# Coefficient of Thermal Expansion of RCA Concrete Made by Equivalent Mortar Volume
## 4 Test Results
### Concrete COTE Test Results
#### 4.2.1 Dependence of Total Coarse Aggregate Volume  
In the present study, both RCA and NCA were based on similar granite aggregates, and thus the effect of the aggregate type was considered to be negligible. Assuming that concrete comprises coarse aggregate and mortar (water, cement, fine aggregate, air void), it was predicted that the COTE of concrete would increase as the volumetric ratio of mortar increased or that the COTE of concrete would decrease as the volumetric ratio of the coarse aggregate increased.  
Using Equation (3), the total coarse aggregate volume in the mix was calculated using the data shown in Tables 1 and 2:  
\[V_{TCA}=\frac{W_{NCA}}{SG_{NCA}\times 1000}+\frac{W_{RCA}\times\left(1-\frac{R \text{MC}}{5}\right)}{SG_{RCA}\times 1000} \tag{3}\]  
where \(V_{TCA}\) is the sum of the volume of natural aggregate (\(\frac{W_{NCA}}{SG_{NCA}\times 1000}\)) and the volume of original virgin aggregate (\(\frac{W_{RCA}\times\left(1-\frac{R\text{MC}}{5}\right)}{SG_{RCA}\times 1000}\)) and where \(SG_{NCA}\) and \(SG_{RCA}\) are the specific gravities of natural coarse aggregate and of RCA, respectively; RMC is residual mortar content from Equation (2) and 'S' is a scale factor, as explained before and in reference [42].  
Figure 9 illustrates the quadratic relations of the mean COTE values of the specimens prepared by applying the individual mixes of mix series 1-3 and the volumetric ratio of coarse aggregate of the individual mixes. In test series 1, the volumetric ratios of the coarse aggregate of the reference CNR mix and the ERR68 and ERR68-2 specimens of the EMV mix were 0.34, 0.35 and 0.35, respectively. The volumetric ratios of the coarse aggregate of the CRR68 and CRR33 specimens of the conventional mix design were 0.24 and 0.29, respectively. Figure 9a shows that as the total volumetric ratio of the virgin coarse aggregate in the recycled aggregate mix increased, the COTE of concrete specimens decreased with a determination coefficient of 0.98. As also described in many previous reports, our results clearly show that the volumetric ratio of the aggregate is one of the factors influencing the COTE of concrete specimens.  
In test series 2, on the contrary, the volumetric ratios of the coarse aggregate of the reference CNR mix and the ERP25 and ERP50 specimens of the EMV mix were all about 0.39. The volumetric ratios of the coarse aggregate of the CRP25 and CRP50 specimens of the conventional mix design were 0.36 and 0.34, respectively. As shown in Figure 9b, with the determination coefficient of 0.95, the COTE of concrete specimens still decreased as the total volumetric ratio of the virgin coarse aggregate in the recycled aggregate mix increased.  
Figure 8: Average relative COTE values from mix series 2 and 3.  
On the other hand, in mix series 3, besides the specimens prepared using the same mix design as used for mix series 2, additional specimens were prepared by applying the RA aggregate and the EMV mix design. Figure 9(c) shows the experimental results obtained from the specimens as a function of the total coarse aggregate volume. The volumetric ratio of the coarse aggregate was about 0.39 in the reference CNP specimen and in the ERP50 and ERA50 specimens of the EMV mix design. The volumetric ratio of the coarse aggregate of the CRP50 specimen, prepared by the conventional mix design, was 0.34. Figure 9(c) shows that as the total volumetric ratio of the virgin coarse aggregate in the recycled aggregate mix increased, the COTE of the concrete specimens decreased with a determination coefficient of 0.99. However, it is reported by literature [10; 11; 12; 21] that the COTE value of concrete is proportional to the volume ratio of total coarse aggregate. Further study is needed to verify if the COTE value of concrete is linear or nonlinear to the volume ratio of total coarse aggregate.