Transcript 6.3.2 Small-size Hollow Block

§6.3 Wall Blocks
Introduction
Small-size Hollow Block
Fly Ash and Silicate Mediumsize Block
Small-size Hollow Block
Produce
The classifications and grades
Strength grades
Other properties
Applications
Small-size Hollow Block
Produce
The cement and aggregate are stirred
and cured in the water and, to produce
the block
Classification
It can be classified into two types: loadbearing block and non-bearing block, or
first-grade and second-grade by quality.
Classifications
Load-bearing Block
Non-bearing Block
Classifications
First-grade
Second-grade
By quality
Strength Grades
By GB8329-1997
According to compressive strength of
blocks, small-size hollow block can be
divided into 6 grades: Mu20.0, Mu15.0,
Mu10.0, Mu7.5, Mu5.0 and Mu3.5
(Tab.6.3.1)
Divided by the gross acreage of the press
side, we can get compressive strength
Tab.6.3.1 Compressive Strength of
Concrete Small-size Block
Strength Grades
Mu3.5
Mu5.0
Mu7.5
Mu10.0
Mu15.0
Mu20.0
Compressive Strength
（MPa）≥
Average of Five Minimum Value
Blocks
of Single
3.5
2.8
5.0
4.0
7.5
6.0
10.0
8.0
15.0
12.0
20.0
16.0
Other Properties
Water Absorption
Softening Modulus
Dry Shrinkage
Thermal Conductivity
Water Absorption
Water absorption of block is about 6-8%
Block can be divided into M and P by requirements
Type P has no requirement of water absorption
Softening Modulus
Softening modulus of block is about 0.85-0.95
Dry Shrinkage
Due to drying, block shrink leads to wall crack.
The dry shrinkage of the ordinary concrete
blocks is 0.235-0.427mm/m.
The dry shrinkage of the blocks, which is used
as main wall and exterior wall, are required to
be less than 0.05%, and that of the non-bearing
wall or the interior wall less than 0.06%.
Thermal Conductivity
The thermal conductivity varies in the
holes and space of the concrete. For example,
common cement concrete small-size hollow
block is 0.26W/m·K when the space is 50%.
They can be used in the interior and
exterior walls in low and middle height
buildings.
When using blocks as wall material, we
must abide by the design criterion and
construction rules.
The blocks and bricks must not be mixed
together in the main wall.