Global Civil Engineering

Cement & Concrete Basics FAQs

  • Are there different types of Portland cement?

    Though all portland cement is basically the same, eight types of cement are manufactured to meet different physical and chemical requirements for specific applications:

    • Type I is a general purpose portland cement suitable for most uses.
    • Type II is used for structures in water or soil containing moderate amounts of sulfate, or when heat build-up is a concern.
    • Type III cement provides high strength at an early state, usually in a week or less.
    • Type IV moderates heat generated by hydration that is used for massive concrete structures such as dams.
    • Type V cement resists chemical attack by soil and water high in sulfates.


  • How can you tell if you’re getting the amount of concrete you’re paying for?

    The real indicator is the yield, or the actual volume produced based on the actual batch quantities of cement, water and aggregates. The unit weight test can be used to determine the yield of a sample of the ready mixed concrete as delivered. It’s a simple calculation that requires the unit weight of all materials batched. The total weight information may be shown on the delivery ticket or it can be provided by the producer. Many concrete producers actually over yield by about ½ percent to make sure they aren’t short-changing their customers. But other producers may not even realize that a mix designed for one cubic yard might only produce 26.5 cubic feet or 98 percent of what they designed.

  • How do you control the strength of concrete?


  • How do you protect a concrete surface from aggressive materials like acids?

    Many materials have no effect on concrete. However, there are some aggressive materials, such as most acids, that can have a deteriorating effect on concrete. The first line of defense against chemical attack is to use quality concrete with maximum chemical resistance, followed by the application of protective treatments to keep corrosive substances from contacting the concrete. Principles and practices that improve the chemical resistance of concrete include using a low water-cement ratio, selecting a suitable cement type (such as sulfate-resistant cement to prevent sulfate attack), using suitable aggregates, water and air entrainment. A large number of chemical formulations are available as sealers and coatings to protect concrete from a variety of environments; detailed recommendations should be requested from manufacturers, formulators or material suppliers.

  • How do you remove stains from concrete?




  • How is portland cement made?

    Cement manufacturers mine materials such as limestone, shale, iron ore, and clay, crushed and screened the rock, and place it in a cement kiln. After being heated to extremely high temperatures, these materials form a small ball called “clinker” that is very finely grounded to produce portland cement.

    Lime and silica make up about 85 percent of the ingredients of cement. Other elements include alumina and iron oxide. The rotating kiln that cooks the materials resembles a large horizontal pipe with a diameter of 10 to 15 feet and a length of 300 feet or more. One end is raised slightly. The raw mix is placed in the high end and as the kiln rotates the materials move slowly toward the lower end. Flame jets at the lower end heat all the materials in the kiln to high temperatures that range between 2,700 and 3,000 degrees Fahrenheit. This high heat drives off, or calcines, the chemically combined water and carbon dioxide from the raw materials and forms new compounds (tricalcium silicate, dicalcium silicate, tricalcium aluminate and tetracalcium aluminoferrite). For each ton of material that goes into the feed end of the kiln, two thirds of a ton comes out the discharge end, called clinker. This clinker is in the form of marble sized pellets. The clinker is very finely ground to produce portland cement. Manufacturers often add gypsum and/or limestone during the grinding process.

  • Is there a universal international specification for portland cement?

    Each country has its own standard for portland cement, so there is no universal international standard. The United States uses the specification prepared by the American Society for Testing and Materials-ASTM C-150 Standard Specification for Portland Cement. There are a few other countries that also have adopted this as their standard, however, there are countless other specifications. Unfortunately, they do not use the same criteria for measuring properties and defining physical characteristics so they are virtually “non-translatable.” The European Cement Association located in Brussels, Belgium, publishes a book titled “Cement Standards of the World.”

  • What are recommended mix proportions for good concrete?


    • A minimum cement content of six bags per cubic yard of concrete,
    • A maximum water content of 6 gallons per bag of cement,
    • A curing period (keeping concrete moist) a minimum of six days, and
  • What are the decorative finishes that can be applied to concrete surfaces?

  • What is 3,000 pound concrete?

    It is concrete that is strong enough to carry a compressive stress of 3,000 psi at 28 days. Concrete may be specified at other strengths as well. Conventional concrete has strengths of 7,000 psi or less; concrete with strengths between 7,000 and 14,500 psi is considered high-strength concrete.

  • What is alkali-silica reactivity (ASR)?

    Alkali-silica reactivity is an expansive reaction between reactive forms of silica in aggregates and potassium and sodium alkalis, mostly from cement, but also from aggregates, pozzolans, admixtures and mixing water. External sources of alkali from soil, deicers and industrial processes can also contribute to reactivity. The reaction forms an alkali-silica gel that swells as it draws water from the surrounding cement paste, thereby inducing pressure, expansion and cracking of the aggregate and surrounding paste. This often results in map-pattern cracks, sometimes referred to as alligator pattern cracking. ASR can be avoided through 1) proper aggregate selection, 2) use of blended cements, 3) use of proper pozzolanic materials and 4) contaminant-free mixing water.

  • What is the difference between cement and concrete?




  • Why do concrete surfaces flake and spall?


  • Why does concrete crack?


  • Will concrete harden under water?


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