EXPERIMENTAL STRATEGY As mentioned above only two types of materials are reported in this paper. Both materials are designed to achieve 40 ...
EXPERIMENTAL STRATEGY As mentioned above only two types of materials are reported in this paper. Both materials are designed to achieve 40 MPa compressive strength. The mechanical properties of the two materials are shown in Table 1. The ingredients used are not disclosed here due to the commercial nature of the product. Four test cylinders (76 mm diameter x 150 mm high) were cast from each mix type. They were initially cured at 35ºC for 45 minutes and then at 25ºC for 5 days. Results obtained from the initial tests indicated that the specimens gained full strength within 3 to 7 days. The disc specimens were primarily grouped into two categories, namely control specimens and specimens to be subjected to accelerated weathering.
The accelerated weathering was simulated by subjecting the specimens into wetting and drying cycles in an aggressive environment. The specimens subjected to the accelerated weathering conditions were also divided into two groups. The specimens in one of the groups were only subjected to fan drying under the laboratory conditions, whereas the specimens in other group were oven dried after every five cycles for weight measurements. The control specimens and the specimens which were not subjected to oven drying were finally tested for strength tests. Table 1. Material Types Investigated Material Type Type A Type B Compressive Strength (MPa) 40MPa 40MPa Flexural Tensile Strength (MPa) 10.5MPa 10.7MPa Density (kg/m3 ) 1440kg/m3 1530kg/m3 3 EXPERIMENTAL PROCEDURE Approximately 10 mm thick circular specimens were cut and placed back together in their original positions within the cylinder. Each test specimen (circular disc) was numbered sequentially in the cylinder for future reference. Altogether 32 circular discs were prepared for the investigation. For the durability tests, some of the specimens (circular discs) were subjected to accelerated weathering while others were left as control specimens. 3.1 Durability Assessment In order to understand the durability characteristics, an appropriate test as well as a performance indicator is needed. The type and nature of the test will depend upon its intended use and a wide range of variables must be considered in developing the test. Further, the accelerated laboratory experiments should be corroborated using long term monitoring of the in-situ durability performance of the material. As a consequence of the brittle nature of polymer concrete, flexural tensile strength has been widely used as a performance indicator. In this study splitting tensile strength of the material under diametral loading was selected as the performance indicator due to the following reasons.
· Simplicity of the test set up · Several test specimens (1 cm thick discs) can be prepared from the same cylindrical specimen · Effect of the variability of the material in different test specimens can be minimised since several test specimens can be prepared from the test cylinder. · Because specimens are relatively small, it is easy to perform the drying and wetting cycling tests.
· Cylindrical specimens are large enough to be representative of the material as a whole · Effect of the aggressive agent can be assumed uniform through the thickness of the test specimen because of its thinness. · To the authors knowledge, this is the first time the splitting test method has been used for the assessment of strength degradation of specimens subjected to exposure. Therefore, this study would also allow assessing the suitability of the test technique to such applications. 9DBMC-2002 Paper 101 Page 3 Continuous assessment of deterioration is a difficult task, as the deterioration is progressive and small in its early stages. Visual inspection, change in volume/dimensions and change in weight are some of the commonly used parameters to assess the degree of deterioration. The weight loss or gain of the specimens was monitored in this study. Because of its non-destructive nature, weight loss/gain can be used as an indicator to identify the time at which the destructive splitting tests should be carried out
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