MEASUREMENT OF SHRINKAGE IN CONCRETE SAMPLES BY USING DIGITAL 
: PHOTOGRAMMETRIC METHODS 
F. Yilmaztiirk®, S. Kulur?, B.Y. Pekmezci® 
* [TU, Civil Engineering Faculty, 80626 Maslak Istanbul, Turkey - (yilmazturk, kulur,pekmezcil)@itu.edu.tr 
Commission V 
KEY WORDS: Calibration, Close Range, Adjustment, Comparison, Analysis 
ABSTRACT: 
This paper shows the use of digital photogrammetry for measurement of shrinkage in concrete sample (4x4x22 cm) during the hydra- 
tion process. A vision system consist of two digital video cameras was established to measure vertical displacement. The system was 
calibrated because of the cameras were designed for high accuracy measurement purposes. This was done by imaging a calibration 
object placed within the workplace. A least squares bundle adjustment determines the camera calibration parameters as well as the 
exterior orientation parameters of the cameras. Measurements were conducted at 2 epochs over 24 h. The estimated precision of the 
3-D points positions is in the order of 0,1 mm, which is sufficient for this application. The resulting points can then be used for a de- 
formation analysis. 
1. INTRODUCTION 
The measurement of objects such as deforming parts has often 
been realized using methods such as interferometry, Moiré 
techniques, theodolite measurement systems, or coordinate 
measurement machines. But various disadvantages (high prices, 
system have to rest stable during the whole campaign, measur- 
ing effort, influence of touching the object) lead to the demand 
of new techniques. 
With the development of solid-state sensor imaging devices and 
powerful computer platforms, new image-processing-based so- 
lutions for a large number of 3-D measurement tasks have been 
successfully applied for many years. Compared with those 
techniques mentioned above, there are some obvious reasons, 
which make the use of digital photogrammetry more than just a 
useful alternative: Photogrammetry is non-contact, requires no 
manual reading of dials, yields three-dimensional measure- 
ments, and provides visual records of the testing. (Maas, 1994, 
Whiteman, 2002). 
Concrete and cement paste show shrinkage and settlement dur- 
ing the hydration process. Although there are several measure- 
ment techniques to obtain the length variation of hardened con- 
crete, we have serious problems on the determination of 
settlement in fresh state (Neville, 2000). 
The paper reports on how to use digital close-range photo- 
grammetric techniques for measurement of shrinkage and set- 
tlement of concrete sample in fresh and hardened state (Fig. 1) 
during the hydration process. Using digital photogrammetry, we 
were able to achieve a sufficient relative accuracy. 
2. SYSTEM CONFIGURATION 
2.1 Design 
For the determination of an appropriate configuration and the 
calculation of the camera parameters, the following input was 
used: 
e object size, 
e principal distance and 
e the size of the digital image. (Suthau, 2001) 
  
Figure 1: Concrete sample 
The system was arranged convergently at a distance of ap- 
proximately 0.50 m from the concrete sample (Figure 2). Con- 
crete specimens having the dimensions of 40x40x220 mm were 
used for the experimental study. Measurements were carried out 
on the specimen, which had not been demoulded, to obtain the 
fresh state behavior. 
  
Figure 2: Camera configuration 
   
   
    
   
   
    
   
  
   
  
    
  
  
  
  
  
  
  
    
  
   
   
  
  
  
   
    
   
   
  
  
   
    
  
   
   
   
  
   
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
   
  
     
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