WO2000027774A1

WO2000027774A1 - Process and composition for latex modified rubber crumb reinforced cement

Info

Publication number: WO2000027774A1
Application number: PCT/US1999/026281
Authority: WO
Inventors: Hosin Lee; Jang-Soo Moon
Original assignee: University Of Utah
Priority date: 1998-11-06
Filing date: 1999-11-06
Publication date: 2000-05-18
Also published as: WO2000027774A9; AU1471500A

Abstract

Compositions of the invention are made from a mixture of cement binder, ground rubber particles, water, latex, and mineral aggregate. The cement binder may be Portland cement or any other suitable cement. These compositions have high flexural strength and dynamic impact resistance and can be used to make concrete (10), mortar (20), and cement board (30).

Description

TITLE

PROCESS AND COMPOSITION FOR LATEX MODIFIED RUBBER

CRUMB REINFORCED CEMENT

FIELD OF THE INVENTION The present invention relates to improvements in the cement-latex concrete structures.

BACKGROUND OF THE INVENTION

Conventional concrete is a mixture cement (Ca, Si, Al, Fe, Mg, Na and K), sand, aggregate and water. Portland cement concrete is one of the most popular and widely used construction materials in the world, despite its low tensile strength, low ductility, volume instability, and low strength-to-weight ratio. Latex modified concrete is a mixture of portland cement concrete with latex. Latex modified concrete is said to improve the bonding and flexibility and to decrease permeability.

The latex modified concrete was invented by Cresson in 1923, British Patent No. 191,474. Over the years, many improvements have been made in using various types of latex in concrete, for example, in British Patent Nos. 217,279 (1924); 242,345 (1925); 369,561 (1932); German Patent No. 680, 312 (1939); U.S. Patent Nos. 2,227,533 (1941); 2,311,233 (1943). Since the 1960s, styrene-butadiene rubber, polyacrylic ester, and polyvinylidene chloride-vinyl chloride modified concretes have been used increasingly in practical applications.

While the improvements by adding various types of latex in concrete represent advances in the cement concrete structures, they are said to do nothing in the areas of crack resistance, and shock absorption.

Therefore, rubber crumb-reinforced cement concrete was invented to implement the above-mentioned improvements by Frankowski in 1994, U.S. Patent No. 5,290,356. Rubber crumb-reinforced cement concrete is a mixture of portland cement concrete with rubber crumb. Rubber crumb-Reinforced concrete is said to improve the resistance to cracking, shock wave absorption, and noise reduction and to lower heat conductivity. However, the rubber crumb-reinforced cement concrete was found to lower both compressive and flexural strength of the regular portland cement concrete. This is shown in Table 1 and Table 2, respectively. The lower compressive and flexural strengths are due to the lack of bonding between rubber crumb and portland cement concrete structure.

The Frankowski patent, No. 5,290,356, discloses a crumb rubber added cement. Other references, such as Tamura (no. 5,069,721) and Schad (No. 5,366,550) have disclosed a latex added to cement and aggregate mixtures. Alder et al. (No. 4,403,962) and Portin (No. 4,082,888) disclose mixtures of latex resin emulsion and rubber particles, components that are bonded to concrete surfaces. Thelen et al. (No. 4,564,310) discloses a paving system with rubber particles and latex covering a mineral aggregate, but there is no disclosure of mixed latex, rubber particles, and aggregate. Further, Thelen et al. does not disclose a composition with cement.

Objects of the Invention Accordingly, it is an object of the present invention to provide Latex Modified

Rubber Crumb Reinforced Cement Concrete structures that will implement the above mentioned improvements of rubber crumb reinforced cement concrete, but without lowering the compressive and tensile strengths of the mixture.

Another object of the invention is to provide a latex modified rubber crumb reinforced cement concrete that is superior to rubber crumb reinforced cement concrete.

Further objects of the invention will become evident in the description below.

BRIEF SUMMARY OF THE INVENTION

The invention includes a composition where high levels of shredded tires with latex are mixed in a concrete mix binder to produce a superior grade of construction material. The process involves adding shredded rubber to latex, and mineral aggregates. The present invention can be described as comprising three basic components (1) crumb rubber, (2) latex, and (3) cement.

There are three basic properties that are improved through practice of the invention; aging, flexibility and adhesion. The addition of tire rubber introduces polymer chains into the latex, which provide synergistic action that results better adhesion to the cover aggregate, improved toughness under heavy traffic, and increased flexibility during thermal expansion/contraction.

Shredded tires are mixed with latex to improve the bonding capacity between 5 tire and Portland cement. In the prior-art, a Portland cement/tire concrete loses its strength due to the lack of physical bonding. Concretes according to the invention show improved workability and ductile behavior. Based on laboratory experience, the workability of the concretes of the invention is better than a typical latex modified concrete with lower cost. The strength of the concretes of the invention are superior l o to Portland cement/tire concrete and is equal to or better than latex modified concrete at a significantly lower cost. This demonstrates the synergistic action of the latex/rubber/cement combination in providing a superior product.

Since the major deterioration of concrete pavements can be attributed to its brittleness, using the concrete of the invention in highway pavement will make the

15 highway system last longer. Other benefits of invention include decrease in traffic noise, and better resistance to rutting and cracking. The concrete can be used as noise walls and load bearing walls with a superior noise reduction characteristics.

The present invention is suitable for manufacture of the following products; 1) General purpose latex concrete (up to 5.000 psi) 20 2) Exterior-interior cement board,

3) Mortar, all of which provides resistance to cracking, improves shock wave absorption, lowers heat conductivity, and reduces noise levels simultaneously, and

4) Sound adsorbing blocks for adsorbing traffic noise.

BRIEF DESCRIPTION OF THE DRAWINGS

25 Figure 1 is a perspective view of concrete product of the present invention.

Figure 2 is a perspective view of a brick wall using mortar of the present invention.

Figure 3 is a perspective view of a cement board of the present invention. DETAILED DESCRIPTION OF THE INVENTION

The present invention is an improvement over the prior-art systems comprising cement and rubber crumbs. The mixture of rubber crumbs and latex, added to cement compositions, synergistically improves the bonding capacity between rubber crumbs and portland cement concrete. Three types of modified concrete: latex modified concrete, rubber crumb reinforced cement concrete, and latex modified rubber crumb reinforced cement concrete lost their compressive strengths in comparison with regular portland cement concrete due to the weak inclusion by rubber crumb as shown in Table 1.

However, in the flexural strength test, as shown in Table 2, the latex modified rubber crumb reinforced cement concrete of the invention showed a significant improvement over all three other concretes: regular portland cement concrete, latex modified concrete, and rubber crumb reinforced cement concrete due to a synergistic improvement of physical bonding in mixing all three components of latex, rubber, and cement.

Table 1 Compressive Strengths of Four Types of Concrete

Table 2 Flexural Strengths of Four Types of Concrete

To validate the above significantly improved flexural strength of latex modified rubber crumb reinforced cement concrete, additional Charpy dynamic impact tests (ASTM E23) were conducted at two different energy levels: 120 Ib-ft and 5 lb-ft.

The improvement in flexural strength of the compositions of the invention is unexpected, in light of the deterioration of flexural strength of rubber concrete over regular concrete. It would be expected that addition of rubber to any concrete would lower the flexural strength. However, in the compositions of the invention, the flexural strength is not lower, but is surprisingly superior to even the latex/cement concrete.

Table 3 and Table 4 show the comparative data on absorbed impact energy among (1) regular portland cement concrete, (2) latex modified concrete, (3) rubber crumb reinforced cement concrete, and (4) latex modified rubber crumb reinforced cement concrete of the invention at 120 lb-ft and 5 lb-ft energy levels, respectively.

Both tables show a striking improvement in the dynamic impact absorbing property of the invention as predicted by its higher flexural strength due to the synergistic improvement in mixing all three components, latex, rubber, and cement.

Table 3 Impact Energy Absorption of Four Types of Concrete at 120 lb-ft Energy Level

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Table 4 Impact Energy Absorption of Four Types of Concrete at 5 lb-ft Energy Level

The improved impact energy absorption is particularly surprising. Adding only latex or only rubber, improved the impact energy absorption only modestly, or not at all. It would be expected that a rubber/latex/concrete system would show similar results. Unexpectedly, the latex/rubber concrete shows a significant and synergistic improvement over the other three types. This is due to the synergistic bonding achieved the rubber/latex/concrete system of the invention.

The present invention provides latex modified rubber crumb reinforced cement concrete structures that will implement the above-mentioned improvements over three other types of concrete. The flexural strength and dynamic impact resistance of the latex modified rubber crumb reinforced cement concrete is superior to any of the three other concretes.

For a further understanding of the nature and object of the present invention, reference should also be had to the following description take in conjunction with the accompanying drawings, in which like parts are given like reference materials. The improved latex modified rubber crumb reinforced cement concrete structures of this invention are composed of cement, sand, aggregates, rubber crumbs, and latex. The rubber crumbs, recovered from the scrap tires have emerged as a unique and significant reinforcing composite, which when mixed with the above materials produce the following advantages: resistance to cracking, improved shock wave absorption, lowered heat conductivity and reduced noise levels simultaneously without lowing the compressive and tensile strengths of the portland cement concrete. Referring to Figure 1, the concrete 10 of the present invention is latex modified rubber crumb reinforced cement concrete consisting of 100 parts by weight of cement, from about 100 to 200 parts by weight of sand, from about 200 to 400 parts by weight of aggregate, from about 1 to 30 parts by weight of rubber crumbs, from about 40 to 50 parts by weight of water, from about 15 to 20 parts by weight of latex, and a very small portion of additives. This concrete is characterized by improved non-structural cracking, shock wave absorption, some chemical resistance to acids and alkaline, heat conductivity reduction, and noise level reduction without lowering the compressive and tensile strengths of the portland cement concrete.

Referring to Figure 2, the mortar 20 of the present invention is latex modified rubber crumb reinforced cement mortar consisting of 100 parts by weight of cement, from about 100 to 300 parts by weight of sand, from about 1 to 30 parts by weight of rubber crumbs, from about 40 to 70 parts by weight of water, from about 10 to 15 parts by weight of latex, and a very small portion of additives. This mortar is characterized by improved non-structural cracking, shock wave absorption, some chemical resistance to acids and alkaline, heat conductivity reduction, and noise level reduction without lowering the compressive and tensile strengths of the portland cement mortar.

Referring to Figure 3, the cement board 30 of the present invention is latex modified rubber crumb reinforced cement concrete consisting of 100 parts by weight of cement, from about 100 to 200 parts by weight of light aggregate, from about 15 to 30 parts by weight of rubber crumbs, from about 40 to 60 parts by weight of water, from about 5 to 10 parts by weight of latex, and a small portion of additives. This cement board is characterized by improved non-structural cracking, shock wave absorption, some chemical resistance to acids and alkaline, heat conductivity reduction, and noise level reduction without lowering the compressive and tensile strengths of the portland cement concrete.

Another embodiment of the invention is a composition /rubber/latex product made from a mixture comprising (a) 100 parts by weight of a material from the group consisting of alumina and portland cement; (b) 15-30 parts by weight of rubber crumb; (c) 40-60 parts by weight of water, (d) 5-20 parts by weight of latex; and (e) 100-200 parts by weight of light aggregate. This material is particularly suitable for cement board, and may all of the material of part (a) may be alumina. The new structures described herein made of cement-like material have as a discrete internal portion of the cross section a predetermined undirectionally aligned reinforcement comprised of recycled scrap rubber crumbs, (1% to 30% by weight of cement) (natural and synthetic) and latex (5% to 20% by weight of cement) (natural and synthetic) which provide the following benefits: 1) crack resistance; 2) heat conductivity reduction; 3) shock absorption and crumbling reduction; and 4) noise level reduction through its increased flexural strength.

While this invention has been described with reference to certain specific embodiments and examples, it will be recognized by those skilled in the art that many variations are possible without departing from the scope and spirit of this invention, and that the invention, as described by the claims, is intended to cover all changes and modifications of the invention which do not depart from the spirit of the invention.

Claims

CLAIMSWhat is claimed is:

1. A concrete composition comprising a mixture comprising cement binder, ground rubber particles, water, latex, and mineral aggregate.

2. A concrete composition as in Claim 1 wherein the cement binder comprises portland cement, or alumina.

3. A concrete composition as in Claim 1 wherein the mineral aggregate comprises sand, aggregate, light aggregate, or mixtures thereof.

4. A concrete composition as in Claim 1 wherein concrete composition is a general purpose concrete, mortar, cement board, or sound barrier.

5. A concrete composition as in Claim 1 wherein the ground rubber particles are derived from rubber tires.

6. A concrete/rubber/latex composition made from a mixture comprising:

(a) 100 parts by weight of portland cement;

(b) 1 -30 parts by weight of rubber crumb;

(c) 40-70 parts by weight of water;

(d) 5-20 parts by weight of latex;

(e) 100-200 parts by weight of material from the group consisting of sand, aggregate, light aggregate, or a mixture thereof.

7. A concrete/rubber/latex composition made from a mixture comprising:

(a) 100 parts by weight of portland cement;

(b) 1-30 parts by weight of rubber crumb;

(c) 40-70 parts by weight of water;

(d) 5-20 parts by weight of latex;

(e) 100-600 parts by weight of material from the group consisting of sand, aggregate, light aggregate, and mixtures thereof.

8. The composition of claim 7, wherein the amount of water is 40-50 parts by weight, the amount of latex is 15-20 parts by weight, and the material in (e) is 100- 200 parts by weight of sand and 200-400 parts by weight of aggregate.

9. The composition of claim 7 wherein the concrete/rubber/latex product is mortar, the amount of latex is 10- 15 parts by weight, and the material in (e) is 100- 300 parts by weight of sand.

10. The composition of claim 7 wherein the amount of rubber is 15-30 parts by weight, the amount of water is 40-60 parts by weight, the amount of latex is 5-10 parts by weight, and the material in (e) is 100-200 parts by weight of light aggregate.

11. The composition of claim 8 wherein the product is a general purpose concrete.

12. The composition of claim 9 wherein the product is mortar.

13. The composition of claim 10 wherein the product is cement board.

14. A composition /rubber/latex product made from a mixture comprising:

(a) 100 parts by weight of a material from the group consisting of alumina and portland cement;

(b) 15-30 parts by weight of rubber crumb;

(c) 40-60 parts by weight of water,

(d) 5-20 parts by weight of latex; and

(e) 100-200 parts by weight of light aggregate.

15. The composition of claim 14 wherein the concrete/rubber/latex product is cement board.

16. The composition of claim 14, wherein: the major portion in (a) is the alumina.

17. A concrete composition comprising a mixture of cement particles, rubber crumb particles, and latex.

18. A process for producing a concrete product comprising mixing cement binder, ground rubber particles, water, latex, and mineral aggregate, and allowing the mixture to cure to a concrete product.