CONCRETE 101 – 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. Fly Ash
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 fly ash) makes up the difference. At Sierra Ready Mix we use a Type II/V Portland Cement; Type II cement is rated as “Moderate Sulfate Resisting” and Type V cement is rated as “High Sulfate Resisting”. Sulfate Resistance is crucial in the Las Vegas valley due to the naturally occurring conditions in our soil. Below, you will find a table defining the types of Portland Cement. The coarse and fine aggregates we use at Sierra Ready Mix 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 fly ash in many different situations, which will be discussed fully later; our fly ash is a type F. Sierra Ready Mix uses Euclid Chemical Company Admixtures for concrete.
CONCRETE IS A MIXTURE OF SIX COMPONENTS
Type I – Normal
Type IA – Normal, air-entraining
Type II – Moderate sulfate resistance
Type IIA – Moderate sulfate resistance, air-entraining
Type III – High early
Type IIIA – High early, air-entraining
Type IV – Low heat of hydration
Type V – High sulfate resistance
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 Sierra Ready Mix 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 + fly ash 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.
FLY ASH Fly Ash is a mineral admixture used in concrete to enhance finishing characteristics, make the mix more economical, and to improve pumping. Fly ash 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 fly ash. Fly ash is less expensive than cement, therefore the mix costs less. You may have heard that fly ash decreases the compressive strength of concrete, this is only partially true. Fly ash does slow the initial strength gain, however at 28 days the strength of a fly ash mix and a cement mix are the same. We urge our customers to use fly ash mixes whenever it fits into the specifications for the project.
CHEMICAL ADMIXTURES Sierra Ready Mix uses Euclid Chemical Company Admixtures for concrete. 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!!)