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310 New Trends in Eco-efficient and Recycled Concrete

each case, the EFU in RAC were obtained by computing the K factor. With this
approach, it is possible to design structural elements made with RAC similar to
those made with NAC.
The scope for this validation included the following relevant conditions:

NAC slab thickness between 12 and 18 cm;
2
Other permanent loads (from 2.0 to 3.0 kN/m );
2
Live loads (2.0 and 4.0 kN/m );
Environmental classes XC2, XC3, XD1 and XS1;
Concrete strength classes from C20/25 to C50/60;
Structural class S4, for durability purposes;
Rebar diameters between 8 and 12 mm and rebar spacing between 0.075 and 0.150 m,
with 0.05 m increments, and 0.20 m;
The creep coefficient for NAC assumed to be equal ϕ(N, t 0 ) 5 2.5.
Various geometry and boundary conditions were tested, including one- and two-
way slabs, as well as simply supported versus fixed support conditions. The slabs’
spans ranged from 4.0 to 6.0 m and tow-way slabs were square, for simplification
purposes.
When NAC was considered, the mean compressive strength obtained in the tests
needed to be fit to the classes established in Eurocode 2. The remaining properties
(e.g., E cm and f ctm ) for NAC were based on the values provided by Eurocode 2.
RAC was related to NAC by the fundamental parameters that lead to the definition
of the EFU, K. Eqs. (11.11) (11.14) show the previously established K α for slabs:

h RAC 20:356
5 α 1 (11.11)
h NACα 1
ð
h RAC h NAC 1 2 3 α 3 2 1Þ 3 c min;NAC
5 (11.12)
h NAC
h NACα 3
ð
h RAC h NAC 1 2 3 α 4 2 1Þ 3 c min;NAC
5 (11.13)
h NAC
h NACα 4
0:4154
h RAC α 6
5 0:9983 3 (11.14)
α 2
h NACα 6 =α 2
where h RAC and h NAC are the total heights of the structural elements in RAC and
NAC, respectively, c min, NAC the minimum cover of slabs (Eurocode 2). The data
was collected from several sources (Gonza ´lez-Fonteboa et al., 2011; Amorim et al.,
2012; Cakır, 2014; Pedro et al., 2014; Bravo et al., 2015a,b,c; Cartuxo et al., 2015,
¸
2016). Most RAC properties could be obtained directly, by multiplying the corre-
sponding NAC value by the respective fundamental parameter. The exception is the
compressive strength, of which the characteristic values are used. Those could be
obtained from the mean values by adding 8 MPa, according to Eurocode 2. Even