Low-quality cement how to determine. How to understand that the cement has expired? Special instruments for express analysis
Modern construction has long been unimaginable without the great invention of the 19th century - Portland cement. The cement sales market is huge, and this circumstance could not go unnoticed by all sorts of scammers who are trying to sell counterfeit, low-quality or non-compliant cement.
Meanwhile, industrial construction is carried out with mixtures with an exact dosage of cement and fillers. A technologist at a reinforced concrete plant, by calculating the proportions of mixtures, can obtain building concrete with desired properties. And in the case of low-quality cement, this becomes simply impossible.
That is why laboratories must operate at each precast concrete enterprise, where Portland cement will be tested before it enters the commercial batch of concrete.
Cement falsification
As a dilution of cement, fraudsters can use mineral powder for the production of asphalt concrete, dolomite dust (used as a filler in powder fire extinguishers), old clumped and re-ground cement, fly ash, etc.
Express analysis of cement
It should be noted that a complete and reliable test of the quality of cement can only be carried out in the laboratory. But there is also an express analysis, which is done literally in 15-20 minutes. This rapid test can reveal outright fake when obviously foreign substances are added to the tested cement powder.
So, cement is a finely dispersed powder, completely homogeneous, gray (in a shade from light to dark gray or gray-green) in color. Fresh cement powder, especially after being unloaded from a cement truck by pneumatic blowing, is as fluid as water. The cement, which has lain a little, begins to clump. When the lumps are soft and easily disintegrate when squeezed with fingers - it's okay, such raw materials are quite suitable for the production of concrete, reinforced concrete products, etc. If, however, a significant force is required to break the lump, and it breaks up into particles with sharp edges or hard grains of sand, then the cement is spoiled and has lost some of its activity.
If the appearance of the cement is not suspicious, then an additional check can be carried out. To do this, you need ordinary salt-alkaline mineral water. On this water you need to knead the cement dough. From this dough it is necessary to mold a mold in the form of a discoid with a thick middle part and thin edges. High-quality Portland cement sets in 5-10 minutes, while the molded form heats up noticeably.
A mixture of counterfeit (fly ash, mineral powder) does not heat up and almost does not set during the first 40-60 minutes. Cements with “additives”, especially poorly mixed ones, seize in fragments and crack. If the form has set normally, it must be kept in a humid environment (in an airtight bag) for 1-2 days and examined after removal. If the binder is of poor quality or poorly mixed, then the sample will be covered with cracks, it may crack in the hands. A sample of a good cement binder holds its shape (shallow cracks from thermal deformations are acceptable).
It should be noted that during the express analysis of cement, special instruments can also be used, as a rule, evaluating the activity of cement.
For example, contraction meters or, as they are often called, contractometers. Their principle of operation is based on the observation of the reduction in the volume of the water-cement mixture that occurs during the hydration of the cement binder.
It is also worth mentioning devices that determine cement activity by measuring the specific conductivity of a freshly prepared water-cement mixture.
At the same time, it should be remembered that express analysis and similar types of “quick tests” are unable to adequately assess the quality of the cement binder. Everything is very, very conditional. Only full-fledged laboratory tests and casting of control samples are the only reliable way to determine the quality of the binder.
Laboratory analysis of cement quality
The method of checking for compliance of the cement binder with the declared brand is regulated by two GOSTs. For cement marked in accordance with the old standard (marking of the type PC400D20, PC500D0, etc.) - this is GOST 310.4-81. For the new standard (CEM II-32.5, CEM I-42.5, etc.) - GOST 30744-2001, the requirements of which are similar to the current European standards of the EN 196 series. These documents describe in detail the procedure for creating samples, the terms and conditions of aging samples before the start of inspections, requirements for equipment and testing process.
The new GOST 30744-2001 provides for the following procedures for checking the quality of cement:
- determination of the fineness of cement grinding,
– determination of the start and end dates of setting,
– determination of the uniformity of volume change,
determination of flexural and compressive strength.
As a rule, the first three procedures are performed with pure cement, without the addition of sand and do not require significant time.
The last check lasts 28 days. It starts with the creation of samples, which are stored in the laboratory under special conditions until they are fully cured.
To create samples, normalized sand according to GOST 6139 is used, consisting of a mixture of sand of three fractions: fine, medium and coarse, with a moisture content of not more than 0.2%. The normalized cement-sand mortar is prepared in a ratio of 1:3 by weight of the components at a water-cement ratio of 0.5. Samples withstand 28 days (with the exception of special types of cements that require a different period of time for complete curing), after which they are subjected to tests. The average test results (always several samples are tested) give real indicators of the strength of the tested batch of cement.
It is worth noting that a whole arsenal of devices is used to conduct a full-fledged check of the main characteristics of cement, such as: a granulometer (it is used to determine the fractional composition); Blaine's device (used to determine the specific surface of "cement grains"); various vibrating tables and laboratory stirrers; special presses, chambers for wet storage of control samples, devices for testing the activity of a cement binder; Vika's device, etc.
At the same time, it should be noted that at present, not every concrete plant or shop for the production of dry building mixtures can afford to purchase and maintain such equipment. This is especially true for private mini-enterprises that use cement binder in their production. Therefore, in most cases, manufacturers who are not able to check and control Portland cement on their own and are forced to trust the accompanying invoices and quality certificates for the raw materials received. They only have to hope that the supplier is reliable, and the cement plant has not let us down. Otherwise, the production of concrete, dry mixes and reinforced concrete products from uncontrolled raw materials can turn into big problems, both for the producers themselves and for consumers of their products.
Cement is one of main types of building materials.
It is important to know the storage and operating conditions on which it directly depends.
About, what is the expiration date has cement of various brands, we will tell in the article.
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Does he exist?
Like all building mixtures, cement has a certain expiration date.
Long-term storage leads to a decrease in its activity, which directly affects the quality of its composition.
The higher the activity, the faster there is a loss of quality building material. By following these rules, you can avoid unreasonable financial costs when purchasing cement and extend its original qualities:
- cement must be purchased at specialized points of sale;
- it is not recommended to buy material in broken packaging;
- you should not buy cement in advance and stock up for future use.
It is important to know that if the period indicated on the package has expired, even if not long ago, this material is no longer suitable.
What does it depend on?
Compliance with optimal storage conditions will ensure the suitability of the cement and extend the period specified by the manufacturer. One of the main characteristics is air resistance, which affects the preservation of the level of properties determined by the cement manufacturer in air.
Storage certain conditions must be met:
It is also necessary to provide good ventilation at the storage location.
Shelf life according to GOST
Each brand of cement, even if all storage conditions are observed after 3 months loses about 15% of its original qualities.
Cement brand M-500 is stored in bags for no more than 6 months, then the "grade" will drop to the level of M-400, which can also be stored for six months, and in the future it will no longer be suitable for use.
Depending on the brand of cement allowed to be stored for a certain period of time:
- M-600 - 3 months;
- M-500 - 6 months;
- M-400 - 6 months.
The shelf life of the material sold in bags, established by GOST, is one year, but at the same time, the quality of products decreases by 15% every 3 months.
GOST 10178-85 is:
- 45 days - high-speed cement grades;
- 60 days - other types of cement.
Does the shelf life depend on the material in which the cement is packaged? Currently, cement is packed in paper bags weighing up to 50 kg, where at the same time it is in polyethylene packaging.
When fully sealed, this container provides complete protection against moisture ingress.
It is also shipped in bulk. With this type of storage, the material is most susceptible to moisture penetration and decrease in active qualities cement.
Bulk cement should be stored in barrels, the top of which is wrapped with a film. Storage plays an important role.
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How does long-term storage affect quality?
cement activity during long-term storage is significantly reduced.
Even a purchased product of a higher quality loses all its original qualities after 2-3 months.
Initially, cement is a loose substance, but over time and if the basic storage rules are not followed, cement turns into stone. Hence it follows that don't stock up.
How to store in winter and summer?
To store the material both in winter and in summer, a dry and ventilated room is required. It is important to observe the temperature regime (it is necessary to maintain the temperature regime).
Cement should be placed on pallets, the distance from the bag to the ground should be not less than 30 centimeters. Each bag is hermetically wrapped in cellophane film. In summer, the bags can be stored outdoors for some time, after laying a water-repellent material between them.
Storage of cement is unacceptable in places like:
- open canopy;
- basement;
- unheated rooms with high moisture content.
The perfect place storage - a sealed room with a minimum level of humidity.
You can learn about how much and how to properly store cement from the video:
On obtaining a building permit you will find on our website.
How to understand that cement is unsuitable for use?
A number of simple actions will help to check the suitability of the material for further work.
When the powder is compressed in the palm of the hand, a lump is formed from the mass, but at the same time it should be crumbly: this is a sign of the quality of the cement.
You can lightly tap a bag of cement: if fossils are felt, then this material is no longer suitable for work.
There is another way to check the quality of the goods. For this you need to use:
- Plastic bag.
- A container in which the material is mixed.
- Hydrocarbonate-sodium mineral water.
After kneading the cement, a small cake is made with a thickening in the center. Setting usually occurs within 10 minutes, and the middle of the resulting mass is slightly heated.
This is a sign of high quality products. If this does not happen, then the composition of the cement does not meet the necessary standards, and such material is not suitable for use.
If you follow the above points, you will be able to avoid additional financial costs. It should not be forgotten that even if all requirements for storage conditions are met, after 10 years, the cement will still lose its properties.
If the appearance of the cement is not suspicious, then an additional check can be carried out. To do this, you need salt-alkaline mineral water, for example, Essentuki No. 17. On this water you need to knead the cement dough. Attention! Work with gloves and goggles, because. during stirring, the mixture becomes very caustic and prone to spattering. From the dough, you need to quickly mold a mold in the form of a discoid with a thick middle part and thin edges. High-quality Portland cement sets in 5-10 minutes, while the molded form heats up noticeably.
A mixture of counterfeit (fly ash, mineral powder) does not heat up and almost does not set during the first 40-60 minutes. Cements with "additives", especially poorly mixed, seize in fragments and crack. If the form has set normally, it must be kept in a humid environment (in an airtight bag) for 1-2 days and examined after removal. If the binder is of poor quality or not mixed, then the sample will be covered with cracks, it may crack in the hands. A sample of a good cement binder holds its shape (shallow cracks from thermal deformations are acceptable).
In addition to "big-eyed" control methods, there are special devices for testing the activity of cement. Here we can mention contraction meters or, as they are often called, contractometers, the principle of operation of which is based on observing the reduction in the volume of the water-cement mixture that occurs during the hydration of the cement binder. It is also worth mentioning devices that determine cement activity by measuring the specific conductivity of a freshly prepared water-cement mixture. In this situation, we are talking about such devices as IATs-04M and others like them.
I would like to note that express analysis and similar types of "quick tests" are unable to adequately assess the quality of the cement binder. Everything is very, very conditional. As Yesenin says: "Great is seen at a distance." "Large" in this case is the final brand or strength class of the cement, and the distance for us will be the time required for hardening and curing of control samples. Actually laboratory tests and casting of control samples is the only reliable way to determine the quality of the binder.
Laboratory analysis of cement quality
The method of checking for compliance of the cement binder with the declared brand is regulated by two GOSTs. For cement marked in accordance with the old standard (marking of the type PC400D20, PC500D0, etc.) - this is GOST 310.4-81. For the new standard (CEM II-32.5, CEM I-42.5, etc.) - GOST 30744-2001, the requirements of which are similar to the current European standards of the EN 196 series. These documents describe in detail the procedure for creating samples, the terms and conditions of aging samples before the start of inspections, requirements for equipment and testing process.The new GOST 30744-2001 provides for the following procedures for checking the quality of cement:
- determination of fineness of cement grinding
- determination of start and end dates
- determination of the uniformity of volume change
- determination of flexural and compressive strength
In St. Petersburg State Technical University, laboratory tests of cement are carried out on samples in the form of beams 40x40x160 mm or cubes 30x30x30 mm, cast from cement paste of normal density according to GOST 310.3. The control samples cast into molds are kept over a vessel with water at t of about 20°C and air humidity of about 95% for a day. After a day, the beams or cubes are removed from the molds and their compressive strength is immediately tested. Thus, the activity of the binder is determined. For this, the following formula is used: R-daily = P / S * 98 (MPa), where R-daily is the compressive strength of the press in megapascals; P is force in kg/s, S is sample surface area in sq/cm. To conduct a full test of the main characteristics of cement, a whole arsenal of instruments is used, such as:
- Granulometer, which is used to determine the fractional composition.
- Blaine's instrument for determining the specific surface area of "cement grains".
- Various vibrating tables and laboratory stirrers
- Special presses
- Wet storage chambers for control samples
- Apparatus for testing the activity of a cement binder: IATs-04M devices, contraction meters.
- Vika's device
- etc.
Not every concrete plant or workshop for the production of dry building mixtures can afford to purchase and maintain such equipment. What can we say about private mini-enterprises that use cement binder in their production. As the saying goes: "Not to fat ...." That is why in most cases, manufacturers who are not able to check and control Portland cement on their own are forced to believe the accompanying waybills and quality certificates for the raw materials they receive. They only have to hope that the supplier is reliable, and the cement plant has not let us down. Otherwise, the production of concrete, dry mixes or reinforced concrete products from uncontrolled raw materials can bring huge problems to both the producers themselves and the consumers of their products.
In conclusion, I would like to add that our company provides a complete package of accompanying documentation for the Portland cement supplied by us. Starting with certificates and passports, ending with factory invoices for cargo. The most transparent terms of delivery: fair weight, real brand and always in stock products of the largest Russian manufacturer - the holding
It's no secret that in terms of sales, cement is one of the most popular building materials in Russia. Indeed, the cement market is huge and the demand for it is growing from year to year. Of course, this fact has long been in the field of view of scammers. They are trying by all available means to sell either low-quality cement or a "gray mixture", which, in fact, is not cement.
And if large construction companies or reinforced concrete factories have their own laboratories that allow you to accurately determine the basic properties of cement (activity, grade, speed and uniformity of setting), then small contractors and "ordinary" people can only rely on the "honest word" of the seller.
Fortunately, not everything is so bad. There are several ways that will help you check the quality of cement in 10-15 minutes and weed out obviously bad material.
Where is the danger?
So, in practice, you run the risk of buying either stale cement, which has lost the lion's share of its activity (and, therefore, brand strength), or a material that has nothing to do with cement. As a rule, these are mineral powder for the production of asphalt concrete, dolomite dust (filling powder fire extinguishers), re-ground cement, fly ash, etc. All these "mixtures" are gray, which confuses buyers. They can even seize, but strength is out of the question.
How to protect yourself from fake?
The first and most important advice is to buy cement only from those sellers that you are confident in. The supplier must work on the market for at least 2-3 years. In no case do not take the cement "from hand".
In addition, for each batch of cement, the seller must provide a full package of accompanying documents, ranging from certificates and quality passports to factory waybills for the goods, which indicate the brand of cement, its weight, date of manufacture and shipment.
Of course, this will not help you protect yourself from counterfeiting by 100%, but it will significantly reduce the risks, which is not bad.
How to determine the quality of cement?
First of all, you should "evaluate" the appearance of the cement. It is a dry homogeneous powder of gray color - from light to dark gray, sometimes with shades of green. Fresh powder is quite heavy (much heavier than gypsum) and flows like water.
Note that if the cement "lie down" a little, lumps form in it. If they are soft to the touch and easily fall apart when squeezed with your fingers, it's okay. But if a significant effort is needed to destroy them and they break up into hard particles with sharp edges, the cement is spoiled and has already lost the lion's share of its activity. We do not recommend using it.
The appearance of cement does not raise suspicions? Then we turn to the express analysis of its quality.
For the "experience" you will need mineral water (for example, Essentuki No. 17), a disposable plate, a plastic bag and rubber gloves (protection from chemical burns). So, we knead the cement in a plate on our water, and then from the “dough” we quickly sculpt a “cake” with a thick middle and thin edges.
Let's look at the result:
- good cement seizes immediately - in 5-10 minutes, and the “cake” itself noticeably heats up in the thick part;
- mixtures of mineral powders and other obscure ingredients do not set within 30-60 minutes and almost do not heat up;
- highly diluted cement seizes in fragments, with the formation of subsidence and cracks;
- Chinese cement of not very high quality seizes strongly almost immediately, heats up quickly (sometimes to vaporization) and often bursts from thermal deformations;
- electrostatic precipitator dust and other wastes do not react in any way.
If the “cake” has seized, we tightly wrap it in a bag along with a wet rag and leave it for 1-3 days in a warm place. We evaluate the result. Good cement is hard, almost crack-free, rings when tapped, and breaks when dropped. The bad one is all cracked, it can break into several pieces in the hands or crumble into crumbs.
Another tip - if you take cement in bags or big bags, feel their edges. Solid? This means that the cement is “stale” and it is not worth taking it.
The company "01Beton" works absolutely honestly and only with trusted cement manufacturers, so we provide a full package of accompanying documentation for each batch. We guarantee the quality of our products, so we are not afraid to reveal the secrets of its verification.
Right now you can familiarize yourself with, as well as
Today, it is not uncommon to find fake bulk materials, low-quality cement, sand, etc. At the same time, it is not possible to check the quality of cement because it is in bags (no one will allow you to open bags of cement).
But high-quality and real cement is a very important element at a construction site. If the cement is poor, of poor quality, then concrete, plaster, floor screed, etc., will also not have ideal characteristics. How can you check the quality of cement? What happens if you use bad cement for construction?
Poor-quality cement will definitely make itself felt in a short period of time. In addition, when using bad cement, its consumption increases significantly, which, of course, leads to unforeseen financial waste.
Whether it's a floor screed or a foundation, it doesn't matter what concrete strength can we talk about if bad cement was used to prepare it? Of course, then, over time, cracks appear on the walls due to shrinkage of the foundation or the floor screed bursts due to the use of low-quality cement. 
Today, it is increasingly possible to buy low-quality cement in the construction markets. Not only is it also overdue for a couple of months, it is not clear what components were taken for its manufacture. Below, in this article from a construction magazine, we will talk about what exactly fake cement is made of.
Fake cement - how do you replace a real product?
So you came to the market hoping to buy cement. We found the lowest price, came home, and let's build. Did you know that you may have purchased fake cement, because a good and high-quality product cannot cost a little money. 
If we talk about fake, then instead of cement you can buy:
- Dolomite dust (large percentage of content) instead of the main components;
- Powder from fire extinguishers, thoroughly mixed with dust from the filters of cement plants;
- Expired cement, which is ground back to the desired consistency.
Accordingly, having bought fake cement, you can forget about the quality of the concrete structure once and for all. That is why it is so important to buy cement only from trusted companies and manufacturers who value their reputation more than profit.
Now let's look at several ways to check the quality of cement without leaving the cash register. First of all, it should be understood that no one will let you open a bag of cement in a store without purchasing it. Secondly, you should know that the weight of cement is much lower than that of a gypsum mixture, so you can determine in advance, by weight, the quality of the products sold (however, this is not always accurate).
If we talk about the store check of cement, then you can go one more way: check how loose the cement remained in the corners of the bags. If there is even the slightest suspicion of a possible cement fossil, then it is best to immediately refuse to buy it, because you have expired cement of poor quality. 
You can more accurately determine how high-quality cement is either in the laboratory or at home. To test cement at home, take a small amount of Essentuki 17 mineral water, after which, try to mix, using mineral water, a small amount of cement in a metal bowl.
If you have high-quality cement in front of you, then it is sure to:
- Will change color, become slightly greenish or bluish;
- Hardens almost immediately (poor-quality cement can harden for half an hour or more, in time);
- The metal container for mixing the cement mortar will become noticeably warmer (the cement will begin to generate heat).
In the event that it is possible to touch and feel the cement with your hand, before buying, then pay attention to the following points:
- When squeezed in the hand, high-quality cement will not become a lump, it will surely crumble into dust after the palm is unclenched.
- High quality cement has a uniform color, there is not even the slightest suspicion of lumps in it.
If you still doubt and are not sure of the correctness of your actions, then follow the most proven method of determining the quality of cement, of all of the above. 
Firstly, do not deprive the laboratories of work, because you can always turn to specialists for help. Secondly, read the real reviews of cement buyers in your city, for sure there are such in every region of Russia, Ukraine, and other countries.