Table I provides test data on the relationship between particle size of concrete powder arl(l L)H of concrete. The data show that a finer concrete sample has a higher pH measurement as compared to a coarser sample. A satisfactory sample for this test was obtained by sanding the concrete surface using 51)-grit sandpaper. Table 2 shows the test data on different sanding durations using 50-grit sandpaper and the corresponding scarified depths. The sanding duration of 60 seconds generated enough concrete powder sample for testing and limited the scarification depth to approximately 0.036 in. (less than 1 mm).
Figures 1 through 4 show the effects of several variables, such as type of concrete, sample size, dilution ratios, soaking time, and temperature of the pFI values. The test results show that the dilution ratio and the temperature have the most pronounced effects on the measured p1-1 of concrete as compared to the sample size and soaking time.
The dilution ratio of 1:1 resulted in a higher pH measurement than a dilution ratio of 1:20. However, a dilution ratio of 1:1 creates a mixture that is too stiff and can cause damage to the pH meter probe. A dilution ratio of 1:20 creates a fluid mixture that can be used to safely insert a pH meter probe. For example, in Fig. 2, the pH readings for the diluton ratio of 1:1 was approximately 12.6 and for a dilution ratio of 1:20 was 12.45. For flooring purposes, a pH reading of 12.45 measured using a dilution ratio of 1:20 is accurate enough for selecting an appropriate adhesive for the flooring. Therefore, the proposed method uses a dilution ratio of 1:20.
It is essential to note that once the concrete surface is covered with an impervious flooring such as sheet vinyl, the moisture will redistribute within the concrete. If this redistributed moisture condenses under the impermeable flooring, the pH of concrete surface will likely increase, which may have a detrimental effect in altering the bonding capability of the adhesive. It should also be remembered that the moisture in the substrate below the concrete slab can vary with time and environmental conditions. The increase in pH can have detrimental effect on the flooring adhesive. The adhesive could lose its bonding characteristics.ACI 364.17T pdf download.