Whether you should use ready-mix concrete or site-mix concrete depends on the project at hand, given that each comes with benefits and disadvantages. topremodelers.com can recommend you quality contractors ,but what you can be sure of, though, is that ready-mix concrete is more durable of the two, and if the site permits, it may well be a better alternative.
The use of ready-mix concrete (RMC) began in the 1930s, although it found widespread popularity only by the 1960s. Since then, using ready-mix concrete has become commonplace in most parts of the world. Manufactured in a factory or a batching plant, ready-mix concrete comes with a mixture of materials in exact proportions. Delivery typically takes place through in-transit mixers or barrel trucks. In some cases, the ready-mix is delivered dry and then mixed on site using a volumetric concrete mixer.
Ready-mix concrete uses a mixture of cement and water along with aggregates such as sand, crushed stone, and gravel. Manufacturers usually sell ready-mix concrete by volume, expressed in cubic yards in the US. While purchasing raw materials required for making ready-mix concrete is simple, it might take multiple efforts before you get the proportions right. As a result, it is best that you get it through a dependable manufacturer.
While ready-mix concrete comes with advantages, it also has its share of limitations too.
- Quality. When sourced through a reputable manufacturer, you can be sure that the ready-mix concrete is made using high quality raw materials and in the right conditions.
- The time factor. Construction speed can be considerably faster when you use ready-mix concrete instead of site-mixed concrete. Since the concrete is mixed before it gets to your site, and with no mixing equipment to erect and dismantle, you can focus on what you do best and save some time for your business. What also helps is that you get timely delivery no matter whether your requirement is large or small.
- Reduced cost. Ready-mix concrete generally comes with more durability when compared to site-mixed concrete. This results in an increase in the life of the structure and lower life-cycle costs. In addition, since you will not need to hire any equipment, there are no depreciation costs to worry about.
- Reduced use of cement. Typical ready-mix concrete results in the reduction of cement use by around 10%. This is because of using correct proportions as well as better handling. Reducing the use of cement even more is possible by the addition of suitable cementitious materials or mineral admixtures.
- Reduced pollution. Ready-mix concrete makes use of cement in bulk so you don’t have to worry about the dust pollution that results from using bagged cement. This will also lead to a slight reduction in how much cement you will need.
- Better for the environment. Reduced cement use leads to a reduction in environmental pollution, both noise and air. Besides, this aspect also helps in conserving resources and energy.
- Versatility. Getting ready-mix concrete tailor-made to meet your needs is easy, and this gives you the freedom to use it and place it in different ways.
- The human touch. In case of mixing concrete, an absence of the human touch might just work in your favor. Ready-mix concrete reduces dependency on labor and also benefits through minimized human errors.
- No need for storage space. If you plan to use site-mixed concrete, you will need to account for space where you can store raw materials such as cement, aggregates, admixtures, and water.
- Distance and accessibility. The mixing process begins at the batching plant and travel time can be a concern in cases of longer distances. In case the distance between a plant and a site is too long, using an admixture such as retarder is a solution. Access roads and the site itself play roles in the transportation of the mixture, given that they should be able to withstand the weight of the truck and the mix. If this is a problem, consider using companies that provide smaller ready-mixers.
- The setting. The placement of untreated ready-mix concrete should ideally take place within three and a half hours from the time the batching begins. The use of admixtures such as retarders, plasticizers, and superplasticizers helps override this problem. However, these additives may result in a longer-than-expected setting time that may lead to problems with placement. Incorrect use of these additives may also lead to decreased durability.
- Placing arrangements. Given usual requirements, a large quantity of ready-mix concrete is made available is relatively short time period. This requires that you make special arrangements for placing ahead of time. You should also factor in some loss of workability because placement cannot take place immediately after the mix is prepared.
Ready-Mix vs. Site-Mix Concrete
Comparing ready-mix concrete with site-mix concrete requires that you address different aspects, which include:
- Cost. Site-mix concrete usually serves as a more cost effective alternative in the short-term.
- Manpower. Site-mix concrete requires skilled and unskilled labor for mixing, shifting the mix, laying, and compacting. With the read-mix alternative, you will only need skilled labor to lay and compact the concrete.
- Consistency of concrete. Achieving the right consistency with site-mix concrete requires expertise, whereas the proportioning of materials that go into a ready-mix is handled by a computer program.
- Time taken. Using site-mix concrete will require that you spend around 50% more time when compared to using ready-mix concrete.
- Quality control. When working with site-mix concrete, it is crucial that you maintain high quality to achieve the required compressive strength. With ready-mix concrete, you simply need to pick a reliable manufacturer.
- Required space. Working with site-mix concrete requires that you have enough space to store raw materials and machinery. In case of ready-mix concrete, access to the site should come through no less than a 30-foot road, giving the mix truck enough room to maneuver.
- Lab testing. While site-mix concrete rarely makes it to a lab for testing, reputable manufacturers of ready-mix concrete make sure they carry out all required tests.
Site-Mix Concrete Ratio
The ratio of constituents used in site-mix concrete may vary depending on the application at hand. For example, the use of C20 or Gen 3 concrete is common in projects that involve driveways or bases for workshops. C35 or PAV2 concrete, on the other hand, is more heavy-duty, and finds use in surfaces that are subject to constant loading and scraping because of industrial vehicles and/or machinery.
Ratio for a C20P Concrete Mix
When going for a C20P mix, you will need one part Portland cement, two parts fine aggregate, and four parts of coarse aggregate. If you plan to use premixed ballast, the ratio will be one part cement to six parts of ballast. In ideal weather conditions, the cement to water ratio stands at 1 to 0.55. Make sure you account for the sand containing some moisture, in which case you will need lesser water. More than required water will make the mix sloppy, in which case it might not be able to support itself.
Ratio for a C35P Concrete Mix
If you require this heavy-duty mix, you will need one part Portland cement, one part stone, and two parts sand. Alternatively, you can go with one part of Portland cement and three parts of ready-mixed aggregate.
Getting the measurements right is crucial no matter what kind of a mix you are after. While using a simple bucket might do the trick, consider using a builder’s bucket if you are going for exact proportions. If you need no more than a small amount of mix to carry out a task such as concretizing a few fence posts, take care not to whip up a large quantity. For small jobs, you may even consider getting a do-it-yourself concrete kit from your local home improvement store.
Using your hand to mix concrete is not a good idea, even if you have a small project. It is highly unlikely that you will get the right consistency, which will result in a weak end-product. If you don’t want to buy a cement mixer, you may consider renting one from a local tool shop.
No matter what kind of concrete mix you need, use this order when going through the process. Start with around 75% of water and 50% of the aggregates. Follow this by adding all the cement, and then add the remaining water and aggregates.
The table below gives you a fair indication of how much raw material you need to come up with one cubic yard, or 27 cubic feet, of 3,000 psi and 4,000 psi concrete.
|For 3,000 psi concrete||For 4,000 psi concrete|
|Cement||517 lb||611 lb|
|Sand||1,560 lb||1,450 lb|
|Stone||1,600 lb||1,600 lb|
|Water||32 to 42 gal||33 to 35 gal|
The mixing ratio for 3,000 psi concrete will result in a strong mix that will work well with most projects. Adding extra cement and slightly lesser sand, as is the case when preparing 4,000 psi concrete, will give you even stronger concrete that is best used in projects that involve industrial spaces, commercial garages, outdoor patios, driveways, and pool-decks.
If you’re wondering how much concrete you might need, one cubic yard of concrete can help you fill 80 square feet at a thickness of four inches. If you increase the thickness to six inches, you will have enough concrete to fill 52 square feet.