Original Version
Rule 48.3
48.3 Reinforced Concrete
Values used for ultimate strengths of reinforced concrete, in conjunction with safety factors given in Rule 44, shall not exceed the following:
Reinforcing steel, tensile or compressive strength, pounds per square inch55,000
Concrete, 1:2:4 mixture 
Age 
Compressive Strength 
7 days 
900 lbs per sq in. 

30 days 
2,400 lbs per sq in. 

90 days 
3,100 lbs per sq in. 

6 mos 
4,400 lbs per sq in. 
If reinforced concrete is designed for higher strength values which are proven by test, such values may be used in lieu of the figures given.
Strikeout and Underline Version
Rule 48.3
48.3
Reinforced
Concrete
A. Reinforced Concrete
Values used for ultimate strengths of reinforced concrete, in conjunction with safety factors given in Rule 44, shall not exceed the following:
Reinforcing steel, tensile or compressive strength, pounds per square inch55,000
Concrete, 1:2:4 mixture 
Age 
Compressive Strength 
7 days 
900 lbs per sq in. 

30 days 
2,400 lbs per sq in. 

90 days 
3,100 lbs per sq in. 

6 mos 
4,400 lbs per sq in. 
If reinforced concrete is designed for higher strength values which are proven by test, such values may be used in lieu of the figures given.
B. Prestressed Concrete
Structural Members and their connections shall he designed and constructed so that the structures and parts thereof will not fail or be seriously distorted at any load less than their maximum working loads (developed under the current construction arrangements with loadings as Specified in Rule 43) multiplied by the safety factor specified in Rule 44."
The minimum strength of the materials used in prestressed concrete structures used in conjunction with the safety factors given in Table 4 shall be as follows:
Reinforcing Steel  yield strength 40,000 lb.. per sq. inch
Prestressing Steel  yield strength 188,000 lbs. per sq. inch
Concrete  compressive strength 4,000 lbs. per sq. inch at 28 days
Other strength Values may be used provided the strength values used for design are proven by tests.
Final Version
Rule 48.3
48.3 Concrete
A. Reinforced Concrete
Values used for ultimate strengths of reinforced concrete, in conjunction with safety factors given in Rule 44, shall not exceed the following:
Reinforcing steel, tensile or compressive strength, pounds per square inch55,000
Concrete, 1:2:4 mixture 
Age 
Compressive Strength 
7 days 
900 lbs per sq in. 

30 days 
2,400 lbs per sq in. 

90 days 
3,100 lbs per sq in. 

6 mos 
4,400 lbs per sq in. 
If reinforced concrete is designed for higher strength values which are proven by test, such values may be used in lieu of the figures given.
B. Prestressed Concrete
Structural Members and their connections shall he designed and constructed so that the structures and parts thereof will not fail or be seriously distorted at any load less than their maximum working loads (developed under the current construction arrangements with loadings as Specified in Rule 43) multiplied by the safety factor specified in Rule 44.
The minimum strength of the materials used in prestressed concrete structures used in conjunction with the safety factors given in Table 4 shall be as follows:
Reinforcing Steel  yield strength 40,000 lb.. per sq. inch
Prestressing Steel  yield strength 188,000 lbs. per sq. inch
Concrete  compressive strength 4,000 lbs. per sq. inch at 28 days
Other strength Values may be used provided the strength values used for design are proven by tests.