High Performance Fibre Reinforced Concrete: optimization of the concrete matrix with porcelain stoneware powder

UHPFRCs feature high performance in terms of compressive strength (> 150 MPa – 21755 psi) and tensile strength (> 5 MPa – 725 psi). Compared to normal concrete, their matrix is designed with lower water/cement ratios (  0.25), higher cement content and smaller aggregate size. Since their crack pattern is typically characterized by small cracks, the use of short fibers to reinforce the matrix is more appropriate. In general, UHPFRC production requires plenty of non-renewable natural raw materials with polluting emissions mainly related to the high dosage of cement. In this framework, the presented work proposes the usage of porcelain stoneware waste powders from rectification, as part of fine-grained components. The paper presents preliminary results of an experimental campaign aimed at optimizing the flexural and compressive performances of concrete admixtures with porcelain stoneware waste materials, using design of experiments. All the admixtures contained the same quantity of PVA fibers. The performances of the mixes were evaluated by means of four point bending and compressive tests, performed after 28 and 60 days. Introducing stoneware waste powders it was possible to obtain high strength materials with a reduced cement content.