Development of methods for assessing the frost resistance of clay bricks

The aim of the project was to develop a rapid method for estimating the frost resistance of clay bricks. The method was to be reliable but also simple and fast enough for routine quality control at brick factories. The frost resistance of the bricks was determined with one-sided freeze-thaw tests in accordance with Finnish standard SFS 5513 method 2, which in practice is the same as DIN 52252 Part 3. The tests involved 100 freeze-thaw cycles in place of the 50 required by the above mentioned standards. A method based on the following properties of extruded red clay bricks was developed to estimate the frost resistance: Rockwell C hardness, water absorption, saturation coefficient and capillary suction rate. All of these properties can be measured in 2 days, also in brickwork conditions. The equipment, Rockwell hardness tester and balance are inexpensive. The frost resistance of bricks was estimated on the basis of the above mentioned properties using mathematical PLS modelling (PLS = Partial Least Squares) with Unscrambler-EX version 4.00 program (Camo A/S, Trondheim, Norway). According to the results obtained, the capacity of these one-sided frost-resistance tests can be increased by testing two brick qualities simultaneously. This requires a sufficient number of samples, as similar a water content as possible between different brick types, a single layer of alternating bricks of each types, and measurement of the brick temperature in many parts of the test wall.