V. PORTLAND CEMENT CONCRETE 



1 . Introduction . 



Concrete, a diversified construction material, exists in two physical 

 states--the first as a semifluid or plastic state while being mixed, 

 transported and placed in final forms; the second as a solid after having 

 set and cured. These features of concrete give it a wide application of 

 use in coastal and waterfront structures under many special conditions. 

 Ingredients for making concrete exist in virtually all areas of the world 

 and the use of it in coastal structures depends only on the understanding 

 and knowledge of the materials, design, and processes required for its end 

 use. Concrete has proven to be an excellent construction material. The 

 use of concrete is adaptable to many coastal structures. With good 

 planning it will probably find many additional uses in the future to take 

 advantage of its physical qualities. 



Concrete can be considered to be made of two components, aggregates 

 and paste. Aggregates are generally classified into two groups, fine and 

 coarse. Fine aggregates consist of sand with particle sizes smaller than 

 6 millimeters (0.25 inch); coarse aggregates are those with particle 

 sizes greater than 6 millimeters. Aggregates make up about 60 to 80 percent 

 of the concrete. The paste is composed of cement, water, and sometimes 

 admixtures and entrained air. Cement paste ordinarily constitutes 25 to 40 

 percent of total volume of concrete, cement being 7 to 15 percent and water 

 14 to 21 percent. Air and admixtures contents may range up to 8 percent. 



Formulation of concrete in this manner was developed in Portland, 

 England. Subsequently, the term Portland cement concrete has been used to 

 describe cement concretes generally. 



The durability of Portland cement concrete, defined as its ability to 

 resist weathering action, chemical attack, abrasion, or any other process 

 of deterioration, is a major factor in its excellence as a coastal con- 

 struction material. Durable concrete will retain its original form, 

 quality, and serviceability when exposed to its environment. 



This section discusses the material used in making concrete, including 

 additives that enhance its properties, the mixing of concrete, and the more 

 important causes of concrete deterioration in coastal structures. It gives 

 suggestions on how to prevent such damage, with particular attention to 

 damage caused by freezing and thawing, aggressive chemical exposure, 

 abrasion, reactive aggregates, and corrosion of embedded materials. 

 Repair methods for concrete that has not withstood the forces of deterior- 

 ation, and the use of protective coatings to enhance durability are also 

 discussed . 



2. Types of Portland Cement . 



Portland cement types and characteristics for coastal structures are 

 specified in ASTM Standards C150-78: 



(a) Type I cement is used in ordinary structural concrete for 

 foundations, roads, curbs, and ongrade foundations not subject to 

 marine exposure or freezing and thawing conditions. 



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