Recycling waste fresh paste through a Dormant & Awaking re-utilization approach

Abstract

This paper proposed a Dormant & Awaking approach for the management and recycling of waste fresh paste (WFP), a significant byproduct of concrete mixing plants. The approach involves inducing dormancy in WFP using citric acid to slow down cement hydration; whereas calcium aluminate cement (CAC) was utilized to awaken the dormant WFP. Experimental results revealed that treating WFP with citric acid effectively impeded cement hydration, allowing for extended collection and storage time. The addition of CAC facilitates rapid hydration by absorbing and utilizing free water in the pore solutions of cement. Consequently, dormant WFP can be awakened through the rapid precipitation and assembly of hydration products. By adding 17.4% or 26.1% CAC, the compressive strength of WFP at 28 days of curing can be mostly recovered to levels comparable to the blank mixture. A flexible and efficient solution for WFP recycling is thus provided.

Keywords

• waste fresh concrete
• dormancy
• awakening
• Hydration
• Compressive strength