FIELD OF INVENTION

Chemistry in the field of construction materials comprising modified celluloses

BACKGROUND

The cracking of the walls of buildings or constructions can occur due to several causes which include those that are not related to the structural works. The examples of which include the cracking of walls or plaster in the form of crazes distributed all over the walls. The said cracking may be due to the issue of plaster losing a significant amount of water too fast. This can be influenced by the level of water absorption of brick walls, atmospheric heat, etc. Furthermore, the problems regarding the cracking of the construction walls can be due to mistakes during the operational steps such as the lack of sufficient curing which leads to the early loss of water thereby resulting in the early shrinkage of plaster.

The said cracking problems of the walls of buildings and constructions which are not due to the structural works can be solved by the addition of super-absorbance in the types of polyacry] amide, glycerol, or polyglycol in order to allow absorbance during the plaster curing period and prevent bleeding from happening too fast. Furthermore, there has been a use of synthetic fibers in order to assist in the bonding of cement thereby increasing early tensile strength and reducing cracking. However, the use of such super-absorbance and synthetic fibers in construction materials such as plaster still have some limitations and disadvantages, namely the high cost of super-absorbance and synthetic fibers, the low density and low level of absorption of synthetic fibers, and the smoothness of synthetic fiber surfaces. When combined with plaster o mortar, fibers will float on the surface of workpieces and will not blend into the plaster or mortar. Such work pieces obtained may have lower compressive strength due to the insufficient strength of bonding between cement and synthetic fibers. Thereafter, natural cellulose fibers were used to increase the adhesion ability and create strong hydrogen bonds with plaster. However, with the polarity of natural cellulose fibers, the distribution of said fibers in plaster is inconsistent thereby reducing the strength of workpieces and causing locations where the fibers are clustering to be fragile.

From the above problems, there were efforts in inventing and developing construction materials comprising cellulose fibers that have better properties.

The examples of the prior arts related to construction materials comprising various cellulose fibers as the compositions are as follows:

WO 02/28796 A2 discloses composite building materials comprising cementitious matrix and cellulose fibers containing inorganic/ organic compositions which suppress the flow of water. Said cellulose fibers are obtained from the chemical reaction and or the physical coating in order to reinforce construction materials that require lower water absorption and penetration.

WO 02/28795 A2 discloses composite building materials comprising cementitious matrix and cellulose fibers in which the surfaces are improved by blocking hydrophilic fibers using a sizing-agent which is an inorganic and/ or organic resin. The said sizing- agent comprises hydrophilic and hydrophobic compositions. The cellulose fibers in which the surfaces are improved according to this invention are used in construction materials that require lower water absorption and penetration.

US 2004/ 0168615 Al discloses composite cement reinforced with bleached cellulose fibers and mixed with non-bleached cellulose fibers which are used for substituting partial or all premium grade fibers. The process of manufacturing cement composite according to this invention provides a product which has a modulus of rapture and toughness comparable or higher than those of composite cement materials reinforced with premium grade cellulose fibers. US 7,972,433 B2 discloses the composition of cement reinforced by using fibers comprising hydraulic inorganic material, siliceous material, and wood reinforcing materials having the length of fibers in the range of 0.5-3.0 millimeters and diameter of 10- 100 microns, mica and polyvinyl alcoholic resin. The said wood reinforcing materials comprise non-bleached kraft fibers and/ or bleached kraft fibers obtained from needle- leaves-tree and used newspaper paper in the ratio of 1 : 1 to 4: 1.

SUMMARY OF THE INVENTION

This invention is related in particular to construction materials having modified celluloses which comprise cementitious materials, aggregates, and modified celluloses. According to this invention, the said modified celluloses are obtained from modified cellulose morphology using base or base metal salts. The said modified celluloses have the crystal linity index in the range of 20-50%.

The objective of this invention is to provide construction materials comprising modified celluloses that have advantages in various technical effects namely construction material products comprising modified celluloses according to this invention that have the ability to delay cracking and have higher flexural strength while maintaining high compressive strength when compared to general construction materials reinforced with natural cellulose and anti-cracking cellulose available in the market. Moreover, construction material products according to this invention provide good workability without the addition of a flow adjusting substance when the construction materials contain a suitable amount of modified celluloses.

BRIEF DESCRIPTIO OF THE DRAWINGS Figure 1 shows the distribution of ( a) natural cellulose fibers and ( b) modified cellulose fibers according to this invention through a scanning electron microscope. Figure 2 shows the test results regarding restrained shrinkage of construction materials comprising natural cellulose fibers and construction materials comprising modified cellulose fibers according to this invention in comparison to the controlled construction materials without any fibers.

Figure 3 shows the results of the physical test regarding the flexural strength of construction materials comprising natural fibers, construction materials comprising modified cellulose fibers according to this invention, and general construction materials comprising anti-cracking cellulose fibers in comparison to the controlled construction materials without any fibers.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Detailed descriptions of the invention will now be further described.

According to this invention, construction materials having modified celluloses comprising cementitious materials, aggregates, and modified celluloses characterized in that said modified celluloses are the modified celluloses obtained from the modified cellulose morphology using base or base metal salts. The said modified celluloses have crystallinity index in the range of 20-50%.

According to this invention, the changes in the molecular structure of natural celluloses which are modified using ba.se or base metal salts are as follow:

Natural celluloses Modified celluloses according to this invention Natural celluloses which are modified will have lower dipole moment thereby reducing the level of water absorption at the surface of the cellulose fibers without losing the water absorption and bleeding properties and allow better distribution in water. The modified cellulose morphology will provide a wider gap between cellulose molecules which will lead to the ability to partially absorb water and bleed during the cement curing period. Furthermore, the decrease in the dipole moment causes a decrease in the water absorption at the surface of the modified natural celluloses.

According to this invention, construction materials comprising modified celluloses have the ratio of amorphous cellulose higher than the ratio of crystalline cellulose. When analyzing said modified celluloses for their unique characteristics using the X-ray diffraction technique ( XRD) , it was found that there is a change in the XRD pattern namely crystalline structures at 2Θ equal to 10°- 17° and 20°- 25° disappeared and the amorphous structure at 2Θ equal to 18°- 23° appeared. Additionally, when further analyzing said modified celluloses using infrared spectrography, the significant wave number was found to be in the range of 1300 - 900 cm ¹ .

Furthermore, when analyzing said modified celluloses according to this invention and natural celluloses using a scanning electron microscope (SEM), it was found that the said modified celluloses have a better distribution when compared to that of natural cellulose. Details of which are shown in Figure 1. According to this invention, said modified celluloses have the proper crystallinity index in the range f 35 - 45%.

According to this invention, said modified celluloses have water retention in the range of 45 - 65% and have proper water retention in the range of 50 - 60%.

According to this invention, said modified celluloses have voltage in the fiber surface area ( system zeta potential) in the range of -75 to - 1 35 millivolts. According to this invention, the amount of said modified celluloses is in the range of 0.05 - 2.0% by weight of cementitious materials and the proper amount of said modified celluloses is in the range of 0.2 - 0.7 % by weight of cementitious materials.

According to this invention, the amount of said cementitious materials is in the range of 5 - 95% by dry weight of construction materials comprising modified celluloses and the proper amount of said cementitious materials is in the range of 5 - 50% by dry weight of construction materials comprising modified celluloses.

According to this invention, said natural celluloses are obtained from sources selected from the group consisting of hard-wood, soft-wood, non-wood, and mixtures of the aforesaid.

According to this invention, proper natural celluloses are obtained from hardwood in which the proper hardwood includes eucalyptus.

According to this invention, said natural cellulose fibers may be either bleached natural cellulose or unbleached natural cellulose. According to this invention, cementitious materials are selected from a group of materials consisting of portland cement, white cement, iron slag, and the mixture of the said cements.

According to this invention, portland cement is selected from a group of portland cement consisting of ordinary portland cement type 1 , ordinary portland cement type 2, ordinary portland cement type 3, ordinary portland cement type 4, ordinary portland cement type 5, and a mixture of said cements.

According to this invention, construction materials comprising modified celluloses further comprise supplementary cementitious materials or pozzolanic materials. According to this invention, said pozzolanic materials are selected from a group of materials consisting of silica fume, ground limestone, fly ash, and mixture of the said materials.

According to this invention, wherein said aggregate is selected from a group of materials consisting of fine aggregate, coarse aggregate, recycled aggregate, porous aggregate, and a mixture of the said aggregate. The proper aggregate is selected from a group consisting of sand, rock, ground limestone, clay, and a mixture of the said materials.

According to this invention, construction materials comprising modified celluloses further comprise admixture selected from a group of substances consisting of rheology modifier, superplasticizer, retarder, accelerator, and mixture of the said admixtures.

According to this invention, said salt base of metal is a salt base of metal selected from sodium, magnesium, and potassium metal.

This invention will be further explained by way of examples. However, it shall be understood that such examples will not in any way limit the scope of this invention.

The examples of the test results regarding the properties of construction materials comprising modified celluloses according to this invention:

1. The test result of restraining shrinkage according to the standard of ASTM C1581/C1581M for measuring the period of time that the cracking of the construction materials occurs

The test to find the period of time that the cracking of the construction materials occurs and measure the restraining shrinkage is operated by molding plaster around a metal ring. When comparing construction materials comprising natural cellulose fibers and modified celluloses according to this invention and the controlled construction materials ( without any fibers) , it was found that constructions materials comprising natural fibers can delay the cracking for 20 - 25 hours. Moreover, construction materials comprising modified celluloses according to this invention can delay the cracking for 45 - 100 hours when compared to the controlled construction materials. Details of which are shown in

Figure 2.

2. Test results regarding the flexural strength

According to this invention, construction materials, namely mortar, were prepared based on the mixing ratio of cement and sand of 1 : 1-3 by volume and the water to cement ratio is 0.25 - 0.5. Thereafter, the construction materials as prepared were tested in order to investigate flexural strength by using fiber as additive in the amount of 0. 10 - 0.35% by volume of mortar. From the result, it was found that construction materials comprising modified cellulose fibers and construction materials comprising natural cellulose fibers have higher flexural strengths of 24% and 40% respectively which are more than general construction materials comprising anti-cracking cellulose fibers ( as shown in Figure 3 ) . However, though construction materials comprising fibers as additive provided a higher flexural strength for mortar, compressive strength was decreased. In this regard, when comparing with controlled construction materials ( mortar) , it was found that the compressive strength of the construction materials comprising modified cellulose according to this invention only had a slight decrease of 5%. In comparison, the decrease of the same in general construction materials comprising natural fibers and cellulose fibers for preventing cracking is 16%.

3. Test results regarding the flow

According to this invention, construction materials, namely mortar, were prepared based on the mixing ratio of cement and sand of 1 : 1-3 by volume and the water to cement ratio is 0.25 - 0.5. Thereafter, the construction materials as prepared were tested in order to compare the flow of construction materials comprising natural cellulose fibers and construction materials comprising modified celluloses according to this invention in different amounts. The controlled flow value is 105 +5%. From the result, it was found that construction materials comprising modified celluloses in the amount of 0. 1 - 0.35% by volume of mortar can provide a flow value comparable to that of the controlled construction materials without the addition of plasticizers. Therefore, it can be concluded that construction materials comprising modified cellulose according to this invention, particularly those comprising the modified cellulose fibers in the proper amount, will not affect the flow when being used. The amounts of plasticizers used for adjusting the flow value of mortar to be at 105 ±5% are demonstrated in the table below.

Table demonstrating the amounts of plasticizers used in flow testing

From the tests regarding the properties of construction materials as mentioned above, it can be seen that construction materials comprising modified celluloses according to this invention can provide benefits in terms of technical effects namely construction materials comprising modified celluloses can further delay cracking and increase flexural strength while maintaining high compressive strength. Thus, the said materials are suitable for use in the works requiring the decrease in cracking, particularly for the efficient use as plaster.

Based on the details as explained above, construction materials comprising modified celluloses according to this invention comprise the compositions, amount, and details as aforementioned provide advantages. However, the construction materials comprising modified celluloses according to this invention are not limited to the compositions, amount, and details as aforementioned and may be modified or amended and deemed to be within the concepts and scope of this invention. BEST MODE OF PRACTICING THE INVENTION

As disclosed in the detailed descriptions of the preferred embodiments.