Strain Hardening of Polypropylene Microfiber Reinforced Composite Based on Alkali-Activated Slag Matrix.

Aleksandr Alekseev,Olga Smirnova,Mikhail Popov,Dmitry Petrov,Ignacio Menendez Pidal

doi:10.3390/ma15041607

Abstract

A comparative study of the fracture features, strength and deformation properties of pseudo strain-hardening composites based on alkali-activated slag and Portland cement matrices with polypropylene microfiber was carried out. Correlations between their compositions and characteristics of stress–strain diagrams under tension in bending with an additional determination of acoustic emission parameters were determined. An average strength alkali-activated slag matrix with compressive strength of 40 MPa and a high-strength Portland cement matrix with compressive strength of 70 MPa were used. The matrix compositions were selected for high filling the composites with polypropylene microfiber in the amount of 5%-vol. and 3.5%-vol. ensuring the workability at the low water-to-binder ratios of 0.22 and 0.3 for Portland cement and alkali-activated slag matrices, respectively. Deformation diagrams were obtained for all studied compositions. Peaks in the number of acoustic signals in alkali-activated slag composites were observed only in the strain-softening zone. Graphs of dependence of the rate of acoustic events occurrence in samples from the start of the test experimentally prove that this method of non-destructive testing can be used to monitor structures based on strain-hardening composites.

Highlights

The important advantages of such composites are the significant increase of the value of tensile stresses corresponding to the sample destruction compared with the value of tensile stresses corresponding to the first microcrack and sufficiently large relative deformations of cement composite under uniaxial tension due to a significant increase of the volume of microcracking before destruction [9,10,11]
The mechanical properties of four types of composites are summarized in Table 5 including the compressive strength and the tensile strength in bending at the age of 28 days
Strength and deformation properties of pseudo strain-hardening composites based on inorganic binders with polypropylene microfiber under compression and tension in bending with the additional determination of the quantity of acoustic emission signals were carried out

Summary

Introduction

A high relative deformation of up to 5% is the result of the sequential formation of multiple, densely spaced microcracks under increasing uniaxial tensile loading [12] This behavior of the material under tension is achieved by fulfilling a number of micromechanical conditions for the formation of microcracks, their propagation and overlap with fibers [13,14,15]. This cement composite can be used as the main material in structures and as thin reinforcing layers for repairing and strengthening the existing structures taking into consideration its high deformation ability [16,17,18,19]. Microcracking, namely the number and width of cracks determines the pseudoplasticity of composites and affects their durability that depends on the composite permeability [31,32]

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