[A-GE28] Energy-Environment-Water Nexus and Sustainable Development

[AGE28-06] Characterization of particle breakage of recycled concrete aggregates with different fines contents under different compaction energies

*Thai Hong Nam¹, Akira Kato¹, Ken Kawamoto¹ (1.Graduate School of Science and Engineering, Saitama University, Saitama, Japan)

Keywords:Recycled concrete aggregate, Compaction, Fines content, Particle breakage

Many factors affect the mechanical properties of granular materials including recycled concrete aggregates (RCA). Among them, particle size distribution is one of the most important factors. However, the particle size distribution usually changes after specimens are compacted due to particle breakage. The comparison between particle size distribution after compaction and original particle size distribution of RCA aggregates shows the particle breakage of samples, and the particle breakage index (B_g) normally use to characterize the particle breakage. The particle breakage depends on many factors such as compaction energy (E_c), the single-strength of particle, particle shape, particle size, etc. This study concentrates on the characterization of particle breakage under different compaction energies and different particle size condition [i.e. different fine content fines content (F_c; typically, the particle size of fines < 0.075 mm), and different maximum particle size]. Samples were prepared with two different maximum diameters (D_max) of 25 and 37.5mm, and four different F_c of 0, 5, 10 and 20%. Modified proctor method (E_c = 2631 kJ/m³) was used to compact samples for measurement maximum dry density, optimum water content, and compare the particle breakage with different water content. Three different compaction energies, E_c = 580, 2631, 5262 kJ/m³ were applied to compact samples with optimum water contents to measure the effect of compaction energy on particle breakage. The results of this study showed that the maximum dry densities of RCA samples were highest with F_c = 5-10% regardless D_max, and optimum water contents were around 9.5-10.5%. The dry densities of RCA samples were dropped to minimum values when “bulking” occurred with water contents were around 6-7%. B_g increased with the increase of E_c, and B_g decreased when F_c increased because of the cushioning effect. Besides, regardless D_max, E_c and water content, the fraction of 25-37.5 mm gave the highest % decrement (i.e., the most breakage) and the fraction of 0.475-2.36 mm gave the highest % increment.