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Calculate exact amounts of cement, sand, gravel, and water for your concrete project. Get accurate material quantities and cost estimates for different concrete mix strengths.
For 0.00 cu yd
0 lbs (94 lb bags)
0.00 tons
0.00 tons
~5.5 gal per bag of cement
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A concrete mix is a combination of four main ingredients: Portland cement, sand (fine aggregate), gravel (coarse aggregate), and water. The proportions of these materials determine the strength, workability, and durability of the concrete.
The mix ratio is typically expressed as cement:sand:gravel by volume. For example, a 1:2:3 mix means 1 part cement, 2 parts sand, and 3 parts gravel. Water is added separately based on the desired consistency and typically ranges from 5-6 gallons per 94-pound bag of cement.
The ratio directly affects the concrete's compressive strength (PSI rating), workability, and cost. Higher cement content increases strength but also cost. Lower cement content may save money but produces weaker concrete unsuitable for structural applications.
| Application | PSI | Ratio | Cement (bags/cu yd) | Sand (cu ft) | Gravel (cu ft) |
|---|---|---|---|---|---|
| General Purpose | 3000 | 1:2.8:4.2 | 5 | 14 | 21 |
| Foundation | 3500 | 1:2.36:3.55 | 5.5 | 13 | 19.5 |
| High Strength | 4000 | 1:2:3 | 6 | 12 | 18 |
| Sidewalk/Driveway | 3000 | 1:2.8:4.2 | 5 | 14 | 21 |
Water: Add approximately 5-6 gallons per bag of cement for proper consistency
The binding agent that hardens and binds the aggregates together. Standard bags weigh 94 pounds (1 cubic foot). Type I/II is most common for general construction.
Types: Type I (general), Type II (moderate sulfate resistance), Type III (high early strength), Type IV (low heat), Type V (high sulfate resistance)
Fills voids between gravel and provides workability. Use clean, coarse sand free of clay, silt, and organic matter. Typical density: 100 lbs/cu ft.
Best practice: Use concrete sand (also called sharp sand or masonry sand) rather than fine play sand for better strength
Provides bulk volume and strength to concrete. Common sizes: 3/8 inch, 1/2 inch, 3/4 inch, and 1 inch. Larger projects typically use 3/4 inch gravel.
Sizing rule: Maximum aggregate size should be no more than 1/3 the thickness of the slab or 3/4 the spacing between reinforcing bars
Activates cement and allows concrete to be workable. Too much water weakens concrete; too little makes it difficult to work with. Use clean, potable water.
Water-cement ratio: For 4000 PSI concrete, use 0.45 water-to-cement ratio by weight (approximately 5.5 gallons per 94 lb bag)
| Strength (PSI) | Common Applications | Cure Time |
|---|---|---|
| 2500 PSI | Residential footings, patios | 28 days |
| 3000 PSI | Driveways, slabs, sidewalks | 28 days |
| 3500 PSI | Foundations, structural slabs | 28 days |
| 4000 PSI | Commercial floors, columns, beams | 28 days |
| 5000+ PSI | Heavy duty industrial, prestressed | 28 days |
PSI (pounds per square inch) measures compressive strength after 28 days of curing. Concrete reaches ~70% strength in 7 days and ~90% in 14 days.
Concrete should be wet enough to pour but not soupy. It should hold its shape when molded but flatten out slowly. Think "thick oatmeal" consistency.
Standard concrete mix begins setting in 30-90 minutes. In hot weather, work faster or use retarding admixtures. Mix only what you can place in 1 hour.
Consider accelerators (faster setting), retarders (slower setting), air entrainers (freeze resistance), or plasticizers (workability) for special applications.
Cement is just one ingredient in concrete - it's the powder that binds everything together. Concrete is the final product made from cement, sand, gravel, and water. Think of cement as flour and concrete as bread.
Yes. While more cement increases strength, excessive cement makes concrete more expensive, prone to cracking from shrinkage, and can reduce durability. Stick to proven mix ratios for your application.
For most applications, a water-to-cement ratio of 0.40 to 0.60 by weight is ideal. Lower ratios (0.40-0.45) create stronger concrete but are harder to work with. Higher ratios (0.55-0.60) are easier to place but weaker. A ratio of 0.50 (about 5.5 gallons per 94 lb bag) balances strength and workability.
For most residential projects, 3/4 inch crushed stone works well. Use 3/8 inch for thin slabs (less than 4 inches). The maximum aggregate size should not exceed 1/3 of the slab thickness. Larger aggregate (1-1.5 inch) is used for mass concrete pours.
Concrete reaches handling strength in 24-48 hours and walking strength in 3-7 days. However, it continues curing for 28 days to reach full design strength. Keep it moist during this time - spray with water or cover with plastic sheeting.
Rebar (#3 or #4) is recommended for structural applications, driveways, and slabs over 4 inches thick. Wire mesh (6x6 W1.4xW1.4) works for sidewalks and thin slabs. Fiber reinforcement can be added to the mix for crack control in both cases.
Ideal temperature is 50-85°F. Below 40°F, use heated water and insulating blankets. Above 90°F, work early morning, add ice to mix water, use retarding admixtures, and keep concrete moist to prevent rapid drying and cracking.
Admixtures modify concrete properties. Common types: plasticizers (improve workability), accelerators (faster setting in cold weather), retarders (slower setting in hot weather), air entrainers (freeze-thaw resistance), and waterproofing agents. Consult manufacturer guidelines for proper dosing.
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