Analytical Models and Laboratory Measurements to Explore the Potential of GPR for Quality Control of Marble Block Repair through Resin Injections

Marjan Izadi-Yazdanabadi,Diego Arosio,Azadeh Hojat,Saeed Karimi-Nasab,Luigi Zanzi

doi:10.3390/app12030987

Marjan Izadi-Yazdanabadi, Diego Arosio + Show 3 more

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https://doi.org/10.3390/app12030987

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Abstract

This work aims to analyze theoretically and with laboratory tests the sensitivity of high-frequency GPR (Ground-Penetrating Radar) to resin injections used in the building and ornamental stone industries to repair marble blocks before final slab cutting. We simulate uniform fractures in the laboratory using small regular marble blocks and we compare the results of GPR tests with the analytical model of the thin bed reflections. We performed two series of GPR surveys with a 3 GHz antenna, progressively increasing the fracture thickness from 0.25 mm to 16 mm, to analyze the results on two simulated conditions: open fracture and repaired fracture. The repaired condition was simulated by substituting the resin layer with polyvinyl chloride (PVC) sheets because the permittivity of PVC is quite similar to the permittivity of epoxy resin. According to the analytical models, when a thin air-filled fracture is filled with resin, the received signal amplitude is expected to decrease by 33% (26% if resin is simulated with PVC). The results showed a very good match between the predictions and the real data observations when the fracture is thicker than 4 mm. Although the analytical and laboratory results show some deviations when the fracture is thinner than 4 mm, the qualitative trend of the amplitude variations is still consistent with the predictions and the 3 GHz antenna can resolve the change in the filling material down to the minimum tested thickness (0.25 mm). As a result, our findings validate the GPR method as a proper tool for nondestructive quality control of resin injections in marble fractures.

Highlights

Introduction published maps and institutional affilDiscontinuities and defects of natural building stones have always concerned quarry engineers and experts engaged in the restoration and conservation of stone monuments.Fractures and voids are a critical problem when the natural stone is supposed to be used for decorative and ornamental purposes
We considered the thin layer between two marble blocks as a fracture in a homogenous rock to analyze the potential of the ground penetrating radar (GPR) method to perform nondestructive quality control of resin injections
By progressively increasing the thin layer thickness from 0.25 mm to 16 mm, we tested the GPR response at 3 GHz before and after injections, where the after-injections situation was simulated by filling the thin layer with polyvinyl chloride (PVC) sheets, the permittivity of PVC being very similar to the permittivity of epoxy resin

Summary

Introduction

Introduction published maps and institutional affilDiscontinuities and defects of natural building stones have always concerned quarry engineers and experts engaged in the restoration and conservation of stone monuments.Fractures and voids are a critical problem when the natural stone is supposed to be used for decorative and ornamental purposes. Discontinuities and defects of natural building stones have always concerned quarry engineers and experts engaged in the restoration and conservation of stone monuments. Fractures and voids are a critical problem when the natural stone is supposed to be used for decorative and ornamental purposes. There has been an increasing interest in repairing natural stones by injecting a filling material in their fractures

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