CONCRETE PIPE Cementitious Materials Portland Cement Portland cement, is a closely controlled chemical combination of calcium, silicon, aluminum, iron, and small amounts of other compounds, to which gypsum is added in the final grinding process to regulate the setting time of the concrete. Some of the raw materials used to manufacture cement are limestone, shells, and chalk or marl, combined with shale, clay, slate or blast furnace slag, silica sand, and iron ore. Lime and silica make up approximately 85 percent of the mass. Each step in the manufacture of portland cement is monitored by frequent chemical and physical tests. The finished product is analyzed and tested to ensure compliance with the applicable standards of specifying agencies. Type I. Normal Portland Cement — a general purpose cement suitable for all uses when the special properties of the other types are not required. It is used in pavement and sidewalk construction, concrete buildings and bridges, and any use not subject to sulfates or where the heat of hydration is not critical. Type II. Modified Portland Cement — has a lower heat of hydration than Type I, improved resistance to sulfate attack, and is intended for use in structures of considerable size to minimize temperature rise. Applications include large piers, heavy abutments and heavy retaining walls when the concrete is placed in warm weather. Type II cement is also intended for places where protection against sulfate attack is required, as in drainage structures where soil sulfate concentrations are higher than normal but not unusually severe. Type III. High Early Strength Portland Cement — is used where high early strengths are desired, such as when forms need to be removed as soon as possible, or when the concrete must be placed in service as quickly as possible. Other uses include cold weather construction so that the required period of protection against low temperatures can be reduced. Type IV. Low-Heat Portland Cement — is used where the amount and rate of heat generated must be kept to a minimum, but strength development also proceeds at a slower rate. It is intended for use only in mass concrete, such as large gravity dams, where temperature rise is a critical factor. Type V. Sulfate-Resistant Portland Cement — Type V cement is a special cement intended for use in structures exposed to severe sulfate action. It has a slower rate of strength development than normal portland cement. Type V cement has a maximum allowable C3A content of 5 percent, which provides better sulfate resistance than Type II cement. Lafarge utilizes Type V (Type 50) cement or similar blend (Type HS or HSb) as part of its standard concrete mix for concrete pipe. Fly Ash1 Fly ash is the finely divided residue that results from the combustion of pulverized coal, and is carried from the combustion chamber of a furnace by exhaust gases. Most commercially available fly ash is a byproduct of thermal-power-generating stations. 1 Concrete Pipe Design Manual, Ontario Concrete Pipe Association, 1998, Page 3-3 PAGE 14 LAFARGE PIPE eMANUAL