The strength of roofing tiles is an important aspect that needs to be evaluated to ensure that they meet the required standards. The transverse strength test is commonly performed to estimate the breaking transverse load of the tile. This test is carried out in the laboratory according to applicable standards such as ASTM 1167-11 and IS 13801. Both wet and dry methods are used in this test.
Roofing tiles are rectangular flat or bent units that are made from different materials like terracotta, slate, concrete, plastic, or waterproof glaze. They are designed to resist moisture penetration and are usually hung from the framework of a roof. The transverse strength of the tile is a crucial requirement that needs to be met to ensure the success of the project.
Aim
Estimate the transverse breaking strength of roofing tiles
Apparatus
The tile testing machine
Specimen Preparation
The testing of tiles for quality assurance purposes involves either wet or dry testing. The wet testing method requires five tiles to be submerged in water for 24 hours at a temperature range of 24 to 30°C, and then tested. On the other hand, the dry testing method involves heating five tiles in a ventilated oven for 24 hours at a temperature of 110 to 115°C before being tested. The decision to use either the wet or dry method must be agreed upon by both the specifier and the supplier.
The testing process involves using a span to measure the tiles. The span used for testing should be 30.5 cm Plus/Minus 5 % or 2/3 of the tile length, whichever is greater. In cases where the tile length is less than 30.5cm, a shorter span can be used. However, the shorter span must not be less than two-thirds of the tile length. The chosen span for the test is dependent on the tile size. In accordance with IS 13801, the chosen span for testing is 15cm, 20cm, and 25cm for tile sizes 20x20cm, 25x25cm, and 30x30cm, respectively.
Testing Machine Specifications
To test the tile in a three-point bending mode, the setup must follow the schematic illustrated in Figure 2. The support members and loading member must have 25 mm wide faces and can be made of either metal or hardwood. However, if hardwood is used, it must be backed up with steel bearing plates that are at least 13 mm thick.
To ensure accurate results, a rubber shim strip with a thickness of 4.8 mm and width of 25 mm must be placed between the support and loading members’ faces and the surface of the tile. IS 13801 recommends using plywood with a thickness of 3 mm and width of 20 mm.
The length of the support and loading members must be greater than the width of the tile. Moreover, longitudinal and transverse rotation of the support members and loading with respect to the test specimen is not allowed. Therefore, the supporting and loading members must be adjusted to avoid transverse and longitudinal rotations. According to IS 13801, at least one support member should be self-adjusting.
Test Procedure
Based on the given context, it appears that the task at hand is to test the strength of roofing tiles. To conduct this test, a testing machine needs to be set up. Once the machine is set up, a uniform and continuous load is applied on each tile without any shock. The load should be applied at the maximum rate of 4550N/min, or 2000N/min based on the IS13801 standard. The load is applied until the tile fractures, and the load in kilograms at the point of fracture is recorded for each of the five tiles. (The IS13801 standard requires testing of six tiles.)
To report the results, the average load at fracture for the five tiles should be calculated, as well as the minimum load at fracture for any individual tile. It is not specified whether the results should be reported in kilograms or newtons, but since the load is initially measured in newtons, it may make sense to report the results in newtons as well.
Calculation and Results
ASTM C1167-11 provides table 1 for the classification of the tested tile based on the transverse strength test.
Table 1 Transverse Breaking Strength Requirements
| Type (All Grades) | Wet Transverse Strength, min, N | Wet Transverse Strength, min, N | Dry Transverse Strength, min, N | Dry Transverse Strength, min, N |
| – | Average of five tiles | Individual tile | Average of five tiles | individual tile |
| Type I-High profile | 1334 | 1157 | 1779 | 1556 |
| Type II-Low profile | 1001 | 890 | 1334 | 1112 |
| Type III-others | 1001 | 890 | 1334 | 1112 |
It seems that you have provided some information related to the calculation of wet transverse strength of tiles according to the IS 13801 standard. The equation 1 shows the calculation of wet transverse strength based on the breaking load, span between supports, tile width, and fracture thickness.
However, you have also mentioned some conditions related to the span of the testing specimen. If the span is smaller than 30.5 cm, the values in table 1 should be multiplied by (12/span used (in.)). On the other hand, if the span is greater than 35.6 cm, the values in table 1 should be multiplied by (width in (in.)/14).
It is not clear from your question what specific information or help you are seeking. If you could provide more context or clarify your question, I would be happy to help you further.