Everything you need to know about concrete:
Concrete is a mixture of six components:
1. Cement
2. Coarse Aggregate (rock)
3. Fine Aggregate (sand)
4. Water
5. Flyash
6. Chemical Admixtures (to enhance a variety of characteristics)
The aggregate comprises from 60% to 75% of a concrete mixture, and cement paste (the combination of cement, water, and possibly flyash) makes up the difference. At Cantera Materials we use a Type II Portland Cement; Type II cement is rated as "Moderate Sulfate Resisting." Below, you will find a table defining the types of Portland Cement. The coarse and fine aggregates we use at Cantera Materials meet ASTM C-33, which ensures their quality and consistency. We use potable water, which can be provided at 35 degrees Fahrenheit in the summer, or 140 degrees Fahrenheit in the winter. We suggest the use of flyash in many different situations, which will be discussed fully later; our flyash is a Boral flyash.
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Types of Cement:
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Type I
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Normal
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Type IA
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Normal, air-entraining
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Type II
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Moderate sulfate resistance
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Type IIA
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Moderate sulfate resistance, air-entraining
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Type III
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High early
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Type IIIA
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High early, air-entraining
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Type IV
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Low heat of hydration
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Type V
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High sulfate resistance
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WATER-CEMENT RATIO The Water-Cement Ratio of a concrete mixture is critical to its overall quality. Generally, a lower water-cement ratio allows for increased compressive and flexural strength, a better bond between the concrete and reinforcing steel, reduced shrinkage cracking, lower permeability, and a better resistance to wear and weather. In other words, the less water the better!
INCREASED COMPRESSIVE AND FLEXURAL STRENGTH These are engineered properties of a concrete mixture. At Cantera Materials all our mixes have been tested and rated based on their compressive strength. If you require compressive strength histories on our mixes for qualification purposes please speak with our sales staff.
HOW TO DETERMINE THE WATER-CEMENT RATIO The water-cement ratio is determined simply by dividing the weight of the water in a cubic yard of the mix by the weight of the cement + flyash in the mix. The ratio will generally range from .35 to .70, and over .70 in grout mixtures. Water-cement ratio can also be determined by testing a hardened sample of the concrete in a Spectrographic SS laboratory.
FLYASH Flyash is a mineral admixture used in concrete to enhance finishing characteristics, make the mix more economical, and to improve pumping. Flyash is finer in consistency than cement, and its particles are round. These fine particles make the mix finish easier, and pump easier. It economizes the mix because it allows up to 30% of the cement volume to be replaced by flyash. Flyash is less expensive than cement, therefore the mix costs less. You may have heard that flyash decreases the compressive strength of concrete, this is only partially true. Flyash does slow the initial strength gain, however at 28 days the strength of a flyash mix and a cement mix are the same. We urge our customers to use flyash mixes whenever it fits into the specifications for the project.
CHEMICAL ADMIXTURES Admixtures are used to:
- Reduce water (lower water-cement ratio)
- Accelerate concrete setting time
- Retard concrete setting time
- Entrain air (for freeze thaw durability, YES it freezes in the desert!!)
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