2.1. Specimen Production
- (1)
Basic mixing ratio settings
The basic mixing ratio applied in this study is presented in
Table 2 below, and the ratios were derived such that the scope of application of the results derived from the study can be determined with clarity. Currently, various types of self-adhesive waterproof sheets exist in Korea, and in the case of compounds, different raw materials and mixing ratios are applied by each manufacturer [
18]. The basic mixing ratio suggested here was set by referring the manufacturer specifications during actual production and has been confirmed to satisfy all the quality standards set by KS.
- (2)
Range settings for raw materials used
As shown in the basic mixing ratio given in Section (1), the materials used in this study were composed of butyl rubber, carbon black, inorganic fillers, polybutene, and a coupling agent; a total of 6 raw materials, including reclaimed butyl rubber to replace the new butyl rubber, were used. In general, the self-adhesive waterproofing sheet is made by mixing 8 to 10 raw materials [
19,
20]. However, in this study, the use of functional additives was avoided in order to investigate the effects of an increase in the ratio of reclaimed materials to new materials on the self-adhesive waterproofing sheet. The physical properties of each raw material used in the present research are shown in
Table 3,
Table 4,
Table 5,
Table 6 and
Table 7 below.
- (3)
Mix design
The mix proportion for the test sample composition was designed to replace the new butyl rubber in units of 5% based on the basic mixing ratio, which is the same as the mix proportion designed in the previous research. Therefore, the mix design was applied, as shown in
Table 1.
- (4)
Mixing plan
Prior to the experiment, the process of mix proportion was carried out according to the planned mix design. Following the fabrication of test samples for each mixing ratio, the samples were subjected to chemical aging treatment. The adhesion performance (peel-out) evaluation was conducted on the chemically treated test sample, and the performance change characteristics were then examined. The overall research flow is shown in
Figure 2.
- (5)
Test sample composition
As there is no official manufacturing standard for the production of experimental specimens for this testing, specimens were prepared using a Kneader compounder, an item of rubber-material-only compounding equipment used for research by actual manufacturers. This compounder is a minimized version of the equipment used in the production of butyl rubber self-adhesive waterproof sheet, and it is designed specifically to be used by manufacturers to mix small amounts for research purposes.
Table 8 shows the specifications of the kneader for experimental mixing used in the study.
The test sample mixing sequence and status are shown in
Figure 3. The test compound produced via the kneader mixer was processed and pressed using a hydraulic press into a waterproofing sheet material in order to complete the test sample fabrication.
2.2. Test Methods
- (1)
Deterioration treatment
In general, a non-exposure waterproofing method that does not expose a waterproofing layer, due to the installation of a separate protective layer and reclamation after the installation of the waterproofing layer, is applied as a method using the self-adhesive waterproofing sheet in the waterproofing market for construction. Therefore, in this study, deterioration conditions resulting from UV rays and heat were excluded from the deterioration treatment condition settings for the prepared test samples, and only chemical aging conditions in the ground were applied in the research. Accordingly, deterioration treatment on the test sample was conducted in accordance with ‘KS F 4935: 2008 Sealer of injection type for water leakage maintenance of adhesive flexible rubber asphalt series’ (hereafter, KS F 4935), which stipulates both the chemical environment of the concrete surface to which the waterproofing material is applied and the underground chemical aging conditions inside the soil, among the Korean Industrial Standards (hereafter, KS) related to waterproofing materials for construction [
21]. Meanwhile, most of the waterproofing-related standards, including KS F 4935, stipulate that the deterioration treatment period should be 168 h (7 days). However, in this study, the treatment period was set to 21 days in accordance with the ‘Korea, Ministry of Land, Infrastructure and Transport of specification standard 2010’, which sets the chemical water (brine) treatment period three times longer than the period set in the standard [
22]. In this context, it would be appropriate to apply the quality testing methods and criteria specified in the standard specification, which require higher levels than those specified in the KS related to non-exposure methods, for a comparison of quality stability in the long term.
Table 9 and
Figure 4 show the specimen deterioration treatment method and period applied for this study [
23].
- (2)
Test
The test was conducted with two test items: adhesive strength (with CRC board surface) and peel strength (between sheet joint). For adhesive strength, an oil-based primer was applied to a cellulose reinforce cement board (CRC board) with a thickness of 9 ± 1 mm. After drying for two hours or more under standard conditions, a test sample with a width of 50 mm and a length of 150 mm was produced, and a 60 mm part in the longitudinal direction was treated with a release paper and attached to the base specimen (base plate for test) in order to fabricate the specimen. After fabrication, the specimen was placed at room temperature for two hours. As shown in
Figure 5, the fabricated specimen was fixed to the attachment jig, and one end, which was not attached to the base plate, was then fixed to a tensile test device. After that, a 20 mm part was peeled off with the peel angle set at 90 ± 5°, and then the sheet was peeled off at a tensile rate of 100 mm/min. The adhesive strengths of five specimens were measured, and the peeling load-peeling length curve was divided into four equal parts at a point where the peel angle is 90 ± 5°, except for the initial peeling length of 20 mm. This was in order to read the peeling load value Pi (P₁, P₂, P₃, P₄, and P₅) at a point of intersection (point t) between the bisectrix and the loading curve and represents the average value of the five specimens calculated by using Equation (1).
Figure 6 shows the specimen fabrication and test status.
F = Adhesive strength (N/mm)
Pi = Peeling load value at point t (N)
Figure 5.
Peel-out (with CRC board surface) test method.
Figure 5.
Peel-out (with CRC board surface) test method.
Figure 6.
Peel-out (with CRC board surface) test specimen preparation and test status. (a) Test preparation; (b) Test status.
Figure 6.
Peel-out (with CRC board surface) test specimen preparation and test status. (a) Test preparation; (b) Test status.
For the peel strength, the release paper of the 110 × 50 mm test sample was attached with the adhesive side facing down, and another test sample was then stacked up by 50 mm on it. In a standard condition, the 10 mm part of both ends, which was not adhered to, was mounted on a tensile tester, and the tensile load was measured at a tensile rate of 200 mm/min with an interlocking interval of 100 mm; the strength was then calculated by using Equation (2).
Figure 7 shows the specimen fabrication and test status.
TB: Adhesive strength (N/mm)
PB: Maximum load (N)
W: Width of the specimen (50 mm)
Figure 7.
Peel-out (between sheet joint) test specimen preparation and test status. (a) Preparing for the test. (b) Test status.
Figure 7.
Peel-out (between sheet joint) test specimen preparation and test status. (a) Preparing for the test. (b) Test status.