As concrete aggregate, porous materials such as lightweight
aggregate and bottom ash are utilized for the purpose
of waste management and improvement of concrete
properties. One of the main problems for the use of porous
aggregate is the moisture property of the aggregate which is
usually higher than that of normal aggregate. Previous
studies have reported that concrete mixed with bottom
ash and recycled concrete-crush was very stiff and nonworkable
due to a significant water demand from their porous
properties [1–3]. In addition, workability reduced due
to the immobility of the porous aggregate caused by its surface
friction which was due to its angular shape and rough
texture. The difficulty of measuring the true moisture properties
of bottom ash was also reported [1–4].
Water retainability has been introduced by some
researchers for analysis and design of fresh concrete properties
[5–8]. It is defined as the water required to completely
fill in pores and dependently restricted on surface of aggregate
particles under gravitational condition as illustrated in
Fig. 1. Moisture property of concrete consists of water
absorption and water adsorption and affects the free water
amount in fresh concrete [6–8]. For concrete incorporating
porous aggregate, it is reasonable to apply water retainability
instead of water absorption to design mixture proportion
and to control fresh concrete properties, especially
workability.