Comparative study on the similarity between ancient white bricks and the self-developed imitative white bricks

Abstract

Many architectural heritages in China are built with ancient white bricks (AWB), which behave very differently from traditional blue and red bricks. Indeed, AWB buildings have undergone centuries of historical changes and weathering with time, and require urgent repair. Since replacing ancient bricks with imitative bricks when restoring heritage buildings has become a consensus, it is necessary to develop imitative white bricks (IWB) similar to AWB in many respects to be used for restoring ancient buildings. Therefore, this paper develops a novel IWB and analyses its similarity with the AWB by means of X-ray diffraction, X-ray fluorescence, mercury intrusion test, scanning electron microscopy, and ultrasonic pulse velocity. The results reveal that the self-developed IWB is highly similar to AWB in mineral and chemical composition, micro-morphology, internal appearance, apparent densities, water absorption rate, saturation coefficient, porosity, and these bricks are concentrated in micropores with similar radii. Besides, the durability is somewhat similar in terms of salt crystallization and resistance to freeze-thaw cycles. The IWB and AWB are classified as susceptible to salt crystallization, while good resistance to these white bricks' freeze-thaw cycles. The ultrasonic pulse velocity of the self-developed IWB along the height direction is close to the ultrasonic pulse velocity along other AWB directions. Besides, ultrasonic pulse velocity along the height direction is linearly correlated to the compressive strength of and the IWB and AWB, which has important reference significance for evaluating the mechanical properties of architectural heritages by ultrasonic non-destructive testing technology. These results can provide theoretical and technical support for the in-situ repair of damaged AWB and are significant for restoring and conserving brick masonry architectural heritages.