with DRMS Cordless 1 DRMS: PORTABLE DEVICE FOR THE DRILLING - - PowerPoint PPT Presentation

Statistical analysis of mortars with DRMS Cordless

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DRMS: PORTABLE DEVICE FOR THE DRILLING RESISTANCE MEASUREMENT

The Drilling Resistance Measurement System (DRMS) is a tool for the determination of the mechanical properties of the materials used in historic masonry buildings.

Statistical analysis of mortars

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DRMS: PORTABLE DEVICE FOR THE DRILLING RESISTANCE MEASUREMENT

Statistical analysis of mortars

• Suitable for both laboratory and “in situ” tests
• It measures the Force necessary to drill the material
• The mean value of the Drilling Resistance can be

correlated with the Uniaxial Compression Strenght (UCS)

• Works at constant operating conditions: Rotation

speed (20-1000 RPM) and Penetration rate (5-80 mm/min)

• Records the resistance profile of the first layer of a

stone material (up to 50 mm depth)

• Uses diamond drill bits to reduce the wear effect

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THE DRILLING RESISTANCE TEST METHOD

The Drilling Resistance Test Method can be used for the characterization of historic masonry materials, to obtain information concerning the mechanical properties of materials and to evaluate the performance of consolidation

• treatments. The test consists in drilling a small hole at a set constant rotational

speed and penetration rate, and in measuring the penetration force versus depth.

Statistical analysis of mortars

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Some materials (e.g. mortars and concrete) present high fluctuations in the drilling resistance around the mean value, due to their intrinsic non homogeneity. These materials need to be characterized not only with average parameters but also through statistical indices that take into account the non uniformity of the material.

Statistical analysis of mortars

Statistical analysis of mortars

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Main statistical indices

Parameter Symbol Formula/Definition Mean 𝑦 σ𝑗=1

𝑜

𝑦𝑗 𝑜 Variance 𝑡2 𝑡2 = σ𝑗=1

𝑜 (𝑦𝑗 − 𝑦)2

𝑜 Standard Deviation 𝑡 𝑡 = σ𝑗=1

𝑜 (𝑦𝑗 − 𝑦)2

𝑜 − 1 Coefficient of Variation 𝐷𝑊% 𝐷𝑊 = 𝑡 𝑦 ∗ 100 Minimum Value 𝑌𝑛𝑗𝑜 Maximum Value 𝑌𝑛𝑏𝑦 Range 𝑆 𝑆 = 𝑌𝑛𝑏𝑦 − 𝑌𝑛𝑗𝑜 Skewness γ1

σ𝑗=1

𝑜 𝑦𝑗−𝑦 𝑡 3

𝑜

Measure of the asymmetry of the probability distribution Kurtosis γ2

σ𝑗=1

𝑜 𝑦𝑗−𝑦 𝑡 4

𝑜

Indicate hether the shape of the distribution of the data corresponds to the Gaussian distribution First Quartile 𝑅1 number below which lies 25 percent of the bottom data Second Quartile 𝑅2 number below which lies 50 percent of the bottom data Third Quartile 𝑅3 number below which lies 75 percent of the bottom data Median 𝑁 𝑁 = 𝑅2 Interquartile Range IQR 𝐽𝑅𝑆 = 𝑅3 − 𝑅1

Statistical analysis of mortars

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Test procedure

• 1. Repeat tests on the same material (at least 10 holes)
• 2. Use the same penetration rate in all the tests
• 3. Use the same revolution speed in all the tests
• 4. Acquire data in Streaming mode (300 Hz)
• 5. Apply a software filter to reduce the noise related to drill bit vibration (low

pass filter at 3Hz)

• 6. Discard the first mm of penetration data to remove drill bit surface

penetration effect

• 7. Discard the last mm of penetration data to reduce the effect of the drilling

swarf

• 8. Post-elaboration with DRMS software to extract a set of statistical indices
• 9. Graphical representation with box-plot, histogram, Qqplot and trend
• 10. Repeat the post-process elaboration without the data beyond the outliers

Statistical analysis of mortars

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Test parameters

In this case, the tests were carried out for two different types of mortars: N2/04 and N2/01 with the following drilling parameters:

• Penetration speed of 40 mm/min
• Rotational speed of 300 rpm
• Diamond drill bit with 5 mm diameter
• Low pass filter at 1.5 Hz

Statistical analysis of mortars

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Mortar N2/04: Mean curves

Statistical analysis of mortars

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Mortar N2/04: Histogram and box-plot

Statistical analysis of mortars

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Mortar N2/01: Mean curves

Statistical analysis of mortars

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Mortar N2/01 : Histogram and box-plot

Statistical analysis of mortars

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