1. Chapter 5
Construction Mortar

2. §5. 3 Technical Properties
Chapter 5
§5. 3 Technical Properties
Mobility (consistency)
Water retentivity
Strength
Durability

3. Strength
In order to assure the strength of whole structure, there is certain requirements for the strength of masonry mortar for foundation, walls, columns etc.
Technical Properties

4. Strength
Compressive strength average f2(design strength) and strength grade
Compressive strength average f2 (design strength)
The pressure of cube specimen (the length of 70.7), cured in standard condition, aged of 28, has 85% strength guaranty. (Temp=20C±)
The standard condition of hydraulicity cementitious material : 24± 5℃, Rh>90%curing 28d in humidity, 20±3℃, humidity Rh=60～80%

5. Fig5.3.2 stirring meter of mortar

6. Compressive Strength Average
Strength Grade
Strength Grade
According to compressive strength average f2, mortar can be divided into 6 grades:
M2.5 M5
M7.5
M10
M15
M20
Compressive Strength Average
M 5
Mortar

7. Strength Choice of grade Technical Properties
Choices of grade, considering more
force in size
environment
importance of project
Usually grades are M2.5～M10
M15 , M20 are used in significant structure
Technical Properties

8. Strength Strength formula and influencing factors
The major differences between the influencing factors of concrete are
Lacking coarse aggregate;
Setting hardening and the process of increasing strength are influenced by hygrophanous beds, that is to say, different mortar strengths for different beds.

9. Strength formula and influencing factors
Dense substrate
Dense substrate (Imhygrophanous beds-Stone)
Similar to concrete, strength lies on cement strength and W/C.
Formula
fmo=Afce(C/W－B)
fce—28d survey compressive strength of cement (MPa)
fmo —28 day strength of mortar (N/mm2 or MPa)
A,B—empirical coefficient (according to testing statisticdata)
C/W—water cement ratio

10. Qc—cement quantity in mortar (Kg/m³)
Strength formula and influencing factors
Porous substrate
Porous substrate (Hygrophanous beds)
Different from concrete, strength lies on cement strength and quantity.
Formula
fmo=A·fce·Qc/1000+B
Qc—cement quantity in mortar (Kg/m³)
fce—survey cement strength
A,B—empirical coefficient

11. Strength formula and influencing factors
Empirical coefficient A,B can be chosen from Tab5.3.2
Tab Empirical Coefficient A,B A B
Cement Mix Mortar
1.50
-4.25
Cement Mortar
1.03
3.5

12. Strength formula and influencing factors
Explanation
Why the strength of mortar in porous substrate lies on cement quantity
porous substrate absorb water for mortar while construction.
Water remained in substrate depends on cement quantity.
For the same reason, the actual W/C depends on cement quantity.
So the strength of mortar in porous substrate depends on cement quantity, not W/C.

13. Strength formula and influencing factors
Note
Mortar strength formula is much immature, changes according to construction materials dosage, material properties in different areas, mixing methods, and can be modified according to local experience and data.