Evaluation of the compressive strength of ancient clay bricks using microdrilling

Abstract

Nondestructive testing techniques are increasingly being used to obtain the geometry of structural and nonstructural elements and hidden features such as voids, cracks, and detachments. However, the evaluation of the compressive strength and other mechanical properties of ancient materials using such techniques remains a challenge. To reliably assess mechanical properties, it is usually necessary to directly test the strength and deformation of materials by destructive methods. To avoid coring and sampling of the historic fabric, a recent minor-destructive methodology based in microdrilling is used in this paper for the characterization of clay brick. For this purpose, 148 brick specimens from the 12th to 19th centuries were collected from six monasteries in Portugal. A wide range of compressive strength was found by destructive compressive testing, ranging from 6.7 to 21.8 N/mm2. The paper shows that it is possible to reliably estimate the compressive strength of bricks by means of regression curves using the adopted microdrilling technique.