Page 351 - New Trends in Eco efficient and Recycled Concrete

308 New Trends in Eco-efficient and Recycled Concrete

1.700
1.600
1.500 y = 0.9983x 0.4154
h RAC /h RC 1.400 R² = 0.9916

1.300
1.200
1.100
1.000
1.000 1.200 1.400 1.600 1.800 2.000 2.200 2.400 2.600 2.800 3.000 3.200 3.400
α 6 /α 2
as a function of α 6 /α 2 (slabs).
Figure 11.5 K α 6 =α 2

1.450
1.400
–0.932
1.350 y = x All values
1.300 Minimum values
h RAC /h RC 1.250 y = x –0.356 Maximum values
1.200
1.150
values
1.100 Line minimum
1.050
1.000
0.400 0.500 0.600 0.700 0.800 0.900 1.000 1.100
α 1

as a function of α 1 (slabs).
Figure 11.6 K α 1
11.6.3 K as a function of bending ULS
In a multi-criteria analysis, h RAC /h NAC cannot be expressed as a function of α 1 ,as
deformation SLS are the conditioning verification. Additionally, the need for an
increased cover due to durability issues leads to a higher cross-section, and there-
fore a higher ULS bending moment. The parametric study conducted by
Dobbelaere et al. (2016) for slabs presented the variation of h RAC /h NAC as a func-
tion of α 1 (Fig. 11.6).
was computed using three values of α 1 , that took into account the
The ratio K α 1
different required rebar covers in each load combination. Higher values of rebar
cover lead to lower values of α 1 , assuming constant h RAC /h NAC . This because the
effective height (d RAC ) is affected by the rebar cover used. If a higher cover is
used, the parametric effective height (d NAC ) is smaller and d RAC has larger relative
changes due to Δc.
All cases studied cases of RAC, regardless of the quality of the aggregates, com-
ply with the criteria if α 1 is equal or bigger than 0.56. The average value of α 1 is
approximately 0.9 in the case of 100% RAC. For that situation, h RAC /h NAC reaches
1.08, which is a feasible result for practical purposes.