Title: Characteristics of Lightweight Aggregates for High-Strength Concrete

Author(s): Min-Hong Zhang and Odd E. Gjorv

Publication: Materials Journal

Volume: 88

Issue: 2

Appears on pages(s): 150-158

Keywords: absorption; density (mass/volume); high-strength concretes; lightweight aggregates; lightweight concretes; particle shape; porosity; surface texture; Materials Research

DOI: 10.14359/1924

Date: 3/1/1991

Abstract:
Lightweight aggregates are produced from a wide variety of raw materials, and their production conditions may also vary. Therefore, the characteristics of lightweight aggregates may vary within wide limits. For high-strength concrete, the characteristics of the aggregate are more important for the concrete properties than for low- to medium-strength concretes. For production of high-strength lightweight concrete, it is urgent, therefore, to provide information on the characteristics of the aggregate. In this paper, an investigation of some high-strength lightweight aggregates available on the European market is reported. For the various aggregates, particle shape, surface texture, and pore structure varied within wide limits. Most of the pores in the aggregate were open, and thus susceptible to water absorption. The pore sizes also varied considerably. The shapes of the pores were rather irregular. In all the aggregates, there were some relatively large voids and fissures that made the aggregate weak and friable. Some of the aggregates had a distinct dense outer shell. The particle density varied from 1.07 to 1.54 g/cm3. This variation was related to characteristic differences in macroscopic and microscopic pore structure. After the first 30 min, the water absorption varied from 8 to 13 percent by weight, but most of the water absorption took place within the first 2 min. Within the first 30 min, more than half of the 24-hr water absorption was observed. For cut particles of some aggregates with a dense surface layer, the water absorption within the first 30 min was approximately 30 percent higher than that of whole particles of the same specific surface. 113-391