Mechanical properties of natural aggregate paricles and their influence on the mechanical behavior of concrete.

Author(s)

Natalia Vieira da Silva

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Escola Politécnica (EP/BC)
• Defense date: 2018-02-22

Examining board members

Sérgio Cirelli Angulo; Aline da Silva Ramos Barboza; Luis Marcelo Marques Tavares

• Advisor: Sérgio Cirelli Angulo

Abstract

The aim of this work is to establish a simple test method to determine the tensile strength and elastic modulus of individual natural aggregate particles subjected to a compression load. The test method was developed based on the Point Load Test, that allows to obtain the tensile strength of particles. For the determination of the elastic modulus, an LVDT was coupled to the method and the condition for application of Hertz contact theory (curved-plane contact between the particles and the load application fixations) was satisfied. Initially, the method was evaluated using glass particles as reference (with geometries similar to aggregates). After validation on the glass, the test method was applied to coarse granite aggregates. A method of particle selection was proposed based on its absorption frequency distribution, in order to reduce the amount of mechanically tested particles required to obtain the Weibull distribution of tensile strength (and elastic modulus). For this purpose, the determination of the individual water absorption of hundreds of particles selected by random sampling of the population of aggregates was made. Based on the results, it was possible to determine the Weibull distribution of the tensile strength and elastic modulus of the particles. The tensile strengths ranged from 3 to 15 MPa. The aggregates had approximately 10% of the particles population with tensile strength less than 5 MPa, which may influence the classes of concrete with compressive strength > 50MPa. The elastic modulus of the aggregates was also variable (18-67 GPa), with approximately 10% of the particle population with elastic modulus <30 GPa. This may limit the elastic modulus of the concrete (usually around 27 GPa) depending on how the aggregates are selected. The fundamental inverse exponential functions between these mechanical properties and the porosity were confirmed (for mean values). (AU)

• FAPESP's process: 16/02902-0 - Resistance of natural coarse aggregate particles and its influence on the mechanical behavior of concrete
• Grantee: Natália Vieira da Silva
• Support Opportunities: Scholarships in Brazil - Master