--- title: "Non-destructive tests for masonry" subject: "Concrete Technology and Masonry Structure" chapter: 10 key: "semester_5/concrete_technology_and_masonry_structure:ndt-masonry-tests" source: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/ndt-masonry-tests site: BCT Engineering --- # Non-destructive tests for masonry Concrete Technology and Masonry Structure · Chapter 10: Testing of masonry elements - Asked in: 2078 Kartik, 6 marks; 2076 Chaitra, 6 marks; 2075 Ashwin, 3 marks (asked 3 times) - Video: [Non Destructive Testing Methods](https://www.youtube.com/watch?v=rZAw8CRz6J8) — SCOE Youtube - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/ndt-masonry-tests - Whole chapter: https://www.bctengineer.com/md/semester_5/concrete_technology_and_masonry_structure/chapter-10 ## Question Describe (list out) the non-destructive testing techniques for masonry structure / brick masonry wall. ## Short answer Common NDT methods include visual inspection, rebound hammer, ultrasonic pulse velocity, sonic tomography, flat‑jack tests, push shear tests, ground penetrating radar, infrared thermography, and borescope. These assess strength, voids, cracks, moisture, and deformation without damaging the masonry. ## Answer **Non-destructive testing (NDT)** is used to assess the condition, strength and defects of existing masonry without damaging the structure. Common techniques: 1. **Visual inspection and crack mapping** with crack gauges to monitor crack width. 2. **Rebound (Schmidt) hammer test:** surface hardness of the masonry unit or mortar joint, correlated with strength; quick and cheap, but surface-limited. 3. **Ultrasonic pulse velocity (UPV) and sonic tests:** the speed of a pulse through the wall relates to quality, density and voids; detects cracks, voids and delamination. 4. **Elastic wave (sonic) tomography:** many sonic readings in a grid across the wall are processed to form an image of the internal condition (voids, repairs, damage). 5. **Flat-jack test:** a thin steel bag is placed in a slot cut in a mortar joint to measure the in-situ stress (single jack) and deformability and strength (two jacks). This is a minor-destructive test. 6. **Push shear test:** a brick is pushed horizontally to measure the shear strength of bed joints (minor-destructive). 7. **Ground penetrating radar (GPR):** detects voids, moisture, steel bars and layers. 8. **Infrared thermography:** detects moisture, voids and different materials from surface temperature differences. 9. **Borescope / endoscope:** a small camera in a drilled hole to see internal voids and cavities. 10. **Core sampling and Windsor probe/pull-out:** minor-destructive tests for mortar strength. ```text NDT of masonry |-- Surface: visual, rebound hammer, thermography |-- Wave: UPV, sonic, tomography, radar `-- In-situ minor-destructive: flat jack, push shear, core ``` ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What is the aim of NDT on masonry? A. Assess condition and strength of existing masonry without damaging it B. Find the strength of new bricks by crushing C. Measure only moisture D. Replace laboratory testing of mortar Answer: A. NDT assesses existing structures with no or minimal damage. (Key point: NDT meaning) 2. What does ultrasonic pulse velocity indicate? A. Surface colour B. Quality, density and voids from the pulse speed C. Only reinforcement position D. Joint shear strength Answer: B. Pulse speed relates to quality; low speed signals cracks, voids or delamination. (Key point: UPV) 3. Which pair is minor-destructive? A. Rebound hammer and thermography B. Flat-jack and push shear C. GPR and borescope D. UPV and visual inspection Answer: B. Flat-jack and push shear need a slot cut or a brick freed, so they are minor-destructive. (Key point: Minor-destructive tests) 4. Which technique detects moisture and voids from surface temperature differences? A. Ground penetrating radar B. Infrared thermography C. Rebound hammer D. Borescope Answer: B. Infrared thermography reads temperature differences at the surface to reveal moisture, voids and different materials. 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