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CT Measurements of SAP Voids in Concrete



Sara Laustsen, Dale P. Bentz, Marianne Hasholt, Ole M. Jensen


This paper describes how X-ray computed tomography (CT) scanning can be used to determine the void distribution in hardened concrete. Three different approaches are used to analyse a binary data set created from CT measurement. One approach classifies a cluster of connected, empty voxels (volumetric pixel of a 3D image) as one void, whereas the other two approaches are able to classify a cluster of connected, empty voxels as a number of individual voids. Superabsorbent polymers (SAP) have been used to incorporate air into concrete. An advantage of using SAP is that it enables control of the amount and size of the created air voids. The results indicate the presence of void clusters. To identify the individual voids, special computational approaches are needed. The addition of SAP results in a dominant peak in two of the three air void distributions. Based on the position (void diameter) of this peak, it is possible to calculate the liquid absorption of the SAP within the fresh concrete. This estimated liquid absorption is in agreement with measurements carried out in previous studies.
Proceedings Title
Use of Superabsorbent Polymers and Other New Additives in Concrete
PRO 74
Conference Dates
August 15-18, 2010
Conference Location
Lyngby, DK


Air voids, Concrete, Superabsorbent polymer, X-ray computed tomography


Laustsen, S. , Bentz, D. , Hasholt, M. and Jensen, O. (2010), CT Measurements of SAP Voids in Concrete, Use of Superabsorbent Polymers and Other New Additives in Concrete, Lyngby, DK, [online], (Accessed March 4, 2024)
Created August 14, 2010, Updated October 12, 2021