PSI - Issue 64

Salvatore Benfratello et al. / Procedia Structural Integrity 64 (2024) 1935–1942 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

1937

3

compression strength splitting test strength H

shear modulus of the masonry height of the masonry panel

L length of the masonry panel distributed vertical load 0 shear strength of the masonry specific weight of the masonry 2. Experimental analysis and numerical modelling of sisal reinforced geopolymer

The geopolymeric matrix was prepared by using metakaoline (Silicon to Aluminum molar ratio of 1.3:1 and grain size distribution between 1 and 100 μm) as precursor. It was activated by using a 7 M alkaline solution of potassium peroxide KOH, obtained by mixing KOH pellets (99% purity) and Potassium silicate (K2O·nSiO2) powder with deionized water. Both commercial reagents were supplied by Carlo Erba Reagents S.r.l. (Italy). River sand with a nominal maximum diameter of 2 mm was used as aggregate. Sisal plants were collected in a plantation of northern Sicily and the extracted fibers were washed and then dried at 25°C for 48 hours. It is well known that the effect of natural fibers on the overall mechanical performances strongly depend on the replacing percentage. In this paper attention is focused on the mechanical response of the above-described geopolymer replacing 2% weight content of aggregate with short sisal fibers (i.e., 2.5 mm length). The weight replacement selected percentage represents an upper limit of the replacement of aggregate with fibers because, as reported in Ranjbar and Zhang (2020), regardless of the fiber types, the increase of compressive strength is more expectable when the fiber content is less than 2%, while above this value adverse effect of fiber is more possible. The mechanical behavior of the above-described sisal reinforced geopolymer samples has been characterized through a wide campaign of experimental tests consisting in compression and splitting (Brazilian indirect tensile) tests. The specimens for compression tests have been arranged following EN 1015-11 standard. The specimens were cured at room temperature for 28-days and then tested under three-point bending test setting the span length equal to 100 mm (Figure 1a), followed by testing under compression the cube specimens (side about 40 mm) obtained by cutting the broken half-parts at the end of the bending test (Figure 1b). The bending and compression tests were carried out by using the universal testing machine (UTM) model ETM-C (WANCE, China), equipped with a 50 kN load cell and a pre-loading equal to 10 N was applied before recording data. Both tests were performed in displacement control, the bending one with a rate of 1 mm/min while the compression one with a rate of 0.5 mm/min. The tensile strength was determined by splitting tensile test performed on cylindrical samples, according to ASTM D3967 standard, adopting cylindrical specimens with nominal diameter and thickness equal to 50 mm (Figure 1c). The splitting tests were performed by using the same UTM adopted for compression and bending ones, in stress control with a rate equal to 0.05 MPa/s. Three specimens were tested for each batch for all the experimental mechanical tests. All the specimens were equipped with a HBK strain gage (K-CLY4, 120 Ohm, 6 mm measurement grid) to gather the strain during the tests. The acting load and strain were recorded by HBK MGCPlus data acquisition system driven by MGCPlus assistant. The experimental results (in terms of compression stress-strain curve and tensile ultimate strength) have been adopted as input information for generating ABAQUS input data for the Concrete Damage Plasticity (CDP) material model through the ABAQUS_CDP_Generator tool (Elkady (2023)). The above-described experimental tests have been modelled in Abaqus (2017) (C3D8R 3D element, contact between specimen and steel with 0.15 friction coefficient and penalty friction formulation), performing the tests in displacement control. The comparison between experimental and numerical tests are reported in Figure 2.