical outlet of microscope (

Axis (measured line)

Light color

Dark color

Z tm

R t

R a

Z tm

R t

R a

7,72

23,55

2,52

8,71

58,05

3,29

7,29

28,80

2,41

6,32

20,72

2,31

8,30

37,62

2,82

6,84

17,02

2,60

9,30

31,76

3,22

10,22

66,93

3,39

11,27

37,65

4,46

15,04

166,09

6,70

7,85

24,54

2,89

8,38

26,67

2,98

6,23

20,32

2,83

13,23

100,30

4,25

6,39

26,05

2,38

5,76

17,88

2,54

6,98

26,12

3,13

8,77

30,77

3,47

7,41

23,50

2,80

8,24

26,47

3,27

Mean

7,87

27,99

2,95

9,15

53,09

3,48

Fig. 4. Boundary of a light (left) and dark (right) color of concrete surface.

The main goal of the experiment was the evaluation of an influence of various separation

agents applied on surface of form work on a quality of final surface layer of a concrete.

Separation agents of various bases were used for separation of the concrete (see Table 2).

Besides these means comparative samples without using any agents were produced.

Preparation of experimental samples simulated a production of prefabricated elements where

bottom of a form creates a face side of fair-face element. For a production of experimental

samples cylindrical forms with a diameter 150 mm and height 50 mm. As a covering a

fiberboard with a laminated surface was used. To make a fabrication of a fresh concrete

constant, each sample was vibrated on a vibration table with frequency 50 Hz. Vibration time

was equal the double of consistency VeBe test result that was carried out, too.

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Kolá ř K. i inni: Influence of separation agents on quality of concrete surface

Table 2. Used separation agents an no. of specimen

Agent No. Name of separation agent Material base

Dem Oleo 50

Synthetic oil

Dem Bio 4

vegetable oil

Dem Oleo 31

Mineral oil

Dem Ekla 12

water emulsion

Dem Graisse

wax paste

Alop

–

Without separator

–

Mould

–

Separation means mentioned above were tested on three concrete mixtures with a constant

skeleton of aggregates. The first concrete mixture without using of plasticizing admixtures

was suggested. At the second and third concrete mixture a plasticizer from Chryso company

was used to avoid chemical reaction between a plasticizer and separation agents. Plasticizer

based on carboxyl-ether was used. Dose of plasticizer was 0,75% cement mass. This way the

cement-water ratio was reduced from 0,5 to 0,4.The third concrete mixture was designed to a

consistency corresponding with VeBe test = 4s. Final composition of all concrete mixtures is

in following table.

Table 3: Composition of concrete mixtures

Component

Mixture 1

Mixture 2

Mixture 3

Dose [kg]

Sand 0 – 4

814

Crushed gravel 4 – 8

407

Crushed gravel 8 – 16

739

CEM I 42,5R

398

water

200

160

190

Plasticiser carboxyl-ether

2,94

Chemical composition and basic norm characteristics of a used cement CEM I 42,5 R are

given in Tables 5 and 6.

Table 4: Results of VeBe consistency test and water – cement ratio

Mix. 1 Mix.2 Mix.3

Consistency test VeBe, [ s ] 16

Water – cement ratio, [ - ]

0,5

0,4

0,48

Table 5: Chemical composition of a cement

Components SiO 2 Al 2 O 3 Fe 2 O 3 CaO

Content [%] 23,9 5,2 2,9 58,8

Components SO 3 MgO Na 2 O K 2 O

Content [%] 2,5

3,0

0,3

0,8

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