Frequently Asked Questions
Cement & Concrete Technology Home > FAQs

Questions are grouped by the following topics:

• Cement Basics
• Concrete Design and Production
• Concrete Construction
• Troubleshooting/Repair
• Special Concretes
• Testing
• Durability

Click on the questions to get the answers.

Cement Basics

• What is the difference between European and ASTM cement specifications and where can I order foreign standards?
• What are Type I/II or Type II/V cements?
• How is white cement different and why is it used in decorative concrete?
• What is "natural" cement?
• What are the different forms of sulfate in portland cement and how can I analyze cement for SO₃?

Concrete Design and Production

• What is the relationship between compressive and flexural strength?
• How much cement is needed for a small concrete mixture?
• What are the unit weights (densities) of cement and concrete?
• On what basis is air content for concrete specified?
• Can we add air-entraining admixture at the jobsite?
• What is meant by "saturated surface dry condition" of aggregates?
• How do I design for moisture sensitive floor coverings?
• What are supplementary cementitious materials (SCMs) and how do they differ from blended cements?
• Which type of portland cement should be used for concrete countertops?
• How much additional curing time will be required for mass concrete applications?
• What are typical strength ranges of concrete and where is it appropriate to use them?

Concrete Construction

• Can fibers replace wire mesh or welded wire fabric in a concrete slab on ground?
• What precautions do I have to take during cold-weather concreting?
• What precautions do I have to take during hot-weather concreting?
• Joints: What types are used and where?
• How are exposed-aggregate concrete finishes produced?
• What are the best ways to store bags of cement?
• What construction practices can affect the air content of concrete?
• What is the effect of high concrete temperature (above 77°F) on transporting, placing, and finishing concrete, and on hardened concrete properties?
• Are there risks in using aluminum railings for concrete balconies?
• What are the differences between Codes, Standards, and Specifications, and how are they related?
• What curing method should be used for slabs that will receive a moisture sensitive floor covering?
  

Troubleshooting/Repair

• What causes concrete slabs to curl/warp, and how can this mechanism be minimized?
• What can I do about moisture problems in a new concrete building?
• What causes concrete to crack?
• Does muriatic acid darken concrete?
• How can I remove graffiti from concrete?
• What could have caused dark spots in a driveway?
• How can I repair a pitted concrete platform surface?
• Pinto concrete—Is there a cure?
• Does penetration and saturation of concrete by machine lubricating oil cause concrete deterioration and strength loss?
• What is "scaling" and how does it affect long term durability of flatwork?
• What causes random concrete cracks and can they be avoided?
• What causes early stiffening and what is the difference between false set and flash set?
• What is the moisture content of concrete?
• What can be done to repair a widened joint on a patio due to settling subgrade?

Special Concretes

• What is self-consolidating concrete (SCC) and how is it tested?
• What differences can I expect in the behavior and properties of recycled-aggregate concrete compared to concrete made with natural aggregates?
• Where can I go for concrete countertop information?
• Can I use colorants/pigments in a shotcrete application and change the color over the length of a wall?
• How can pervious concrete be used for storm water management?
• What happens to oil that drips on pervious concrete?
  

Testing

• What are advantages and disadvantages of the different air tests?
• How can I test for alkali-silica reactivity (ASR)?
• Can rebound hammer reliably measure compressive strength?
• How are fire resistance ratings for concrete determined?
• What are the Sound Transmission Class (STC) ratings for concrete and masonry walls?
• What test methods are available to determine water-soluble sulfates in soil or water that could be included in a project specification?
• When should field-cured cylinders be used versus laboratory-cured cylinders?

Durability

• How does rain affect fresh concrete?
• Is there an admixture that prevents scaling?
• What effects do deicers have on concrete?
• What causes efflorescence and how can it be avoided?
• What is ettringite and does it or the sulfate in cement contribute to expansion and
  disintegration of portland cement concrete?
• Can water cause deterioration of concrete?
• How do you diagnose damage from alkali-silica reaction (ASR) in a concrete structure?
• Can lightweight concrete be used for bridge construction?

For questions and answers related to concrete pavements click here.

For basic Q&A about cement and concrete click here.

Couldn’t find an answer to your question? Call Terry Collins at 847-972-9170 or email tcollins@cement.org.

 
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