NANO CRYSTALLINE CELLULOSE IN CONSTRUCTION APPLICATIONS

Abstract

Provided are cementitious formulations including nano crystalline cellulose (NCC).

Claims

1.-30. (canceled)

31. A formulation comprising nano crystalline cellulose (NCC) and at least one acryl-based polymer or precursor thereof.

32. The formulation according to claim 31, wherein the polymer is selected from (meth)-acrylic polymers, acrylic acid, methacrylic acid, and butyl acrylate.

33. The formulation according to claim 31, wherein the polymer is poly(methyl methacrylate-co-methacrylic acid-co-butyl acrylate.

34. The formulation according to claim 31, wherein the NCC concentration is between 0.05% and 10%.

35. The formulation according to claim 34, wherein the NCC concentration is 0.05%, 0.1%, 0.2%, 0.6%, 0.7% or 0.8%.

36. The formulation according to claim 31, comprising silane.

37. The formulation according to claim 36, wherein the silane is 3-(trimethoxysilyl)propyl methacrylate.

38. A combination of NCC and 3-(trimethoxysilyl)propyl methacrylate for increasing tensile strength of an acryl-based formulation.

39. An acryl-based paint formulation comprising NCC.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

[0061] FIG. 1 depicts load tests using mortar formulations comprising various concentrations of NCC.

[0062] FIG. 2 depicts proposed interaction between NCC and calcium disilicate.

[0063] FIG. 3 shows the FTIR of NCC and concrete at different concentrations.

[0064] FIG. 4 shows SEM of pure concrete where the cementitious grout components and sand are noted.

[0065] FIG. 5A-B show samples prepared according to the invention (FIG. 5A) and provide clear indication of the fibrillar network of NCC in concrete and the interface between the NCC and cement components being close to each other (FIG. 5B).

[0066] FIGS. 6A-D: FIG. 6A shows SEM of 0.5% NCC concrete; FIG. 6B shows SEM of 1% NCC concrete; FIG. 6C shows SEM of 1.5% NCC concrete and FIG. 6D shows SEM of 3% NCC concrete.

SPECIFIC EMBODIMENTS OF THE INVENTION

Experimental Examples

NCC reinforcement of Acrylic Films

[0067] Acrylic polymers are highly common in construction mixes. Acrylic resins, such as poly(methyl methacrylate-co-methacrylic acid-co-butyl acrylate) was used as a base material to form mortar mixes.

[0068] The objective of the below experiments were to test the effect of NCC when mixed into the acrylic resins which were used as the base for the complex systems containing aggregates either of cement or gypsum. Initially the NCC in different concentrations was mixed directly into the acrylic polymer. The composite was opaque indicating that the NCC formed agglomerates due to lack of compatibility to the acrylic resin. Such compositions could have uses in various applications.

[0069] To adapt the compositions for a more generic use, the surface of the NCC was modified with a silane 3-(trimethoxysilyl)propyl methacrylate, C.sub.10H.sub.20O.sub.5Si, in order to improve the interaction between the NCC and the acrylic emulsion. NCC concentrations (w/v) were at the values of 0.05%, 0.1%, 0.2%, 0.6%, 0.7% and 0.8%. The mixture was homogenized with Ultra Turrax for one minute. NCC dispersed was made into an emulsion using sonication for a minute. The different concentrations of NCC diluted in water and silane were added into the acrylic resin emulsion followed by casting of films.

[0070] The sheets were prepared by casting into round molds (diameter 5 cm) and stored at room temperature and 55% humidity for one week, permitting water evaporation. As a result transparent homogenous composite films were achieved indicating homogenous dispersion of the NCC in the polymer.

[0071] Based on the successful homogenous dispersion of the NCC in the acrylic polymers, several experiments were performed using different concentration of NCC mixed into the acrylic resins.

[0072] 200 m composite film samples containing different NCC concentrations were evaluated by tensile testing.

[0073] The results indicate significant increase in the modulus and tensile strength as a result of increasing NCC concentration. On the other hand, in concentrations >0.1 there was a significant decrease in the tensile strain.

[0074] The best reinforcement results were observed with 0.05% NCC expressed in 64% increase in tensile strength and 31% increase in energy to break compared to the control neat acrylic film, as shown in FIG. 1. At a concentration of 0.6%, the tensile strain was significantly decreased.

Utilization of Nano Crystalline Cellulose (NCC) for Cement Application

[0075] Cellulose fibre-cement products have been used in a large number of building and agriculture applications. The main reason for incorporating these fibres into the cement matrix was to improve the toughness, tensile strength, and the cracking deformation of the composite. These properties may be improved or modified by incorporating NCC in cement where the surface area and rougher surfaces are playing major contributions. As a consequence, there is an increase of adhesion at the fibre/cement interface and a decrease of microcracks, which contributes to the enhancement in the strength and durability of the fibre/cement composite (concrete).

[0076] As shown in the figures, NCC demonstrates needle-like structures having average length of 100 nm to few micrometers and an average width of 104 nm The calcium di-silicate of the cement forms chemical interactions between hydroxyl groups of NCC during hydration and thereby increases the mechanical strength of the concrete. The high tensile strength of the crystalline NCC bears the load transfer from cement components in end-user concrete applications. Since the interface is connected though hydrophilic hydration and chemical interaction, the concrete performs better and exhibits improved mechanical properties.

[0077] The NCC materials used in this work were prepared by sulphuric acid (64%) hydrolysis of the paper waste materials and the final concentration of NCCs in water suspension was 3 wt. %. The ordinary Portland cement was purchased from local shops. The NCC/cement concrete was prepared by mixing cement, sand, water and NCC components together with the help of a mechanical mixture followed by degassing of the concrete by vacuum. The mixer was set to mix at a speed of 400 rpm for 180 s. After the mixing was complete, the fresh cement pastes were cast in plastic cylinders (5 cm in diameter and 1 cm in height) and sealed at room temperature for curing. After 24 h of curing, the cylinder samples were demolded and put in beakers containing water for one week. After one week it was dried and was kept in sealed covers. Cement/NCC concrete were prepared at a water to cement ratio (w/c) of 0.35 with 0, 0.5, 1, 1.5, 2, 2.5 and 3 wt. % of NCC concentrations.

[0078] FIG. 3 shows the FTIR of NCC and concrete at different concentrations.

[0079] The FTIR of all NCC/concrete composites showed resemblances with the concrete only sample. The addition of NCC introduced no additional peaks or an increase in the intensity of the peak at 3400 cm.sup.1, being the predominant peak of NCC three hydroxyl units. If the interaction with the NCC and the cement molecules were merely physical, one should have expected its contribution on the peak intensities of the resultant NCC/concrete FTIR. The proposed interaction suggested in FIG. 2 shows the chemical interaction between calcium disilicate hydrate of the cement components and the hydroxyl groups of NCC. The same reaction leads to the loss of extra contributions of NCC components in the FTIR absorbance of the resultant NCC/cement concrete which is clear in FIG. 3. Hence the interactions between the NCC and the calcium disilicate hydrate cement components are not merely physical but chemical which is a significant observation to get a cement product with enhanced mechanical and durability properties.

[0080] FIG. 4 shows the SEM of pure concrete where the cementitious grout components and sand are noted.

[0081] FIGS. 5A-5B provide a clear picture of the fibrillar network of NCC in concrete and the interface between the NCC and cement components are close to each other. The homogenous dispersion of NCC in cement matrix is also clear from these pictures. The NCC-calcium disilicate hydrate cement component interaction is very clear in lower concentration (0.5%, FIG. 5B and FIGS. 6A-D) which is expected due to the chemical linkage between the components as discussed in FTIR. The higher concentration (3%) NCC/cement concrete shows the agglomerated crystal clusters which influence the mechanical properties.

[0082] As noted from the experiments provided herein, the NCC-cement interaction is not merely physical but chemical due to the bonding between NCC-calcium disilicate hydrate components. It suggests a cement product with enhanced mechanical and durable properties for structural application via NCC addition in cement concrete construction technology.

[0083] NCC at concentrations of 0.2-3% are dispersed in water using sonication. NCC dispersions at different concentrations are added to the dry mortar/gypsum powder as the liquid portion, at the required powder to water ratio and mix thoroughly. Specimens are prepared by casting the wet mixtures into appropriate molds and curing, according to ASTM practice C31/C31M-12. Compression strength are measured according to ASTM test method C39/C39M-15, and flexural strength according to ASTM test method C78/C78M-10e1.

[0084] At certain concentrations, NCC increases compression/flexural strength, modulus and energy to break relative to the reference (without NCC).

[0085] In another experiment, the NCC is spray dried into a powder. The NCC is added to the dry mix in different concentrations.

[0086] NCC powder is mixed in the mortar/gypsum powder at NCC to mortar weight ratios of 1:1000-1:50. After addition of the required amount of water, specimens are prepared by casting the wet mixtures into appropriate molds and curing, according to ASTM practice C31/C31M-12. Compression strength are measured according to ASTM test method C39/C39M-15, and flexural strength according to ASTM test method C78/C78M-10e1.

[0087] At certain concentrations, NCC increases compression/flexural strength, modulus and energy to break relative to the reference (without NCC).

[0088] The NCC containing admixtures have improved properties compared to current standard admixtures.