*Article* **Assessment of Internal Structure of Spun Concrete Using Image Analysis and Physicochemical Methods**

### **Jarosław Michałek and Maciej Sobótka \***

Faculty of Civil Engineering, Wroclaw University of Science and Technology, 50-370 Wroclaw, Poland; jaroslaw.michalek@pwr.edu.pl

**\*** Correspondence: maciej.sobotka@pwr.edu.pl; Tel.: +48-71-320-4127

Received: 23 July 2020; Accepted: 8 September 2020; Published: 9 September 2020

**Abstract:** Taking into account the possibilities offered by two imaging methods, X-ray microcomputed tomography (μCT) and two-dimensional optical scanning, this article discusses the possibility of using these methods to assess the internal structure of spun concrete, particularly its composition after hardening. To demonstrate the performance of the approach based on imaging, laboratory techniques based on physical and chemical methods were used as verification. Comparison of obtained results of applied research methods was carried out on samples of spun concrete, characterized by a layered structure of the annular cross-section. Samples were taken from the power pole E10.5/6c (Strunobet-Migacz, Lewin Brzeski, Poland) made by one of the Polish manufacturers of prestressed concrete E-poles precast in steel molds. The validation shows that optical scanning followed by appropriate image analysis is an effective method for evaluation of the spun concrete internal structure. In addition, such analysis can significantly complement the results of laboratory methods used so far. In a fairly simple way, through the porosity image, it can reveal improperly selected parameters of concrete spinning such as speed and time, and, through the distribution of cement content in the cross-section of the element, it can indicate compliance with the requirement for corrosion durability of spun concrete. The research methodology presented in the paper can be used to improve the production process of poles made of spun concrete; it can be an effective tool for verifying concrete structure.

**Keywords:** concrete centrifugation; morphology; image processing; porosity; aggregate; cement
