<b>ABSTRACT</b>

An experimental method and two discrete Particle Packing Models are assessed for aggregate mix design. The aim is to model the most compacted structure of commercial natural limestone aggregate and electric steelmaking slag fractions. The experimental method is reliable and effective, although somewhat laborious. Regarding the discrete models, the Compressible Packing Model and the 3-Parameter Particle Packing Model showed high reliability when used to perform the most compact of both the ternary and the quaternary aggregate mixtures. Eight concrete mixes were manufactured to produce concretes of low and medium workability, containing the highest possible content by volume of coarse aggregate, and their resultant in-fresh properties, defined through slump and density, confirmed the validity of using the Particle Packing Models for each mix dosage under study.</br>

<b>ACKNOWLEDGEMENTS </b>

The authors wish to express their gratitude to: the pre-doctoral funding from the Basque Government Department of Education (PRE_2018_2_0289), MCIN/AEI/10.13039/501100011033/FEDER, UE [PID2021-124203OB-I00 and RTI2018-097079-B-C31]. Our thanks also go to the support of the SAREN Research Group (IT1619-22, Basque Government) and likewise to Morteros y Revocos Bikain, HORMOR, FYM Heidelberg Cement Group, and the Amantegui Group for supplying the materials used in this research.