Journal of the Civil Engineering Forum, May 2022, 8(2):139-146 DOI 10.22146/jcef.3797 Available Online at https://jurnal.ugm.ac.id/jcef/issue/archive Development of a Density Gauge for Measuring Water and Mud Density based on a Radioactive Technique Aloysius Bagyo Widagdo * National Research and Innovation Agency, INDONESIA *Corresponding author: aloy001@brin.go.id SUBMITTED 11 October 2021 REVISED 2 December 2021 ACCEPTED 7 January 2022 ABSTRACT The density or concentration of mud is one of the key variables in studying cohesive sediments, due to being accumulated through settlement and consolidation, as well as resuspended through erosion. This indicates that the proper measurement of sediment density is important. Therefore, this study aims to evaluate the accuracy of density measurement by using the gamma-ray attenuatioan method as a non-intrusive technique. For Compton Scattering, gamma-ray attenuation was effectively independent of mineralogy, subsequently depending on only the electron density of material, which is directly related to the bulk density of the mixture. Based on the results, the advantages of utilizing the nucleonic density gauge indicated that the technique was non-intrusive and very flexible for many experimental arrangements, as well as the high accuracy of measurements with errors less than 1%. KEYWORDS Density; Cohesive sediment; Nucleonic gauge; Non-intrusive; High accuracy © The Author(s) 2022. This article is distributed under a Creative Commons Attribution-ShareAlike 4.0 International license. 1 INTRODUCTION The experimental methods for determining the density of sediments are generally categorized as (i) sampling, and (ii) in situ direct measurements. This sampling method involves weighing an accu- rately known volume of samples obtained through a siphon, pipette or other devices. Meanwhile, the in-situ direct technique involves optical or acoustic instruments, which are non-intrusive al- though requires calibration to produce absolute sediment concentrations. These methods have presently been applied in studying suspended lay- ers with materials coarser than mud (i.e., silt and sand). In several previous decades, the initiation of applying the principle of gamma-ray attenua- tion was conducted in measuring the bulk den- sity of cores and sediment samples. This method was used for the in-situ measurement of bulk sea bottom sediment density (Preiss, 1968a,b; Rose and Ronsy, 1971; Krishnamurthy et al., 1973; Ger- land and Villinger, 1995; Blum, 1997), where ver- tical distribution was determined at distances be- tween 2-5 cm, with the accuracy of +1%. It was also applied for measuring the spatial variability of soil bulk density (Pires et al., 2009). Further- more, the gamma-ray attenuation method was used as a proof-of-concept for non-intrusive and undisturbed measurement of sediment infltration masses. This led to a good accuracy with a devia- tion of less than 5% (Mayar et al., 2020). Based on this present study, the development and evaluation of a nucleonic density gauge are required, as a non-intrusive method for the ac- curate concentration measurements of mud pro- fles. This density gauge is a device for measur- ing the attenuation of a collimated gamma-ray beam after passing through a test material, e.g., the sediment-water mixture. The gauge utilized in this application uses a 111 MBq source, which emits a narrow collimated beam of gamma-rays at 662 keV. At this energy level, attenuation is found to occur by the Compton scattering of the inci- dent gamma-rays from the collimated beam. This method is non-intrusive and has the additional important advantage that the calibration factor (i.e., the ratio between the measured gamma-ray attenuation and the calculations from the pub- lished coeffcients of the kaolin and water com- 139