Comparing fracture openings in mortar using different imaging techniques

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Summary of average fracture opening obtained using X-ray computed tomography (XRCT), 14C-PMMA autoradiographs (14C-PMMA) and heaviside-digital volumetric correlation (H-DVC) methods_ The numbers of data used to calculate the average values are indicated in brackets_

	#5 (µm)	#39 (µm)	#16 (µm)
XRCT	21.2 ± 9.1 [585]	32.1 ± 13.1 [1549]	120.1 ± 68.3 [3685]
H-DVC	18.6 ± 8.1 [741]	-	-
14C-PMMA	18.6 ± 5.7 [3414]	26.1 ± 8 [3331]	180.2 ± 72.4 [6051]

Comparison of fracture densities calculated using the XRCT and 14C-PMMA methods_ These results were obtained from the same data used to calculate the mean aperture values presented in Table 2, except for the 14C-PMMA method for sample #16 where all the data were considered_

	Fracture densities (mm−1)
	XRCT	14C-PMMA
#5	3.3 ± 0.3 × 10−2	3.7 ± 0.4 × 10−2
#39	3.8 ± 0.4 × 10−2	3.5 ± 0.4 × 10−2
#16	9.1 ± 0.9 × 10−2	7.6 ± 0.8 × 10−2

Process duration and constraints for each method of aperture and density analysis_

	Process duration	Disadvantages
OM	A few hours	Manual analysis of few points / Difficulties of fracture observation
SEM	1 day	Manual analysis of few points / long analysis time
XRCT	1 day	Fracture detection depends on image resolution
H-DVC	A few weeks / months	Fracture detection depends on image resolution / long process and analysis time, two image acquisitions
14C-PMMA	A few months	Use of radioactive tracer / long process time / semi-destructive method

Summary of average fracture opening obtained using microscopy methods: optical microscopy (OM) and scanning electron microscopy (SEM)_ The number of observation points is indicated in brackets_

	#5 (µm)	#39 (µm)	#16 (µm)
OM	15.6 ± 5.5 [12]	29.3 ± 14.6 [80]	131.8 ± 85.7 [33]
SEM	15.8 ± 6.1 [59]	25 ± 14.2 [121]	129.5 ± 136.8 [137]