Scope

Introduction

Basic Relationship

Chemical Admixtures

Background Data

Design Parameters

Design Procedure

BASIC RELATIONSHIP

ACI 211.1-91, Reapproved 2009, states: "Concrete proportions must be selected to provide workability, consistency, density, strength, and durability, for the particular application.

Workability: The property of the concrete that determines its capacity to be placed and consolidated properly and be finished without harmful segregation.

Consistency: It is the relative mobility of the concrete mixture, and measured in terms of the slump; the greater the slump value the more mobile the mixture.

Strength: The capacity of the concrete to resist compression at the age of 28 days.

Water-cement (w/c) or water-cementitious (w/(c+p)) ratio: Defined as the ratio of weight of water to the weight of cement, or the ratio of weight of water to the weight of cement plus added pozzolan. Either of these ratios is used in mix design and considerably controls concrete strength.

Durability: Concrete must be able to endure severe weather conditions such as freezing and thawing, wetting and drying, heating and cooling, chemicals, deicing agents, and the like. An increase of concrete durability will enhance concrete resistance to severe weather conditions.

Density: For certain applications concrete may be used primarily for its weight characteristics. Examples are counterweights, weights for sinking pipelines under water, shielding from radiation, and insulation from sound.

Generation of heat: If the temperature rise of the concrete mass is not held to a minimum and the heat is allowed to dissipate at a reasonable rate, or if the concrete is subjected to severe differential or thermal gradient, cracking is likely to occur."

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