Resistance of Clay Brick Masonry Façades to Wind-Driven Rain : Repointing of Eroded Mortar Joints

Abstract: Clay brick masonry façades are commonly used due to their high-performance durability. However, exposure to climate agents such as wind-driven rain (WDR), freeze-thaw cycles, and wind abrasion cause deterioration of masonry façades over time. WDR as a significant source of moisture may contribute to the erosion of mortar joints and lead to increased moisture content and risk of water penetration. Accordingly, a maintenance technique, repointing of eroded mortar joints, is recommended as a measure to mitigate moisture/water penetration related to WDR. Repointing is a labor-intensive and costly measure, and there are today no established criteria to determine when repointing is necessary. As such, to enable rational decision-making in maintenance, there is a need for a systematic approach to assessing the need for repointing.Water penetration in masonry exposed to WDR is dependent on a wide range of parameters such as rain intensity, wind velocity, building geometry, the presence of cracks, the profile of mortar joints, the type and quality of masonry units, the compatibility of units and mortar, and the workmanship. There are several experimental methods available through standards and research studies aiming to study water penetration in masonry. Nevertheless, the test conditions, including water spray rate and differential air pressure, of those methods are rather extreme and not representative of actual conditions.In this regard, a new test setup has been developed to study water absorption and penetration in masonry. The key feature is to enable uniform water spray exposure at considerably lower water application rates than in existing standards while continuously recording both the amount of absorbed and penetrated water. Further, the test setup was equipped with a digital camera to record visible dampness, enabling the damp area on the backside of the specimen to be monitored over time. The test setup was used in two experimental campaigns to study the interaction of clay brick masonry and WDR, providing a fundamental basis for developing a framework for rational repointing of clay brick masonry façades.In the first experimental campaign, two series of clay brick masonry specimens were prepared, with two different types of bricks and three different mortar joint profiles. As a representative of eroded mortar joints, specimens with the raked joint profiles were prepared to study how eroded mortar joints might affect WDR related water absorption and penetration. The tests were conducted at zero differential air pressure, at water spray rates varying between 1.7 and 3.8 l/m2/h. In the second experimental campaign, the water spray rate was increased to around 6.3 l/m2/h; yet no air pressure was applied. Further, compared to the first campaign, three different types of bricks with different water absorption properties were considered.The obtained results indicate that water absorption and penetration are highly dependent on the water spray rate and water absorption properties of bricks, whereas the effect of mortar joint profile on water absorption and penetration is negligible. It should be mentioned that no considerable amount of water penetration in the first campaign was recorded; hence, only the results regarding water absorption and damp patches are presented for the first campaign. The newly developed test setup might facilitate verification of moisture simulations and provide a basis for rational decision-making concerning clay brick masonry design and maintenance.

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