Unfortunately, the reality of the Russian construction market is such that a thorough check of the purchased raw materials by express methods is required. As for cement, an unambiguous method for quick verification without specialized equipment has not yet been invented, so you have to use several methods to somehow protect yourself from scammers.
What can an unscrupulous seller slip instead of cement? The most common option: expired powders for filling fire extinguishers. In fact, it's worthless garbage. Such a powder does not carry any real practical properties, therefore it pure water fraud.
Another option is colored mineral powders. In general, the cement should have a gray color ranging from white-gray to grey-greenish. The latter is good, as it indicates a high iron content in the cement, which is an indicator of quality.
But, to be fair to the Russian construction market, it must be said: outright fakes are rarely sold under the guise of cement. More often they use low-quality, stale goods with impurities of the same powders, minerals or ash. Sometimes hardened cement is ground and re-sold. This approach is also unacceptable.
Well, the third option is junk additives to increase the weight of a quality product. This trick on the part of the seller is harder to detect than others and therefore is the most dangerous for the buyer's wallet.
Ways to check the quality when buying
Cement, in addition to color, has a number of other properties:
- Setting time and uniformity
- Fineness of grinding
- Compression and bending resistance
Good cement does not have hard lumps; it cannot be stored without a decrease in quality for more than six months. Moreover, storage for a period of six months is possible only in the form of perfectly ventilated columns of cement bags. Any other method of storage leads to deterioration of the material.
Visual
The first and easiest way to check cement: visual. The fact is that good finely ground cement that has not lain in a warehouse for a very long time will resemble water: waves will be visible on the surface of the spilled mixture, the cement itself moves relatively easily over the surface. On the one hand, this verification method is simple, but on the other hand, all visual sensations are very conditional, and therefore it is impossible to speak of a 100% quality determination in this way. In addition, the grinding of minerals can be selected in such a way that it will not be possible to visually distinguish cement from debris.
For compression
Compression is a logical continuation of the previous method. Good cement flows like water. In any case, this is what process engineers who control the production of cement like to say. If good cement is taken into a fist and squeezed, then it will pass through the fingers without encountering obstacles, finding the slightest leaks in the palm of your hand.
Small soft lumps that are easily kneaded with your fingers are normal - this is the result of too fine grinding. Concrete particles are charged with different charges, and therefore are easily attracted and just as easily repelled.
Excess moisture leads to the formation of lumps, which are then difficult to crush. Only grind again, but this significantly degrades the quality of the cement.
For grasping
To test the cement for setting, you will have to make a cement paste and measure the setting time. For cement, this is 40-60 minutes. If after a few minutes the solution seizes, it is a fake. The same applies to excessively long setting times. Ideally, put the solution in an airtight bag and wait a couple of days for it to harden to assess for cracks, but in fact, when buying, it is rare when there is such an amount of time.
Chemical
The chemical method is the most reliable, but at the same time the most dangerous. For the experiment, a rubberized apron, goggles and gloves are useful. You need to knead the cement dough based on the Esintuki-17 mineral water. Today it is the most salty alkaline mineral water, which can be easily purchased at the store. You can knead only with a foreign tool: false, stick, rod.
A disk is molded from the dough with a thickening in the center and sharp transitions to thin edges. The diameter of the disc is approximately 10 cm. High-quality cement will react with a salt solution, which is a mineral water and begin to generate heat, i.e. the dough will heat up. If heating does not occur, then the cement is fake. If after 1-2 days the disc cracked, then this is just a low-quality product, possibly with additives. Especially high-quality cement can change the color of the dough to blue-green.
Express analysis in the laboratory
To begin with, it is worth clarifying one point: it will not be possible to find out the brand of cement by the express method. To determine the brand, cubes or beams with a certain cement-sand composition are kept for 28 days at optimal humidity until they are fully cured, after which they are tested for bending and compression. That is, all the experiments will take about a month. According to the results of these experiments, cement is assigned a brand.
At home, it is impossible to determine the brand, since without the equipment it will not work correctly to hang the mixture of mortar, it will not be possible to withstand the required humidity and it will not work out correctly to carry out strength tests.
Express method in the laboratory can check:
- Fineness of grinding
- Setting time
- Drawdown uniformity
The fineness of grinding is determined using a granulometer. The setting time can be determined using the Vicat device, and the uniformity of subsidence is determined experimentally.
As a rule, the laboratory issues a certificate of quality, so such a certificate can be requested from the seller. If everything needed is almost in place, then the cement mixture has been checked and only the date of shipment needs to be checked. It is better not to purchase cement older than 3 months. This is fraught with the preparation of poor-quality solutions.
The main thing in choosing cement is to rely on a trusted manufacturer who has not changed the brand, name and sign for many years. Attention should be paid to the presence of the company's legal address and telephone number, the range of bags (at large plants, cement is packed in bags of 50 kg, without bothering with a canopy of 30-40 kg bags. Therefore, the main thing in checking the quality of cement is not sophisticated experiments, but careful choice of the seller.It is better to make the first purchase in a small batch of 1 bag, after all the checks it will become clear whether it is worth working with the seller further or not.
How to determine the quality of cement
By eye or other folk methods, you will not determine the brand of cement. This is the lot of specialized laboratories, where they check chemical composition cement, as well as the mechanical properties of products from it (special cubes are made).
When the cement is in the bag, you can only take it in your hand and determine some of the properties.
Flowability. Real cement, taken in hand, flows like water from clenched fingers. It's impossible to keep him. If this is not the case, then there are harmful additives in the cement, which are added by unscrupulous manufacturers to increase the mass (volume). As a rule, these are wastes from metallurgical production (melted slags). Naturally, the strength of such cement is much lower.
Homogeneity of the mixture. There should be no lumps in the cement. In general - none. If they are, then the cement is stale, long-standing. The more it lies, the more lumps there are inside. Lumps indicate that the strength of the cement is also reduced.
Package. The packaging must be marked with the manufacturer, the date of manufacture, the name of the regulatory authority. The best thing is to buy cement from well-known factories that have been working in this field for a long time. Little-known factories or one-day enterprises should inspire distrust.
You can learn how to determine the quality and brand of cement from this short article. It clearly and clearly describes what exactly you should pay attention to when choosing, buying high-quality cement.
First of all, you need to pay attention to the reputation of the manufacturer, because the more famous the company, the higher the chances that cement will meet all production and technological quality standards.
Perhaps the most primitive way to check the quality of cement as such does not exist, if only to pour it into cubes, dry it, and then subject it to mechanical stress, and then it will be possible to talk and reason about the quality of cement.
It is not even worth determining by the marking, since the indicated marking on the packaging always does not correspond to reality and the brand of cement is always overestimated.
Storage conditions have a bad effect (hardening) on the quality of cement, especially if the air is with high humidity.
Almost in everything I agree with Andrew. From myself I want to add the following - where I live, the cement of the local cement plant is in demand and in no case can you believe the packaging - everything can be fine on the packaging, but inside instead of brand 500 there can be brand 400 and even worse when brand 300. Therefore I recommend buying from trusted stores.
P.S. Tested from personal experience
The only thing you can check is the date of manufacture on the packaging. Nothing more can be done in the store, because the cement is packed and hardly anyone will allow breaking the packaging. So you need to take cement in stores that you trust and take only those manufacturers who, as they say, are well known. As for how storage conditions affect quality, here's what you can say. If the cement in the bag does not sag when pressed and lies in a lump, then most likely it has already accumulated moisture and there will be little sense from it. And if cement has lain for more than a year in a warehouse, then you can safely throw out a hundred from its brand and it will be, for example, with a declared brand of 400 already 300. Here is such arithmetic. In general, it is better to take cement, which, as they say, only from the factory.
Quality control of cement
Modern construction has long been inconceivable without the great 19th century invention of 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. In the case of low-quality cement, this becomes impossible. Hence, laboratories must operate at each precast concrete enterprise, where Portland cement will be tested before it enters the commercial batch of concrete.
Cement falsification
Express analysis of cement
Unfortunately, a full and reliable test of the quality of cement can only be carried out in a laboratory, but an elementary express analysis is done in just 15-20 minutes. A quick check can reveal outright fake when obviously foreign substances are added to the tested cement powder. Full-fledged tests for compliance with the declared brand are performed in laboratory conditions.
So, cement is a finely dispersed powder, completely homogeneous, gray (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 effort 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 salt-alkaline mineral water, for example, Essentuki 17. This water needs to be used to knead 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 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 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 handy-eyed control methods, there are special devices for testing the activity of cement. Here we can mention contractometers 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 rapid tests are unable to adequately assess the quality of the cement binder. Sun is very, very conditional. How is it: Big is seen at a distance. Big in this case is the final grade or strength class of 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
builder
Good day Now, as it were, the construction season has ended ... and cement has fallen in price. We sell even at 90 rubles per bag (50 kg) is it worth it now to buy cement for not expensive, with the expectation that it loses 5 per month % of your strength? Is it even possible to buy cement without a production date? How to check the quality of cement upon delivery? (quick way)
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Such what is!
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builder
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alagg
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Don't take if you won't consume. Designated Cement is not gravel or sand. They store the current in purged columns and then not for long, it seems up to 6 months. and then the brand falls. If the cement is of high quality, he gets kirdyk faster.
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I want to give!!!
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I just signed up, welcome.
11 years worked at a cement plant. was a process engineer, was a shift foreman in shipping and packaging (source of information - experience and specialized education).
Strictly speaking, you can't test it without a lab. As always, there is one BUT.
if we talk about the use of such cement in low-rise construction - with the appropriate REASONABLE tolerances for strength and setting time, then there is a small arsenal of methods for express analysis of cement quality.
A. Is it cement? our dealers manage to "suck in" under the guise of cement any mineral powders of a more or less gray color, insoluble in water. these are trivial mineral powders for the production of asphalt concrete and for filling powder fire extinguishers (dolomite dust), this is the dust of electrostatic precipitators of cement plants, this is cement "activated" in artisanal mills of various kinds, ground together with "additives", such as sand (sand cement), slag, concrete waste and so on. the common property is NOT astringent. it can catch on. but it is better to keep silent about strength, about predictability.
B. cement. quality? you can talk for a long time about manufacturers, about standards, about the country of origin, about alites, belites and aluminoferrites. sending those interested, for example, to Duda's book "Chemistry of Cement" and to any textbooks on the topic "building materials", I will say that we are interested in 3-4 parameters:
1. it is not, not a brand. this is the rate of strength development, which is expressed in terms of the setting start time (so that the cement begins to set not 3 minutes after mixing with water and not 3 hours), but in the range of 40-60 minutes. this indicator indirectly reflects the entire chemistry of cement.
2nd indicator, this is not, not a brand. this is the uniformity of hardening - it manifests itself in the absence of cracks and deformations in the cement cake (thick dough is made from cement and water, cow cake D 10 and 1.5 cm thick is made from dough, it hardens in a humid environment for 3 days. Warping and cracks (hello, Chinese cement!) should not be.
3. yes. it's a brand. why not important? yes, because at home it is not possible to prepare a CB mixture with the desired WCO (water-cement ratio) and compact it for the full use of the declared brand. when preparing concrete from what is in what is, we will inevitably pour out 2-5 times more cement than it should be, based on the required strength of this structure. therefore, the requirements for the actual brand of cement can be omitted, respectively, by 2-3 times. from this place in more detail: cement mainly comes with grades 400 and 500 (we are not talking about the British standard (BS) and ISO). brand of cement is an average (arithmetic average of samples in a batch) indicator of activity (such a term) of cement. from a self-respecting plant, cement is released by ... hm ... 5-10% higher than the declared grade. just in case. cement activity is determined by the surface properties of each grain of cement and its chemical and mineralogical properties, but - through the surface of this very tiny grain. accordingly, the activity can be "stretched" in 2 ways: by the chemistry of the starting materials (through the overestimation of aluminoferrites) and by mechanics - through the surface area, i.e. by increasing the fineness of the grind. the result will be approximately the same - the required activity (the strength of the cube at the age of 28 days).
3 1/2 - additives. oooh, ShPTs, D0, D20 - how many feathers are broken ... in short: ShPTs (aka D40 and above) is distinguished by a long time for the onset of setting. slow increase in strength - these are minuses. pluses - excellent corrosion resistance (to sulfate and other aggressive groundwater, barn drains, septic tank filling, etc.), almost complete absence of warping and deformation, high winter hardiness, above average fire resistance, low heat generation in the array is not of interest. D0 - high rate of curing, close to the minimum setting time, NOT high corrosion resistance, winter hardiness and fire resistance. D20 - average between extremes. "innovative" types of cements, sand cement, activated cements (in which the input of additives sometimes exceeds 80%) - maybe. see checks.
4 and the last - not the GOST term "stability". it has the most direct relation to the brand, setting speed and warping, since it determines the most important parameter for the operator (not for the builder, for the operator!) - the preservation of the declared properties over time.
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Participant
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Now, on to the test method itself.
lice check. alas, this is Russia (Ukraine, Kazakhstan, etc.) - the risk of running into a one-day company selling with a good discount 100 (1000, you need to enter) tons of powder for fire extinguishers taken FOR DISPOSAL is a common thing for us. Accordingly, potential suppliers should be left either with those retail outlets that have not changed signs for decades (they are not in one place, namely, they do not change signs while sitting in one place), or structures affiliated with cement manufacturers (although ...).
quality check.
physical properties. cement should be a fine powder from light to dark gray, very heavy (much heavier than gypsum). shades of green indicate sufficient iron content, which is GOOD. fresh after pneumatic transport or after grinding, its properties are similar to water - it flows, waves over the surface, if such cement is in big bags, but is declared as imported from afar - I would NOT take it. or a dry powder stuck together in plasticine, leaving a sticky feeling on the fingers, sticking together into a "snowball" - this is normal. adhesion occurs due to the fact that each particle of cement loses its electrostatic charge (during storage, pouring, vibration) and, accordingly, its personal air jacket, after which the particles begin to stick together with each other. grains: if the grains are (when kneading in the fingers, this is not dangerous, usually) pebbles with sharp edges or grains of sand, into the furnace. if the grains are rounded and covered with caked cement pebbles in the center of which round balls are felt - this is normal. oldish cement, you can go further. smell: yes. often "grave" is heavy, this is normal.
chemistry. the most delicious of all my opus.
based on the high reactivity of the cement grain surface.
for analysis, you will need a mineral water like Essentuki-17 (the most salty or similar) and rubber gloves, or knead something. a disposable plate, the same spoon, a plastic bag for a humid atmosphere and a rag or newspaper for the same. I haven’t really tried other types of mineral water, so I can’t recommend them.
to gain experience, a sample of known good cement is highly desirable.
actual check: pour half a glass of the cement to be tested into a plate, with a spoon (do not climb with your hands without gloves! chemical burns are almost guaranteed!) -7 cm and from 1 to 0 to the edges, it’s good if you make a sharp transition from the thick part to the thin one in one part, it’s sharp. take a close look at:
high-quality cement begins a false setting almost immediately, which is overcome with a spoon, becomes plastic again. sets within 5-10 minutes, heats up noticeably in the thick part, can change color to blue-green (D0). take.
mineral powders, powders for fire extinguishers, etc. - practically do not seize within 30-60 minutes, do not heat up. cement - in the furnace. the seller - in the snout.
mixed badly mixed and body cements: they seize in pieces, with the formation of subsidence and cracks, they can warm up or not. into the furnace. the seller - on the kidneys.
many Chinese cements, ours are highly active in chemistry: they seize almost instantly, heat up strongly, to vaporization, and often burst from thermal deformations. into the furnace, although ... if a masonry or plaster mortar with lime - you can, in principle, take it. if concrete is on fine and contaminated with silt, clay, dust, sands - you can take it (with caution, do not use hardening accelerators, moderately plasticizers, plasticizers and vibration - carefully. activity buffer - clay, silt, dust, but this is a separate issue). decide individually.
electrostatic precipitator dust and other waste: KhZ. who how. pure dust from filters - does not react in any way, does not harden. into the furnace. dust from bag filters (aka ultra-high grade cement) - like good cement, a little more energetic, due to the developed surface. take.
Everything about everything takes 10-15 minutes.
the sample, together with a plate and a wet rag (even with water from a puddle, it doesn’t matter), we shove it into a bag and wrap it tightly. preferably for a day or three, in the warmest place (only so that the package does not burn out). if there is no time, then for several hours. Well, at least for an hour.
normal cement: hard, without cracks (almost without), rings when tapped, breaks when dropped. when dried in air - may be covered with salt. verification passed, you can take.
mineral powders, bad cements, and other mura: it will most likely seize, with cracks up to a split into several parts or crumbling into crumbs. into the furnace.
yes, still: if the cement is in bags or in big bags, it may be important to check for setting. hammer. tapping run, you can bags. from the grasped hammer bounces with a ringing. we look at small bags during loading - even the most compacted cement in the bag will allow the bag to bend and deform in the hands of the worker. tap on pallets selectively, from above and from the corners. when receiving cement from a cement truck - we listen. stones, cylpebs and other rubbish make a cheerful "ding-ding" sound.
I hope the information is helpful:
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Participant
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Here is an interesting article I found.Feri detergent, and cement masonry mortar
For a long time I worked as a bricklayer at various construction sites and covens, and therefore I have first-hand knowledge of everything related to this difficult craft.
To begin with, the work itself at a construction site is a very time-consuming process that requires enormous physical costs. And it doesn't matter if you're a plasterer, a painter or a bricklayer. The important thing is that it is really very hard. I still know the feeling of fatigue to such an extent that even hands do not rise after a long day at work, not to mention something else. And it happens day after day, year after year!
No, no, I'm not going to complain at all! In the end - who studied what, especially since in addition to difficulties, there is also a lot of positive: For example, do you often feel satisfaction with the results of your work at the end of the working day? And for me, if I build a house, this feeling is always present, because every evening I personally observe what my people have done. with my own hands. And it's worth it. This is what makes a person feel needed and useful! A kind of driving force!
But this is all a saying, and I want to talk about masonry mortar, and about the difficulties that a hardworking bricklayer has to face while working with him. If you have ever worked with a cement masonry mortar, then you know perfectly well what happens to the prepared mortar during the day: it simply gradually shrinks, losing its softness and the necessary elasticity. In the end, after a while, this solution becomes simply impossible to work with. It is good if the solution was brought from the solution unit, where the necessary plasticizers were added. But there are also moments when plasticizers are not added, and the solution itself has been riding in the back of ZILka for another hour before getting to the construction site, where masons are looking forward to it. Naturally, such a solution must be rejuvenated within a couple of hours after unloading. There were moments in my practice when the helpers put on tarpaulin boots and stirred the solution with their feet, trampling it, and cursing strongly at the same time, since it became impossible to break the formed lumps with a shovel. If the solution was kneaded by hand, then it was also necessary to thoroughly think about the substances that give it softness and elasticity. In private construction, clay was often used for these purposes, but, as you know: the more clay in the cement mortar, the weaker it becomes after setting. So, this is also not an option.
Unbelievable, but true - in Russia and the CIS countries they have learned to fake even blue vitriol. What can we say about such a demanded and irreplaceable building material as cement. It is also counterfeited, sold expired or, for one reason or another, lost its quality.
How to test cement?
In order to check the quality of cement, you will have to purchase a small batch - one bag, and subsequently, with a positive result, order an industrial batch from this outlet, this particular manufacturer, it is best from this supply.
First of all, evaluate the type of powder. It should be dry, grey-green in color, flow through your fingers like water, and not have hard lumps. At the same time, it’s okay if there are lumps that crumble into powder when pressed with your fingers.
If the lumps break up into smaller solid lumps, the cement is either expired or was in conditions of high humidity and most likely lost a significant part of its activity.
Such material can only be used as a filler. Also, when buying cement in bags, you should feel the corners of the bags and the bag itself - there should be no hardening in them, and the cement bag itself should be “live”, and not “stone”.
How to check the quality of cement at home?
For express analysis, the following materials will be required:
- Tested cement;
- Alkaline medical-table mineral water: Lipetskaya, Narzan, Fiuggi, Essentuki 4 or Borjomi;
- Latex gloves;
- Disposable plate;
- Polyethylene.
In a plate, on mineral water, the test cement is kneaded to the state of "dough". From the cement dough, a sample is formed in the form of a cake:
- Quality cement will set within 10 minutes and be warm to the touch;
- Counterfeit material does not heat up and sets within an hour, or does not set at all;
- Expired or diluted cement seizes in separate fragments and cracks;
- Initially low-quality (as a rule, it is cement produced in China) seizes instantly with high heat release, often with vaporization and bursts from uneven thermal deformations.
After setting, a high-quality cement cake is wrapped in polyethylene and aged for 3 days under normal conditions. Sample from cement good quality should be integral, solid, ringing when tapped and split only under strong mechanical stress - falling from a height of 1.5 meters.
If the sample crumbles in your hands, you should not buy such cement.
Undoubtedly, laboratory tests can give the most accurate result. However, due to various reasons (territorial remoteness of the laboratory, refusal to analyze, etc.), this is not always possible.
How to protect yourself from counterfeit and low-quality material?
These are common truths that are often simply neglected:
- Firstly. The price of high-quality cement of domestic production deviates up or down from the weighted average in the region by more than 5-7%. If you are offered very cheap material, explaining the low price by “direct deliveries”, most likely you are being offered outright counterfeit goods (less commonly stolen goods). In other words: "good things will never be very cheap";
- Secondly. Purchase material in stationary outlets that have been operating on the market for several years or more. The seller, aimed at long-term trading activity, very rarely takes on the implementation of a delay, and even more so a fake;
- Third. Ask the seller for the accompanying documents for the batch and pay attention to the date of shipment - it must be “fresh”.
It cannot be discounted that the accompanying documents are “fake”, and the seller encroached on momentary profits and sells bad cement.
Portland cement as a building material is used in many operations - from pouring foundations and erecting walls to road construction and various repairs. Since the sales volume of this material is significant, there are also unscrupulous manufacturers trying to sell counterfeit products at the price of a quality mixture. It is clear that the use of a counterfeit cannot ensure compliance with the performance characteristics for construction works, and therefore it is mandatory to carry out cement quality control.
How cement is faked
To make a fake, a quality mixture is diluted:
- mineral powders;
- dolomite dust;
- ash;
- crumpled old cement.
Express methods of verification. Visual control
Cement quality control when using it at especially critical facilities, it must be carried out in a laboratory. But for private construction, it is quite enough to conduct an express analysis, which allows you to quickly identify a falsification. It is based on the properties of cement that change during storage.
How to check the quality of cement for a few minutes? You need to take a few lumps and try to crush them with your fingers. If, when pressed, the lump is soft and easily disintegrates, then the raw material is quite suitable for the preparation of high-quality concrete. When the destruction requires considerable effort or hard and sharp particles remain, then the cement is damaged.
After assessment appearance an additional check can be carried out by kneading the cement dough on saline-alkaline mineral water such as Essentuki. Please note that the mixture will be very caustic. A discoid (cake) is made from the solution - the hardening time of high-quality cement will be less than 10 minutes, and the figure will also get very hot. Falsified mixtures do not heat up and almost do not set for an hour.
Also express analysis of cement can be carried out with special devices - contractometers. They monitor the volume reduction of the water-cement mixture. There are also devices that measure conductivity and evaluate cement activity.
Laboratory Test Methods
Laboratory techniques allow you to accurately establish the compliance of cement with the declared brand and are fully regulated by GOSTs - GOST 310.4-81 or GOST 30744-2001 for old and new standards, respectively. The standards govern procedures for determining fineness of grind, setting times, uniformity of volume change and flexural/compressive strength.
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