EP2723696A1 - Composition hydraulique soumise à un traitement thermique - Google Patents

Composition hydraulique soumise à un traitement thermique

Info

Publication number
EP2723696A1
EP2723696A1 EP12734843.1A EP12734843A EP2723696A1 EP 2723696 A1 EP2723696 A1 EP 2723696A1 EP 12734843 A EP12734843 A EP 12734843A EP 2723696 A1 EP2723696 A1 EP 2723696A1
Authority
EP
European Patent Office
Prior art keywords
mechanical strength
sulphate
thermal treatment
calcium
hydraulic composition
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP12734843.1A
Other languages
German (de)
English (en)
Inventor
Michel Testud
Xiaolin Pardal
Rémi BARBARULO
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Lafarge SA
Original Assignee
Lafarge SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Lafarge SA filed Critical Lafarge SA
Publication of EP2723696A1 publication Critical patent/EP2723696A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
    • C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
    • C04B2103/10—Accelerators; Activators
    • C04B2103/12—Set accelerators
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
    • C04B2201/05—Materials having an early high strength, e.g. allowing fast demoulding or formless casting

Definitions

  • the present invention relates to the pre-cast industry and more particularly to thermal treatments used in this field.
  • the present invention relates to a process to improve the mechanical strength 28 days after mixing of a hydraulic composition submitted to a thermal treatment.
  • Thermal treatments are often used in the field of the pre-cast industry to accelerate the hydration of hydraulic compositions, in particular with the aim of obtaining high early-age mechanical strength (for example 8 hours after mixing a hydraulic composition).
  • the aim of the thermal treatment is to speed up the removal of the formwork and/or the handling of the moulded objects for the construction field obtained, and thus to increase productivity.
  • thermal treatments are known to present the disadvantage of decreasing the long-term mechanical strength, in particular 28 days after the mixing.
  • the problem which the invention intends to solve is to provide a new means to improve the mechanical strength 28 days after mixing of a hydraulic composition which is submitted to a thermal treatment.
  • the present invention provides a process to improve the mechanical strength 28 days after mixing of a hydraulic composition submitted to a thermal treatment, the hydraulic composition comprising a hydraulic binder and optionally a mineral addition, wherein the process comprises the addition of a calcium salt and an optimized quantity of sulphate to the hydraulic composition.
  • the invention may present one of the advantages described herein below.
  • the nitrites used according to the present invention may also be used as corrosion inhibitors.
  • the use of the calcium salt and of the optimised quantity of sulphate may result in a reduction of the duration of the thermal treatment.
  • a thermal treatment generally lasting 14 hours, may be reduced to 3 and a half hours, more preferably to 6 hours.
  • the hydraulic composition may be heated earlier than what is typically done in the field.
  • the process of the present invention may shorten the pre-curing time.
  • the procuring time is the first phase of the thermal treatment cycle, during which the hydraulic composition is maintained at ambient temperature.
  • the pre-curing time precedes the phase during which the temperature increases to reach the target temperature of the thermal treatment.
  • Thermal treatment generally comprises heating a hydraulic composition poured into a mould or a formwork, at a temperature typically from 40°C to 90°C.
  • the thermal treatment may suitably be carried out at atmospheric pressure.
  • the process of the present invention requires the addition of a calcium salt to the hydraulic composition.
  • the quantity of calcium salt may be from 0.5 to 3.5 %, more preferably from 0.5 to 3 %, most preferably from 0.5 to 2 % by mass relative to the mass of hydraulic binder and optional mineral additions.
  • the calcium salt is calcium nitrite or calcium nitrate, more preferably calcium nitrite.
  • the process of the present invention requires the addition of an optimised quantity of sulphate.
  • the optimised quantity of sulphate may vary according to the raw materials of the hydraulic composition and can be determined by the person skilled in the art according to known methods.
  • the quantity of sulphate is from 2 to 5.5 %, more preferably from 2 to 4 %, percentage expressed by mass of S0 3 relative to the mass of hydraulic binder and optional mineral additions.
  • the sulphate used according to the present invention is added in the form of calcium sulphate selected from gypsum (dehydrated calcium sulphate, CaS0 4 .2H 2 0), hemi hydrate (CaS0 4 .1/2H 2 0), anhydrite (anhydrous calcium sulphate, CaS0 4 ) and mixtures thereof.
  • gypsum dehydrated calcium sulphate, CaS0 4 .2H 2 0
  • hemi hydrate CaS0 4 .1/2H 2 0
  • anhydrite anhydrous calcium sulphate, CaS0 4
  • Gypsum and anhydrite exist in their natural state.
  • the calcium sulphate also exists in the form of a by-product of certain industrial processes. These two sources of calcium sulphate may be used in the process of the present invention.
  • the process of the present invention requires the thermal treatment of a hydraulic composition.
  • the hydraulic composition comprises a hydraulic binder and optionally mineral additions.
  • a hydraulic binder is a material which sets and hardens by hydration.
  • the hydraulic binder is suitably a cement. Suitable cements include Portland cement.
  • the mineral additions may be selected from, for example, slags (for example as defined in the "cement” standard NF EN 197-1 standard, paragraph 5.2.2), pozzolans (for example as defined in the "cement” standard NF EN 197-1 standard, paragraph 5.2.3), fly ash (for example as defined by the "cement” NF EN 197-1 standard, paragraph 5.2.4), calcined shales (for example as defined by the "cement” NF EN 197-1 standard, paragraph 5.2.5), calcium carbonate (for example limestone as defined by the "cement” NF EN 197-1 standard, paragraph 5.2.6), silica fume (for example as defined by the "cement” NF EN 197-1 standard, paragraph 5.2.7), metakaolin or mixtures thereof.
  • slags for example as defined in the "cement” standard NF EN 197-1 standard, paragraph 5.2.2
  • pozzolans for example as defined in the "cement” standard NF EN 197-1 standard, paragraph 5.2.3
  • fly ash for example as defined by the “
  • the hydraulic composition may also include, in addition to the hydraulic binder and mineral additions, water, aggregates and admixtures.
  • the hydraulic composition according to the invention may be a cement slurry, a mortar or a concrete.
  • the term hydraulic composition includes both fresh and hardened concrete.
  • Aggregates used in the compositions of the invention include sand (whose particles generally have a maximum size (Dmax) of less than or equal to 4 mm), and gravel (whose particles generally have a minimum size (Dmin) greater than 4 mm and preferably a Dmax less than or equal to 20 mm or more).
  • the aggregates include calcareous, siliceous, and silico-calcareous materials. They include natural, artificial, waste and recycled materials.
  • the aggregates may also comprise, for example, wood.
  • the hydraulic composition may also comprise an admixture, for example in accordance with the EN 934-2, EN 934-3 or EN 934-4 standards, for example an air- entraining agent, a viscosity modifying agent, a retarder, a clay inertant, a plasticizer and/or a superplasticizer.
  • an air- entraining agent for example an air- entraining agent, a viscosity modifying agent, a retarder, a clay inertant, a plasticizer and/or a superplasticizer.
  • a polycarboxylate superplasticizer in particular from 0.05 to 1.5%, preferably from 0.1 to 0.8%, by dry mass relative to the mass of hydraulic binder.
  • Clay inertants are compounds which permit the reduction or prevention of the harmful effect of clays on the properties of hydraulic binders. Clay inertants include those described in WO 2006/032785 and WO 2006/032786.
  • superplasticizer as used in this specification and the accompanying claims is to be understood as including both water reducers and superplasticizers as described in the Concrete Admixtures Handbook, Properties Science and Technology, V.S. Ramachandran, Noyes Publications, 1984.
  • a water reducer is defined as an additive which reduces the amount of mixing water of concrete for a given workability by typically 10 - 15%.
  • Water reducers include, for example lignosulphonates, hydroxycarboxylic acids, carbohydrates, and other specialized organic compounds, for example glycerol, polyvinyl alcohol, sodium alumino-methyl-siliconate, sulfanilic acid and casein.
  • Superplasticizers belong to a new class of water reducers chemically different from the normal water reducers and capable of reducing water contents by about 30%.
  • the superplasticizers have been broadly classified into four groups: sulphonated naphthalene formaldehyde condensate (SNF) (generally a sodium salt); sulphonated melamine formaldehyde condensate (SMF); modified lignosulfonates (MLS); and others. More recent superplasticizers include polycarboxylic compounds such as polycarboxylates, e.g. polyacrylates.
  • the superplasticizer is preferably a new generation superplasticizer, for example a copolymer containing polyethylene glycol as graft chain and carboxylic functions in the main chain such as a polycarboxylic ether.
  • a polycarboxylic ether such as a polycarboxylic ether.
  • Sodium polycarboxylate-polysulphonates and sodium polyacrylates may also be used.
  • Phosphonic acid derivatives may also be used.
  • the amount of superplasticizer required generally depends on the reactivity of the cement. The lower the reactivity the lower the amount of superplasticizer required. In order to reduce the total alkali content the superplasticizer may be used as a calcium rather than a sodium salt.
  • the setting is generally the passage of the hydraulic binder to the solid state by hydration reaction.
  • the setting is generally followed by a hardening period.
  • the hardening is generally the development of mechanical strength of a hydraulic binder.
  • the hardening generally occurs after the end of the setting.
  • the process of the present invention requires the presence of a calcium salt and an optimized quantity of sulphate.
  • Mixing may be effected, for example, by known methods.
  • the calcium salt and the sulphate may be added to the hydraulic composition separately or at the same time.
  • the calcium salt and the sulphate may be added to the hydraulic composition at any suitable stage.
  • the calcium salt and the sulphate may be introduced:
  • the calcium salt and/or the sulphate may be directly added to a hydraulic binder, for example a celent, before the production of a hydraulic composition.
  • the hydraulic composition used according to the present invention may be shaped to produce, after hydration and hardening a shaped article for the construction field.
  • Shaped articles for the construction field include, for example, a slab, a floor, a screed, a foundation, a base, a shear wall, a beam, a work top, a pillar, a bridge pier, a block of foamed concrete, a pipe, a conduit, a post, a stair, a panel, a cornice, a mold, a road system component (for example a border of a pavement), a roof tile, a surfacing (for example of a road), a jointing plaster (for example for a wall) and an insulating component (acoustic and/or thermal).
  • Figure 1 represents the results of 6-hour compressive mechanical strength tests obtained for Example 1 .
  • the Blaine specific surface is determined according to the EN 196-6 Standard, paragraph 4.
  • Example 1 Example of a method to optimise together the quantity of the sulphate and the quantity of the nitrite
  • the mix comprising the inert silica, the calcium nitrite and the gypsum represented 10 % by mass relative to the mass of cement.
  • % added gypsum % added S0 3 x (M(gyp S um) M(so3)) x (100/pureness of the gypsum expressed in percentage)
  • M(gyp S um) is the molar mass of the gypsum and M (S o3) is the 0 molar mass of the S0 3 .
  • Superplasticizer Glenium ACE 43: non-chloride polycarboxylate (supplier: BASF). The superplasticizer was used in the form of an aqueous solution, and the water contained in the solution of superplasticizer was taken into account in the total water content.
  • the relative humidity is monitored at 100% during the cycle.
  • the results of the compressive mechanical strength at 6 hours are represented in Figure 1 .
  • the mechanical strength vary depending on the quantity of calcium nitrite (y axis) and the quantity of total S0 3 (x axis). Each curve represents a level of mechanical strength in MPa.
  • the points represent experimental data (B1 to B7). The circle limits the zone inside which the mechanical strength may be predicted.
  • the measured mechanical strength for formulations B1 to B7 were the following:
  • the 6-hour compressive mechanical strength increased with the quantity of total S0 3 .
  • a quantity of 3.60 % of total S0 3 gave a 6-hour compressive mechanical strength of 16 MPa (refer to point B6), whilst a quantity of 4.20 % of total S0 3 gave a 6-hour compressive mechanical strength of 31 ,5 MPa (refer to point B3).
  • the optimum quantity of total S0 3 did not appear to have been reached in these tests. Complementary tests would have to be carried out using greater quantities of total S0 3 to observe this optimum.
  • Example 2 Effect of the calcium nitrite on the mechanical strength at 28 days for a hydraulic composition submitted to thermal treatment
  • Water/Cement ratio 0.35 and 0.50.
  • Cooling time thirty minutes at 20°C in the laboratory.
  • the relative humidity was monitored at 100%.
  • Plateau time total cycle time (not including the cooling time) - (pre-setting time + temperature increase ramp time)
  • Table 4a Recapitulative table of the steam curing cycles at 60°C and 80°C for a one- hour pre-setting time
  • Table 4b Recapitulative table of the steam curing cycles at 60°C and 80°C for a two- hour pre-setting time
  • the plateau time was nil for the 3h30 cycle at 80°C. For an initial conservation time of two hours, the plateau time for each cycle was reduced by one hour. The plateau time was therefore nil for the 3h30 cycle at 60°C and it was no longer possible to carry out the 3h30 cycle at 80°C (duration: - 60 minutes).
  • Reference mortar formulae
  • the water provided by the plasticizer (z g of Glenium ACE 43) was subtracted from the total water content.
  • the wetting water was 6 % relative to the mass of standardized sand.
  • the quantity of superplasticizer (z) was adjusted for each formulation in order to obtain a 270 mm spread, according to a practice known to the person skilled in the art.
  • the mechanical strength tests were carried out using two bags of standardized sand (1 ,350 kg per bag) and a double volume of mix, i.e. 1 ,754 litres.
  • the spread was measured at T 0 + 5 minutes after the end of the mixing, just before using the mortar.
  • the spread measurement was carried out using a bottomless mould with a truncated shape, which is a reproduction at the scale 1 ⁇ 2 of the Abrams cone (refer to the NF P 18-451 Standard of 1981 ):
  • the other pieces of equipment required for this measurement are a steel tapping rod (diameter of 6 mm and length of 300 mm), and a plate of glass.
  • the sulphate addition of the binders was optimised by a supplementary addition of gypsum to the calcium sulphate already present in the industrial cement. This optimisation was carried out according to the W/C ratio and to the different cycle profiles studied after one hour of initial conservation time.
  • the calcium nitrite had a positive impact whatever the temperature and the duration of the thermal treatment. For example, at 60°C, for a 6-hour thermal treatment and a W/C of 0.35, the mechanical strength increased from 46 MPa without calcium nitrite to 57 MPa with calcium nitrite.
  • the calcium nitrite had a strong positive impact on the entire range, in particular for the 6-hour thermal treatment.
  • the mechanical strength increased from 3 MPa without calcium nitrite to 21 MPa with calcium nitrite.
  • the negative effect of the steam curing on the 28-day performances decreased by the presence of the calcium nitrite.
  • the 28-day mechanical strength increased from 50 MPa without calcium nitrite to 61 MPa with calcium nitrite, whilst the 28-day mechanical strength of the control specimen at 20°C were 62 MPa.
  • the 28-day mechanical strength of a specimen submitted to a thermal treatment and with an addition of calcium nitrite were higher than the 28-day mechanical strength of the control specimen at 20°C, whilst they were always lower than those of the control specimen at 20°C when calcium nitrite was absent.
  • the 28-day mechanical strength increased from 77 MPa without calcium nitrite to 95 MPa with calcium nitrite, whilst the 28-day mechanical strength of the control specimen at 20°C were 87 MPa.
  • the addition of calcium nitrite substantially reduced the negative impact of the steam curing, in particular for the longer steam curing times.
  • the 28-day mechanical strength increased from 55 MPa without calcium nitrite to 86 MPa with calcium nitrite, whilst the 28-day mechanical strength of the control specimen at 20°C were 86 MPa.
  • the addition of calcium nitrite made it possible to increase the 28-day strength of a specimen submitted to a thermal treatment to approximately the same level as those measured after 28 days on the control specimens at 20°C.
  • the 28-day mechanical strength increased from 46 MPa without calcium nitrite to 57 MPa with calcium nitrite, whilst the 28-day mechanical strength of the control specimen at 20°C were 61 MPa.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Inorganic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Curing Cements, Concrete, And Artificial Stone (AREA)

Abstract

Cette invention concerne un procédé permettant d'améliorer la résistance mécanique, 28 jours après mélange, d'une composition hydraulique soumise à un traitement thermique, ladite composition hydraulique comprenant un liant hydraulique et éventuellement un additif minéral, ledit procédé consistant à ajouter un sel de calcium et une quantité optimisée de sulfate à la composition hydraulique.
EP12734843.1A 2011-06-24 2012-06-22 Composition hydraulique soumise à un traitement thermique Withdrawn EP2723696A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR1155611A FR2976938B1 (fr) 2011-06-24 2011-06-24 Composition hydraulique soumise a un traitement thermique
PCT/EP2012/062069 WO2012175660A1 (fr) 2011-06-24 2012-06-22 Composition hydraulique soumise à un traitement thermique

Publications (1)

Publication Number Publication Date
EP2723696A1 true EP2723696A1 (fr) 2014-04-30

Family

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EP12734843.1A Withdrawn EP2723696A1 (fr) 2011-06-24 2012-06-22 Composition hydraulique soumise à un traitement thermique

Country Status (3)

Country Link
EP (1) EP2723696A1 (fr)
FR (1) FR2976938B1 (fr)
WO (1) WO2012175660A1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2990938B1 (fr) * 2012-05-22 2015-08-07 Lafarge Sa Liant hydraulique rapide comprenant un sel de calcium
NO339038B1 (no) * 2012-09-25 2016-11-07 Yara Int Asa Anvendelse av kalsiumnitrat for å fremstille en sementbasert sammensetning og/eller et sementbasert fast legeme og fremgangsmåte for å herde en sementbasert sammensetning ved høye omgivelsestemperaturer.
CA3106877A1 (fr) 2020-01-24 2021-07-24 Permabase Building Products, Llc Panneau de ciment avec additif resistant a l'eau

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ES2376579T3 (es) 2004-09-21 2012-03-15 Lafarge Composición de inertización de impurezas.
WO2006032785A2 (fr) 2004-09-21 2006-03-30 Lafarge Procede d'inertage d'impuretes

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2012175660A1 *

Also Published As

Publication number Publication date
FR2976938B1 (fr) 2016-05-13
FR2976938A1 (fr) 2012-12-28
WO2012175660A1 (fr) 2012-12-27

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