Patent ID: 12227457

DESCRIPTION OF EMBODIMENTS

The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings are only schematic and are non-limiting. The size of some of the elements in the drawings may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention.

The terms first, second and the like used in the description as well as in the claims, are used to distinguish between similar elements and not necessarily describe a sequence, either temporally, spatially, in ranking or in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

When describing the invention, the terms used are construed in accordance with the following definitions, unless indicated otherwise.

The term “and/or” when listing two or more items, means that any one of the listed items can by employed by itself or that any combination of two or more of the listed items can be employed. In particular the term “activating, deactivating and/or changing’ or “activation, deactivation and/or change” includes either activating, either deactivating, either changing, as well as any combination for example activating followed by deactivating or deactivating followed by activating.

When referring to the endpoints of a range, the endpoints values of the range are included.

The term “cementitious material” refers to materials comprising cement as for example concrete or mortar and includes fresh cementitious material, partially or fully hardened cementitious material. For a person skilled in the art, it is clear that cementitious material also comprises water and aggregates. Cementitious material may further comprise other additional components and/or additives, such as additional components and/or additives known in the art, in particular mineral additional components and/or additives, for example mineral additional components and/or additives in powder form.

The term “cement” refers to materials capable of binding aggregate particles together and includes for example Portland cement, calcium aluminate cement, lime, gypsum, geopolymer cement or other inorganic binders that provide positive electrostatic charges at least locally at their particle surface.

The term “aggregates” refers to granular material and comprises for example sand, gravel, crushed stones and iron blast-furnace slag. The granular material has preferably an average particle size that is several times larger than the average particle size of the cement particles.

The term “placing”, also referred to as “pouring”, relates to the process of transferring fresh concrete from the mixing unit to the place where it is to harden, generally the framework.

The term “setting” refers to the stiffening of the cementitious material and relates to the changes of the cementitious material from a fluid to a solid state.

The term “hardening”, also referred to as “curing”, relates to the gain of strength of a cementitious material (although during setting of the cementitious material some strength is acquired).

The term “processing cementitious material” refers to any of the process steps or any combination of the process steps including mixing, pumping, conveying, placing, setting and hardening of cementitious material.

The term “fresh” refers to cementitious material that has been (recently) mixed and is still fluid.

The term “hardened” refers to cementitious material that has gained enough strength to bear (some) load.

The term “admixture” refers to material other than water, aggregates and cement used as ingredient of a cementitious material to modify its (freshly) mixed, setting or hardened properties added before or during mixing.

The term “plasticizer” or “water reducing admixture” refers to an admixture that either increases slump of (freshly) mixed cementitious material without increasing water content or maintain slump with a reduced amount of water.

The term “superplasticizer” also referred to as “high-range water reducing admixture” relates to an admixture capable of producing large water reduction or great flowability without causing undue set retardation or entrainment of air in the cementitious material.

The term “formwork” refers to the system of supporting freshly placed cementitious material.

The term “3D printing” refers to an additive manufacturing technique comprising the joining of material to produce objects, layer upon layer, from 3D model data or other electronic data source. In particular, 3D printing refers to a technique comprising the joining of successive layers of material under computer control by means of an industrial robot.

EXAMPLES

1. First Type of Examples

A first example of an admixture1according to the present invention is schematically represented inFIG.1aandFIG.1b.FIG.1ashows the admixture1before the application of the external trigger signal.FIG.1bshows the effect induced by the application of the external trigger signal. The admixture1comprises a backbone2provided with at least one first functionality3and at least one second functionality5. The second functionality5comprises one or more sterically active groups4bfor providing sterical hindrance between neighbouring cement particles.

Optionally, the backbone2is further provided with one or more additional functionalities4a. Examples of such additional functionalities4aare functionalities comprising a sterically active group.

The backbone2comprises a polymer backbone for example a polymer backbone comprising acrylic, methacrylic, maleic acid, and related monomers, possibly grafted with one or more polyoxyalkylene side chains such as polyethylene oxide (PEO) and/or polypropylene oxide (PPO). The grafting may comprise, but is not limited to ester, ether, amide and/or imide.

The at least one first functionality3comprises for example a negatively charged group, such as a COO−group, adapted to adsorb to the cement particles of the cementitious material when the admixture is added to and optionally mixed with the cement particles of the cementitious material.

The at least one second functionality5comprises for example a sterically active group4b, such as a polyethylene oxide (PEO) group of formula (C2H2CH2O)s, with s preferably ranging between 1 and 50, for example between 1 and 10. The sterically active group4bmay be responsive to the external trigger signal to influence its steric effect. Optionally, the second functionality5comprises a responsive element such as a responsive linking group A for linking the sterically active group4bto the backbone chain2and/or the second functionality comprises a responsive group B positioned down the sterically active group4b.

The optional sterically active group4acomprises for example a side chain such as polyethylene oxide (PEO) groups of formula (CH2CH2O)q, with q preferably ranging from 1 to 50, more preferably from 1 to 30, for example from 12 to 25.

When the admixture1is added to the cementitious material, the negatively charged groups adsorb to the cement particles. Preferably, the cementitious material is mixed during or after the addition of the admixture1.

As long as no external trigger signal is applied (FIG.1a), the admixture1acts as a superplasticizer known in the art, with steric hindrance as the main mechanism. However, when an appropriate external trigger signal, for example an electromagnetic signal, is applied (FIG.1b), the steric effect provided by the second functionality5is changed. In the example shown inFIG.1bthe second functionality responds by a spatial reorganization of the sterically active group as indicated inFIG.1bby arrow6.

It is clear that the application of the external trigger signal, for example the electromagnetic signal, may also influence the steric effect of one or more additional functionalities4a.

By activating or changing the external trigger signal, for example an electromagnetic signal, the rheology of the cementitious material can be influenced or controlled in an active way and this at any time during the processing of the cementitious material, for example during placing or setting of the cementitious material.

2. Second Type of Examples

2.1 General Description

A second example of an admixture1′ according to the present invention is schematically represented inFIG.2aandFIG.2b.FIG.2ashows the admixture1′ before the application of the external trigger signal.FIG.2bshows the effect induced by the application of the external trigger signal. The admixture1′ comprises a backbone2′ provided with at least one first functionality3′. The backbone2′ is further provided with at least one second functionality5′.

Optionally, the backbone2′ is further provided with one or more additional functionalities4′. Examples of such additional functionalities4′ are functionalities comprising a sterically active group.

The backbone2′ comprises a polymer backbone for example a polymer backbone comprising acrylic, methacrylic, maleic acid, and related monomers, possibly grafted with one or more polyoxyalkylene side chains such as polyethylene oxide (PEO) and/or polypropylene oxide (PPO). The grafting may comprise, but is not limited to ester, ether, amide and/or imide.

The at least one first functionalities3′ comprises for example a negatively charged group, such as a COO−group, adapted to adsorb to the cement particles of the cementitious material when the admixture is added to and optionally mixed with the cement particles of the cementitious material.

The at least one second functionality5′ comprises a compound comprising at least one site or group adapted to be oxidized or adapted to be reduced. A preferred second functionality5′ comprises a localized group or site comprising a nitroxide free radical adapted to be oxidized to form an oxoammonium cation such as a TEMPO radical (2,2,6,6-tetramethylpiperidine-1-oxyl) or a derivate of a TEMPO radical.

The optional sterically active group4′ comprises for example a side chain such as polyethylene oxide (PEO) groups of formula (CH2CH2O)q, with q preferably ranging from 1 to 50, more preferably from 1 to 30, for example from 12 to 25.

When the admixture1′ is added to the cementitious material, the negative groups of the first type of the first functionality3′ will adsorb to the cement particles, while the optional additional functionalities4′ will provide a steric effect. The cementitious material is preferably mixed during or after addition of the admixture1′.

Without application of an external trigger signal the TEMPO radicals of the second functionalities5′ are neutral. Consequently, the negatively charged functional groups will remain absorbed to the cement particles.

However, by application of the external trigger signal, for example an electromagnetic signal, the TEMPO radical will form a cation. The positive charge of the cation will at least partially neutralize the negative charge of the negatively charged first functionalities3′. The process of charge neutralization of the negatively charged functional groups3′ is shown by6′ inFIG.2b.

As a result, the negative charge of the admixture1′ will be reduced or even totally neutralized, and the admixture1′ shows a reduced adsorption capacity to the cement particles.

It is clear that the application of the external trigger signal, for example the electromagnetic signal, may also influence the steric effect of one or more additional functionalities4′.

The response of the admixture according to the second example is reversible, as the reduction-oxidation process controlled by the trigger signal is reversible. In this way, a controllable adsorption of the superplasticizer and consequently a controllable rheology of the cementitious material is obtained.

2.2 Synthesis and Responsive Effect

a. Synthesis of Redox-Responsive Copolymers

A first admixture, referred to as Poly(MAA-co-PEGMA500-co-TEMPO), was synthesized starting from methylacrylate (MAA), poly(ethylene glycol)methacrylate (Mn500 Da) (PEGMA500) and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO).

A second admixture not having PEGMA side chains, referred to as Poly(MAA-co-TEMPO), was synthesized starting from MAA and TEMPO.

The products have been characterized after synthesis, confirming the expected polymer structure.

b. Redox-Responsiveness of the Polymers

Redox-responsiveness of the polymers (Poly(MAA-co-PEGMA500-co-TEMPO) and Poly(MAA-co-TEMPO)) was checked by cyclic voltammetry. Cyclic voltammetry graphs were recorded in an aqueous solution of the polymers (0.02 M of TEMPO in the presence of an electrolyte (LiClO4or NaOH)). The samples were positioned on a screen printed electrode (DropSens®) that was connected to a potentiostat (Gamry®). The measurements were performed at a scan rate of 5 mV/s.

FIG.4ashows cyclic voltammetry graphs on Poly(MAA-co-PEGMA500-co-TEMPO) in water containing 0.1 M LiClO4as electrolyte.FIG.4bshows cyclic voltammetry graphs of Poly(MAA-co-TEMPO) in an alkaline (NaOH) electrolyte.

FIG.4aandFIG.4bclearly indicate the redox-responsiveness of the polymers.FIG.4aandFIG.4bfurthermore show that the curves are repeatable. The required voltage levels are low enough to be applicable in cement paste.

c. Experimental Verification of Plasticizing Efficacy

The plasticizing effect of the polymers Poly(MAA-co-PEGMA500-co-TEMPO) and Poly(MAA-co-TEMPO) was evaluated by rheometry. Cement pastes containing a predetermined amount of the polymers Poly(MAA-co-PEGMA500-co-TEMPO) and Poly(MAA-co-TEMPO) were prepared, the paste samples were loaded in a parallel plate rheometer (Anton Paar®) and sample conditions were checked. Subsequently, the shear rate was varied from 100 to 400 s−1and the shear stress was measured. The results (shear stress as a function of shear rate) are shown inFIG.5for a reference cement past with water to cement ratio (W/C) of 0.4 and without admixture, and for the same paste including a predetermined amount of Poly(MAA-co-TEMPO).

Experiments demonstrated that the plasticizing effect can be limited to strong, depending on the detailed architecture of the redox-responsive polymer. A clear plasticizing effect was noticed for Poly(MAA-co-TEMPO) as shown inFIG.5.

d. Experimental Verification of Rheological Response

The rheological response of the polymers Poly(MAA-co-PEGMA500-co-TEMPO) and Poly(MAA-co-TEMPO) was evaluated using combined rheometry and voltammetry. A rudimentary setup was assembled in which the paste was positioned on a screen printed electrode (DropSens®) similar to the setup in Ping et al. (DOI: 10.1038/ncomms9050). The electrodes served as the static bottom plate while a top geometry sheared the paste as it was connected to the rotating part of the rheometer. The shear rate was constant throughout all these experiments and the shear stress was registered by the top geometry.

FIG.6aandFIG.6bshow the viscosity evolution for both the reference paste (FIG.6a) without admixture and the same paste with Poly(MAA-co-TEMPO) (FIG.6b) is shown. The grey colored areas inFIG.6aandFIG.6bembracing the curves indicate the standard deviation intervals. Only fitted data are shown and axis labels are omitted because of the rudimentary character of the employed setup.

For both types of pastes, there is an initial decrease in viscosity observed due to flow startup phenomena. This decrease was fitted with a power law curve. Up to the vertical line (i.e. at 120 s) indicated inFIG.6aandFIG.6b, no electric field was applied.

At 120 s the electrodes were set and maintained at 0.7 V. It can be observed that once the voltage is applied, the linear behavior of both types of pastes deviates. For the reference paste without admixture, the slope of the fit is −2.8 and for the paste with admixture the slope is 12.7. This clearly demonstrates the electrochemical trigger response of the admixture, as all other factors remain constant.

3. Third Type of Examples

3.1 General Description

A third example of an admixture according to the present invention is schematically represented inFIG.3. The admixture1″ comprises a backbone2″ provided with at least one first functionality3″ and at least one second functionalities5″. Optionally, the backbone2″ is further provided with one or more additional functionalities4″. Examples of such additional functionalities4″ are functionalities comprising a sterically active group.

The backbone2″ comprises a polymer backbone for example a polymer backbone comprising acrylic, methacrylic, maleic acid, and related monomers, possibly grafted with one or more polyoxyalkylene side chains such as polyethylene oxide (PEO) and/or polypropylene oxide (PPO). The grafting may comprise, but is not limited to ester, ether, amide and/or imide.

The at least one first functionality3″ comprises for example a negatively charged group, such as a COO−group, adapted to adsorb to the cement particles 7″ of the cementitious material.

The at least one second functionality5″ comprises one or more magnetizable nanoparticles C, for example one or more Fe3O4particles. The Fe3O4particles are for example connected to the backbone2″ by dopaminemethacrylate (DMA), based on catechol.

The Fe3O4particles as shown inFIG.3are added to the cementitious material as polymer functionalized particles adapted to adsorb to the cement particles of the cementitious material by means of the negatively charged groups3″.

When a sufficient amount of polymer functionalized particles is attracted to the surface of the cement particles 7″, the cement particles 7″ become magnetizable particles.

When no magnetic field is applied, the magnetizable cement particles 7″ will be dispersed in the cementitious material. Possibly, a superplasticizer known in the art is added to the cementitious material to influence or improve the dispersion.

When a magnetic field is applied, the magnetizable cement particles 7″ will respond to the imposed magnetic field lines and will start forming a cluster of connected particles along these field lines. This means that by the activation of the magnetic field the rheology of the cementitious material is influenced by influencing the interparticle interaction between magnetizable cement particles 7″ in a reversible way.

3.2 Synthesis and Responsiveness

a. Synthesis of Redox-Responsive Copolymers

Three different admixtures (copolymers) referred to as Polydopa2, Polydopa5 and Polydopa10 are synthesized starting from dopamine (DOPA), methyl acrylate (MAA) and poly(ethylene glycol)methacrylate (Mn500 Da) (PEGMA500) with feed molar ratio as given in Table

TABLE 1copolymer[DOPA][MAA][PEGMA500]Polydopa224949Polydopa5547.547.5Polydopa10104545
b. Experimental Verification of Plasticizing Efficacy

The plasticizing effect of the polymers Polydopa2, Polydopa5 and Polydopa10 was evaluated by rheometry. Cement pastes having a water to cement ratio of 0.35, with Polydopa2, Polydopa5 and Polydopa10 with a polymer concentration of 1% (mass % relative to cement), without magnetic nanoparticles, were prepared. The paste samples were loaded in a parallel plate rheometer (Anton Paar®) and sample conditions were checked. The results (shear stress as a function of shear rate) of the different pastes are given inFIG.7.FIG.7indicates that there is a plasticizing effect and that the effect is increasing with an increasing percentage of DOPA in the copolymer. This suggests adsorption of the copolymer to cement grains and also suggests that DOPA is contributing to the steric hindrance.

c. Experimental Verification of Responsive Effect by Applying a Magnetic Field

The influence of a magnetic field on the rheological properties of paste comprising magnetic nanoparticles was evaluated using rheometry. Cement pastes having a water to cement ratio of 0.3, with Polydopa2, Polydopa5 and Polydopa10 with a polymer concentration of 1% (mass % relative to cement) and 1% magnetic nanoparticles (Fe3O4particles with an average particle size of 20 nm). were prepared.

The results (shear stress as a function of shear rate) of the different pastes without the application of a magnetic field and with the application of a magnetic field (0.5 T) are given inFIG.8a(Polydopa2),FIG.8b(Polydopa5) andFIG.8c(Polydopa10).FIG.8a,FIG.8bandFIG.8cindicate that there is a clear influence of the magnetic field on the flow curves and thus that the rheological behaviour is controllable by applying a magnetic field. For Polydopa2 (FIG.8a) the application of a magnetic field induces a slight effect of reduced flowability; for Polydopa5 (FIG.8b) the application of a magnetic field results in a more pronounced effect showing a clearly reduced flowability and for Polydopa 10 (FIG.8c) the application of a magnetic field induces a slight effect improving the flowability.

d. Responsive Effect, SAOS with Magnetic Field (Storage Modulus G′)

The storage modulus G′ as a function of time was determined using an Anton Paar® rheometer. Cement pastes having a water to cement ratio of 0.3, with Polydopa2 (FIG.9a, Polydopa5 (FIG.9b) and Polydopa10 (FIG.9c) with a polymer concentration of 1% (mass % relative to cement) and 1% magnetic nanoparticles were prepared.

Tests were performed without magnetic field and with the application of a magnetic field (0.5 T).

FIG.9a,FIG.9bandFIG.9cindicate that there is a clear influence of the magnetic field on the development of stiffness modulus (G′). For Polydopa2 (FIG.9a) and Polydopa5 (FIG.9b) the application of a magnetic field induces a pronounced effect with resulting an in increased G′. For Polydopa10 (FIG.9c) the application of a magnetic field induces a less pronounced effect. Nevertheless, the experimental results clearly suggest that the development of G′ is controllable with the magnetic field.