Effect of clinoptilolite on properties and fractal characteristic of pore structure of polypropylene fiber-reinforced cement-based composite

•The effect of clinoptilolite content on the mechanical properties is tested.•The microstructure of matrix is compared and analyzed by XRD, SEM and MIP.•Adding clinoptilolite can improve the strength and compactness of the matrix.•The fractal characteristic of pore structure is indicated by fractal dimension.•A relationship model between property and pore fractal characteristics is proposed. To further analyze the effect mechanism of clinoptilolite on the macro-mechanics and microstructure of polypropylene fiber-reinforced cement-based composite, the samples with 0, 5%, 10%, 15%, 20% and 25% clinoptilolite contents were investigated by compression test, flexural test, X-ray diffraction (XRD), scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP), and the pore structure characteristics were quantitatively analyzed by fractal theory. Results showed that: With the increase of clinoptilolite content, the compressive strength, flexural strength and porosity of samples first increased and then decreased. The addition of clinoptilolite reduced the 7-day strength but increased the 28-day compressive strength, 60-day compressive strength, 28-day flexural strength and 60-day flexural strength of the samples by about 6%, 14.3%, 13.9% and 19.1%. It was recommended that the clinoptilolite content should not exceed 15%. Due to the filling effect and pozzolanic effect of clinoptilolite, adding clinoptilolite into the matrix could promote a hydration reaction to produce more C-S-H gels and reduce the proportion of more harmful pores and harmful pores, effectively improving the internal pore structure of the matrix. Meantime, it was found that the evolution law of pore structure based on fractal dimension calculated by the thermodynamic fractal model was consistent with the variation law of the pore size distribution curves and pore volume measured by MIP. Furthermore, a polynomial relationship model between clinoptilolite content, the quantitative fractal characteristic of pore structure and the macroscopic mechanical behaviors was established, which indicated that the pore fractal dimension could quantitatively describe the effect of clinoptilolite content on the pore microstructure.