# Carbstone Paves: A Sustainable Solution for the Urban Environment
## 3 Results and Discussion
### Environmental Quality
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & **Total** & **Column** & **Column** & **Column** & **VLAREMA** & **VLAREMA** & **Dutch Soil** \\  & **Concentration** & **7 Fractions** & **1 Fraction A** & **1 Fraction B** & **Annex 2.3.2B** & **Future** & **Decree** \\ \hline  & \multicolumn{4}{c}{**Metals**} & \multicolumn{4}{c}{**limit values**} & \multicolumn{2}{c}{**proposed**} \\  & & & & & **limit values**} & **limit values** \\ \hline As (mg/kg) & \textless{}2 & 0.053 & \textless{}0.050 & \textless{}0.050 & 0.8 & 0.8 & 0.9 \\ \hline Cd (mg/kg) & \textless{}0.5 & 0.011 & \textless{}0.010 & \textless{}0.010 & 0.03 & 0.03 & 0.04 \\ \hline Cr (mg/kg) & 3160 & 0.26 & 0.21 & 0.22 & 0.5 & 2.6 & 0.63 \\ \hline Cu (mg/kg) & 67 & 0.057 & \textless{}0.050 & \textless{}0.050 & 0.5 & 0.8 & 0.9 \\ \hline Hg (mg/kg) & \textless{}0.2 & \textless{}0.0020 & \textless{}0.0020 & \textless{}0.0020 & 0.02 & 0.02 & 0.02 \\ \hline Pb (mg/kg) & 7.1 & 0.11 & \textless{}0.10 & \textless{}0.10 & 1.3 & 1.3 & 2.3 \\ \hline Ni (mg/kg) & 836 & 0.053 & \textless{}0.050 & \textless{}0.050 & 0.75 & 0.75 & 0.44 \\ \hline Zn (mg/kg) & 31 & 0.11 & \textless{}0.10 & \textless{}0.10 & 2.8 & 2.8 & 4.5 \\ \hline Ba (mg/kg) & 180 & 0.70 & 0.28 & 0.43 & & 20 & 22 \\ \hline Co (mg/kg) & 31 & 0.053 & \textless{}0.050 & \textless{}0.050 & 0.5 & 0.54 \\ \hline Mo (mg/kg) & 128 & 2.3 & 0.50 & 1.4 & & 55 & 1 \\ \hline Sb (mg/kg) & \textless{}4 & 0.11 & \textless{}0.10 & \textless{}0.10 & 1 & 0.32 \\ \hline Se (mg/kg) & \textless{}4 & 0.21 & \textless{}0.20 & \textless{}0.20 & 2 & 0.15 \\ \hline Sn (mg/kg) & \textless{}4 & 0.11 & \textless{}0.10 & \textless{}0.10 & 1 & 0.4 \\ \hline V (mg/kg) & 925 & 0.20 & 0.71 & 0.51 & 2.5 & 1.8 \\ \hline  & \multicolumn{4}{c}{**Anions**} & \multicolumn{4}{c}{**target value**} \\  & & & & **(n)** & \\ \hline Bromide (mg/kg) & - & 4,0 & \textless{}10 & \textless{}10 & 20 & 20 (\({}^{2}\)) \\ \hline Chloride (mg/kg) & - & 350 & 330 & 370 & 1000 & 616 (\({}^{2}\)) \\ \hline Fluoride (mg/kg) & - & 98 & 100 & 98 & 55 & 55 (\({}^{2}\)) \\ \hline Sulphate (mg/kg) & - & 230 & 240 & 250 & 2200 & 2430 (\({}^{2}\)) \\ \hline \hline \end{tabular} (\({}^{1}\)) For anions, the future VLAREMA legislation only imposes target values. These must be monitored, but are not grounds for exclusion. (\({}^{2}\)) When using building materials in places where direct contact with sea water or brackish water with a natural chloride content of more than 5000 mg/L is possible, no maximum emission values for chloride and bromide are imposed. Maximum emission values for fluoride and sulphate are multiplied by a factor of 4.  
\end{table} 
Table 3: Total element content and leaching concentrations (mg/kg dry matter) as determined by upstream column percolation testing. Figure 9: Leaching behavior of paver aggregates as a function of cumulative L/S. (**a**) Leaching of Ba, Cr, F and Mo (**b**) Leaching of chloride, sulphate and V.  
To further support the environmental quality, a concrete mix was made with crushed Carbstone payers replacing all natural aggregates. This simulates what would happen in the so-called \"second and third life\", when pavements made with Carbstone payers are demolished, and the resulting construction and demolition waste is used to make recycled aggregates for concrete. For the concrete mix, a worst-case scenario was selected in which both the fine (0-4 mm) and coarse (4-20 mm) natural aggregates are fully (100%) replaced by recycled Carbstone payer aggregates. This situation will normally not occur in practice, because Carbstone payers will always be mixed with other construction and demolition waste. Furthermore, most standards (e.g., [41]) recommend or, in some countries, only allow part of the natural aggregates to be replaced by recycled aggregates in certain applications because of their technical properties (higher water absorption, Los Angeles coefficient or Micro Deval value, etc.).