# Porcelain Tile Polishing Residue in Concrete as an Additive or Replacement for Portland Cement
## 2 Experimental Program
### Testing Methods  
For the fresh-state tests, a sample of each mixture was used to determine the slump according to ABNT NBR NM 67 [32]. For the hardened state, compressive strength tests were conducted at 7, 28, and 90 days of hydration in 10 \(\times\) 20 cm cylindrical samples according to ABNT NBR 5739 [33]. At least three samples were used for each age group. The compressive strength was determined using a UH-I universal testing machine (Shymadzu Coorporation, Kyoto, Japan) at a constant speed of 3 mm\(\cdot\)min\({}^{-1}\). Neoprene discs were used to correct irregularities at the top and bottom of the concrete samples. More details in the experimental setup can be seen in Figure S1 (see Supplementary Material). Water absorption via immersion (gravimetric method) was tested with three samples (10 \(\times\) 20 cm samples) at the age of 28 days in wet curing according to NBR 9778 [34]. The capillary water absorption test at 28 days of curing was performed with three specimens (10 \(\times\) 20 cm samples) based on the criteria established by NBR 9779 [35].  
Three types of acids--acetic acid (CH\({}_{3}\)COOH, 0.1 M), hydrochloric acid (HCl, 0.1 M), and sulfuric acid (H\({}_{2}\)SO\({}_{4}\), 0.1 M)--were used for the acid attack samples (five months of curing; extracted from the core of the concrete sample; 2 \(\times\) 2 \(\times\) 1.4 cm). The samples were dried in an oven at 65 \(\pm\) 5 \({}^{\circ}\)C for 48 h, weighed, and then immersed in a 1 L container containing 500 mL of acid. The containers were agitated at 30 rpm for 24 h following NBR 10005 [36]. The final masses of the samples were measured after drying in an oven at 65 \(\pm\) 5 \({}^{\circ}\)C for 48 h; then, they were compared to the initial masses. The results are expressed as percentages. More details on the testing setup can be seen in Figure S2.  
\begin{table}
\begin{tabular}{l c c c c c c} \hline  & **Cement** & **Sand** & **Gravel** & **PPR** & **Water * & **Superplasticizer** \\ \hline REF & 1.00 & 1.94 & 2.62 & - & 0.50 & 0.010 \\ S10 & 0.90 & 1.92 & 2.62 & 0.10 & 0.50 & 0.010 \\ S20 & 0.80 & 1.90 & 2.62 & 0.20 & 0.50 & 0.010 \\ S30 & 0.70 & 1.88 & 2.62 & 0.30 & 0.50 & 0.020 \\ S  
The electrical resistivity was measured using two probes at frequencies of 200 kHz applied at 300 mV with alternating current to avoid polarization effects [14; 15] according to [PERSON] et al. [26]. Three half-cut cylindrical specimens were used after one year and three months of curing with a height of 10 cm; they were dried at 100 \({}^{\circ}\)C for 24 h in an oven followed by cooling to room temperature. Samples were placed in an apparatus comprising two copper plates at the end, where moist sponges were placed between the sample and plate to maintain electrical contact [17]. Excess water from the sponges was expelled by the application of uniform pressure; all measurements were performed for less than 2 min to minimize any variation in the sponge moisture content [17]. More details can be seen in Figure S3.  
After 28 days of wet curing, three samples of each mixture were exposed to the laboratory environment for the natural carbonation for one year and two months. Further, the carbonation depth was measured using the colorimetric test method [18] on the freshly broken samples (longitudinal direction) with a phenolphthalein solution diluted in alcohol (1 g\(\cdot\)100 g\({}^{-1}\)). Figure S4 illustrates the testing procedure.