## 3 Experimental Methods for Environmental Assessment
### Determination of the Leaching Behaviour of Monolithic Specimens  
Leaching tests on concrete monoliths were conducted according to the 24 h tank test (CEN-TS 15862:2012), for basic characterisation of concrete specimens, and the dynamic Dutch standard with periodic leachant renewal (NEN 7343:2004), for long-term leaching assessment of concrete pieces. In the NEN 7343:2004 standard, each monolith was placed in a plastic container and a given volume of de-ionized water was introduced to completely submerge the monolith and reach a \"liquid to contact area ratio\" (L/A ratio) of 8 cm\({}^{3}\)/cm\({}^{2}\). The top surface of the monolith was kept at least 2 cm below the surface of the water and the distance between the surfaces of the monolith and the walls of the reactor was kept above 2 cm. At time intervals of 0.08, 1.00, 2.25, 8.00, 14.00, 15.00, 28.00 and 36.00 days, the aqueous solution was completely removed from the reactor and replaced with the same volume of deionised water. Before water renewal, the pH and electrical conductivity were measured and a sample was extracted for testing. In the CEN-TS 15862:2012 standard, monoliths samples were contained in deionised water for 24 h with a L/A ratio of 12 cm\({}^{3}\)/cm\({}^{2}\). All of the samples that were collected from the different tests conducted were filtered through a cellulose-acetate membrane of 0.45 \(\upmu\)m pore size and the solution was analysed within 24 h, for several elements and/or anions using ICP-MS and ionic chromatography, respectively. In the diffusion leaching tank test in monolithic materials, release levels are expressed as leached quantity per unit area: \(E_{i}^{*}\), defined as the measured leaching of a component in the fraction \"\(i\)\" (expressed in mg/m\({}^{2}\)). This value can be calculated for each component using Equation (1):  
\[E_{i}^{*}=\frac{c_{i}\times V}{f\times A} \tag{1}\]  
where:  
* \(c_{i}\) is the concentration of the component in fraction \(i\) in \(\upmu\)g/L;
* \(V\) is the volume of the eluate in L;
* \(A\) is the surface area of the test piece in m\({}^{2}\);
* \(f\) is a conversion factor: 1000 \(\upmu\)g/mg. Equation (2) allows the calculation of the cumulative values. The parameter \(\varepsilon_{n}^{*}\), expressed in mg/m\({}^{2}\), measures the cumulative leaching of a component for a period (n) which comprises fraction \(i\) = 1 to n, n being the number of periods equal to the number of specified replenishment times (in this case, n = 8). \[\varepsilon_{n}^{*}=\sum_{i=1}^{n}E_{i}^{*} \tag{2}\]  
One of the main objectives of monolithic leaching testing is the determination of the diffusion coefficient, \(D_{e}\), which can only be calculated when leaching is diffusion controlled. \(D_{e}\), calculated according to Equation (3), is the effective diffusion coefficient which is used to assess the long-term leaching behaviour for an element in the monolith. For this calculation, it is necessary to use the availability data (\(U_{availability}\)) estimated in Section 3.2. \[D_{e}=\left(\frac{\varepsilon_{64}}{2653\times\rho\times U_{availability}} \right)^{2}\times f \tag{3}\]  
where:  
* \(D_{e}\) is the average, effective diffusion coefficient for a given component (m\({}^{2}\)/s);
* \(\varepsilon_{64}\) is the derived cumulative leaching of the component over 64 days determined with Formula (4) (mg/m\({}^{2}\));
* \(\rho\) is the density of the test piece (kg dry matter per m\({}^{3}\));\(U_{availability}\) is the leachable, available quantity derived according to NEN 7371 (mg per kg dry matter);
* \(f\) is a factor equal to 1.