Page 391 - New Trends in Eco efficient and Recycled Concrete

346 New Trends in Eco-efficient and Recycled Concrete

every 7, 14, 28, 56 and 84 days of reaction. Subsequently leachates are analysed to
determine the pH and are filtered using a membrane of 22 μm. The filtrate is analysed
for cation (total Cr, Zn, Pb and Ni) concentrations by ICP MS or AAS (Atomic
Absorption Spectrometry). This test is not used often.
CEN / TS 15862: 2012: This is a one-stage batch leaching test for monoliths at a fixed
liquid to surface area ratio (L:A) for test portions with fixed minimum dimensions:
This is the most current standard to study leaching of concrete monoliths. This compli-
ance leaching test for monolithic waste consists of a single batch leaching test with a
2
3
L:A ratio of 12 cm :cm . The test portion obtained originally or after pre-treatment has
a minimum dimension of 40 mm in all directions.
It is possible to prepare different shapes and sizes of monoliths, there is a table with
this information in Appendix. For example, if we prepare a cubic monolith with 10 cm
2
3
of height, corresponding to 600 cm area, it is necessary to apply 1000 cm of water
volume and the distance between the container and the sample should be 2 6.6 cm.
The distance between the sample and water is from 2 to 19.7 cm and the diameter of
the container from is 18.1 27.3 cm.
The test portion is brought into contact with the distilled water under defined condi-
tions for 24 h. After filtration, the properties of eluates are measured using advanced
methods developed for water analysis adapted to meet the criteria for an analysis of
leaching, ICP MS (Inductively coupled plasma mass spectrometry) or ICP-AES
(Atomic emission spectroscopy).
This method is based on two previous standards, NEN 7375:2004 and NF X 31-211:
2000. The fundamental difference of this norm with the norm DIN 7375 is that a sam-
ple of leached coma is extracted and, with the norm NF X, the size of the test tube is
different.
EPA Method 1315:2013: Mass transfer rates of constituents in monolithic or com-
pacted granular materials using a semi-dynamic tank leaching procedure:
This test was designed to produce specific release rates of the inorganic analytes that
appear in granular materials, both monolithic and compacted. The observed diffusivity
and tortuosity are analysed through the data resulting from the leaching tests.
This method is similar to others, such as NEN 7375, ANSI/ANS 16.1 and ASTM
C1308. However, the EPA method presents significant differences since the leaching
intervals are modified as well as the preparation of the sample for the mass transfer of
compacted granular samples and the mass transfer that is interpreted by means of more
complex release models.
The samples may be different, both rectangular and those presented in bricks or cylin-

ders as is indicated in concrete specimens or compacted granular material samples.
These specimens could present different faces exposed to the eluent from one-
dimensional (1D), up to three-dimensional (3D) mass transfer cases.
In all cases, a minimum sample size of 5 cm in the direction of mass transfer must be
employed and the liquid-surface-area ratio (L/A) must be maintained at 9 6 1 mL/
2
cm .
The specimens should be immersed in the leaching fluid, so that the total surface is
exposed to the eluent with a minimum of 2 cm between any surface and the vessel
wall.
Fig. 12.7 shows several examples of sample holders and configurations for 3D cases
and one in this method is similar to others discussed where the granular material is
continuously submerged in water and there is a periodic renewal of the solution or
leachate.