Planning and Preparation
Before you begin your project, it is important to properly plan and prepare. Proper planning will save time in the end, and helps to ensure your satisfaction with the final product. If you are unsure of how much concrete you need or if the area is suitable for concrete, give Cascade Mobile Mix & Concrete Line Pumping a call today. Our staff is experienced and will answer all of your questions.
For common household projects - driveways, walkways, and patios – 4 inches thick should do the trick. Thicker concrete is recommended for heavy-duty use or heavy vehicles. It is recommended to use a ¾ minus crushed gravel compacted base. You can get a compactor from a rental equipment store. Drainage industry standard calls for a slope of ¼ inch per foot away from structures. Some projects may be able to use ⅛ inch slope.
While taking care to only dig as deep as necessary (to avoid power lines call your local utilities for a locator), ensure you remove tree roots, leaves, wood and any other organic matter in the desired area.
Install expansion joint material anywhere concrete will come into contact with existing slabs, steps or buildings. The expansion joint should reach the bottom of the slab. This ensures the new slab will be separated from existing structures and will help reduce cracking.
Now that you have your planning down, we suggest you use our Concrete Calculator to determine your exact needs.
Specifying the correct mix for your job can be the difference between long-term satisfaction and disaster. Concrete specifications consist of strength (PSI), slump (thickness) and chemical additives.
Concrete Exposed to freezing and thawing temperatures should have a compression strength of at least 3,000 psi and have at least 5% entrained air (+/- 1.5%). Air entrainment allows for the expanded water when frozen to travel into the air voids created by the air additive. Without the air, concrete is more susceptible to cracking.
For our northwest environment, we recommend a slump of 4 inches (+/- 1"). Note: a slump greater than 4" may prolong the time you have to wait before finishing, particularly in cool weather. It will also increase the tendency for shrinkage cracking.
This will ensure your slab won't settle or vary in thickness. Make sure to compact the soil/gravel base in the area where concrete will be placed.
Take care to stake your forms securely to the ground, while paying close attention to the slope (for proper drainage). Straight 2x4s are perfectly adequate to use as forms. Make sure the edges of your pour are at least 4" thick.
In addition to air entrainment admixtures, chemical additives may be used to accelerate or retard setting, reduce bleed water or plasticize the concrete.