# Porcelain Tile Polishing Residue in Concrete as an Additive or Replacement for Portland Cement
## 4 Conclusions  
This study evaluated the influence of incorporating PPR as an additive or as partial replacement of Portland cement on the properties of fresh and hardened concrete, durability, and CO\({}_{2}\) equivalent emission of the composite. From these results, it can be concluded that:  
1. The incorporation of PPR as cement replacement significantly reduced the concrete workability, while this effect was less significant when PPR was incorporated as an additive. 2. The concretes with cement replacement by RRP in 10-30% showed equivalent or higher strengths than the reference concrete at 7-91 days. With the addition of PPR, the compressive strength increased for all contents and ages, up to 92% (for 50% addition at 28 days). 3. The incorporation of PPR generally improved the durability of concrete (water absorption, capillarity, and acid resistance) and this effect was more pronounced when \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Concrete**} & _bi_ & **Binder** & **Cement** & \multirow{2}{*}{**PPR (kg\(\cdot\cdot\)m\({}^{-3}\))**} & **GWP** & **GWP** \\  & **(kg\(\cdot\)m\({}^{-3}\))** & **(kg\(\cdot\)m\({}^{-3}\))** & **(kg\(\cdot\)m\({}^{-3}\))** & **(CO\({}_{2}\)-eq\(\cdot\)m\({}^{-3}\))** & **Reduction** \\  & & & & & **of Concrete)** & **Reduction** \\ \hline Ref & 9.04 & 488.02 & 488.02 & 0.00 & 564.01 & 0.00\% \\ S10 & 8.63 & 466.17 & 419.55 & 46.62 & 494.17 & \(-\)12.38\% \\ S20 & 9.47 & 511.39 & 409.11 & 102.28 & 492.96 & \(-\)12.60\% \\ S30 & 10.05 & 542.82 & 379.97 & 162.85 & 473.05 & \(-\)16.13\% \\ S40 & 13.03 & 703.56 & 422.14 & 281.42 & 545.99 & \(-\)3.20\% \\ S50 & 14.57 & 786.72 & 393.36 & 393.36 & 534.38 & \(-\)5.25\% \\ A10 & 7.78 & 420.40 & 382.18 & 38.22 & 443.37 & \(-\)21.39\% \\ A20 & 7.74 & 418.05 & 348.38 & 69.68 & 405.52 & \(-\)28.10\% \\ A30 & 7.92 & 427.67 & 328.98 & 98.69 & 384.19 & \(-\)31.88\% \\ A40 & 7.95 & 429.40 & 306.71 & 122.68 & 359.38 & \(-\)36.28\% \\ A50 & 8.24 & 444.94 & 296.63 & 148.31 & 348.66 & \(-\)38.18\% \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Global warming potential results. the waste was incorporated as an additive. In turn, the carbonation depth increased with the partial replacement of cement (as previously reported in the literature for other SCMs), while it slightly decreased with the addition of waste. 4. The incorporation of PPR reduced the equivalent emission of CO\({}_{2}\) per m\({}^{3}\) of concrete for both additive and cement replacement. For a compressive strength of 54 MPa at 91 days, the emission was reduced from 564 kg CO\({}_{2}\)-eq\(\cdot\)m\({}^{-3}\) of concrete for the reference mixture to 473 kg CO\({}_{2}\)-eq\(\cdot\)m\({}^{-3}\) of concrete (i.e., 16%) for 30% replacement and to 349 kg CO\({}_{2}\)-eq\(\cdot\)m\({}^{-3}\) of concrete (i.e., 38%) for 50% addition. For practical engineering applications, this work revealed that using PPR in concrete is beneficial for the durability of the composite and for improving the mechanical strength and eco-efficiency, both as cement replacement and additive. This contributes to cleaner concrete production, reducing cement consumption and enabling the reuse of large-scale industrial waste. As a recommendation for future research, the potential of using PPR in ternary binders (e.g., together with fly ash or slag) may be addressed. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app13052824/s1](https://www.mdpi.com/article/10.3390/app13052824/s1)]([https://www.mdpi.com/article/10.3390/app13052824/s1](https://www.mdpi.com/article/10.3390/app13052824/s1)), Figure S1. Concrete specimen during the compressive strength test. Figure S2. Acid attack resistance test. (a) concrete sample tested (20 \(\times\) 20 \(\times\) 14 mm); (b) experimental setup. Figure S3. Concrete specimens and schematic illustration of the electrical resistivity test. Figure S4. Carbonation depth test. (a) specimen splitting procedure; (b) phenolphthalein colorimetric method. Conceptualization, H.M.M.S. and A.C.V.d.N.