Abstract
This paper examines the fundamental mechanical properties of masonry elements incorporating fired-clay bricks and hydraulic lime mortars under ambient-dry and wet conditions, corresponding to 48 h submersion in water. In addition to complementary material characterisation assessments, two types of specimens are tested: cylindrical cores in compression, and wall elements in compression. Overall, a detailed account of more than 50 tests is given. Apart from conventional measurements, the use of digital image correlation techniques enables a detailed assessment of the influence of moisture on the constitutive response, confinement effects and mechanical properties of masonry components. The uniaxial compressive strengths of wet brick elements and brick–mortar components, resulting from tests on cylindrical cores with height-to-depth ratios of around two, are shown to be 13–18% lower than those in ambient-dry conditions. The tests also show that enhanced confinement levels in brick units mobilise 67–92% higher strengths than in the corresponding unconfined cylinders. Moreover, experimental observations indicate that the presence of significant confinement reduces the influence of moisture on the mechanical properties as a function of the brick and mortar joint thickness and their relative stiffness. As a result, the failure of wet masonry walls in compression is found to be only marginally lower than those in ambient-dry conditions. Based on the test results, the influence of moisture on the constitutive response and mechanical properties of masonry components is discussed, and considerations for practical application are highlighted.
Highlights
Clay bricks and stone blocks have been widely used as the main construction materials in historic structures
The tests described in this paper show that core masonry samples with mortar joints and h/d [ 2.0, (CBW and CCW) in wet conditions, having a moisture content of about 10% by weight had a lower compressive strength of about 14–18% in comparison to those in ambient-dry conditions (CBD and CBW) with a moisture content of about 2.5% by weight
This paper described an experimental investigation into the fundamental mechanical properties of masonry elements incorporating fired-clay bricks and hydraulic lime mortars under ambient-dry and wet conditions, corresponding to 48 h of submersion in water
Summary
Clay bricks and stone blocks have been widely used as the main construction materials in historic structures. These are rarely provided with protection systems against moisture or rising damp, nor against significant temperature variations. Amongst the main causes of degradation of heritage masonry is the presence of high moisture content resulting from the capillary absorption of groundwater. Compressive tests on brick units submersed in water were shown in previous studies to have a lower strength in comparison to their dry counterparts [5]. Average elastic modulus-to-compressive strength ratios obtained from tests on prismatic samples were found to be 14% lower for specimens with high moisture in comparison to those in dry conditions [7]. Other tests on compression elements showed a significant drop in capacity in the range of 60% for a moisture content of 15.81% by weight compared to their counterparts for a 3.5% moisture content by weight [8]
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