Many times, the average person uses the terms “cement” and “concrete” interchangeably without realizing that there is a difference. Even when the handyman refers to “cement,” there is often a question as to exactly what he means. Before going into the details on mixing and various projects, here is a definition of terms:
1. Portland cement is a manufactured product purchased in sacks that usually contain 1 cubic foot.
2. Cement is a mixture of Portland cement, sand and water.
3. Concrete is a mixture of Portland cement and sand with gravel added to give it strength and bulk, plus water. concreter sydney
4. Mortar is a mixture of Portland cement, sand and water with about 10% hydrated lime added.
5. Grout is a flowing mass of cement or concrete.
How Much of Each?
For most cement jobs – to set flagstones or patch a house foundation, you need 1 part of Portland cement to 2½” parts of clean, fine sand.
For concrete jobs, the proportion varies depending upon the use to which the concrete is put.
For mortar mixes – for playing brick or concrete block or repointing brick – use 1 part mortar cement or 1 part Portland cement with 10% lime added to 2½^” parts fine, clean sand plus water.
Basic Tools for Concrete Work
Here are several of the basic tools you need when doing cement or concrete work about the house:
1. General-purpose trowel – for placing cement or concrete when doing any concrete work.
2. Pointing trowel – for smaller repair and patching jobs and also finishing details, especially the joint between rows of brick.
3. Wood float – for finishing the surface, making it smooth but with a gritty texture.
4. Steel float – for finishing the surface, making it smooth, slick and hard.
5. Edger – for finishing sidewalks and large surfaces where rounded corners are desired.
6. Strike board – for striking off the excess of the concrete; it leaves the surface level.
7. Tamper – for removing air inclusions in thick sections of freshly poured concrete.
8. Broom – for finishing surface of concrete jobs with a rough, non-slip surface.
Making a Measuring Box
When doing any extensive mixing of your own cement or concrete, a measuring box is exceedingly helpful, especially when using large quantities. You can make this bottomless measuring box in just a few minutes and avoid counting the ingredients by the shovels-full.
Use ¾” plywood or 1″ thick lumber to make a box with four sides – a cubic foot – 12″ high, 12″ wide and 12″ deep. Secure the sides with screws set about 2″ apart. Two short lengths of 2×2 attached on the sides make it easy to move the measuring box about.
How to Mix
All the ingredients must be thoroughly mixed to do the job. If you have failed to mix the Portland cement with the other materials, you undoubtedly will encounter difficulty later; the job just won’t turn out right. If you follow several basic rules, you will be able to handle cement and concrete like an expert.
1. Mix the cement or concrete near the place where it is to be used.
2. Mix the cement or concrete just before you are ready to use it. Once mixed, the cement or concrete begins to set.
3. You can mix cement or concrete in a wheelbarrow, on any concrete surface or on a sheet of ply-wood. However, once you have finished pouring the mix, wash the surface off completely so that no cement or concrete hardens and sticks.
4. It is best for the homeowner doing a job to mix about a half a bag of Portland cement with the needed amounts of sand and gravel (when making concrete). This is about the most convenient amount for a handyman to handle at one time.
5. Mix the Portland cement and sand thoroughly when dry. After these two are fully mixed you can add gravel when making concrete.
6. Only after the gravel is thoroughly blended in with the Portland cement and sand should you add the water.
7. Always measure the ingredients – don’t just guess. As a guide, if you don’t have a “measuring box,” use a shovel to measure. Remember that 1 shovel of Portland cement is equal to 1 shovel of damp sand or 2 shovels of dry sand or 2 shovels of gravel.
8. Follow the formula necessary for the mix you are preparing. Cement and concrete used for different purposes contain different proportions of Portland cement, sand and gravel.
9. When mixing concrete, the size of the gravel you use depends upon the thickness of the concrete you are pouring. The gravel should be not less than one-fourth nor more than one-third the thickness of the concrete mass. For example, when pouring a 4″ thick layer of concrete, use clean, hard gravel in sizes from ¼” up to about 1″ or 1½”.
READY-MIXED CONCRETE – Relatively new is the availability of already mixed concrete from local companies. The concrete is delivered in a special truck and is ready for pouring in place.