A study of the quality, the design and the economy of concrete

Abstract

Abstract The outstanding results brought out by this investigation were: 1. 1. The Strength and practically all other desirable qualities of concrete except volume changes, increase uniformly with the increase in cement concentration in the amount of water in the concrete at the time of hardening. 2. 2. For a given type and gradation of aggregates the net amount of mixing water in the concrete remains practically constant as long as the placeability 0f the concrete remains approximately constant. Changes in richness of mix may therefore be accomplished by simply substituting g a g c pound of aggregate for each one pound change in the cement content. 3. 3. The economy 0f plain concrete increases very markedly with the increase in strength, with variables such as gradation of aggregates and strength-quality of cement less important. 4. 4. The cost ratio between steel and concrete for equal economy in reinforced concrete columns is: P s P c ′ = 0.18( ƒ 8 ƒ c ′ ) for welded reinforcement and P s P c ′ = 0.15( ƒ 8 ƒ c ′ ) for spliced reinforcement. 5. 5. The strength of the concrete has relatively small effect upon the economy of reinforced concrete members subjected to flexure. 6. 6. The balanced reinforcement approaches the most economical design for present-day cost ratios and ordinary strength of the concrete. 7. 7. The economy of the reinforcing steel is directly proportional to the ratio between its unit price and yield-point stress.