Manufacturing and performance of environment-friendly lightweight aggregates with core-shell structure

Abstract

The production of lightweight aggregates (LWAs) involves much energy consumption and emission of pollution during the sintering process. The increasing worldwide demand for functional concrete for use in modern construction has promoted this negative trend to a more serious level. This study reports an artificial lightweight capsule aggregates (CAs) based on an encapsulation technology from the viewpoint of green manufacturing. The novel CAs are composed of a fly ash-cement inorganic shell and sodium alginate organic core. A series of experiments were conducted to study the influences of the rotation rate, duration time, curing conditions and surface conditions for sodium alginate beads (SAB) on the physical and mechanical characteristics of the CAs. The results indicate that CAs with a wet density of 1340 kg/m3 and corresponding crush strength of 2.46 MPa can be achieved. The CAs density can be further decreased by a third via sodium alginate dehydration. CAs with optimized performance can be synthesized by using a rotation rate of 150 rpm, duration time of 30 s and C/A ratio of 2.0. A low rotation rate and high duration time have a negative effect on the CAs characteristics. A saturated surface dry (SSD) condition process for the SAB was found to greatly contribute to the optimization of CAs density. Findings from this study can provide a novel and viable way to reuse industrial wastes and biomass resources to manufacture core-shell structured LWAs with stable and adjustable performance. These artificial LWAs have great application potential in the preparation of the advanced lightweight concrete.