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Aggregate Shape and Tensile Strength Measurement

de Freitas Seben, Getulio Jr1; Corá, José Eduardo2; Fernandes, Carolina2; Lal, Rattan3

doi: 10.1097/SS.0b013e3182a4a0a6
Technical Article

Tensile strength (TS) of soil aggregates is an important indicator of soil quality. However, TS varies with aggregate shape. Thus, the objective of this study was to quantify the influence of aggregate shape on TS and propose a shape standardization protocol to increase accuracy in the measurement of TS. The latter was determined on 7,560 aggregates divided into three shapes, (i) irregular shape (IS), (ii) spherical shape (SS), and (iii) flat surface (FS), while preserving the inherent structure of the aggregate. The aggregates with IS had a larger range in the TS (306 kPa) because of the shape variability when compared with SS (238 kPa) and FS (129 kPa). The TS determined in aggregates with FS had smaller coefficient of variation (46%) in comparison with those of IS (70%) and SS (66%), indicating that the aggregate uniformity reduced the influence of shape on the TS. A smaller force (42.12 kPa) was needed to rupture aggregates with FS than IS (58.43 kPa) and SS (56.89 kPa) because of better force distribution in causing the tensile stress. The use of aggregates with the FS enables an accurate assessment of TS in relation to a wide range of management treatments.

1Sao Paulo State University (UNESP), Campus of Jaboticabal, São Paulo, Brazil.

2Soil Science Department, Sao Paulo State University (UNESP), Campus of Jaboticabal, São Paulo, Brazil.

3The Ohio State University, School of Environment and Natural Resources, Columbus, Ohio, USA.

Address for correspondence: Dr. Getulio de Freitas Seben, Jr, University of São Paulo State–UNESP, Campus of Jaboticabal, São Paulo, Brazil. E-mail:

Financial Disclosures/Conflicts of Interest: This study was part of the master’s thesis of the first author and was supported by FAPESP (Project 08/52560-1).

Received June 3, 2013.

Accepted for publication July 10, 2013.

© 2013Wolters Kluwer Health | Lippincott Williams & Wilkins