Page 71 - Design of Reinforced Masonry Structures

2.24 CHAPTER TWO

TABLE 2.7 Aggregate Type-Concrete Unit Weight Relationships [2.1]

Concrete Unit weight, lb/ft 3
Sand and gravel concrete 130–145
Crushed stone and sand concrete 120–140
Air-cooled slag concrete 100–125
Coal cinder concrete 80–105
Expanded slag concrete 80–105
Pelletized-fly ash concrete 75–125
Scoria concrete 75–100
Expanded clay, shale, and sintered fly ash concrete 75–90
Pumice concrete 60–85
Cellular concrete 25–44

Concrete masonry units may be classified by their unit weights or applications. A con-
crete masonry unit is considered as follows (see Table 2.8):
3
1. Lightweight if it has a density of 105 lb/ft or less.
3
2. Medium weight if it has a density between 105 and 125 lb/ft .
3
3. Normal weight if it has a density of more than 125 lb/ft .
Approximate weights of various hollow units may be determined from Fig. 2.17.

TABLE 2.8 Weight Classification for Load-Bearing Concrete Masonry Units
Oven-dry weight Maximum water
Weight classification of concrete absorption
3
Lightweight 105 lb/ft max. 18 lb/ft 3
Medium weight 105–125 lb/ft 3 15 lb/ft 3
Normal weight ≥125 lb/ft 3 13 lb/ft 3

FIGURE 2.17 Weights of some hollow units for various concrete densities [2.1].