Synthesis of C-S-H seeds using the waste solution of acid treatment of recycled concrete aggregates and black liquor

Abstract

• Finer and well-dispersed C-S-H seeds was prepared using the two waste solutions. • Lignin in black liquor kept C-S-H seeds globular rather than traditional foil-like. • C-S-H seeds from the two waste solutions had a more prominent accelerating effect. For preparing finer and well-dispersed calcium-silicate-hydrate (C-S-H) seeds at a lower cost, the waste solution of acid treatment of recycled concrete aggregates (RCAs) and black liquor from pulping were used for the synthesis of C-S-H seeds. The results show that C-S-H seeds can be successfully fabricated by chemical co-precipitation reaction using the two waste solutions. Interestingly, it was globular rather than traditional foil-like. Furthermore, C-S-H seeds synthesized using the two waste solutions had smaller particle size and better dispersibility. More importantly, it had a more prominent accelerating effect to the strength development of mortar, significantly enhancing the early and long-term compressive strength of mortar.