The document summarizes research into the microstructure and length change behavior of autoclaved aerated concrete (AAC). It examines the hydration products, morphology of hydration products, and pore size distribution that make up the microstructure of AACs. Graphs show the pore size distributions of different AAC samples. The length change behavior of AAC is also analyzed under different relative humidity conditions and with different admixtures. The shrinkage behavior and water retention of Vietnamese and Japanese AAC samples are compared.

1. 5.1 Microstructure of AACs
The microstructure of AACs were studied
through:
- Hydration products;
- Morphology of hydration product;
- Pore size distribution.
1

2. Pore size distribution (MIP)
2
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
1 10 100 1,000 10,000 100,000
dV/dlog(r),
ml/g
Pore radius (r), nm
VN3 VN4
VN6 VN5
JP2 JP1
VN1 VN2

3. Pore size distribution (MIP)
3
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
1 10 100 1,000 10,000 100,000
dV/dlog(r),
ml/g
Pore radius (r), nm
VN3 VN4
VN6 VN5
JP2 JP1
VN1 VN2

4. Pore size distribution (MIP)
4
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
1 10 100 1,000 10,000 100,000
dV/dlog(r),
ml/g
Pore radius (r), nm
VN3 VN4
VN6 VN5
JP2 JP1
VN1 VN2

5. 5
5.2 Length change behavior of AAC
AAC material selection
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
1 10 100 1,000 10,000 100,000
dV/dlog(r),
ml/g
Pore radius (r), nm
VN3 VN4
VN6 VN5
JP2 JP1
VN1 VN2

6. 6
5.2 Length change behavior of AAC
AAC material selection

7. 5.2 Length change behavior of AAC
AAC
Vycor glass (Haines & McIntosh)
7

8. 5.2 Length change behavior of AAC
AAC Cement paste (Feldman & Sereda)
8

9. Effect shrinkage reducing agent on length
change behavior of AAC
9
- The shrinkage reduction is
significant at high RHs condition,
and is negligible at low RHs
condition (below 65% RH);
- The significant shrinkage
reduction in the range of about 65-
95% RH further supports for the
action of capillary tension at high
RHs condition.
𝒒 =
2𝜸
𝑟𝑠
Capillary pressure:
rs: the Kelvin radius where meniscus is formed
γ: the surface tension of solution ( γ of solution
for JP1 and JP1-3 are 71.6 and 36.8 mN/m,
respectively).

10. Comparison the length change behavior of
Vietnamese and Japanese AACs
10
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
1 10 100 1,000 10,000 100,000
dV/dlog(r),
ml/g
Pore radius (r), nm
JP1
VN1
VN2
- No expansion in desorption
process was observed for VN1
and VN2. The shrinkage
hysteresis in VN1 and VN2 is also
significantly less than in JP.
- The higher volume of finer pores
leads to the retention of more
water in AAC at high RH;

11. Comparison the length change behavior of
Vietnamese and Japanese AACs
11
0
20
40
60
80
100
0 0.2 0.4 0.6 0.8 1
Ultimate
water
content,
%
P/Po
Desorption JP2 Desorption VN6
Desorption VN5 Desorption VN3
Desorption VN4 Adsorption JP2
Adsorption VN6 Adsorption VN5
Adsorption VN3 Adsorption VN4
-1200
-1000
-800
-600
-400
-200
0
0 0.2 0.4 0.6 0.8 1
Length
change
strain,
μ
P/Po
Desorption JP2 Desorption VN6
Desorption VN5 Desorption VN3
Desorption VN4 Adsorption JP2
Adsorption VN6 Adsorption VN5
Adsorption VN3 Adsorption VN4