What is cement mix? – A cement mix is a preparation of concrete for construction. It is a mixture of cement, stones, sand, and water. The mix is created with the proper ratio of substances, which is eventually used for building purposes. Cement, in this mix, acts as a binder and offers compressive strength.

What is the ratio to mix cement?

In terms of the ratio for concrete, it depends on what strength you are trying to achieve, but as a general guide a standard concrete mix would be 1 part cement to 2 parts sand to 4 parts aggregates. For foundations, a mix of 1 part cement to 3 parts sand to 6 parts aggregates can be used.

What mix makes the strongest concrete?

Q: This summer I’ve got a few outdoor projects that involve pouring small amounts of concrete. I looked into having a ready-mix truck do it, but the cost is so expensive. I’ve seen the bags of concrete mix in stores. Is it any good? Have you used it? Can I modify the mix to increase the strength? If so, what do you use and how? Malcolm McC., Albany, Ga.

A: I can clearly remember my first experience working with this magic material. I formed and poured a large set of steps that led up to the front door of the first house I remodeled. Looking back, it was too big a project for a rookie. That said, the job turned out not too bad! The good news is the bagged concrete mix you can buy at local hardware stores is a fantastic product.

The man who invented it built his first plant just a few miles from my childhood home in Cincinnati. It’s important to realize that basic concrete contains just four ingredients: small rocks, sand, Portland cement and water. The cement is the glue or binder that holds the sand and rocks together.

1. When water is added to the other three ingredients, it starts a chemical reaction.
2. Countless invisible Portland cement crystals start to form and interlock the sand and rock together.
3. I’ve used bagged concrete for years and had great success with it.
4. My two most recent uses were for the in-ground piers that support a massive deck and the piers for my giant two-story shed.

The piers are going to last for many decades because I used the right amount of water to mix the concrete. Add too much water and you’ll ruin the concrete. You can add more Portland cement to bagged concrete to make it stronger. You can also add hydrated lime.

1. To make the strongest concrete, the sand should be sourced from volcanic lava that has a high silica content.
2. This is not easy to locate, and I’d not worry about it.
3. But you should get a bag of pure Portland cement and a bag of lime and add some of those two things.
4. Both ingredients are inexpensive.
5. Most bagged concrete comes in standard-size bags.

If I wanted to make it stronger, I’d take an old kitchen measuring cup and add 16 ounces of Portland cement and eight ounces dry measure of hydrated lime to each bag of concrete. You want to blend the extra cement and lime with the bagged concrete in dry form.

• Use a newer plastic mixing bag and roll around the dry ingredients before adding the needed water.
• The concrete should have the consistency of stiff applesauce when you add the correct amount of water.
• I’ve got many other bagged concrete tips and videos showing the magic plastic mixing bag at my AsktheBuilder.com website.

Just go to go.askthebuilder.com/concreteinabag, Tim Carter can call you on the phone to solve your problem. Go to his website and fill out the form at askthebuilder.com/ask-tim/,

How much water do I add to cement?

The water–cement ratio ( w/c ratio, or water-to-cement ratio, sometimes also called the water-cement factor, f ) is the ratio of the mass of water ( w ) to the mass of cement ( c ) used in a concrete mix: The typical values of this ratio f = w ⁄ c are generally comprised in the interval 0.40 and 0.60. The water-cement ratio of the fresh concrete mix is one of the main, if not the most important, factors determining the quality and properties of hardened concrete, as it directly affects the concrete porosity, and a good concrete is always a concrete as compact and as dense as possible.

1. A good concrete must be therefore prepared with as little water as possible, but with enough water to hydrate the cement minerals and to properly handle it.
2. A lower ratio leads to higher strength and durability, but may make the mix more difficult to work with and form.
3. Workability can be resolved with the use of plasticizers or super-plasticizers,

A higher ratio gives a too fluid concrete mix resulting in a too porous hardened concrete of poor quality. Often, the concept also refers to the ratio of water to cementitious materials, w/cm. Cementitious materials include cement and supplementary cementitious materials such as ground granulated blast-furnace slag (GGBFS), fly ash (FA), silica fume (SF), rice husk ash (RHA), metakaolin (MK), and natural pozzolans,

1. Most of supplementary cementitious materials (SCM) are byproducts of other industries presenting interesting hydraulic binding properties.
2. After reaction with alkalis (GGBFS activation) and portlandite ( Ca(OH) 2 ), they also form calcium silicate hydrates (C-S-H), the “gluing phase” present in the hardened cement paste.

These additional C-S-H are filling the concrete porosity and thus contribute to strengthen concrete. SCMs also help reducing the clinker content in concrete and therefore saving energy and minimizing costs, while recycling industrial wastes otherwise aimed to landfill,

• The effect of the water-to-cement (w/c) ratio onto the mechanical strength of concrete was first studied by René Féret (1892) in France, and then by Duff A.
• Abrams (1918) (inventor of the concrete slump test ) in the USA, and by Jean Bolomey (1929) in Switzerland.
• The 1997 Uniform Building Code specifies a maximum of 0.5 w/c ratio when concrete is exposed to freezing and thawing in moist conditions or to de-icing salts, and a maximum of 0.45 w/c ratio for concrete in severe, or very severe, sulfate conditions.

Concrete hardens as a result of the chemical reaction between cement and water (known as hydration and producing heat ). For every mass ( kilogram, pound, or any unit of weight ) of cement (c), about 0.35 mass of water (w) is needed to fully complete the hydration reactions.

However, a fresh concrete with a w/c ratio of 0.35 may not mix thoroughly, and may not flow well enough to be correctly placed and to fill all the voids in the forms, especially in the case of a dense steel reinforcement, More water is therefore used than is chemically and physically necessary to react with cement.

Water–cement ratios in the range of 0.40 to 0.60 are typically used. For higher-strength concrete, lower w/c ratios are necessary, along with a plasticizer to increase flowability. A w/c ratio higher than 0.60 is not acceptable as fresh concrete becomes “soup” and leads to a higher porosity and to very poor quality hardened concrete as publicly stated by Prof.

Gustave Magnel (1889-1955, Ghent University, Belgium) during an official address to American building contractors at the occasion of one of his visits in the United States in the 1950’s to build the first prestressed concrete girder bridge in the USA: the Walnut Lane Memorial Bridge in Philadelphia open to traffic in 1951.

The famous sentence of Gustave Magnel, facing reluctance from a contractor, when he was requiring a very low w/c ratio, zero-slump, concrete for casting the girders of this bridge remains in many memories: “American makes soup, not concrete”, When the excess water added to improve the workability of fresh concrete, and not consumed by the hydration reactions, leaves concrete as it hardens and dries, it results in an increased concrete porosity only filled by air,

A higher porosity reduces the final strength of concrete because the air present in the pores is compressible and concrete microstructure can be more easily ” crushed “. Moreover, a higher porosity also increases the hydraulic conductivity ( K, m/s) of concrete and the effective diffusion coefficients ( D e, m 2 /s) of solutes and dissolved gases in the concrete matrix.

This increases water ingress into concrete, accelerates its dissolution ( calcium leaching ), favors harmful expansive chemical reactions ( ASR, DEF), and facilitates the transport of aggressive chemical species such as chlorides ( pitting corrosion of reinforced bars ) and sulfates (internal and external sulfate attacks, ISA and ESA, of concrete) inside the concrete porosity.

• When cementitious materials are used to encapsulate toxic heavy metals or radionuclides, a lower w/c ratio is required to decrease the matrix porosity and the effective diffusion coefficients of the immobilized elements in the cementitious matrix.
• A lower w/c ratio also contributes to minimize the leaching of the toxic elements out of the immobilization material.

A higher porosity also facilitates the diffusion of gases into the concrete microstructure, A faster diffusion of atmospheric CO 2 increases the concrete carbonation rate, When the carbonation front reaches the steel reinforcements (rebar), the pH of the concrete pore water at the steel surface decreases.

At a pH value lower than 10.5, the carbon steel is no longuer passivated by an alkaline pH and starts to corrode ( general corrosion ). A faster diffusion of oxygen ( O 2 ) into the concrete microstructure also accelerates the rebar corrosion. Moreover, on the long term, a concrete mix with too much water will experience more creep and drying shrinkage as excess water leaves the concrete porosity, resulting in internal cracks and visible fractures (particularly around inside corners), which again will reduce the concrete mechanical strength.

Finally, water added in excess also facilitates the segregation of fine and coarse aggregates ( sand and gravels ) from the fresh cement paste and causes the formation of honeycombs (pockets of gravels without hardened cement paste) in concrete walls and around rebar.

It also causes water bleeding at the surface of concrete slabs or rafts (with a dusty surface left after water evaporation). For all the afore mentioned reasons, it is strictly forbidden to add extra water to a ready-mix concrete truck when the delivery time is exceeded, and the concrete becomes difficult to pour because it starts to set.

Such diluted concrete immediately loses any official certification and the responsibility of the contractor accepting such a deleterious practice is also engaged. In the worst case, an addition of superplasticizer can be made to increase again the concrete workability and to salvage the content of a ready-mix concrete truck when the maximum concrete delivery time is not exceeded.

What is M10 and M25 concrete?

If 150 mm cube of nominal mix is casted & its compressive strength is checked after 28 days. If it’s found to 10 N/mm2, then it is designated as M10. Similarly, if the compressive strength is 15 or 20 N/mm2 then it’s designated as M15 & M20.

What is the ratio of cement sand and water?

A general teacher’s guide for concrete preparation – The physical properties of density and strength of concrete are determined, in part, by the proportions of the three key ingredients, water, cement, and aggregate. You have your choice of proportioning ingredients by volume or by weight.

Proportioning by volume is less accurate, however due to the time constraints of a class time period this may be the preferred method. A basic mixture of mortar can be made using the volume proportions of 1 water : 2 cement : 3 sand. Most of the student activities can be conducted using this basic mixture.

Another “old rule of thumb” for mixing concrete is 1 cement : 2 sand : 3 gravel by volume. Mix the dry ingredients and slowly add water until the concrete is workable. This mixture may need to be modified depending on the aggregate used to provide a concrete of the right workability.

• The mix should not be too stiff or too sloppy.
• It is difficult to form good test specimens if it is too stiff.
• If it is too sloppy, water may separate (bleed) from the mixture.
• Remember that water is the key ingredient.
• Too much water results in weak concrete.
• Too little water results in a concrete that is unworkable.

Suggestions:

1. If predetermined quantities are used, the method used to make concrete is to dry blend solids and then slowly add water (with admixtures, if used).
2. It is usual to dissolve admixtures in the mix water before adding it to the concrete. Superplasticizer is an exception.
3. Forms can be made from many materials. Cylindrical forms can be plastic or paper tubes, pipe insulation, cups, etc. The concrete needs to be easily removed from the forms. Pipe insulation from a hardware store was used for lab trials. This foam-like material was easy to work with and is reusable with the addition of tape. The bottom of the forms can be taped, corked, set on glass plates, etc. Small plastic weighing trays or Dairy Queen banana split dishes can be used as forms for boats or canoes.
4. If compression tests are done, it may be of interest to spread universal indicator over the broken face and note any color changes from inside to outside. You may see a yellowish surface due to carbonation from CO 2 in the atmosphere. The inside may be blue due to calcium hydroxide.
5. To answer the proverbial question, “Is this right?” a slump test may be performed. A slump test involves filling an inverted, bottomless cone with the concrete mixture. A Styrofoam or paper cup with the bottom removed makes a good bottomless cone. Make sure to pack the concrete several times while filling the cone. Carefully remove the cone by lifting it straight upward. Place the cone beside the pile of concrete. The pile should be about 1/2 to 3/4 the height of the cone for a concrete mixture with good workability. (SEE DIAGRAM)
6. To strengthen samples and to promote hydration, soak concrete in water (after it is set).
7. Wet sand may carry considerable water, so the amount of mix water should be reduced to compensate.
8. Air bubbles in the molds will become weak points during strength tests. They can be eliminated by:
   • i. packing the concrete.
   • ii. Tapping the sides of the mold while filling the mold.
   • iii. “rodding” the concrete inside the mold with a thin spatula.
9. Special chemicals called “water reducing agents” are used to improve workability at low water to cement ratios and thus produce higher strengths. Most ready-mix companies use these chemicals, which are known commercially as superplasticizers. They will probably be willing to give you some at no charge.
10. You can buy a bag of cement from your local hardware store. A bag contains 94 lb. (40kg) of cement. Once the bag has been opened, place it inside a garbage bag (or two) that is well sealed from air. This will keep the cement fresh during the semester. An open bag will pick up moisture and the resulting concrete may be weaker. Once cement develops lumps, it must be discarded. The ready mix company in your area may give you cement free of charge in a plastic pail.

How much cement do I mix with water?

The mixture ratio is as follows: 1 part cement.4 parts sand.0,5 part water.