Well, sort of. Modulus of rupture is done as a flexural test and does not directly measure the tensile strength of concrete.

Does anyone have a formula for the direct tensile strength of concrete?

Another commonly used, but also indirect indicator of tensile strength is the splitting tensile test. Both will generally yield a tensile strength of around 10 percent of the compressive strength. Axial tensile strength of concrete is a more difficult test to run and generally yields slightly lower relational value to the compressive strength. One accepted relationship is f(t)= 7.5 * ((f'c)^0.5) RE: Direct tensile strength of concrete (Structural). Yes I know those indirect formulae. Let me phrase the question differently. What would you expect the direct tensile strength of 35 MPa (5000 ± psi) concrete to be?

If your answer is 10% or 500 psi, or 7.5 x 5000 0.5= 530 psi, I am skeptical because we have never achieved anything like that when we due direct tensile tests of bonded topping and the fracture occurs within the parent concrete below. We would usually get 300 psi, perhaps 330 psi. I suppose we could do some direct tensile tests of monolithic concrete and see what we get.but I was hoping maybe those tests have been done and reported on somewhere.

Any comments would be welcome. RE: Direct tensile strength of concrete (Structural) 28 Jul 16 13:07. Ajk1.comparing a properly done direct tension test in the lab to a 'pull off' tension test of a concrete topping is apples and oranges.

A pull-off test is subject to even more disturbance issues that a typical concrete core, so considering that, if you divide the pull-off strength by.67 or so (0.85 is used for cores in compression), you might get close to the actual axial tensile strength of the concrete. A uniaxial tension test in the lab is done on a specimen that has no influencing finish issues common to floor slabs, even when some surface prep is applied before the topping. It is done on a prepared specimen, much the same as a compressive strength test. Reflexive Games Keygen Free Download. A tensile bond strength of 300 psi is quite good! Jayrod12.no, not semantics.difference in stress orientation. In a flexural test you have both tension and compression acting on the specimen. In a direct tension test, there is no compression component or influence.

In the splitting tensile test, Poisson's ratio comes into play as the test is actually done by compressing the sample along a straight line, not a defined area, and the failure occurs when the compression along that line causes the specimen to pull itself apart. RE: Direct tensile strength of concrete (Nuclear) 29 Jul 16 02:04. Modulus of rupture is done as a flexural test and does not directly measure the tensile strength of concrete. Another commonly used, but also indirect indicator of tensile strength is the splitting tensile test. Both will generally yield a tensile strength of around 10 percent of the compressive strength. Axial tensile strength of concrete is a more difficult test to run and generally yields slightly lower relational value to the compressive strength What is the structural strength of that nominal relationship over time? Would that formula be adequate for a 7-day concrete, or only after a 30 day cure time?

RE: Direct tensile strength of concrete (Structural) 29 Jul 16 05:31. Direct tension testing puts the entire cross section into tension and any weakness will precipitate failure, hence the lower value with direct tension. Flexural tension is more like the condition in service and only the outer fibre will be exposed to maximum tension. Splitting tensile strength, again only exposes a portion of the concrete to maximum tension, again, reflected in a higher tensile capacity.

For the Coef for determining flexural tension capacity, with airport pavements, the value is often as high as 9.0 to 9.2. But, a factor for fatigue, etc. Is often included. Also quality control is often a little better.

Dik RE: Direct tensile strength of concrete (Structural). Thank you all. My own understanding over the years has been pretty much what dik has said. I do believe that there is a significant difference between the direct tensile strength and other measures such as the modulus of rupture. Perhaps the splitting tensile strength may come closer to the direct tensile strength than the modulus of rupture. Yes I did realize shortly after posting my comment about my experience with on-site direct tension test strengths, the point that Ron makes, namely that the quality of the concrete in the top few mm on a slab is not as good as below that, and so the direct tensile strength would probably be less than if that layer were removed before testing. However, our tests are done on projects where the floor was shotblast, so perhaps that weak layer was removed.

Since the tests we conduct on projects are of new topping on an old slab, and the results I am talking about are for those where the failure surface is in the old slab, the age of the concrete should not affect it. Would be nice if there were a published paper somewhere that dealt with gave test results for lab direct tension tests on monolithic concrete.

Maybe ACI has something or an academic has info. The reason behind my original question was to determine if a structurally reinforced bonded topping to an old slab that will be shotblast to 5 mm amplitude, can be considered the same as if the concrete (topping and original slab) was all monolithic, and then horizontal shear stress at the bond line would not be a concern. The proposed live load on the composite slab is 250 psf (unfactored), so there may be some concern about the horizontal shear stress at the bond line and whether the bond is sufficient to safely resist the shear stress.

RE: Direct tensile strength of concrete (Structural) 29 Jul 16 13:33. Just to be clear, you are saying 'direct tensile test' but you are actually referring to pulloff tests. They are different. Direct tensile tests involve removing a sample and machining it in a way that it can be gripped and then pulled in the lab like a steel coupon, but apparently this test is very rarely done.

I suspect one reason why the pulloff tests are not comparable to the actual tensile strength is because they are typically done with a small (50mm) diameter disk which is cored into the substrate. Like Ron said, small diameter samples are more strongly influenced by minor flaws because they make up a greater proportion of the cross section. As well, the damaged surface area from the coring makes up a greater portion of the sample. You have more cut/disturbed aggregates which are no longer effective. Same principle applies for compression tests, which is why we use larger diameters for a more accurate measurement. You really can't compare this test to the actual tensile strength of the concrete.

But you can use it to see where the weak link is: the new concrete, the old concrete, or the bond. There is literature comparing the test results between direct tensile, splitting and MOR tests. I haven't read any, but my concrete textbooks do discuss this difference. It is established that MOR strength >splitting tension >direct tensile.

Maybe I'm not understanding the shear concern, but if the pulloff test is breaking in the substrate, than the bond and new concrete are both stronger than the original concrete, so why would there be a concern about that? RE: Direct tensile strength of concrete (Structural) 29 Jul 16 16:26. Thank you all again. To DamsInc: the test procedure routinely used here in Canada is CSA A23.2 - 6B, 'Method of Test to Determine Adhesion by Tensile Load' (I do not know if there is a corresponding ASTM test or not). The CSA test requires that the minimum diameter of the core bit shall be 3½ times the nominal maximum size aggregate size but in no case less than 75 mm'. The inside diameter of the core is stated to be slightly larger than the fastening disk. I am perhaps a little surprised that you say that pull-off tests are normally done with 2' (50 mm) disks, as most concrete has 20 mm (3/4') diameter coarse aggregate.

Anyway when we do the tests we use 95 mm diameter disks. I don't think that the 20 mm aggregate should then be a significant factor. You do make a good point, namely that if the failure surface is in the original concerte of the substrate slab, then that shows that the bond line is as strong or stronger than the original concrete, irrespective of the failure stress. I also appreciate that you have found that your reference book says that MOR strength >splitting tension >direct tensile. Sometimes the good old fashioned medium is the best! That is what I had thought when I started this string.

Can you tell me the reference book that you found that in.maybe we have it in our office library. Is it Troxell & Davis? To Cnorvall; yes I know but that would be a permissible ultimate stress to be used in limit states design; that is not the actual ultimate failure stress.

The actual ultimate would be some number of standard deviations above that. To JAE; We would specify about 1.5 MPa (218 psi) minimum adhesion strength for normal garage concrete repairs.

Using proper care in surface prep and surface cleanliness and a particular water based epoxy bonding agent with 24 open time, we can get 2.0 MPa (290 psi), but it does take care on site. However on the particular job currently under consideration, the live load is 12 kPa (250 psf) so we wanted something better than 1.5 MPa. RE: Direct tensile strength of concrete (Structural) 30 Jul 16 12:12. To DamsInc: the test procedure routinely used here in Canada is CSA A23.2 - 6B, 'Method of Test to Determine Adhesion by Tensile Load' (I do not know if there is a corresponding ASTM test or not).

The CSA test requires that the minimum diameter of the core bit shall be 3½ times the nominal maximum size aggregate size but in no case less than 75 mm'. The inside diameter of the core is stated to be slightly larger than the fastening disk. I am perhaps a little surprised that you say that pull-off tests are normally done with 2' (50 mm) disks, as most concrete has 20 mm (3/4') diameter coarse aggregate.

Anyway when we do the tests we use 95 mm diameter disks. I don't think that the 20 mm aggregate should then be a significant factor. Right, I wasn't sure what diameter you would be using, but 50mm would be the minimum. Which version of CSA 23.2 are you looking? The 2009 version states that the minimum would be 60mm for the coring bit, for a 50mm sample (strange that they decided to revise that downward).

It was my interpretation that in CSA 23.2 6B, procedure 'A' was the pulloff test, and procedure 'B' was direct tensile, but I could be wrong on that. That's how I've seen/heard it described. Quote (ajk1).

Contents • • • • • • • • • • • • • • • • • • • • • • • • • • • Chemistry [ ] Non-hydraulic cement, such as ( mixed with water), hardens by in the presence of which is naturally present in the air. First (lime) is produced from (limestone or chalk) by at temperatures above 825 °C (1,517 °F) for about 10 hours at: CaCO 3 → CaO + CO 2 The calcium oxide is then spent (slaked) mixing it with water to make slaked lime (calcium hydroxide): CaO + H 2O → Ca(OH) 2 Once the excess water is completely evaporated (this process is technically called setting), the carbonation starts: Ca(OH) 2 + CO 2 → CaCO 3 + H 2O This reaction takes a significant amount of time because the partial pressure of carbon dioxide in the air is low.

The carbonation reaction requires the dry cement to be exposed to air, and for this reason the slaked lime is a non-hydraulic cement and cannot be used under water. This whole process is called the lime cycle. Conversely, hydraulic cement hardens by hydration when water is added. Hydraulic cements (such as ) are made of a mixture of silicates and oxides, the four main components being: (2CaOSiO 2); (3CaOSiO 2); (3CaOAl 2O 3) (historically, and still occasionally, called 'celite'); (4CaOAl 2O 3Fe 2O 3). The silicates are responsible for the mechanical properties of the cement, the tricalcium aluminate and the brownmillerite are essential to allow the formation of the liquid phase during the kiln sintering (firing).

The chemistry of the above listed reactions is not completely clear and is still the object of research. History [ ] Perhaps the earliest known occurrence of cement is from twelve million years ago. A deposit of cement was formed after an occurrence of oil shale located adjacent to a bed of limestone burned due to natural causes. These ancient deposits were investigated in the 1960s and 1970s. Alternatives to cement used in antiquity [ ] Cement, chemically speaking, is a product that includes lime as the primary curing ingredient, but is far from the first material used for cement ation. The Babylonians and Assyrians used to bind together burnt brick or alabaster slabs. In Egypt stone blocks were cemented together with a made of and roughly burnt (CaSO 42H 2O), which often contained calcium carbonate (CaCO 3).

Macedonians and Romans [ ] Lime (calcium oxide) was used on Crete and by the ancient Greeks. There is evidence that the of Crete used crushed potshards as an artificial pozzolan for hydraulic cement. It is uncertain where it was first discovered that a combination of and a produces a hydraulic mixture (see also: ), but concrete made from such mixtures was used by the and three centuries later on a large scale. A kind of powder which from natural causes produces astonishing results. It is found in the neighborhood of and in the country belonging to the towns round about Mt. This substance when mixed with lime and rubble not only lends strength to buildings of other kinds, but even when piers of it are constructed in the sea, they set hard under water.

— Marcus Vitruvius Pollio, Liber II, De Architectura, Chapter VI 'Pozzolana' Sec. 1 The Greeks used volcanic tuff from the island of as their pozzolan and the Romans used crushed volcanic ash (activated ) with lime. This mixture was able to set under water increasing its resistance.

[ ] The material was called pozzolana from the town of, west of Naples where volcanic ash was extracted. In the absence of pozzolanic ash, the Romans used powdered brick or pottery as a substitute and they may have used crushed tiles for this purpose before discovering natural sources near Rome.

The huge of the in and the massive are examples of ancient structures made from these concretes, many of which are still standing. The vast system of also made extensive use of hydraulic cement.

Middle Ages [ ] Although any preservation of this knowledge in literary sources from the is unknown, medieval and some military engineers maintained an active tradition of using hydraulic cement in structures such as,,, and. Cements in the 16th century [ ], a building material using oyster-shell lime, sand, and whole oyster shells to form a concrete, was introduced to the Americas by the Spanish in the sixteenth century. Cements in the 18th century [ ] The technical knowledge for making hydraulic cement was formalized by French and British engineers in the 18th century. Made an important contribution to the development of cements while planning the construction of the third (1755–59) in the now known as.

He needed a hydraulic mortar that would set and develop some strength in the twelve-hour period between successive high tides. He performed experiments with combinations of different limestones and additives including trass and and did exhaustive market research on the available hydraulic limes, visiting their production sites, and noted that the 'hydraulicity' of the lime was directly related to the clay content of the from which it was made.

Smeaton was a by profession, and took the idea no further. In the of the United States, relying upon the oyster-shell of earlier Native American populations was used in house construction from the 1730s to the 1860s. In particularly, good quality building stone became ever more expensive during a period of rapid growth, and it became a common practice to construct prestige buildings from the new industrial bricks, and to finish them with a to imitate stone.

Hydraulic limes were favored for this, but the need for a fast set time encouraged the development of new cements. Most famous was Parker's '. This was developed by in the 1780s, and finally patented in 1796. It was, in fact, nothing like material used by the Romans, but was a 'natural cement' made by burning – nodules that are found in certain clay deposits, and that contain both and. The burnt were ground to a fine powder. This product, made into a mortar with sand, set in 5–15 minutes.

The success of 'Roman cement' led other manufacturers to develop rival products by burning artificial cements of and. Roman cement quickly became popular but was largely replaced by Portland cement in the 1850s. Cements in the 19th century [ ] Apparently unaware of Smeaton's work, the same principle was identified by Frenchman in the first decade of the nineteenth century. Vicat went on to devise a method of combining chalk and clay into an intimate mixture, and, burning this, produced an 'artificial cement' in 1817 considered the 'principal forerunner' of Portland cement and '.Edgar Dobbs of Southwark patented a cement of this kind in 1811.' In Russia, created a new binder by mixing lime and clay. His results were published in 1822 in his book A Treatise on the Art to Prepare a Good Mortar published in St.

A few years later in 1825, he published another book, which described the various methods of making cement and concrete, as well as the benefits of cement in the construction of buildings and embankments. Is considered the inventor of 'modern'., the most common type of cement in general use around the world as a basic ingredient of,,, and non-speciality, was developed in in the mid 19th century, and usually originates from.

Produced what he called 'British cement' in a similar manner around the same time, but did not obtain a patent until 1822. In 1824, patented a similar material, which he called Portland cement, because the render made from it was in color similar to the prestigious which was quarried on the, Dorset, England. However, Aspdins' cement was nothing like modern Portland cement but was a first step in its development, called a proto-Portland cement. Joseph Aspdins' son had left his fathers company and in his cement manufacturing apparently accidentally produced in the 1840s, a middle step in the development of Portland cement. William Aspdin's innovation was counterintuitive for manufacturers of 'artificial cements', because they required more lime in the mix (a problem for his father), a much higher kiln temperature (and therefore more fuel), and the resulting was very hard and rapidly wore down the, which were the only available grinding technology of the time.

Manufacturing costs were therefore considerably higher, but the product set reasonably slowly and developed strength quickly, thus opening up a market for use in concrete. The use of concrete in construction grew rapidly from 1850 onward, and was soon the dominant use for cements. Thus Portland cement began its predominant role. Further refined the production of meso-Portland cement (middle stage of development) and claimed to be the real father of Portland cement.

Setting time and 'early strength' are important characteristics of cements. Hydraulic limes, 'natural' cements, and 'artificial' cements all rely upon their content for development.

Belite develops strength slowly. Because they were burned at temperatures below 1,250 °C (2,280 °F), they contained no, which is responsible for early strength in modern cements. The first cement to consistently contain alite was made by William Aspdin in the early 1840s: This was what we call today 'modern' Portland cement. Because of the air of mystery with which William Aspdin surrounded his product, others ( e.g., Vicat and Johnson) have claimed precedence in this invention, but recent analysis of both his concrete and raw cement have shown that William Aspdin's product made at, was a true alite-based cement. However, Aspdin's methods were 'rule-of-thumb': Vicat is responsible for establishing the chemical basis of these cements, and Johnson established the importance of the mix in the kiln.

In the US the first large-scale use of cement was, a natural cement mined from a massive deposit of a large deposit discovered in the early 19th century near. Rosendale cement was extremely popular for the foundation of buildings ( e.g.,,, ) and lining water pipes.

Was patented in 1867 by Frenchman and was stronger than Portland cement but its poor water resistance and corrosive qualities limited its use in building construction. The next development with the manufacture of Portland cement was the introduction of the which allowed a stronger, more homogeneous mixture and a continuous manufacturing process. Cements in the 20th century [ ].

The National Cement Share Company of 's new plant in. Were patented in 1908 in France by Jules Bied for better resistance to sulfates. In the US, the long of at least a month for made it unpopular after World War One in the construction of highways and bridges and many states and construction firms turned to the use of Portland cement. Because of the switch to Portland cement, by the end of the 1920s of the 15 Rosendale cement companies, only one had survived. But in the early 1930s it was discovered that, while Portland cement had a faster setting time it was not as durable, especially for highways, to the point that some states stopped building highways and roads with cement. Wait, an engineer whose company had worked on the construction of the New York City's, was impressed with the durability of Rosendale cement, and came up with a blend of both Rosendale and synthetic cements which had the good attributes of both: it was highly durable and had a much faster setting time.

Wait convinced the New York Commissioner of Highways to construct an experimental section of highway near, using one sack of Rosendale to six sacks of synthetic cement. It was proved a success and for decades the Rosendale-synthetic cement blend became common use in highway and bridge construction. Modern cements [ ] Modern hydraulic cements began to be developed from the start of the (around 1800), driven by three main needs: • Hydraulic () for finishing brick buildings in wet climates.

• Hydraulic mortars for masonry construction of harbor works, etc., in contact with sea water. • Development of strong concretes.

Modern cements are often or Portland cement blends, but other cements are used in industry. Components of Cement Comparison of Chemical and Physical Characteristics a Property Portland Cement Siliceous (ASTM C618 Class F) Fly Ash Calcareous (ASTM C618 Class C) Fly Ash Slag Cement Silica Fume SiO 2 content (%) 21.9 52 35 35 85–97 Al 2O 3 content (%) 6.9 23 18 12 — Fe 2O 3 content (%) 3 11 6 1 — CaO content (%) 63 5 21 40. Main article: Portland cement is by far the most common type of cement in general use around the world. This cement is made by heating (calcium carbonate) with other materials (such as ) to 1450 °C in a, in a process known as, whereby a molecule of is liberated from the calcium carbonate to form, or quicklime, which then chemically combines with the other materials that have been included in the mix to form calcium silicates and other cementitious compounds. The resulting hard substance, called 'clinker', is then ground with a small amount of into a powder to make 'ordinary Portland cement', the most commonly used type of cement (often referred to as OPC). Portland cement is a basic ingredient of, and most non-specialty. The most common use for Portland cement is in the production of concrete.

Concrete is a composite material consisting of ( and ), cement, and. As a construction material, concrete can be cast in almost any shape desired, and once hardened, can become a structural (load bearing) element.

Portland cement may be grey or white. Portland cement blends [ ] Portland cement blends are often available as inter-ground mixtures from cement producers, but similar formulations are often also mixed from the ground components at the concrete mixing plant. Portland blast-furnace slag cement, or Blast furnace cement (ASTM C595 and EN 197-1 nomenclature respectively), contains up to 95%, with the rest Portland clinker and a little gypsum. All compositions produce high ultimate strength, but as slag content is increased, early strength is reduced, while sulfate resistance increases and heat evolution diminishes. Used as an economic alternative to Portland sulfate-resisting and low-heat cements.

Portland-fly ash cement contains up to 40% under ASTM standards (ASTM C595), or 35% under EN standards (EN 197-1). The fly ash is, so that ultimate strength is maintained. Because fly ash addition allows a lower concrete water content, early strength can also be maintained.

Where good quality cheap fly ash is available, this can be an economic alternative to ordinary Portland cement. Portland pozzolan cement includes fly ash cement, since fly ash is a, but also includes cements made from other natural or artificial pozzolans.

In countries where are available (e. Wxwidgets Serial Port Programming Pdf. g.,,, the ) these cements are often the most common form in use. The maximum replacement ratios are generally defined as for Portland-fly ash cement. Portland silica fume cement. Addition of can yield exceptionally high strengths, and cements containing 5–20% silica fume are occasionally produced, with 10% being the maximum allowed addition under EN 197-1.

However, silica fume is more usually added to Portland cement at the concrete mixer. Masonry cements are used for preparing bricklaying and, and must not be used in concrete. They are usually complex proprietary formulations containing Portland clinker and a number of other ingredients that may include limestone, hydrated lime, air entrainers, retarders, waterproofers and coloring agents. They are formulated to yield workable mortars that allow rapid and consistent masonry work. Subtle variations of Masonry cement in the US are Plastic Cements and Stucco Cements.

These are designed to produce controlled bond with masonry blocks. Expansive cements contain, in addition to Portland clinker, expansive clinkers (usually sulfoaluminate clinkers), and are designed to offset the effects of drying shrinkage that is normally encountered with hydraulic cements.

This allows large floor slabs (up to 60 m square) to be prepared without contraction joints. White blended cements may be made using white clinker (containing little or no iron) and white supplementary materials such as high-purity. Colored cements are used for decorative purposes. In some standards, the addition of pigments to produce 'colored Portland cement' is allowed.

In other standards (e.g. ASTM), pigments are not allowed constituents of Portland cement, and colored cements are sold as 'blended hydraulic cements'. Very finely ground cements are made from mixtures of cement with sand or with slag or other pozzolan type minerals that are extremely finely ground together.

Such cements can have the same physical characteristics as normal cement but with 50% less cement particularly due to their increased surface area for the chemical reaction. Even with intensive grinding they can use up to 50% less energy to fabricate than ordinary Portland cements. Other cements [ ] Pozzolan-lime cements. Mixtures of ground and are the cements used by the Romans, and are present in extant Roman structures (e.g. The in Rome). They develop strength slowly, but their ultimate strength can be very high. The hydration products that produce strength are essentially the same as those produced by Portland cement.

Slag-lime cements. Is not hydraulic on its own, but is 'activated' by addition of alkalis, most economically using lime. They are similar to pozzolan lime cements in their properties. Only granulated slag (i.e. Water-quenched, glassy slag) is effective as a cement component. Supersulfated cements contain about 80% ground granulated blast furnace slag, 15% or and a little Portland clinker or lime as an activator.

They produce strength by formation of, with strength growth similar to a slow Portland cement. They exhibit good resistance to aggressive agents, including sulfate. Are hydraulic cements made primarily from and. The active ingredients are monocalcium aluminate CaAl 2O 4 (CaO Al 2O 3 or CA in, CCN) and Ca 12Al 14O 33 (12 CaO 7 Al 2O 3, or C 12A 7 in CCN). Strength forms by hydration to calcium aluminate hydrates.

They are well-adapted for use in refractory (high-temperature resistant) concretes, e.g. For furnace linings. Calcium sulfoaluminate cements are made from clinkers that include (Ca 4(AlO 2) 6SO 4 or C 4A 3 S in ) as a primary phase.

They are used in expansive cements, in ultra-high early strength cements, and in 'low-energy' cements. Hydration produces ettringite, and specialized physical properties (such as expansion or rapid reaction) are obtained by adjustment of the availability of calcium and sulfate ions. Their use as a low-energy alternative to Portland cement has been pioneered in China, where several million tonnes per year are produced.

Energy requirements are lower because of the lower kiln temperatures required for reaction, and the lower amount of limestone (which must be endothermically decarbonated) in the mix. In addition, the lower limestone content and lower fuel consumption leads to a CO 2 emission around half that associated with Portland clinker. However, SO 2 emissions are usually significantly higher. 'Natural' cements correspond to certain cements of the pre-Portland era, produced by burning at moderate temperatures. The level of clay components in the limestone (around 30–35%) is such that large amounts of (the low-early strength, high-late strength mineral in Portland cement) are formed without the formation of excessive amounts of free lime.

As with any natural material, such cements have highly variable properties. Cements are made from mixtures of water-soluble alkali metal silicates and aluminosilicate mineral powders such as and. Polymer cements are made from organic chemicals that polymerise. Often materials are employed.

While they are often significantly more expensive, they can give a water proof material that has useful tensile strength. Setting and curing [ ] Cement starts to set when mixed with water which causes a series of hydration chemical reactions. The constituents slowly hydrate and the mineral hydrates solidify; the interlocking of the hydrates gives cement its strength. Contrary to popular perceptions, hydraulic cements do not set by drying out; proper curing requires maintaining the appropriate moisture content during the curing process.

If hydraulic cements dry out during curing, the resulting product can be significantly weakened. Safety issues [ ] Bags of cement routinely have health and safety warnings printed on them because not only is cement highly, but the setting process is. As a result, wet cement is strongly (water pH = 13.5) and can easily cause severe if not promptly washed off with water. Similarly, dry cement powder in contact with can cause severe eye or respiratory irritation.

Some trace elements, such as chromium, from impurities naturally present in the raw materials used to produce cement may cause. Reducing agents such as ferrous sulfate (FeSO 4) are often added to cement to convert the carcinogenic hexavalent (CrO 4 2−) into trivalent chromium (Cr 3+), a less toxic chemical species.

Cement users need also to wear appropriate gloves and protective clothing. Cement industry in the world [ ].

See also: In 2010, the world production of hydraulic cement was. The top three producers were with 1,800, with 220, and with 63.5 million tonnes for a combined total of over half the world total by the world's three most populated states. For the world capacity to produce cement in 2010, the situation was similar with the top three states (China, India, and USA) accounting for just under half the world total capacity. Over 2011 and 2012, global consumption continued to climb, rising to 3585 Mt in 2011 and 3736 Mt in 2012, while annual eased to 8.3% and 4.2%, respectively. China, representing an increasing share of world cement consumption, continued to be the main engine of global growth.

By 2012, Chinese demand was recorded at 2160 Mt, representing 58% of world consumption. Annual growth rates, which reached 16% in 2010, appear to have softened, slowing to 5–6% over 2011 and 2012, as China’s economy targets a more sustainable growth rate. Outside of China, worldwide consumption climbed by 4.4% to 1462 Mt in 2010, 5% to 1535 Mt in 2011, and finally 2.7% to 1576 Mt in 2012. Iran is now the 3rd largest cement producer in the world and has increased its output by over 10% from 2008 to 2011. Due to climbing energy costs in Pakistan and other major cement-producing countries, Iran is a unique position as a trading partner, utilizing its own surplus petroleum to power clinker plants. Now a top producer in the Middle-East, Iran is further increasing its dominant position in local markets and abroad. The performance in North America and Europe over the 2010–12 period contrasted strikingly with that of China, as the global financial crisis evolved into a sovereign debt crisis for many economies in this region and recession.

Cement consumption levels for this region fell by 1.9% in 2010 to 445 Mt, recovered by 4.9% in 2011, then dipped again by 1.1% in 2012. The performance in the rest of the world, which includes many emerging economies in Asia, Africa and Latin America and representing some 1020 Mt cement demand in 2010, was positive and more than offset the declines in North America and Europe. Annual consumption growth was recorded at 7.4% in 2010, moderating to 5.1% and 4.3% in 2011 and 2012, respectively.

As at year-end 2012, the global cement industry consisted of 5673 cement production facilities, including both integrated and grinding, of which 3900 were located in China and 1773 in the rest of the world. Total cement capacity worldwide was recorded at 5245 Mt in 2012, with 2950 Mt located in China and 2295 Mt in the rest of the world. Main article: 'For the past 18 years, China consistently has produced more cement than any other country in the world. [.] (However,) China's cement export peaked in 1994 with 11 million tonnes shipped out and has been in steady decline ever since.

Only 5.18 million tonnes were exported out of China in 2002. Offered at $34 a ton, Chinese cement is pricing itself out of the market as Thailand is asking as little as $20 for the same quality.' In 2006, it was estimated that China manufactured 1.235 billion tonnes of cement, which was 44% of the world total cement production.

'Demand for cement in China is expected to advance 5.4% annually and exceed 1 billion tonnes in 2008, driven by slowing but healthy growth in construction expenditures. Cement consumed in China will amount to 44% of global demand, and China will remain the world's largest national consumer of cement by a large margin.' In 2010, 3.3 billion tonnes of cement was consumed globally.

Of this, China accounted for 1.8 billion tonnes. Environmental impacts [ ] Cement manufacture causes environmental impacts at all stages of the process. These include emissions of airborne pollution in the form of dust, gases, noise and vibration when operating machinery and during blasting in, and damage to countryside from quarrying. Equipment to reduce dust emissions during quarrying and manufacture of cement is widely used, and equipment to trap and separate exhaust gases are coming into increased use. Environmental protection also includes the re-integration of quarries into the countryside after they have been closed down by returning them to nature or re-cultivating them.

CO 2 emissions [ ]. Global carbon emission by type to 2004. Attribution: Mak Thorpe Carbon concentration in cement spans from ≈5% in cement structures to ≈8% in the case of roads in cement.

Cement manufacturing releases in the atmosphere both directly when is heated, producing and, and also indirectly through the use of energy if its production involves the emission of CO 2. The cement industry produces about 10% of global man-made CO 2 emissions, of which 60% is from the chemical process, and 40% from burning fuel. Nearly 900 kg of CO 2 are emitted for every 1000 kg of Portland cement produced. In the European union the specific energy consumption for the production of cement clinker has been reduced by approximately 30% since the 1970s. This reduction in primary energy requirements is equivalent to approximately 11 million tonnes of coal per year with corresponding benefits in reduction of CO 2 emissions. This accounts for approximately 5% of anthropogenic CO 2. The majority of carbon dioxide emissions in the manufacture of Portland cement (approximately 60%) are produced from the chemical decomposition of limestone to lime, an ingredient in Portland cement clinker.

These emissions may be reduced by lowering the clinker content of cement. To reduce the transport of heavier raw materials and to minimize the associated costs, it is more economical for cement plants to be closer to the limestone quarries rather than to the consumer centers. In certain applications, reabsorbs some of the CO 2 as was released in its manufacture, and has a lower energy requirement in production than mainstream cement (citation needed). Newly developed cement types from Novacem and can absorb from ambient air during hardening. Use of the during production can also increase energy efficiency. Heavy metal emissions in the air [ ] In some circumstances, mainly depending on the origin and the composition of the raw materials used, the high-temperature calcination process of limestone and clay minerals can release in the atmosphere gases and dust rich in volatile, a.o,, and are the most toxic. Heavy metals (Tl, Cd, Hg.) and also are often found as trace elements in common metal (,,.) present as secondary minerals in most of the raw materials.

Environmental regulations exist in many countries to limit these emissions. As of 2011 in the United States, cement kilns are 'legally allowed to pump more toxins into the air than are hazardous-waste incinerators.'

Heavy metals present in the clinker [ ] The presence of heavy metals in the clinker arises both from the natural raw materials and from the use of recycled by-products or alternative fuels. The high pH prevailing in the cement porewater (12.5.