Cement – Wikipedia

The cement , in construction, indicates a variety of building materials, in particular hydraulic binders, which mixed with water develop adhesive properties (hydraulic properties).

Germany was, in 2014, the first producer in Europe (the second was Italy). ^[first] It is estimated that in 2009 36 million tons of cement were produced, equal to about 601 kg per inhabitant ^[2] . The 2008 world production was 2.83 billion tons, i.e. about 450 kg per capita. ^[3]

Ancient age [ change | Modifica Wikitesto ]

The use of the binder in buildings can be traced back to the third millennium BC, when plaster mortar was used for the construction of wall vestments in stone seizures. The Romans initially employed mainly the air lime. Until the Malta binder was made up only of air lime, the hardening of the concrete took place with extreme slowness, since the consolidation of a lime -based mortar is due to the reaction of calcium hydroxide with carbon dioxide present in the Air, with the subsequent production of football carbonate.

Starting from the first century BC The Romans began to replace the sand constituting the mortar with the pozzolana ( Puteolana pulva ) or with the cocciopesto . The discovery of the Pozzolana marked a revolution in the creation of masonry works. Vitruvius says in the II book of De Architecture that The Pozzolana di Baia or Cuma makes Gagliarda not only any kind of construction but in particular those that are made at sea underwater . Thanks to the pozzolanic behavior of the Pozzolana and the cocciopesto The mortar, consisting of air lime + pozzolana, made it taken and also harden in water, without contact with the air, allowing the production of high resistance binders and rapid hardening.

Middle Ages [ change | Modifica Wikitesto ]

With the fall of the Western Roman Empire he began, especially far from Rome, an inexorable decline in the construction field; This decline continued throughout the Middle Ages. During the Middle Ages, in fact, Pozzolana’s technology was abandoned in favor of binders such as lime grassello. ^{[ without source ]} With humanistic awakening, especially after the fourteenth century, the Latin texts of Pliny the Elder and Vitruvius were translated and noted. The re -edition of the The architecture edited by a Dominican, Giovanni Monsignori (Fra ‘Giocondo). This was followed by numerous other translations, which contributed to clarifying the secret of building according to the Romans. Thus, especially in eighteenth -century France, the art of well build works according to Roman knowledge was rediscovered.

Modern age [ change | Modifica Wikitesto ]

In the Renaissance era they refer to Vitruvius, and to the building Romano, architects of the caliber of Leon Battista Alberti and Andrea Palladio. The latter in 1570 describes in Treaty of architecture, books 4, Venice , the existence of a lime, kicked black , obtained for cooking a limestone originally from Paduan, containing clay impurities, with hydraulic characteristics. In this continuous approach to today’s concrete there was the revolutionary discovery of the hydraulic lime by the British engineer John Smeaton in 1756.

These, in the realization of Eddystone’s lighthouse, used, instead of the lime mixture – Pozzolana, the first hydraulic lime he obtained from the cooking of limestone containing a fair amount (about 11%) of claye impurities. The discovery of the hydraulic lime marks the transition from Roman concrete to the modern one, since the experimenters, with the help of the chemical science just born with Lavoisier, are able to govern a new synthesis process that will first lead to the artificial hydraulic lime, then to the modern Portland cement. Once discovered that the impurities of silica and alumina present in the clay that accompany some limestones are responsible for the formation of silicates and aluminated calcium, capable of hardening under water, the experiments in cooking artificial mixtures of limestone and clay at temperature began higher and higher up to a rudimentary cracking of the final product.

Contemporary age [ change | Modifica Wikitesto ]

Especially in England and France, between the eighteenth and the beginning of the nineteenth century inventions, patents and industrial initiatives that led to the production of the first industrial hydraulic binders, called cements, flourished. In particular in 1796 James Parker made the first quick -grip cement (Parker cement or Roman cement ), cooking in its lime ovens the marly concretions contained in the tamigi clays, while in 1800 Lesage obtained a high resistance hydraulic material by calcing the limestone pebbles of Boulogne Sur Mer. Generally the watershed between the hydraulic lime of Smeaton and the Portland cement Made, it is set to 1818, when the French engineer Louis J. Vicat defines the formula of artificial hydraulic lime.

In fact, Vicat was the first to understand that to obtain a material with hydraulic behavior there was no need to cook natural clay limestones but the same result could be achieved by combining in cooking pure limestones and any portion of clay. The first industrialist to have built slowly gripped hydraulic concrete seems to have been, in 1824, a Fornaciaro di York, Joseph Aspdin, who gave the product the name of Cemento Portland, thanks to the similarity between the mortar and the conglomerate formed with that concrete With a compact limestone (Portland stone) of the island of Portland in England. In 1844 J.C. Johnson highlighted the importance of high temperatures cooking processes that led to the formation of the clinker, the final product of the procedure.

In fact, while 600 – 700 ° C are required for cooking the hydraulic lime, 1450 ° C must be reached to obtain the cement with a slow grip, since a principle must be produced vitrification . In 1860 M. Chatelier established the chemical composition of the concrete allowing the industrialized production of concrete.

Cementist or boiacca pasta, cement plus water, is used as a mixture in mixture with inert materials such as sand, gravel or stone. Depending on the components we can have:

• In the event that the cement paste mixes with an aggregate fine (sand) there is cement mortar;
• In the event that aggregates of different sizes (sand, gravel and gravel), according to a certain granulometric curve, are combined with concrete paste, concrete is obtained;
• In the event that the concrete is coupled with an armor consisting of tondini also called steel “ribar” (Rigate bar), suitably positioned, there is the reinforced concrete (erroneously indicated with the name of reinforced concrete).

There are different types of concrete, different for the composition, for resistance and durability properties and therefore for the intended use.

Portland cement is the basis of almost all types of concrete currently usable in construction. From a chemical point of view, it is generally a mixture of calcium silicates and calcium aluminated, obtained from cooking at high limestone and clay or marl (in this case there is talk of natural cements). The material obtained, called clinker , is finely ground and added with chalk to the extent of 4-6% with the function of grip delay (primary ector). This mixture is marketed with the name of Portland cement; This, once mixed with water, progressively hydrates and solidifies. From the Portland cement, mixed with the additions available on the market in proportions set by UNI EN 197-1, all other types and concrete subtypes are obtained.

The only one who is the exception is the aluminous cement, which however is not taken into consideration by the aforementioned rule.

The common cements compliant with UNI EN 197-1 are divided into five main types:

• 
  ${displaystyle mathbb {I} Rightarrow }$

  Portland cement with a percentage of clinker equal to at least 95%: sink sink abbreviation: none;

• 
  ${displaystyle mathbb {II} Rightarrow }$

  composite portland cement with a percentage of clinker of at least 65%; There are 19 subtypes with the following denominations according to the type of additions:

  • CEMO Portland Alla Loppa (S): Sigla Sottotipi: II A/S, II B/S;
  • Portland cement to silica fumes (D): Sint -sized abbreviation: II A/D;
  • CEMO Pozland Alla Pozzolana: Sigla Sottotipi (P=naturale q=Calinnata): II A/P, II B/P, II B/P, II A/Q, II B/Q;
  • Portland cement to the flying ashes (V = siliceous; W = limestone): sintiveness sink: II A/V, II b/v, II A/W, II B/W;
  • Portland cement to the calcinated shale (t): sink abbreviation: ii a/t, ii b/t;
  • Portland cement to limestone (L and LL): sink sink abbreviation: ii a/l, ii b/l, ii a/ll, ii b/ll;
  • CESMO Portland Composito: Sigla Sottotipi: II A/M, II B/M;
• 
  ${displaystyle mathbb {III} Rightarrow }$

  altitude cement with a percentage of loppa di althoforno (s) from 36 to 95% (3 subtypes provided): sink sintapirs: III A, III B, IIO C;

• 
  ${displaystyle mathbb {IV} Rightarrow }$

  pozzolanic cement with pozzolanic material (p and q) from 11 to 55% (2 subtypes foreseen): Signs subtypes: IV A, IV B;

• 
  ${displaystyle mathbb {V} Rightarrow }$

  composite cement obtained by simultaneous addition of clinker of Portland concrete (from 20 to 64%), of Loppa of altrophorn (from 18 to 50%) and pozzolanic material (from 18%to 50%) (2 subtypes provided): Signs subtypes: V A, V B.

In the various cements, a content of secondary constituents is allowed ( fillers or other materials) not exceeding 5%.

The concrete resistance class depends on the finesse of the same and the percentage of tricalcal silicate compared to the Bicalcico one; The greater the fineness of grinding concrete, the greater the tricalcal silicate tenor than the bicalcic and faster the development of the mechanical resistance.

Each type of concrete is potentially available in six different classes of normalized resistance (at 28 days).

For each class of normalized resistance, two classes of initial resistance are defined (2-7 days):

• the first with ordinary initial resistance, marked with the letter “N”;
• The second with high initial resistance, marked with the letter “R”.

Therefore, according to UNI EN 19/17/1 there are the following classes of cement resistance:

• Class 32.5n: 7 -day initial compression resistance ≥ 16; Standard compression resistance to 28 days ≥ 32.5 ≤ 52.5
• Class 32.5r: 2 -day initial compression resistance ≥ 10; Standard compression resistance to 28 days ≥ 32.5 ≤ 52.5
• Class 42.5n: 2 -day initial compression resistance ≥ 10; standard compression resistance to 28 days ≥ 42.5 ≤ 62.5
• Class 42.5r: 2 -day initial compression resistance ≥ 20; standard compression resistance to 28 days ≥ 42.5 ≤ 62.5
• Class 52.5n: 2 -day initial compression resistance ≥ 20; Standard compression resistance to 28 days ≥ 52.5
• Class 52.5r: 2 -day initial compression resistance ≥ 30; Standard compression resistance to 28 days ≥ 52.5.

The numbers represent the compression resistance, expressed in MPA, which must have cubic provisions prepared in a standardized way with a/c equal to 0.5 and sand/cement ratio equal to 3. It is important to underline that this resistance is to be understood to be understood break.

The start time taken for each normalized resistance class are as follows:

• Classe 32,5: t ≥ 75 min;
• Classe 42,5: t ≥ 60 min;
• Classe 52,5: t ≥ 45 min;

Portland cement is the most used type of concrete, and is used as a binder in the preparation of concrete. It was invented in 1824 in England by the bricklayer Joseph Aspdin and owes the name to the similarity in appearance with the Portland rock, an island in the County of Dorset (England).

It is obtained from the mixing of the clinker , with the addition of plaster in the quantity necessary to regularize the hydration process. The microscopic analysis performed on unknown cement pieces found the presence of four main components and precisely the Alite (Tricalcico silicate), the Belite (Bicalcico silicate), the Celite (Tricalcico aluminated) and the brownmillerite (aluminated Ferrito Tetracalcico).
It is also used in the dental field as MTA (Mineral Trioxide aggregate) to isolate the endodonta from the periodontic.

The phases of the process for the production of cement are as follows:

• raw material extraction;
• control characteristics of raw materials;
• crushing;
• preomogenization;
• drying and grinding raw materials for production of raw mixture (“flour”);
• control characteristics of the flour;
• deposit and homogenization of the flour;
• preparation of fuels;
• Clinker cooking;
• CHARACTERISTIC CONTROL OF THE CLINKER;
• Deposit Clinker;
• Constituent and additives deposit;
• control of the characteristics of the constituents;
• Croomorous additives deposit;
• Cement grinding;
• control characteristics of the cements produced;
• deposit in the silos of the cements;
• sausage;
• control of conformity of CE cement;
• bulk shipping and bags.

The raw materials for Portland production are minerals containing: calcium oxide

${Displaystyle {ce {Ca}}}$

(44%), silicon oxide

${DisplayStyle {this {sio2}}}$

(14.5%), aluminum oxide

${DisplayStyle {this {al2o3}}}$

(3.5%), iron oxide

${DisplayStyle {this {Fe2o3}}}$

(2%) and magnesium oxide

${displaystyle {ce {MgO}}}$

(1.6%). The extraction takes place in mines, underground or open -air, placed near the factory, which generally already have the desired composition, while in some cases it is necessary to add clay or limestone, or iron mineral, bauxite or other residual materials of foundry.

In the case of the cement marl there is talk of mines (also in open -air excavations) and not of quarries (even if underground), since the marl is “cultivated” in the mining concession regime and not of authorization (as in the case of quarries). ^[4]

The mixture is heated in a special oven consisting of a huge cylinder (called kiln ) arranged horizontally with slight inclination and rotating slowly. The temperature grows along the cylinder up to about 1480 ° C; The temperature is determined so that the minerals aggregate but do not base and glass. In the lower temperature section, calcium carbonate (limestone) is split into calcium oxide and carbon dioxide (CO ₂ ), according to the reaction:

${Displaystyle {ce {CaCO3 -> CaO + CO2}}}$

${DisplayStyle {this {Casio3}}}$

It is

${displaystyle {ce {Ca2Si2O5}}}$

). A small amount of Tricalcico aluminated is also formed

${DisplayStyle {CE {CA3 (Alo3) 2}}}$

and by aluminated Ferrito Tetracalcico (C ₄ AF, result of the reaction

${DisplayStyle {this {4cao + al2o3 + fe2o3}}}$

). The resulting material is overall called clinker . The clinker can be kept for years before producing concrete, on condition of avoiding contact with water.

The theoretical energy necessary to produce the clinker It is about 1700 joules per gram, but due to dispersions the value is much higher and can reach up to 3000 joules per gram. This involves a great demand for energy for the production of concrete, and therefore a remarkable release in the atmosphere of carbon dioxide, greenhouse gas. The quantity of carbon dioxide released in the atmosphere is on average equal to 1.05 kg of

${DisplayStyle {this {Co2}}}$

per kilogram of clinker of Portland concrete product.

To improve the characteristics of the finished product at clinker About 2% of plaster or calcium sulphate is added and the mixture is finely ground. The dust obtained is the concrete ready for use.
The concrete obtained has a composition of the type:

When Portland cement is mixed with water, the product solidifies in a few hours and gradually hardens within several weeks. The initial hardening is caused by the reaction between water, chalk and the aluminated of Tricalcico, to form a crystalline structure of hydrated calcium aluminated (CAH), Eterngite (AFT) and monosolfate (AFM). The subsequent hardening and the development of internal voltage forces derives from the slowest reaction of the water with the Tricalcico silicate, to form an amorphous structure called hydrated calcium silicate (Csh Gel). In both cases the structures envelop and bind the individual granules of material present.
One last reaction produces silica gel (

${DisplayStyle {this {sio2}}}$

). All three reactions develop heat.

With the addition of the concrete of particular materials (limestone and lime) the plastic cement, faster socket and greater workability, is obtained. The prepared mortar using a mixture of Portland cement and lime is known as a bastard mortar.
This material is used in particular to cover the external surfaces of the buildings (plaster). In fact, normal cement does not lend itself to being spread.

In 2004 the main world manufacturers of Portland concrete with companies all over the world and also in Italy, are the Lafarge France, the Holcim Switzerland and the Cemex Mexico. In 2014 the French group Lafarge and the Swiss Holcim they were merged, Lafargeholcim, forming the first world cement manufacturer ^[5] .

Some concrete manufacturers were fined for behavior against the free market.

Clinker training reactions [ change | Modifica Wikitesto ]

If you analyze the production process, or what happens inside the cooking oven, it is found that several groups of reactions take place in subsequent temperature intervals:

${DisplayStyle {CE {3CAO + Al2o3 -> 3CAO*al2o3}}}}}}}}}}$

${displaystyle {ce {2CaO + SiO2 -> 2 CaO*SiO2}}}$

${Displaystyle {CE {CaO + Fe2O3 -> CaO * Fe2O3}}}$

${DisplayStyle {CE {Cao*Fe2o3 + 3CAO*Al2o3 -> 4CAO*al2o3*Fe_2O_3}}}$

${displaystyle {ce {2CaO*SiO2 + CaO -> 3CaO*SiO2}}}$

${DisplayStyle {this {3cao*sio2}}}$

(Alite, Tricalcico silicate);

25%
${DisplayStyle {this {2cao*sio2}}}$

(Belite, Bicalcico silicate);

twelfth%
${DisplayStyle {this {3cao*al2o3}}}$

(Celite, Tricalcico aluminated);

8%
${DisplayStyle {this {4cao*al2o3*fe2o3}}}$

(Brownmillerite, aluminated Ferrito Tetracalcico).

To be used for the production of hydraulic binders, the clinker according to EN 197-1 legislation must be made up of at least two thirds in mass of calcium silicates

${DisplayStyle {this {3cao*sio2}}}$

It is

${DisplayStyle {this {2cao*sio2}}}$

. The remaining part consists of clinker phases containing aluminum, iron and other compounds. The mass relationship

${displaystyle {ce {CaO/SiO2}}}$

it must not be less than 2.0. The tenor of

${displaystyle {ce {MgO}}}$

It must not exceed 5% en masse.

Hydration reactions [ change | Modifica Wikitesto ]

The phenomenon of grip and hardening of a concrete is linked to the chemical-physical transformations that take place between cement and dough water.
The most important chemical reactions, from the point of view of mechanical resistance, are as follows:

${DisplayStyle {CE {(3CAO*AL2O3) 2 + (x + 8) H2O -> 4CAO*al2o3*xh2o + 2CAO*al2o3*8h2O}}}$

${displaystyle {ce {3CaO*Al2O3 + 12H2O + Ca(OH)2 -> 4CaO*Al2O3*13H2O}}}$

${DisplayStyle {CE {4CAO*Al2o3*Fe2o3 + 7H2O -> 3CAO*Al2o3*6H2O + Cao*Fe2o3*H2O}}}$

${displaystyle {ce {(3CaO*SiO2)2 + (x + 3)H2O -> 3CaO2*SiO2*xH2O + 3Ca(OH)2}}}$

${displaystyle {ce {(2CaO*SiO2)2 + (x + 1)H2O -> 3CaO2*SiO2*xH2O + Ca(OH)2}}}$

Resistance of cements [ change | Modifica Wikitesto ]

The factors that act on the initial and final resistance for a certain type of concrete are the quality of the raw materials, in particular of the clinker and the finesse of grinding. The most important of water-cement A/C and the seasoning time are more important, which determine the porosity of the cement aggregate and which, in turn, characterizes compression resistance and corrosive agents.

Rapporto Alite/Belite [ change | Modifica Wikitesto ]

The hardening, and therefore the binding power of concrete, is largely due to the formation of calcium hydrate silicates, while the formation of aluminum hydrate silicates are the main cause of the grip ^[6] . The main physical, chemical and mechanical characteristics of the inducement of Portland concrete pastes depend on the hydration of silicates. Among the types of silicates, the Tricalcic one is the fastest in reacting with water and developing mechanical resistance. This determines, in the short deadline, a different behavior of the Portland cements in which the percentage of trical silicate is greater than the Bicalcico one. In fact, the cements rich in Alite reach good mechanical resistance already a few days after the jet and involve, as we will see later, a greater development of the hydration heat.

At long maturations, on the other hand, the hydration products of the two silicates lead to the same values ​​of the mechanical resistance and, therefore, in the long term the mechanical behavior of the cement conglomerate is independent of the Alite/Belite relationship. Therefore, a clinker with a greater content of Tricalcico silicate allows a rapid resistance gain, while one that contains a greater amount of Bicalcico silicate develops resistance less quickly, while reaching equally satisfactory final resistance. In addition, the bicalcic silicate hydrating produces a greater amount of calcium silicates hydrated than the Tricalcic silicate.

Another difference between the two silicates is that, during the hydration of the Tricalcic silicate, a greater percentage of calcium hydroxide is produced

${displaystyle {what {ca (oh) 2}}$

(30-40%) compared to that produced during the hydration of the Bicalcico silicate (10-15%). Therefore, the cewing richest in Bicalcico silicate are the most indicated in the case, for example, of rampant waters or sulphate attack.

Finesse of grinding [ change | Modifica Wikitesto ]

To influence the development of initial resistances, in addition to the relationship between the Tricalcic silicate and the Bicalcico silicate, there is also the finesse of grinding. A fine concrete has a greater specific surface and therefore greater hydration speed.

Hydration heat [ change | Modifica Wikitesto ]

All the hydration reactions of the clinker constituents are exothermic. The hydration heat depends on the type and class of cement. The greater the Portland concrete tenor, the greater the finesse of grinding (i.e. the resistance class), the greater the heat of hydration. Therefore, mixture cements produce less hydration heat compared to Portland cement. The quantities of heat emitted during the hydration of the main constituents of the Portland clinker are:

As a result of the hydration heat, concrete undergoes a heating with respect to the initial temperature of the jet that coincides with that of the environment. The temperature trend in a concrete following the hydration of the cement is of the type To Campana , in fact in the first 2-3 days it will be growing since the heat of hydration develops at high speeds. Subsequently it will decrease, since the dissipation of heat towards the external environment prevails over the heat due to hydration, which after about 7 days is produced much more slowly.

This trend To Campana It takes on different values ​​according to whether it refers to the cortical area or the internal nucleus. In the first case, the outdoor dissipation action is more marked than the one in the second case, therefore inside in the same period there are higher temperatures than those of the most superficial area. This thermal gradient determines the onset of self -intentions since the internal (warmer) nucleus opposes the greater contraction of the cortical area (colder).
As far as the nucleus is compressed while the cortical part is tense; This tensional state can cause cracks in the surface with repercussions on the durability of the material. As a rule, this risk is limited since concrete at this stage has just started the hardening process, therefore the tensions that arise are limited due to the low value of the Young module and the effects of the viscous relaxation of the material.

This phenomenon is instead more insidious in the massive jets such as those for the creation of dams where, due to the low coefficient of conductivity of the concrete, the nucleus cools very slowly. Therefore the contraction of the internal part of the concrete takes place in very hardened concrete (therefore to values ​​of the Young module close to those of operating and with less accentuated viscosity values). In these conditions, the opposition made by the most superficial part to the internal contraction determines much higher self -intentions than the previous situation, also in this case it is the nucleus that is subject to traction with the risk of uncompable and therefore more dangerous internal cracks.

Function of chalk [ change | Modifica Wikitesto ]

The plaster is usually added to the clinker to adjust the socket. Its presence makes sure that the start of the socket is greater than 75 minutes for the compression resistance class 32.5 N/mm², 60 minutes for the resistance class 42.5 N/mm² and greater than 45 minutes For the 52.5 N/mm² class. The chalk reacts with the Tricalcic aluminated to form an expansive salt called Ettingite (primary ector). The speed of reaction between the

${DisplayStyle {this {ca3a}}}$

and the

${DisplayStyle {CE {Caso4}}}$

It is very high, but slows down quickly due to the formation of protective layers on the surface of the aluminated. The kinetics of the reaction also depends on the temperature, the reaction surface, and the water/solid ratio.

(High) 3 Al 2 O 3 + 3 (case 4 2h 2 O) + 26H 2 O → (high) 3 Al 2 O 3 3CASO 4 32H 2 O

The cements in accordance with UNI EN 197 must contain depending on the resistance class a quantity of sulphates expressed as

${displaystyle {ce {SO3}}}$

≤ 3.5% for classes 32.5; 32.5 r; 42.5; while for classes 42.5 r; 52.5; 52.5 r; the amount of

${displaystyle {ce {SO3}}}$

It must be ≤ 4.0%.

The amount of sulphates like

${displaystyle {ce {SO3}}}$

In cements it is determined according to the EN 196-2 standard.

Moduli [ change | Modifica Wikitesto ]

The modules are characteristic values ​​of any concrete or lime, which allow you to know in what relationship the different components are in the percentage of the final product. For the concrete Portland you have:

${Displaystyle m_ {i} = {frac {$

ratio between the basic and acid component of cement varies 1.7 to 2.2

${displaystyle M_{s}={frac {$

relationship between cementants (

${DisplayStyle {this {sio2}}}$

) and dark (

${DisplayStyle {this {al2o3}}}$

It is

${DisplayStyle {this {Fe2o3}}}$

). The greater its most difficult value will be cooking;

${displaystyle M_{c}={frac {$

${Displaystyle m_ {f} = {frac {$

Portland concrete classification according to ASTM [ change | Modifica Wikitesto ]

The American legislation provides for 5 types of Portland cements:

• ordinary – i
• modified – II
• rapid hardening – III
• low heat of hydration IV
• sulphates resistant – V

Special Portland cements [ change | Modifica Wikitesto ]

I Special Portland cements They are cements that are obtained in the same way as Portland, but which have different characteristics from this due to the different percentage composition of the components.

Portland Ferrico [ change | Modifica Wikitesto ]

Portland Ferrico is a particular type of Portland characterized by a dark form module of 0.64 and is obtained by introducing ashes of pyrite or iron mineral powder. This means that this concrete is very rich in iron and, precisely, which has an equal or almost equal number of iron atoms and aluminum atoms. In these all cements, or almost all, the alumina is contained in the Ferric phase and therefore has a very low or even null percentages of aluminated tricalcio (celite).

Since the Tricalcico aluminated is among the constituents of the clinker what during hydration develops more heat, the Portland Ferrici cements have the characteristic of producing little heat during hydration and therefore are particularly suitable for thrown into hot climates or for massive jets (dams, foundation audiences, etc.).

Thanks to their reduced Tricalcico aluminated content, Portland Ferrici cements are more resistant than normal Portland to the sulphate attack. The best iron cements are the low limestone module. They contain, in fact, a lower amount of alite (

${DisplayStyle {this {3caosio2}}}$

), whose hydration produces the greatest amount of free lime (

${displaystyle {what {ca (oh) 2}}$

). Since free lime is the component most attacked by aggressive waters, these cements, containing less quantities, are also more resistant to the action of these waters. The inconvenience of these cements is that precisely for the low Ticalcico aluminated tenor, which is the fastest of the clinker components to take hold, they hydrate more slowly, with consequent slower development of the mechanical properties.

Cements resistant to sulphates [ change | Modifica Wikitesto ]

One of the basic components of clinker It is the Tricalcico aluminated,

${displaystyle {ce {C3A}}}$

, which in contact with sulphate waters or senitous soils, reacts giving rise to henternity. Therefore in structures subject to the sulphate attack, such as those with exposure class XA1, XA2 or XA3, for the UNI EN 206-1: 2006 and UNI 11104 standards, the use of sulphates resistant cements is essential.

They are defined resistant cements to the sulphates, those cements (of type I, II, III, IV) made with Portland Ferrici cements, which for their composition mainly have a low Tricalcico aluminated content (Celite), and alumina is present in the most in the form of a tetracalcic aluminated ferrito (Ferrica phase –

${DisplayStyle {this {c4af}}}$

), and among these those with low limestone module also have a low Tricalcico silicate tenor which during hydration produces a greater amount of lime.

In the pozzolanic (type IV) or siderurgical cements (type III), as well, since both the pozzolana and the altlap loppa hydrated by producing neither aluminated trintage nor lime (indeed in the activation of the pozzolana there is also a part), l Protective effect on the sulphate attack is even more marked.

For type I cements, for example, the UNI 9156 standard classifies the cements as follows:

The amount of sulphates expressed as

${displaystyle {ce {SO3}}}$

In cements it is determined according to the EN 196-2 standard.

Regarding the exposure class, the UNI 8981-2 standard prescribe the following:

• for the XA1 exposure class (weak attack) – Moderate chemical resistance to the sulphates (M.R.S.);
• for the XA2 exposure class (moderate attack) – high chemical resistance to the sulphates (A.R.S.);
• For the XA3 exposure class (strong attack) – cement with very high chemical resistance to the sulphates (AA.R.S.).

For more severe attacks than those envisaged by the aforementioned classes of exposure (very strong attack) it is necessary to resort to additional protections, using surface protections such as sheaths, resins or waterproofing paintings.

Resistant cements [ change | Modifica Wikitesto ]

During the hydration of the concrete, calcium hydroxide is produced, commonly called lime . If the concrete comes into contact with dilapant waters, or very pure or rich waters of aggressive carbon dioxide, the lime is delased, leaving micropors in the cement matrix with the consequent reduction of the degree of durability, since these pores facilitate the entry of aggressive agents all interior of concrete. In the case of waters also calcium hydroxide, which is rather soluble in water, spontaneously passes in solution and is dilated, while in the presence of aggressive carbon dioxide the lime, reacting with this, turns into calcium bicarbonate, which, Being soluble, it is delated by the water. Therefore, in structures subject to dilapant waters such as those with exposure class XA1, XA2 or XA3, they must be made with cements to particular performances called celesses resistant to the flooding.

Since calcium hydroxide is mainly due to the presence of Tricalcic silicate, from whose hydration the greatest quantity of lime is produced free the resistant cements to the widening have a reduced alite tenor such as cements packaged with special Portland cement.

Since the altitude and pozzolanic cements what they hydrate do not produce solubled calcium hydroxide, indeed in pozzolanic ones a part is consumed to activate pozzolana, the protective behavior to the rampant action of these binders is even more marked.

The UNI 8981-3 standard prescribe the following:

• for the XA1 exposure class (weak attack) – Moderate resistance to the delaw (M.R.D.);
• for the XA2 exposure class (moderate attack) – high resistance cement (A.R.D.);
• For the XA3 exposure class (strong attack) – highly resistance to the expansion (AA.R.D.).

For more severe attacks than those envisaged by the aforementioned classes of exposure it is necessary to use surface protections such as sheaths, resins or waterproofing paintings.

Low -heat hydration cements [ change | Modifica Wikitesto ]

The low-heat hydration cements, or LH type, according to UNI EN 197-1 are ordinary cements whose heat of hydration cements must not exceed the characteristic value of 270 j/day (according to the EN 196-8 at 7 days e le EN 196-9 at 41 h).

Generally they are packaged cements with Portland Ferrico with a low Tricalcic and aluminated Tricalcio silicate tenor, which are the two main constituents of the clinker that produce greater hydration heat, as well as are grinded more coarse than common ones (less hydration speed) .

Pozzolanic cements and the althanks also develop a low heat of hydration.

They are used for massive jets, since in these cases, since the concrete is a bad heat conductor, the heat innermost to the jet is eliminated when the conglomerate is already hardened.

Therefore the contraction of the central nucleus is contrasted by the cortical part of the concrete; It follows the onset of internal tensions that can disintegrate concrete.

This type of concrete must be used in general when the thermal gradient between the interior and the exterior of the jet is: δt ≥ 25-30 ° C.

For concrete jets in large reservations of withholding taxes, VHL hydration of hydration compliant with the UNI EN 14216 standard must be used.

White cements [ change | Modifica Wikitesto ]

Contrary to Ferric cements, the white cements have a very high grade module, equal to 10. They will therefore contain a very low percentage of FE ₂ O ₃ But also of Manganese.

The white color is due precisely to the iron deficiency that gives a grayish color to the normal Portland and a darker gray to ferric concrete ^[7] .

But since Fe ₂ O ₃ It is the component that allows the merger in the cooking phase, its dark action will be restored by adding darks such as fluorite (CAF ₂ ) E la criolite (na ₃ AlF ₆ ).

White cements are often used to pack open -sided concrete where light color inert are also used.

Colored cements [ change | Modifica Wikitesto ]

Other special Portland cements are colored ones that are obtained by mixing white concrete with a colored pigment. It is important that the pigment does not contain harmful substances both for the hydration of the cement and for the durability of the concrete.

I Cements of mixture They are obtained by adding other components such as the pozzolana or the Loppa to normal Portland. The addition of these components gives these types of cements new characteristics compared to normal Portland.

Pozzolanic cement [ change | Modifica Wikitesto ]

Pozzolana is a fine volcanic ash traditionally extracted in Pozzuoli, on the slopes of the Solfatara, but also in several other volcanic regions. Already Vitruvius described four types of pozzolana: black, white, gray and red.

Mixed with lime (2: 1 relationship) it behaves like pozzolanic cement and allows you to prepare a good mortar, capable of taking also under water.
This property allows an innovative employment in the construction of concrete structures, as the Romans had already well understood:
The ancient port of what was made of pozzolana mixed with lime just before use and thrown under the water, probably using a long tube to deposit it on the bottom without dispersing it in sea water.
The three moles are still visible today, with the underwater part still in good condition after 2100 years.

Pozzolana is a acidic stone, very reactive as very porous and obtainable at low cost. A pozzolanic cement contains approximately:

• 45-89% of clinker Portland
• 11-55% of Pozzolana
• 2-4% of chalk

Since the pozzolana reacts with the lime (

${displaystyle {what {ca (oh) 2}}$

), there will be a lower amount of the latter. But precisely because the lime is the component that is attacked by aggressive waters, the pozzolanic cement will be more resistant to the action of these. Also, since

${DisplayStyle {this {Caco3*al2o3}}}$

It is present only in the component constituted by clinker Portland, the throttle of the pozzolanic cement will develop less reaction heat. Furthermore, a lower Tricalcico aluminated content guarantees greater resistance to the sulphate attack. This concrete can therefore be used in particularly hot climates or for large throwns or when you are in the presence of aggressive or sulphate waters.

Siderurgical concrete or altitude cement [ change | Modifica Wikitesto ]

The Pozzolana was in many cases replaced by ash of coal from the thermoelectric power plants, foundry waste or residues obtained by heating the quartz. These components that take the name of Loppa, have a latent hydraulic activity and therefore, suitably ground, are used as mineral additions and mixed with Portland cement in proportions ranging from 36 up to 95%.

Unlike the pozzolanic cements, which must have a clinker tenor such as to guarantee a lime content necessary for the activation of the pozzolana, the Loppa needs only small quantities of lime, and therefore of the clinker of Portland, to accelerate its hardening .

Therefore the percentage of Loppa granulata of altrophorn in a steel cement can be very high, but as the Loppa tenor grows, since his hardening process is slow, the value of the mechanical resistance to short seasoning (2 – 7 days) of the mechanical resistance decreases steel cement; This value is essentially due to the action of the Portland clinker and grows to the increase in clinker tenor. Therefore, for Loppa tenors above 90%, short -term compression resistance is practically absent, being the amount of small Portland cement; In these percentages it is not possible to produce resistance class cements 42.5r, 52.5 and 52.5r, since these steel cements cannot guarantee the minimum resistance values ​​with 2 days compression provided for by UNI EN 197-1. Within certain limits, the initial slowdown can be compensated by increasing the finesse of grinding and acting on the seasoning conditions.

Given the low clinker tenor compared to that present in the Portland cement, the steel cement presents the same performance as the pozzolanic concrete, indeed, since the clinker tenor can be very low as it is not necessary that a lime content necessary to the necessary lime is guaranteed ‘activation of the pozzolana, these properties are more marked.

Furthermore, the so -called above -sized cements that the UNI EN 197 -1 identify with the abbreviation CEM III/c are part of the steel cements.
They are the high percentage of Loppa (80-85%) and chalk (10-15%) steel surgical cements, while they have a Portland clinker tenor around 5%.

Therefore, among the products of hydration, in addition to the Silicati di Calcio hydrates (C-S-H) we also find crystalline eternity (we are in the absence of lime due to the low clinker tenor) which compared to the colloidal one, which is formed in normal cements following the sulphate attack, is not swollen. This cement has a good resistance to chemical attacks (chlorides and sulphates) and the attack of acids (solutions with pH> 3.5).

Hydration of mixture cements [ change | Modifica Wikitesto ]

Once the hydration of the fraction of the Portland clinker has started present in the mixture of mixture, in addition to the formation of calcium hydrate silicates (C-S-h), lime is also produced. The latter activates the pozzolana or the mix of the mixture of mixture whose hydration produces a further amount of C-S-H. In this way, the lime, which alone does not contribute to the development of mechanical resistance, contributes to the process of hardening the concrete. The formation of this further rate of hydrate calcium silicates determines a system richer in fibrous material and, therefore, less porous and less permeable than a Portland concrete with the same water/cement ratio. Furthermore, the lesser quantity of lime, both because the clinker tenor is less, and because it is part of this reacts with pozzolana or the Loppa, in association with a more compact matrix, makes these cements less subject to problems of sulphate attack, dilance and carbonation ^[8] .

The Quick socket cement , also said concrete ready, has the characteristic of thickening in a few minutes from mixing with water.
It is produced similar to Portland concrete, but with lower cooking temperatures.
The grip speed depends on both the quantity and quality of the additives and on the amount of mixture chalk.

It is used alone or mixed with sand (mortar) and is suitable for small fixing and repair works, while it is not suitable for major works, as there is no time to carry out a good jet.

I Expansive cements They consist of a mixture of concrete and expansive additives and are used to compensate the negative effects due to retreat or forgress.

Their behavior is based on training, during the hydration of expansive products, of:

Currently the US standards identify three types of expansive cements, according to the additives used:

This type of cements is used to obtain:

• compensated withdrawal cements that cause an initial expansion equal to the subsequent contraction due to the withdrawal within the concrete;
• self -compressed cements (in English Self Compressing Concrete O SCC ) which cause an initial expansion much higher than subsequent retreat contraction within the cement conglomerate. There are mortars based on highly expansive cements (the thrust generated can reach about 6000 t/m²) which are used for demolitions and cuts of rocks and concrete without production of noise, vibrations and debris launches.

The aluminous cement O melted cement It is the product obtained from cooking to the almost complete fusion of a mixture of bauxite and limestone or the calcium carbonate.

Bauxite, made up mainly of hydrate aluminum oxides, sometimes contains even in significant quantities, anhydrical oxides and iron hydrates, silica, aluminum hydrate silicates and small percentages of titanium dioxide. The limestone and bauxite mixture is brought during cooking at a temperature of 1550 – 1600 ° C. For cooking, reference is made to different types of ovens:

The melted cement is poured into molds to form breads, which will then be cooled externally to water and finally ground in ball mills to obtain the finished product.

Aluminous cement has a composition in oxides of:

As for the actual components, you have:

• 60-70%
  ${DisplayStyle {CE {Caal2o3}}}$

  

• 10-15%
  ${displaystyle {ce {2CaOSiO2}}}$

  

• 
  ${DisplayStyle {this {ca4oal2o3fe2o3}}}$

  

• 
  ${DisplayStyle {CE {Ca2oal2O3SIO2}}}}$

  

As for silicon oxide, its presence as impurities must be less than 6%, as the component that originates, the aluminated Silicato Bicalcico (

${DisplayStyle {CE {2CAAAAAAAAAL2O3SIO2}}}}$

), has little hydraulic properties.

Italian legislation prohibits the use of aluminous concrete for the construction of reinforced concrete works.

Aluminous concrete is characterized by rapid hardening and therefore by high values ​​of short -term mechanical resistance.
Another advantage is its resistance to the sulphate attack and the rampant action of the water.

On the other hand it has a high heat of hydration.

Hydration reactions [ change | Modifica Wikitesto ]

• 
  ${Displaystyle {ce {CaAl2O3 + 10H2O -> CaO*Al2O3*10H2O}}}$

  
  ${DisplayStyle {CE {2 (Caoal2O3) + 11h2O -> 2CAO*al2o3*8h2O + Al (OH) 3}}}$

  
  ${displaystyle {ce {2(Ca2OSiO2) + (x + 1) H2O -> Ca3O2*SiO2*xH2O + Ca(OH)2}}}$

  

  ${displaystyle {what {ca (oh) 2}}$

  , aluminous cement is substantially neutral. The presence of aluminum hydroxide (

  ${displaystyle {ce {Al(OH)3}}}$

  ), which is an amphetical and which in this case behaves as an acid, causes the substantial neutralization of the two components and as a result there is a neutral cement.

  Alkalinity [ change | Modifica Wikitesto ]

  After the Portland concrete has been mixed with water, the format formed is very alkaline (about pH 13) due to the release of calcium hydroxides, sodium and potassium. On the skin it has a caustic effect and in case of contact it is necessary to wash immediately with plenty of water. Gloves and glasses should be used to protect the eyes from splashes. Once hardened, the cement can be touched without problems.

  Presence of chromium [ change | Modifica Wikitesto ]

  In concrete, a certain amount of hexavalent chromium can be contained. By now in many countries the hexavalent chromium content is regulated. For example in Europe, according to the European Community legislation, it must not exceed 2 parties per million (mg/kg). Metallic chromium can be contained in higher quantities. To date they are placed in the bulk cement of the additives that transform the hexavalent chromium (carcinogenic-mutagen) into trivalent chrome (not harmful). These additives have a time of efficiency that varies from three to six months.

  The European Directive 2003/53/EC, implemented in Italy through the Ministerial Health Decree D.M. May 10, 2004, prohibits the marketing and use of concrete or preparations containing concrete which, when hydrated, contain more than 0,0002% (2 ppm) of hexavalent hydrosoluble chrome, determined as a mass percentage on dry concrete.
  This decree prevents some problems relating to the possibility of contact allergic dermatitis and risks related to the fact that the

  ${Displaystyle {ce {cr^{Vi}}}}}$

  It is carcinogenic for man.

  The total chromium (state of oxidation II and III) present in the Portland clinker is between 0.002% and 0.02%, respectively 20 and 200 ppm. This value essentially derives from clayey materials, minimally from the fuels, from the grinding bodies of the molino del raw and the refractory. During the cooking process of the clinker all the total chromium is oxidized, and to the thermodynamic conditions in the area, the most stable species is the

  ${displaystyle {ce {Cr^{III}}}}$

  , insoluble, and therefore not dangerous for health.
  During the cooling phase a part of

  ${displaystyle {ce {Cr^{III}}}}$

  It oxidizes in

  ${Displaystyle {ce {cr^{Vi}}}}}$

  It is

  ${displaystyle {ce {Cr^{V}}}}$

  . So in the Portland clinker the chromium is present in three states of oxidation (+3, +4, +5). Of all the chromium present only one part is linked to the clinker phases (77%-93%), while the remaining part (from 7%to 23%) can be easily solubilized, except

  ${displaystyle {ce {Cr^{III}}}}$

  which is insoluble, as mentioned above. The two species soluble in water,

  ${Displaystyle {ce {cr^{Vi}}}}}$

  It is

  ${displaystyle {ce {Cr^{V}}}}$

  , are not stable and therefore disrupt a

  ${displaystyle {ce {Cr^{III}}}}$

  insoluble e

  ${Displaystyle {ce {cr^{Vi}}}}}$

  soluble.

  In order for the Ministerial Decree to be respected May 10, 2004 it is necessary to add a reducing chrome agent. Commonly the most used reductive agent is ferrous sulphate, but other very promising solutions have been identified and created (antimony additives, sodium-trisolphurus, monohydrate ferrous sulphate, stannous sulphate). Ferroso sulphate is dosed at 0.25-0.3% and does not minimally influence the hydration reactions of the cement, but in contact with the air it is carbonated, losing its reduced power towards the hexavalent chromium. For this reason, the packaging date and the conservation period during which the content of

  ${Displaystyle {ce {cr^{Vi}}}}}$

  Hydrosoluble remains less than 0,0002% of the total dry weight of cement.

  Below are the oxide-eradication reactions that take place in the case of use of monohydrate ferrous sulphate or with the threexide of diantimity:

  ${displaystyle {ce {K2Cr2O7 + 6 FeSO4 + 7 H2O -> Cr2(SO4)3 + Fe2(SO4)3 + 4 Fe(OH)3 + 2 KOH}}}$

  

  ${displaystyle {ce {2 K2Cr2O7 + 3 Sb2O3 + 5 H2O -> 2 Cr2(OH)3 + 2 Cr(Sb2O3)3 + 4 KOH}}}$

  Pollution [ change | Modifica Wikitesto ]

  

  A concrete production plant in the 1930s could have important health effects due to the substances issued by the processing processes, as well as by accessory activities (truck traffic, extraction with explosives). Nowadays the evolution of technology and the legislation adopted by all the main developed countries has made it possible to reduce these risks.
  In particular, clinker cooking requires large quantities of fuel, normally pet-cake (product derived from oil), which causes an emission of pollutants, including greenhouse gases, nitrogen oxides (no _x ), sulfur dioxide (

  ${displaystyle {ce {SO2}}}$

  ), carbon monoxide (

  ${displaystyle {what {co}}}$

  ), carbon dioxide (

  ${DisplayStyle {this {Co2}}}$

  ), volatile organic compounds and fine dust (PM10 and PM2.5) ^[9] .

  Cementifications reach combustion temperatures of 1400 ° C. Don’t indicate the coinciding of waste in cement factories because the waste material or the CDR can only be placed through the precalcination area that has temperatures of about 800 ° C, definitely too low and too dangerous.

  The cements, by law, are all equipped with combustion fumes reduction systems such as sleeves filters for very high temperatures: the large amount of air necessary to burn the fossil fuels acting diluting the pollutants contained in waste and therefore in emissions to the fireplace . Despite the absence of specific treatments against dioxins and mercury, there are concentrations of pollutants well lower than the minimum values ​​imposed by the law (European legislation).

  The European registers Ines/Eper confirm that there are no significant lead, mercury, ammonia emissions. ^{[ without source ]}

  Danger of collapse [ change | Modifica Wikitesto ]

  The use of weakened cement has led to numerous collapses in many Italian regions. ^[ten] Roads, bridges, viaducts, railways, galleries, houses, shopping centers and even schools, hospitals and commissioners are at risk of collapses, because they are built with little cement and a lot of sand, so -called weakened cement. The deal is profitable for those who contract public or even private works, winning national and local contracts at low prices, then saving during the execution of the works through the use of low concrete mortars and concrete. ^[11]

  Technological evolution in safety [ change | Modifica Wikitesto ]

  The University of Newcastle made a bio-cement in 2019 capable of self-relevant in the event of cracks or fractures. Inspired by the bacterium FILLA BACILLA , this type of concrete reacts to the changes of pressure of the environment by creating calcium carbonate molecules ^{[twelfth] [13]} .

  Also in Italy a bio-cement from oxygenated water and brewer’s yeast was born that does not need aluminum ^[14] .

  The CE marking does not represent a product quality brand but means that the product meets the essential requirements for that product and for the expected use.

  For concrete there is only one system of certificate of CE conformity:

  • Level 1+: The declaration of conformity to the UNI EN 197 standard is required, issued by the manufacturer and accompanied by the certificate of compliance of the product to the UNI EN 197 standard issued by a notified body.

  Generally the CE marking takes place by affixing a label directly on the products, or on the packaging, by printing the label on the transport document (DDT).

  The lay-out and the label information content are described in the following points.

  

  Until 1993, the Ministerial Decree was in force in Italy 3 June 1968 and S.M.I. containing the rules on the requirements and proof of the cements.

  With the advent of community rules in the European Union in Italy, UNI EN 197-1 has entered into force, which collects all types of cement produced until then in the various member countries in a single classification.

  For European legislation, the fundamental requirements of cements are:

  • the composition;
  • The normalized resistance class (28 days) expressed in MPA with reference to the initial compression resistance (seven days for 32.5n and two days for the other classes).

  UNI EN 197-1 provides five types of cement, twenty-seven subtypes and six resistance classes.

  Therefore, according to the standard, 162 (27 × 6) cements are produced.

  With the entry into force of the UNI EN 197-1 standard, the nomenclature relating to the cements was complicated. In fact, the rule requires that an alphanumeric code consisting of: the abbreviation ‘CEM’, followed by type, subtype, a normal resistance class and type of initial hardening (if rapid is reported, the letter r if ordinary is the letter n). In the case of low -heat cement cements, the abbreviation LH must also be reported. Therefore the Code of Cemento Portland 325 with ordinary initial resistance is now CEM the 32.5 N.

  All reinforced concrete and reinforced concrete artifacts can be performed by using only cement cements of CE compliance certificate that meet the requirements of UNI EN 197-1. All concrete supplies, on site or at the concrete pre -packaging system, must be accompanied by:

  • transport document (DDT);
  • Declaration of conformity EC issued by the manufacturer reporting at least the following indications:
    • data of the manufacturer and the legal representative
    • name of the manufacturer
    • General product descriptions data
    • address of the plant
    • rules and directives to which the product complies
    • number of the CE certificate
    • Information relating to the production Ex: N ° serial number, lot, match, last two digits of the year of production
    • date and autographed signature of those who subscribe to it
  • CEA of CE conformity to the UNI EN 197-1 standard issued by a notified body.

  In addition, the label shows the EC symbol applied on packaging or product or DDT must also be present;
  The supplies made by an intermediary, for example an importer, must be accompanied by the declaration of conformity, issued by the concrete manufacturer and completed with the references to the transport documents (DDT) of the lots delivered by the same intermediary.

  The works manager is required to periodically verify the above, in particular the correspondence of the concrete delivered, as detectable by the aforementioned documentation, with that provided for in the special tender specifications and in the documentation or specific technical documents.

  Label ce [ change | Modifica Wikitesto ]

  The label with the CE marking symbol that must be applied to the product, packaging or on the DDT, in the simplified version must report at least the following information:

  • CE compliance marking, consisting of the “ce” symbol
  • Identification number of the certification body (e.g. 0123)
  • Name or identification brand and address of the manufacturer
  • Last two digits of the year in which the marking was applied (e.g. 10 per 2010)
  • number of the CE conformity certificate (e.g. 0123cpd). Often this number is associated with the previous one (e.g. 0123cpd-010)
  • standard to which the product and compliant (UNI EN 197)

  In the extensive form (method 3) the label can contain:

  • Product description (e.g. CEM II/A – LL 32.5r)
  • Information on product and relevant characteristics.

  • UNI EN 197-1: 2011 – Cement – Part 1: Composition, specifications and conformity criteria for common cements
  • UNI EN 14647: 2006 – Aluminous cement – Composition, specifications and conformity criteria
  • UNI EN 14216: 2005 – Cement – Composition, specifications and conformity criteria for special cements for very low hydration heat

  1. ^ Copy archived ( PDF ), are Aitecweb.com . URL consulted on September 24, 2015 (archived by URL Original on September 25, 2015) .
  2. ^ The consequences of cement , Martinelli 2011, P.76
  3. ^ ( IN ) Jealousy, Activity Report 2008 ( PDF ) ^{[ interrupted connection ]} , p. 4. URL consulted on May 3, 2009 .
  4. ^ See also reference regulations:
     • Royal Decree n. 1443 of 1927 – legislative rules to regulate the research and cultivation of mines in the kingdom.
     • Decree of the President of the Republic n. 128 of 09/04/1959 – Police rules of mines and quarries.

  5. ^ Lafarge -Holcim merger, the first World Cement Manufacturer – News – Italiaoggi was born . are Italiaoggi.it . URL consulted on 29 July 2015 .
  6. ^ Silicates hydrate aluminum contribute in an unmerally significant way to the development of mechanical resistance and in any case their action is expressed mainly during the first hours of the hardening phase.
  7. ^ Common cements are also called gray cements.
  8. ^ Although the percentage of lime is less than an equivalent Portland cement, in mixture cements always remains a sufficient amount to make the water contained in the capillary pores saturated with calcium hydroxide and therefore guarantee the cement matrix a pH (> 12) capable of passing the armor
  9. ^ https://www.renewablematter.eu/articoli/article/cemento-il-materiale-piu-distrutto-del-mondo-o-una-leva-dellevoluzione
  10. ^ In Sicily used weakened cement, collapses risk. Agliastro alarm . The Nissian fact. Chronicle. February 27, 2015.
  11. ^ Ecomafia. Weakened cement, dozens of works at risk of collapse . The print. June 4, 2010.
  12. ^ Biological concrete: an innovative material that is back! – Very habiton . are habitissimo.it . URL consulted on January 13, 2021 .
  13. ^ Biocement: the “living” building material that is repaired by itself . are The patent , 29 November 2019. URL consulted on January 13, 2021 .
  14. ^ Stefania, Super-Isolant bio-cement: the innovative Italian patent . are Renewables , 17 November 2017. URL consulted on January 13, 2021 .

  • Marcus Collepardi The new concrete , Tintoretto (Villorba – TV), 2002
  • P. Pedeferri, L. Bertolini, Corrosion in concrete and natural environments , McGraw-Hill
  • V. pupil Rossetti, Concrete: materials and technology , McGraw-Hill, 2003
  • V. pupil Rossetti, F. Medici, Applied chemistry Ed. Scientifier stellar (Rome), 2007
  • Marcus Collepardi T as temperature – ECO Journal

  • cement . are TRECCANI.IT – encyclopedia online , Institute of the Italian Encyclopedia.
  • ( IT , OF , FR ) Cement . are HLS-DHS-DSS , Historical dictionary of Switzerland.
  • ( IN ) Cement . are British encyclopedia Encyclopaedia Britannica, Inc.
  • Cement , in TRECCANI.IT – encyclopedia online , Rome, Institute of the Italian Encyclopedia.