## 5 Conclusions  
This study assessed the influence of the revised EMV mix proportion method on mechanical strength and drying shrinkage properties of RCA concretes, which are proportioned to have the same W/C ratio, slump and air content. This experimental study used three grades of RCAs with  
Figure 10: Test results of drying shrinkage of concrete samples (**a**) shrinkage, (**b**) relative value.  
different water absorption ratios, where two different RCAs (water absorption ratio of 3.82% and 6.61%) were crushed from the same source of old concrete. The third RCA was produced from old PC concrete sleepers.  
Six mixes were studied for typical structural concrete where the control concrete contained natural coarse aggregate mixed according to the traditional ACI method and the others were prepared with the revised EMV method. From this study, the following conclusions are drawn. Here the test results of ERA2 mix were excluded in the concluding discussion due to low mechanical strength values, which may be ascribed to its low density.  
* Due to the nature of a lower slump problem that often occurs in the modified EMV method, all the mixture slump values were controlled by using a superplasticizer to range between 140-155 mm and air contents values with 3.7-5.8%.
* Except for the split tensile strength, test results showed that the ERR mix with 100% RCA replacement, which was produced from old PC sleepers mixed by the revised EMV mix method, exhibited equivalent compressive strength, Young's modulus, and flexural strength values to the companion reference mix of natural aggregate. In addition, the relative drying shrinkage increased only 2% to the companion control mix.
* In other mixes (except for ERR mix), compared to the drop of 11-20% of the compressive strength, the modulus of the modified EMV mixes resulted in only a 6-10% decrease to the companion control mix, which is the result of the characteristic in the revised EMV method.
* In the modified EMV mixes with RCA replacement of 100%, the flexural strength of concretes decreased by 8-16%. However, with 50% replacement of RCA mixes, the strength increased by 4-10% and thus may be preferred for concrete pavements, which are loaded in bending.
* Although a 7-11% decrease was observed in the modified EMV mixes, the split tension to compressive strength of concrete lineally follows the compressive strength trend.
* At 50 days, test results revealed that drying shrinkage of the modified RMV mixes with RCA exhibited a 4% drop to only an 8% increase. There was one, except for the ERB2 mix with a 24% increase, and this might be affected by relatively higher fine aggregate ratio and cement content, compared to the other EMV mixes.  
Further studies should be carried out to enhance strengthening ITZs of RCA and their surroundings by using minerals such as silica fume, slag, or bottom ashes. The equivalency of mechanical strength properties then may be more clearly acquired by the revised EMV proportioning method with any RCA source.  
This research was funded by the National Research Foundation (2018 Korea Grant of the Korean Government) for a project on \"Structural Performance of Reinforced Concrete Members made with Revised Equivalent Volume Mix Proportioning Method (No. 2016R1A2B4007932)\".  
The author declares no conflict of interest.