Bricktor and expanded metal in 10mm thickness mortar joints: a performance comparison

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Silvester Barnett
6 years ago
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1 Bricktor and expanded metal in 10mm thickness mortar joints: a performance comparison Tested expanded metal and Bricktor

2 Content table 03 Introduction 04 Description of test setup 06 Results and conclusions 2

3 1 Introduction Bekaert has recently undertaken a series of performance tests on two types of masonry bed joint reinforcement steel mesh work: Bricktor and expanded metal as used to provide crack control in masonry construction. The purpose of this exercise was to compare the performance of these products using the pullout test as described in EN This is the most relevant performance test for bed joint reinforcement products and demonstrates how well reinforcement works to increase flexural strength and, therefore, assist in enhancing the ability to provide crack control for the masonry wall against movement caused by shrinkage, stress, settlement or thermal effects. The pull-out test assesses two fundamental properties: The anchorage of the steel meshwork reinforcement in masonry bed joint. The stiffness and tensile strength of the steel meshwork reinforcement. Bekaert masonry reinforcement products, Murfor, Brickforce and Bricktor have been developed to provide structural and crack control benefits for masonry construction and are covered by the European product standard EN845-3 Bed joint reinforcement of steel meshwork. On the CE label, required by EN845-3, for these products, the results of the pull-out performance test from the EN846-2 test method are expressed as the bond strength (in N) for a given anchorage length (in mm). 3

2 Description of test setup The pull-out tests have been completed by Bekaert in accordance with the specifications of the test standard EN846-2.

4 2 Description of test setup The pull-out tests have been completed by Bekaert in accordance with the specifications of the test standard EN As shown in Figure 2 the tests are carried out using a tensile test bench. The steel meshwork is embedded over 24,4cm in a mortar joint. The complete specimen (blocks, joint and steel meshwork) is pre-compressed in the top clamp to 0,1N/mm², according to EN This pre-compression simulates the self-weight effect of the masonry wall in real life. The protruding end of the steel meshwork is clamped in to the bottom clamp set. The test starts as soon as the tensile force is applied. The force/displacement values are recorded until the steel meshwork is pulled out of the mortar joint, or breaks. As per EN846-2, 6 specimens are tested and the average result is calculated. Figure 2: Bekaert pull out test setup according to EN846-2 Specifications of the tested steel mesh work (both types are for non-structural use according to EN 845-3): Bricktor GBT60CCR, 60mm wide, galvanized, containing 4 longitudinal wires Expanded metal, 65mm wide, galvanized 4

joint thickness 10mm M5 strength class mortar Figure 3 shows the specimens

5 Specifications of the used masonry elements and of the mortar and joints in the pull out tests: Perforated clay brick compressive strength 20N/mm² Masonry joint thickness 10mm M5 strength class mortar Figure 3 shows the specimens before testing. Figure 3: Specimens with expanded metal and with Bricktor before testing 5

6 3 Results and conclusions 100% 90% 80% 70% Bricktor Expanded metal Pull-out Force [%] 60% 50% 40% 30% 20% 10% 0% Displacement [mm] The main purpose of this test is to compare the relative performance difference of the tested products. For this reason, in the above graph the pull-out force results are shown as a percentage value relative to the highest performing product: Bricktor. The displacement is shown as an actual [mm] value for both products. The Bricktor load curve is much steeper than the one of expanded metal, achieving high loads with little displacement. This shows that the stiffness and anchorage of Bricktor is much higher than expanded metal The expanded metal curve shows very small pull-out forces in comparison. This is related to the very low yield strength of expanded metal compared to Bricktor. Bricktor is manufactured from steel wire with tensile strengths of more than 450N/mm², whereas in expanded metal products tensile strength values of 150N/mm² are commonly used. In order to take up tensile forces effectively, the steel of the bed joint reinforcement product needs to be aligned parallel to the masonry wall. The longitudinal wires in Bricktor work in this way. However, for 6

diamond-shaped expanded metal, this is not the case. At 1mm displacement, Bricktor developed a pull out force 5 times higher than the pull out force of expanded metal.

7 diamond-shaped expanded metal, this is not the case. At 1mm displacement, Bricktor developed a pull out force 5 times higher than the pull out force of expanded metal. This behaviour can be directly related to the crack control ability of the reinforcing element in the bed joint. Better crack control ability of the bed-joint reinforcement leads to the development of finer cracks called micro cracking - that is more dispersed and evenly distributed over the masonry wall. The high tensile strength of steel wire bed-joint reinforcement prevents these cracks from enlarging. The maximum pull out force of expanded metal is significantly lower than Bricktor and is reached at unacceptably high displacement values: 5mm+. This would indicate that the expanded metal is stretching under load and so, therefore, crack widths may not be controlled as effectively as with Bricktor. This could lead to larger and more visible cracks in the masonry wall. NV Bekaert SA Bekaertstraat Zwevegem - Belgium T F building.benelux@bekaert.com 7

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