Probability distributions of mechanical properties of natural aggregates using a simple method

Abstract

Characterizing the strength and the elastic modulus of single aggregate particles is relevant, in particular for use in high-strength concrete. One problem of methods normally used in this task is the time and effort demanded. The work proposes a rapid and simple test method to measure the probabilistic distributions of those properties for coarse aggregates contained in the range of particle sizes between 9.5 and 25-mm, approximately, applying it to granite and limestone. Water absorption (WA) of a hundred individual particles of each type of coarse aggregate was measured. Afterwards, the Point Load Test method is used to determine the tensile strength of all particles. A Linear Variable Differential Transducer (LVDT) coupled to the mechanical essay measured the displacements, under Hertz contact conditions, between artificially flat-made irregular particles and the testing machine fixture, allowing to determine the elastic moduli. Results were represented using the Weibull probabilistic distribution function. The one hundred individual particles, when stratified on the basis of non-destructive WA measurements, allowed capture the mechanical variability in the data. As such, mechanical tests could be performed only with approximately 20 specially selected particles of each aggregate type. Fundamental inverse exponential functions between the mechanical properties and WA confirmed the possibility of using this artifice. The tensile strengths ranged from 3 to 22 MPa for granite aggregates and from 3 to 16 MPa for limestone aggregates. Elastic moduli of the aggregates were also variable: 18–78 GPa for granite aggregates, and 18–66 GPa for limestone aggregates. Values within these ranges may influence the mechanical performance of high strength concretes.