WO2007054960A2

WO2007054960A2 - A method of production for metallic iron concrete hardener and cement concrete made therefrom

Info

Publication number: WO2007054960A2
Application number: PCT/IN2006/000333
Authority: WO
Inventors: Ibrahimbhai Kalaniya Yusuf
Original assignee: Ibrahimbhai Kalaniya Yusuf
Priority date: 2005-09-06
Filing date: 2006-09-04
Publication date: 2007-05-18
Also published as: WO2007054960A3

Abstract

Cement Concrete construction in today's developing countries is very common and the use of concrete is increasing day by day in many folds. Concrete is the most versatile material in today's world in the construction of buildings, bridges and roadwork etc. During the use of this high grade cement within last decade, pre-mature cracking was observed during construction in the India as a result of the early setting coupled with high shrinkage cracks. These problems initiated this research to develop admixture presented herein. Rock Concrete Hardener (RCH) is a graded aggregate with metallic particles of processed iron. It provides strength, durability and hard surface for the finished concrete. Metallic reaction of RCH in the mixture gives higher values in both compressive and flexural strengths as compared to the normal concrete and better performance. It is a specially designed component to produce High Performance Concrete.

Description

A METHOD OF PRODUCTION FOR METEALLIC IRON CONCRETE HARDENER AND CEMENT CONCRETE MADE THEREFROM

Introduction:

Cement Concrete construction in today's developing, countries is very common and the use of concrete is increasing day by day in many folds. For the construction of highways, airport runways, road, bridges and building work etc. Concrete is the most versatile material in today's world. For the sustainable development, the modern world can not do without the high performance construction material concrete. The durability and efficiency of this construction material is impressively underline by the various innovation and systems developed by the world over.

Various properties of concrete have contributed to its development from the conventional normal concrete to the high strength concrete (HSC) and now to High Performance Concrete (HPC). Its higher performance is due to the fact that it has become a high-tech engineered material. Its characteristics are developed for a particular application, environment and specifications.

1. Field of the invention:

The present invention relates generally to use metallic concrete hardener in concrete mix for better performance then normal concrete. Rock Concrete Hardener is emerging concrete technology that lends to a new dimension to the term "High Performance Concrete" It has immense potential in civil construction due to its superior mechanical and durability properties compared to conventional concrete and could even replacement of reinforcement steel in some applications.

2. Details of the invention:

Concrete road (CC. Pavement) is constructed on the basis of flexural strength as concrete is weak in tensile strength reinforcement is provided to take care of tensile forces. This reinforcement has tendency to undergo corrosion with result durability of RCC Road is reduced to greater extents.

Knowing the above facts as well as poor tensile strength of cement concrete it was decided to under take investigation work to improve the tensile strength of concrete with respect to it's compressive strength for specific purpose, initially working of one year has given very encouraging results in laboratory as well as in field which has been produce here There has been recent research related to admixture to aimed at developing new approaches to modify the brittle properties of concrete and other mechanical properties. Emphasis is given to the recent developments in iron metallic concrete hardener and their influence on the properties and performance. Rock Concrete Hardener are introducing revolutionary changes in the structural application of concrete. RCH is a developing composite material that will allow the concrete industries to optimize material used, generate economic benefit, and civil structures are strong, durable and sensitive to environment. Research reported here was carried out to overcome the problems of concrete and to develop concrete to provide economical and durable structures.

3. Brief Description of the product (Rock Concrete Hardener):

The raw material is available as a by-product from Ferrous & Metallurgical industries, which is processed to manufacture Rock Concrete Hardener. It is produces under good quality control process and tested in well equipped laboratory. Rock concrete hardener (RCH) is a graded aggregate metallic particles of processed iron. It provides strength, durability and hard surface for the finished concrete. Metallic reaction of RCH in the mix gives higher values in both compressive and flexural strengths as compared to the normal concrete and a better performance. RCH was specially designed to enhance the properties of high performance concrete (HPC). If s characteristics are developed for a particular application, environment and specifications.

Various chemical & physical properties of RCH from standard tests were conducted to determine its composition characteristics. They are summarized below:

Physical Appearance Black / Brown Coarse particles

Loss on ignition <1.0%

Fe₂O₃ >30%

SiO₂ <3.0 %

CaO <2.0%

MgO <1.0%

Al₂O₃ <1.0%

Alkalis (Na₂O+K₂O) <1.0%

Inorganic Chlorides Absent ■ Moisture : <1.0%

4. Selection of the raw material:

Raw material is selected from various Ferrous & Metallurgical industries and it's by - products of iron and steel. The particular categories of iron are selected as a raw material for process of the product, this includes iron containing by product. The Iron content in raw material is mostly in oxide form & it is above more than 30%. It is an insoluble in water and alkalis, but soluble in most strong acids.

Raw material is a black/brown, heavy iron based material & the most stable form of ferric oxide in a fully coarse material. It is a one of several oxide components of iron, mainly it is a mixture of three oxides of iron, but for simplicity can be represented as non-corrosion Fe₂O₃ detail as under: a) FeO b) Fe₂O₃ c) Fe₃O₄

Accordingly there is provided a method of production of metallic iron concrete hardener. a) Selecting raw materials from ferrous and metallegical industries; b) Grading the above material at site; c) Sieving in a round rotary screen machine to remove the dust particles; d) Grinding the coarse material to a various mesh size; e) Removing the fine particles below the range by screening; f) Producing cement concrete with metallic iron concrete hardener; g) Testing the cement concrete for compressive strength and flexural strength; etc. h) Packing the metallic iron concrete hardener in HDPE bag for transportation.

5. General Process Description:

Selecting the above types of raw material, gradation of the material is processing in ground rotary screen machine, first of all, fine, dust and other impurities particles is removed from raw material. To collect the over size material discharged by the rotary screen through over size chute, and over size material transfer to grinding machine. Now, above raw material is idle for further process for the production of quality products.

Next process, above selected material is grind in special grinding machine, after grinding, the material is shifted through belt conveyor in rotary screen machine for segregation of the product. The rotary screen consists of a rotating screen made of tapered sieve panel mounted round shape around a shaft and enclosed in a casing. The shaft is driven by a motor and reduction gear. The iron particles of the lesser size passed from screen, over size material goes to end of the screen, fine powder and other impurities are removed. To collect the over size material discharge by the rotary screen through belt conveyor, again material transfer to grinding machine.

Next process is that coarse material passed again in batch wise screen machine for various gradation. Finished product is ready for collection and tested in well equipped laboratory for further chemical & physical test, then quality material is packed in HDPE bag. Main significant research is that, graded coarse material of metallic iron content play a decisive role in the proportioning of concrete mix. Because of the solid-state nature of the process, iron materials are irregular in shape, and characterized by a high degree of interconnected porosity. The high surface area associate with irons, renders them uniquely situated for applications of cement concrete. The cement content of the concrete mix may be reduce effectively by the use of graded metallic iron. As a result of its production process the iron contains internal porosities, which greatly enhance its surface area and therefore reactivity and other inclusions form within its structural matrix have been theorized to further enhance its reactivity exceeding that of similar size of the finished particle. RCH is a non-corrosive material in water, salt water, freezing and hot humid environment. It is very important that, the finished product will not rust as its crystalline composition makes it a stable form of Fe2C>3 (Ferric Oxide) no rust in material means it would not absorb moisture. Material is magnetic nature due to magnetic attraction but it has a very weak susceptibility to magnetic forces.

With the introduction of various new concrete making materials which are generally based on metallic iron. There has be a revolution in concrete technology leading to use of metallic concrete hardener, a new concrete systems resulting in rapid and better quality of construction pavement & such other applications. Iron metallic concrete hardener is a relatively new construction material which essentially consists of High Performance Concrete. Besides enhancing the cracking and flexural strength of the cement/ concrete matrix the incorporation of the iron metallic concrete hardener also improves the engineering performance of the completed structure/ structural components.

6. Process flow chart of Rock Concrete Hardener Product:

7. Flow diagram of Rock Concrete Hardener product:

8. Investigations of the product:

Broad investigations of the product were carried out at Ahmedabad Engineering Research Institute, Ahmedabad, AERI is involved in testing of building materials, quality assurance services and development of non-conventional building material. General purpose is that to determine all technical parameters with iron metallic concrete hardener in cement concrete accordance with the ISI and ASTM standards.

In view of facts, we have worked out the use of admixture that is Rock Concrete Hardener (RCH ) for better performance designing the concrete mix proportion of various grades such as M-20 to M-75 with a view to optimize the concrete for the said grades and achieve HPC in line with the laid down national standard for the stipulated parameter like compressive strength, flexural strength, flexural fatigue strength coupled with high abrasion and impact resistance, low drying shrinkage with reduced permeability. A) RCH Concrete:

The properties of RCH concrete in fresh and hardened states are influenced by the type of aggregates, its composition, volume fraction and material properties of RCH and its interfacial bond characteristics.

B) Fresh Concrete Properties:

RCH concrete mixture is a practical one that enhances transporting, placing, workability, compacting and finishing, and ensures its uniform distribution. RCH is little heavier than other components due to metallic presence, but this does not affect the mixture and distribution in the matrix.

C) Properties of Hardened Concrete with RCH:

Plain concrete has two major deficiencies; a low tensile strength and a low strain at fracture. The tensile strength of concrete is very low because plain concrete normally contains micro cracks. It is the rapid propagation of these micro cracks under applied stress that is responsible for the low tensile strength of the material.

These deficiencies have lead to considerable research aimed at developing new approaches to modify the brittle properties of concrete. Current research has developed a new concept to increase the concrete durability and its energy absorption capacity, as well as to improve overall durability. This new generation technology utilizes iron metallic concrete hardener, are randomly dispersed through the concrete matrix providing for better distribution of both internal and external stress by using a three dimensional reinforcing network. The primary role of the RCH in harden concrete at low volume is to modify the cracking mechanism. RCH significantly delays and controls cracking in the composite concrete. These unstable cracks in concrete are transformed to slowly growing ones. RCH provides mix a ductile matrix and results behavior of components in a ductile fashion significantly different than normal concrete. This strengthening mechanism involves transfer of stress from the RCH matrix by interfacial shear or by interlocking between RCH particles. Properties of hardener in concrete are the result of a complex mechanism, which depends on the type of aggregates, combined gradation method of mixing placing etc. This mechanism of failure causes affects various properties of concrete significantly. These are ductility, toughness, tensile and flexural strengths, fatigue life, abrasion & impact resistance, shrinkage, durability and resistance against cavitations The signification influence of incorporation of metallic hardener is to delay and control the tensile cracking of composite material. Thus an inherently unstable tensile crack propagation in concrete is transform to a slow controlled crack growth. The metallic concrete hardener provides a ductile member in a brittle matrix and the resultant composite has ductile properties which are significantly different from plain concrete.

The strengthening mechanism of iron metallic concrete hardener (RCH) involves transfer of stress from matrix to the iron metallic concrete hardener(RCH) by interfacial shear or by inter locking between the iron metallic concrete hardener (RCH) particles and matrix, the iron metallic concrete hardener (RCH) and matrix shear the tensile force until the matrix cracks and then the total force is transformed to the iron metallic concrete hardener (RCH). This change in mechanism of failure causes significant improvement with iron metallic concrete hardener(RCH) in the following properties as ductility, toughness, impact resistance, tensile and flexural strength, fatigue life, abrasion resistance, shrinkage, permeability, durability and cavitations resistance. Properties of hardener in concrete are the result of a complex mechanism, which depends on the type of aggregates, combined gradation method of mixing placing etc

At present investigation has been made to study the performance characteristics of iron metallic concrete hardener (RCH) admixed with concrete mixes. The study aims to investigate the replacement of cement percentage with iron metallic concrete hardener (RCH) in the concrete mix on their strength properties, durability, permeability, drying shrinkage, abrasion resistance & water absorption characteristics etc.

This research paper deals with an-experimental investigation on the physico-mechanical characteristics of High Performance Concrete (HPC) mixes with different replacement level of cement with RCH.

9. Details of Experimental Investigations in compressive strength:

A) Concrete mix proportion with Rock Concrete Hardener M-20 Grade for Compressive

Strength:

Aggregate/ Cement ratio = 6.20, using L&T Brand 53 Grade

Cement = 50 kg

River sand of Zone III (FA) = 115kg

Coarse Aggregate:

M-I; <10mm = 45 kg M-2; <20mm = 150 kg

Mix Proportions by weight are: C: FA: M-I: M-2 as 1.00: 2.30: 0.90: 3.00

Water Cement ratio = 0.54

Material and Mix Proportion:

The materials used in the casting of the cubes for a compressive test consisted of ordinary Portland cement conforming 16:12269-1987, river sand of Zone III, crushed coarse aggregate, down 10mm & passing through 10mm down 20mm. & Rock Concrete Hardener. All aggregates selected and tested as per IS:23861963 (Part I to VIII).

The mix proportion for all tests the specimens were kept material ratio same as 1.00: 2.30: 0.90: 3.00 by weight of cement, sand and aggregates. AU mix proportions materials used by weight. RCH are introduced into the concrete mix at a ratio of 5.0 to 7.5% by weight of cement used in all concrete mixes. The cement contain of the control concrete was 300kg /M^- The water cement ratio was kept as 0.54 for all specimens.

Casting of Test Cubes:

First, phase of experimental work was to determine the optimum water - cement binder ratio for the various concrete mixes, assuming service exposure condition, the proportion for M-20 mix. The water - cement binder ratio for all mixes was maintained at 0.54. Standards test cubes size 150mm x 150mm were cast with and without RCH. All the 27 standards cubes were demoulded after 24 hours and water cured. At the end of respective curing periods of 3 days, 7 days and 28 days, the cubes specimens were tested for compressive strength. Three specimens were tested for each variable considered. AU the test were conducted as per IS 456-2000, Indian Standard Code of Practice for Plain and Reinforced Concrete (4^th Revision), Indian Standards Institution, New Delhi, India.

Test Results:

The different test results obtained from the mechanical properties of compressive strength grade (M-20) as shown in Table -1 & Figure -1.

Table-1 Compressive strength results of Rock Concrete Hardener (M-20)

Compressive Strength

Rock Concrete 7 Days 28 Days

Rl Normal

80 16.8 — 21.5 — 25.8 — Concrete

R2 5.0 % Blended

77 21.7 29.17 % 28.4 32.09 % 37.1 43.80 % RCH

R3 7.5 % Blended

75 25.3 50.60 % 30.2 40.47 % 38.6 50.77 % RCH

*Test Results from Ahmedabad Engineering Research Institute, Ahmedabad

Figure-1 Variation of Compressive strength with age of curing.

B) Concrete mix proportion with Rock Concrete Hardener M-25 Grade for

Compressive Strength: 1. Design Stipulations: a) Characteristic Compressive strength : 25.00 N/ mm2 required in the field at age of 28days b) Maximum nominal size of aggregates : 6.30mm down (ANGULAR) c) Degree of workability : Medium, Slump: 84mm,

Compaction Factor = 0.965, Density : 2.400 gm/cc d) Method of Compaction : VIBRATION e) Degree of quality control : GOOD f) Type of Exposure : MILD to MODERATE 2. Test data for the materials use: a) Type of cement : Birla Chetak Brand 53 Grade O.P.C. conforming to IS:12269- 1987 b) Specific gravity of cement : 3.15 c) Specific gravity of aggregates: i) Fine Aggregates : 2.65 gm/cc ii) Coarse Aggregates : 2.79 gm/cc d) Water Absorption: i) Fine Aggregates : 0.485% ϋ) Coarse Aggregates : 0.22%

3. Target mean strength of concrete 33.50 N/mm2

4. Water - cement ratio by weight 0.48

5. Additives a) Rock Concrete Hardener 10% by weight of cement

b) Conflow SNS2 admixture

300ml/bag

6. Aggregate - cement ratio by weight 5.60

7. Proportion of Aggregates

(Fine Aggregate : Metal No. 1) 35.71 : 64.29

(6.30mm down)

8. Concrete mix. Proportion by weight (Cement: F.A. Metal No. 1) 1.00 : 2.00 : 3.60

(6.30mm down)

9. Material required per bag of cement a) Fine aggregates - (Sand) 100kg b) Metal No.l-6.3mm (Grit) 180kg c) Metal No.2-20mm/25mm (Kapchi) d) Metal No.3-40mm (Meal) e) Rock Concrete Hardener(10%) 5kg f) CONFLOW SNS-2 300ml g) Water 241tr

Material and Mix Proportion:

The materials used in the casting of the cubes for a compressive test consisted of ordinary Portland cement conforming 15:12269-1987, river sand, crushed coarse aggregate, down 6.3mm (ANGULAR) & Rock Concrete Hardener

The mix proportion for all tests the specimens were kept material ratio same as 1.00: 2.00: 3.60 by weight of cement, sand and aggregates. All mix proportions materials used by weight. RCH are introduced into the concrete mix at a ratio of 10% by weight of cement used in concrete mixes. The cement content of the control concrete was 349kg /M^ with the consideration of 1.00% Air content.

Casting of Test Cubes:

First, phase of experimental work was to determine the optimum water - cement binder ratio for the various concrete mixes, assuming service exposure condition, the proportion for M-25 mix. The water - cement binder ratio for all mixes was maintained at 0.48. Standards test cubes size 150mm x 150mm were cast with RCH. All the standards cubes were demoulded after 24 hours and water cured. At the end of respective curing periods of 3 days, 7 days and 28 days, the cubes specimens were tested for compressive strength. Three specimens were tested for each variable considered. All the test were conducted as per IS 456-2000, Indian Standard Code of Practice for Plain and Reinforced Concrete (4^th Revision), Indian Standards Institution, New Delhi, India.

Test Results:

The different test results obtained from the mechanical properties of compressive strength grade (M-25) as shown in Table-2 & Figure-2.

Table 2 Compressive strength results of Rock Concrete Hardener (M-25)

Compressive Strength

Rock Concrete 3 Days . 7 Days 28 Days Hardener Slum Increases Increases Increases (Present) Mpa in Mpa in Mpa in strength strength Rl Normal

Concrete as per 12.5 18.75 25.00 IS:456 2000

R2 10 % Blended

84 20.5 64.00 % 33.50 78,67 % 39.60 58.40 RCH

Test Results from Ahmedabad Engineering Research Institute, Ahmedabad

Figure-2, Variation of Compressive strength with age of curing.

C) Concrete mix proportion with Rock Concrete Hardener & Fly- Ash M-35 Grade for PQC ROAD PAVEMET WORKS:

1. DESIGN STIPULATIONS:

(a) Characteristic Flexural Strength 4.15 N/m^m2

Compressive Strength 35.00 N/mm² required in the field at age of 28 days

(b) Maximum nominal size of aggregates 20mm size (Angular)

(c) Degree of workability Medium. SLUMP:- 88mm,

Density = 2.580gm/cc

(d) Method of compaction Vibration

(e) Degree of quality GOOD

(f ) Type of Exposure MILD . 2. TEST DATA FOR THE MATERIALS USED:

(a) Type of cement : SANGHI Brand 53 Grade O.P.C as per IS: 12269-1987

Type of Fly-ash : G.E.B. Gandhinagar TPS,

Type of Hardener : Rock Concrete Hardener

(b) Specific gravity of cement : 3.15

(c) Specific gravity of Fly-ash : 2.30

(d) Specific gravity of aggregates:

( i ) Fine Aggregate : 2.655

(ii ) Coarse Aggregate : 2.79

(e) Water Absorption:

( i ) Fine Aggregate : 0.53

(ii ) Coarse Aggregate : 0.37

3. Target mean strength of concrete : 48.00 N/mm2

4. Water - cement ratio by weight : 0.45

5. Aggregate-Cement ratio by weight : 3.20

6. Proportion of Aggregates

(Fine Aggregate : Metal No. 1

Metal No. 2) : 35.94 : 20.31 : 43.75

7. Concrete mix. Proportion by weight (Cement: F.A. Metal No. 1 0.80: 0.20:1.50: 0.65: 1.40 + Fly-ash : Metal No.2)

8. Cement 53 Grade : 50kg

Rock Concrete Hardener (12%) : 6.0kg

Fly-ash : 10kg

a) Fine aggregates - (Sand) : 57.50kg b) Metal No.l-6.3mm (Grit) : 32.50kg c) Metal No.2-20mm/25mm (Kapchi) : 70.0 kgs d) Metal No.3-40mm (Meal) : e) Water : 22.500 Liter

9. Average crushing strength of cubes: at 3 days : 30.00 N/mm2 at 7 days : 42.80 N/mm2 at 28 days : 52.30 N/mm2 10. Average Flexural strength of CC. beams at 7 days : 5.31 N/mm2 at 28 days : 12.20 N/mm2

Material and Mix Proportion:

The materials used in the casting of the cubes for a compressive test consisted of ordinary Portland cement conforming IS:12269-1987, river sand, crushed coarse aggregate, down 20mm (ANGULAR), Rock Concrete Hardener & Fly-Ash from GEB, Gandhinagar, TPS. The mix proportion for all tests the specimens were kept material ratio same as 0.80: 0.20: 1.15 : 0.65 : 1.40 by weight of cement, Fly-Ash, sand and aggregates. All mix proportions materials used by weight. RCH are introduced into the concrete mix at a ratio of 12% by weight of cement used in concrete mixes. The cement content of the control concrete was 352 kg /M^ with the consideration of 1.00% Air content.

Casting of Test Cubes:

First, phase of experimental work was to determine the optimum water - cement binder ratio for the various concrete mixes, assuming service exposure condition, the proportion for M-35 mix. The water - cement binder ratio for all mixes was maintained at 0.45. Standards test cubes size 150mm x 150mm were cast with RCH. All the standards cubes were demoulded after 24 hours and water cured. At the end of respective curing periods of 3 days, 7 days and 28 days, the cubes specimens were tested for compressive strength. Three specimens were tested for each variable considered. All the test were conducted as per IS 456-2000, Indian Standard Code of Practice for Plain and Reinforced Concrete (4^th Revision), Indian Standards Institution, New Delhi, India.

Test Results:

The different test results obtained from the mechanical properties of compressive strength grade (M-35) as shown in Table-3 & Figure -3. Table-3 Compressive strength results of Rock Concrete Hardener with Fly- Ash (M-35)

Compressive Strength

Rock Concrete 3 Days 7 Days 28 Days

Mi Hardener Slum Increases Increases Increase

X (Present) P Mpa in Mpa in Mpa in

(mm) strength strength strength

Rl Normal

Concrete as per 17.5 26.25 35.00 IS:4562000

R2 12 % Blended

30.0 71,43 % 42.80 63.05% 52.30 49.45% RCH

Test Results from Ahmedabad Engineering Research Institute, Ahmedabad

Figure - 3, Variation of Compressive strength with age of curing.

Effects of concrete hardener with fly-ash on compressive strengths of concrete:

Increase in compressive strength due to addition of 12% of Rock Concrete Hardener with fly- ash is variable ranging from 49 to 71 as per shown in Table - 3 & Figure -3. However, there is a change in compressive stress-strain response due to addition of metallic concrete hardener. This change is generally characterized by a noticeable increase in strain at pick load & significant increase in ductility resulting in substantially higher toughness. This increased toughness is useful in preventing sudden explosive failure under static loading and in absorbing energy in dynamic loading. The toughness increases with the volume fraction of RCH and the aspect ratio. The available test data indicates that RCH with Fly-Ash concrete leads to a higher toughness compared to normal concrete.

Matrix properties also have influence on the effectiveness of RCH with Fly- Ash in improving the compressive behavior of concrete. These improvements due to addition of RCH are relatively more significant at lower matrix compressive strengths. Addition of RCH increases the compressive strength and toughness of concrete.

D) Concrete mix proportion with Rock Concrete Hardener M-40 Grade for Compressive

Strength:

Concrete mix proportion by weight:

Cement (43 Grade) : 1.00

F.A. (Sand) : 1.55

Metal No.l (10mm Down) : 0.75

Metal No. 2 (20mm Down) : 1.90

W/C : 0.40

Material and Mix Proportion:

In this study, a High Performance Concrete of M-40 grade was considered. The material used for compressive strength consisted of ordinary Portland cement 43 grade conforming IS:8112- 1989, river sand of Zone III, crushed coarse aggregate, down 10mm & passing through 10mm down 20mm. & Rock Concrete Hardener.

Concrete was mixed in a concrete mixer in the laboratory. The mix proportion for all the specimens were kept same as 1.00: 1.55: 0.75: 1.90 by weight of cement, sand and aggregates. All mix proportions materials used by weight. The cement was partially replaced with RCH in step of 5 to 10% weight of cement is used in all concrete mixes. The cement contain of control concrete was 409 Kg/m^ for all mixes. Casting of Test Cubes:

OPC 43 grade cement conforming IS:8112-1989 was selected to use in concrete. The concrete mix was mixed in a laboratory mixture with and without RCH. The water - cement binder ratio for all mixes was maintained at 0.40. Standards test cubes of size 150mm x 150mm were cast. The RCH was added to in concrete mix from 0.0 to 10% by weight of cement. All the 27 standards cubes were cast and demoulded after 24 hours. Test cubes are cured in water for a period of 3, 7 & 28 days, and tested for compressive strength. Three specimens were tested for each variable considered as per IS 456-2000, Indian Standard Code of Practice for Plain and Reinforced Concrete (4^th Revision), Indian Standards Institution, New Delhi, India. Test Results: The result obtained from the experimental investigation for M-40 grade, the variation in compressive strength with different ages and percentage of RCH, shown as under: tabulated in Table -4 & Figure -4.

Table 4 Comparison of compressive strengths of Normal and RCH Concretes (M-40)

Compressive Strength

Type of RCH Concrete W/CM Cement Details Ratio 3 Days 7 Days 28 Days

Normal Concrete

C - as per IS 456- 0.40 20.00 27.00 40.00 1978/2000

Kamal

Cl 5.0% RCH 0.40 30.56 41.56 55.56 Brand 43

Kamal

C2 7.5% RCH 0.40 31.90 42.20 54.40 Brand 43

Siddhee

C3 10.0% RCH 0.40 36.70 47.30 60.45 Brand 43

*Test Results from Ahmedabad Engineering Research Institute, Ahmedabad

Figure-4, Variation of Compressive strength with age of curing.

Effects of concrete hardener on compressive strengths of concrete:

Increase in compressive strength due to addition of 5 to 10% of Rock Concrete Hardener is variable ranging from 30 to 70% as per shown in Table - 1 & 4 Figure - 1 & 4. However, there is substantial change in compressive stress-strain response. This -change is generally characterized by a noticeable increase in strain at pick load & significant increase in ductility resulting in substantially higher toughness. This increased toughness is useful in preventing sudden explosive failure under static loading and in absorbing energy in dynamic loading. The toughness increases with the volume fraction of RCH and the aspect ratio. The available test data indicates that RCH concrete lead to a higher toughness compared to normal concrete.

Matrix properties also have influence on the effectiveness of RCH in improving the compressive behavior of concrete. These improvements due to addition of RCH are relatively more significant at lower matrix compressive- strengths. Addition of RCH increases the compressive strength and toughness of concrete through increase of the RCH matrix interfacial bond. Table - 1 & 4 shows that the compressive strength increases with the increases of RCH.

10. Details of Experimental Investigations in flexural strength:

A) Concrete mix proportion with Rock Concrete Hardener M-20 Grade for

Flexural strength: Concrete mix proportion by weight:

Aggregate/ Cement ratio = 6.20, using L&T Brand 53 Grade

Cement = 50 kg

River sand of Zone III (FA) = 115kg

Aggregate:

M-I; <10mm = 45 kg

M-2; <20mm = 150 kg

Mix Proportions by weight are: C: FA: M-I: M-2 as 1.00: 2.30: 0.90: 3.00

W/ CM ratio = 0.54

Material & mix proportion:

For, flexural test beams are cast, material used consisted of ordinary Portland cement conforming IS: 12269-1987, locally available river sand, crushed coarse aggregate, down

10mm & passing through 10mm down 20mm. & Rock Concrete Hardener.

The mix proportion for all the specimens was kept same as 1.00: 2.30: 0.90: 3.00 by weight of cement, sand and coarse aggregates. The cement was partially replaced with RCH in step of 5 to 10% weight of cement is used in all concrete mixes. The cement contain of the control concrete was 300kg/ m^ of all mixes. The water cement ratio was kept as 0.54 by weight. Casting of test beams:

Concrete was mixed in the concrete mixer in the laboratory. The beams were vibrated with a mechanical vibrator. Each beam was cast from the same batch of the concrete. A total of 36 beams of size 100mm x 100mm x 500mm (long) were cast standard steel moulds with and without RCH. One day after casting, test beams were demoulded. The test specimens were cured for 3 days, 7 days and 28 days and the beam were tested for flexure strength. Three specimens were tested for each variable considered as per IS 456-2000, Indian Standard Code of Practice for Plain and Reinforced Concrete (4^th Revision), Indian Standards Institution, New Delhi, India.

Testing of beams:

Tests were carried out conforming IS:516 1959 to obtain the flexural strength for various concrete mix. Three beams were cast for each mix tested using two point loading. After the elapse of the required curing period, the test beams were tested using an universal testing machine in accordance with ASTM C-1018. A two - point loading system was adopted in which the beams was simply supported over a span of 600mm. the loads were applied at distance of 200mm from each support. Dial gauge having a least count of 0.01mm was mounted on a specially fabricated frame for accurate measurement of deflection at mid span increased at a rate of 0.05 to 0.10mm /min as specified by ASTM. Deflection measurement were recorded at various stages of loading until the failure of the beam.

Test Results:

The variation of flexural strength of M-20 grade, with age and different percentages of RCH, shown as under: Table - 5 & Figure -5.

Table 5 Flexural Strength results of with Rock Concrete Hardener (M-20)

Flexural Strength

Rock Concrete 3 Days 7 Days 28 Days

Mi Hardener Increases Increases Increases

X (Present) Kg/cm in Kg/αn2 in Kg/cm2 In

2 strength strength strength

Normal

Rl 23.60 32.10 39.00 Concrete 5.0 % Blended

R2 31.30 32.63 % 50.00 55.76 % 67.30 72.56 % RCH

7.5 % Blended

R3 34.00 44.06 % 53.10 65.42 % 78.00 100.00 % RCH

10.0 % Blended

R4 38.90 64.83 % 61.60 91.90 % 89.70 130.10 % RCH

^: Test Results from Ahmedabad Engineering Research Institute, Ahmedabad

Figure-5, Percentage increases in flexural strength over normal concrete.

B) Concrete mix proportion with Rock Concrete Hardener with Fly- Ash M-35

Grade for Flexural strength: Concrete mix proportion by weight:

Cement = 50 kg

Fly-Ash= 10kg

Rock Concrete Hardener=6kg

Fine aggregate (Sand) = 57.5kg

Coarse Aggregates:

Metal no:l:(10mm Grit) : 32.5 kg

Metal no:2:(20/25 mm Kapchi): 70.0 kg

Mix Proportions by weight are: C: FL:FA: M-I: M-2 as 0.80: 0.20: 1.15: 0.65:1.40

Water Cement ratio = 0.45

Material & mix proportion: For, flexural test beams are cast, material used consisted of ordinary Portland cement conforming IS: 12269-1987, Fly-ash, river sand, grit, down 25mm kapchi & Rock Concrete

Hardener.

The mix proportion for all the specimens was kept same as 0.80: 0.20: 1.15: 0.65:1.40 by weight of cement, fly-ash, sand and coarse aggregates. The cement was partially replaced with fly-ash in step of weight of cement is used in all concrete mixes. The cement content of the control concrete was 352 kg/rrv^ of all mixes. The water cement ratio was kept as 0.45 by weight.

Casting of test beams:

Testing of beams:

Tests were carried out conforming IS:516 1959 to obtain the flexural strength for various concrete mix. Three beams were cast for each mix tested using two point loading. After the elapse of the required curing period, the test beams were tested using a universal testing machine in accordance with ASTM C-1018. A two - point loading system was adopted in which the beams was simply supported over a span of 600mm. the loads were applied at distance of 200mm from each support. Dial gauge having a least count of 0.01mm was mounted on a specially fabricated frame for accurate measurement of deflection at mid span increased at a rate of 0.05 to 0.10mm /min as specified by ASTM. Deflection measurement were recorded at various stages of loading until the failure of the beam.

Test Results:

The variation of flexural strength of M-35 grade, with fly-ash (20%) and Rock Concrete Hardener (12%), shown as under: Table - 6 & Figure -6.

Table 6 Results of Flexural Strength with Fly-ash & Rock Concrete Hardener (M-35) Flexural Strength

Rode Concrete 3 Days 7 Days 28 Days

Mi Hardener Increases Increases Increases

X (Present) Kg/cm in Kg/cm2 in Kg/cm2 In

2 strength strength. Strength

Normal

Rl 23.00 — 32.00 41.50 Concrete

12 % Blended

R2 32.80 42.61% 53.10 65.94% 122.20 194.46% RCH

' Test Results from Ahmedabad Engineering Research Institute, Ahmedabad

Figure 6, Gain in Strength for 20% cement replacement with Fly-ash and Rock Concrete Hardener

C) Concrete mix proportion with Rock Concrete Hardener M-40 Grade for

Flexural strength: Concrete mix proportion by weight:

Cement (43 Grade) : 1.00

F. A. (Sand) : 1.55

Metal No.l (10mm Down) : 0.75 Metal No. 2 (20mm Down) : 1.90 W/C : 0.40

Material & mix proportion:

For the flexural strength test of grade M-40, material used as ordinary Portland cement conforming IS: 8112: 1989, and remaining material selected river sand, crushed coarse aggregate as per IS: 2386-1963 (Part I to Part VIII). The mix proportion for all the specimens was kept same as 1.00: 1.55: 0.75: 1.90 by weight of cement, sand and coarse aggregates. The RCH was added to the plain concrete ranges from 0.0 to 10% by weight of cement. The cement content of the control concrete was 409 kg/m3 for all tests. The water cement ratio was kept constant for all test as 0.54 by weight. Casting of test beams:

Experimental work was to determine the optimum water - cement binder ratio for the various RCH concrete mixes. 100mm x 100mm x 500mm (long) size of the beams were cast by using the same water - cement ratio 0.40. The cement was partially replaced with RCH in the steps of 5 to 10%. in concrete mix. Concrete was mixed in the mixture I the laboratory and each beam cast from the same batch of the concrete. The beams were vibrated with a mechanical vibrator.

All the beams were demoulded after 24 hours, at the end of the respective curing period 3, 7 & 28days. The beams specimens were tested for flexural strength. Three specimens were tested for each variable considered as per IS 456-2000, Indian Standard Code of Practice for Plain and Reinforced Concrete (4^th Revision), Indian Standards Institution, New Delhi, India.

Testing of beams:

Test Results:

The test results of various beams for flexural strength of M-40 grade are tabulated in Table-7

& Figure- 7.

Table 7 Comparison of flexural strength of normal and RCH concretes (M-40)

Flexural Strength

RCH Concrete

UMl'.UUH W/C 3 Days 7 Days 28 Days Hardener Percentage Normal Concrete as per

C - - 2.50 3.40 4.43 IS 456-1978/2000

Kamal

Cl Brand 43 5.0% Blended with RCH 0.40 5.07 8.40 12.60

Grade

Kamal

C2 Brand 43 7.5% Blended with RCH 0.40 5.76 7.83 12.12

Grade

Sidhee

C3 Brand 43 10.0% Blended with RCH 0.40 7.27 10.40 13.80

Grade

*Test Results from Ahmedabad Engineering Research Institute, Ahmedabad

Figure-7, Percentage increases in flexural strength over normal concrete.

Effect of RCH on Flexural Strength:

A significant difference in the behavior of plain and RCH concrete is found in the flexural test as shown in Table 5 & 7 Figure 5 & 7. When the RCH concrete beams are loaded in flexural, two stages of behavior are observed in the load deflection curve (Figure-8). The behavior is more or less linear up to the first crack and then curve is significantly non-linear and reaches its peak and the ultimate strength or at the maximum sustainable static load. Two factors that significantly influence the flexural test are RCH type and its volume Figure - 8 presents the flexural load deflects curve for plain concrete beam and that for RCH blended concrete beam with 10% of RCH by weight of cement.

The graded coarse material of metallic iron content play a decisive role in the flexural strength in concrete mix, because of the solid-state nature of the process, iron materials are irregular in shape, and characterized by a high degree of interconnected porosity. The high surface area of concrete associates with irons, renders them uniquely situated for applications of cement concrete. As a result of its production process the iron contains internal porosities, which greatly enhance its surface area and therefore reactivity and other inclusions form within its structural matrix have been theorized to further enhance its reactivity exceeding that of similar size of the finished particle.

The RCH addition also demonstrated its property to arrest cracking. The cracks are prevented from propagating until the ultimate stress in the composite material is reached. This indicates that the RCH particles contribute significantly to increase in bond between RCH particles and cement/sand matrix and its strength. This significance of good bond is indicated by the characteristic load deflection curves in Figure 5. These curves also indicate a ductile behavior and large energy absorption.

The effect of RCH on the ultimate strength is significant and with its better pull-out performance, it is especially effective at large deformations and crack widths.

Figure-8, Load Deflection Curve for Static Loading at 28 Days.

The volume of integrated RCH in the concrete significantly influences the flexural strength. This increase depends upon the volume for fraction of RCH which varies from 5 to 10% by weight of cement and flexural strength is significantly increases by more then 100% as compared to the normal concrete at the different stages The metallic bonding reaction of RCH also causes this positive improvement in the flexural fatigue strength, flexural toughness, impact strength, shock resistance and static flexural strength.

11. Effects of RCH on various properties of concrete: A) Effect of RCH on Fatigue Strength:

Fatigue strength is an important property of RCH concrete because it is the behavior of the material under dynamic loading that clearly distinguishes the material from the plain concrete. In many applications, particularly in pavements and bridge deck overlays, the flexural Fatigue strength is important design parameters because this structure are design in the basis of fatigue load cycles. The greatest advantage of adding RCH to concrete is the improvement in flexural strength in both static and fatigue loading.

B) Effect of RCH on abrasion resistance:

Abrasion resistance is a function of the water - cement ratio (compressive strength) at the top surface of the concrete. When normal concrete can not resist the expected wear and abuse on the concrete, a metallic concrete hardener (RCH) used to improve the surface abrasion of concrete and also significantly improvement in water absorption. A practical investigation in pavers blocks has carried out for a test of abrasion value and water absorption. In pavers block the addition of 10% Rock Concrete Hardener has significant reduction in abrasion value & water absorption value, test carried out as per I.S.1237-1980, Indian Standard for cement concrete flooring tiles and pavers.

Test Results:

The test results of various pavers block for abrasive value and water absorption, results of M- 20 grade are tabulated in Table-8.

Table 8 Comparison of results of pavers blocks with 10% RCH concrete (M-20)

1. Pavers blocks a) Abrasion Value 1.20 mm <3..OO mm b) Water Absorption 2.5 % <10.00 %

2. Pavers blocks a) Abrasion Value 1.20 mm <3..00 mm b) Flexural strength 49.70 kg/ cm² > 30 kg/ cm² c) Water Absorption 0.79% <10.00 %

I.S.1237-1980 is Indian Standard for cement concrete flooring tiles and pavers

C) Effects of RCH on workability:

Addition of RCH in concrete mix caused reduction in water cementitious material ratio and capillary pores, thus improving impermeability in concrete. RCH in the mix lowered the surface tension of water to make cement particles hydrophilic to control the setting of concrete. It also reduced bleeding and easy placement of concrete with reduced porosity and finally resulting in a higher quality concrete surface. The workability is governed primarily by the unit water content of concrete and is relatively in sensitive to variation in cement and RCH content.

D) Effects of RCH on permeability:

Permeability concept is more applicable to the saturated concrete but in actual practice most concretes have different degrees of saturation and therefore the concept of absorptive phenomenon is more relevant. Permeability of concrete is important due to possible indentation or even penetration while casting.

Permeability of concrete tests has been verified in laboratory, the facts has been verified in laboratory test the permeability of concrete is considerably reduced and the ingress of moisture of cylindrical cement concrete sample under split tensile test is less than 5mm from the external face. RCH concrete becomes a composite material with filler and concrete binder due to metallic bonding reaction in the mix. Permeability also affects the corrosion of steel reinforcement and pre-stressed concrete. This is mainly influenced by the cover provided and flue permeability. With RCH a fairly impermeable concrete is obtained by adopting a lower water cement ratio and by ensuring a thorough compaction of concrete.

E) Effects of RCH on Shrinkage & Creep:

A knowledge of shrinkage, creep and creep recovery characteristics of general concrete is essential for the analysis and design of concrete structures. Uniform distribution of RCH throughout the mass of the concrete makes the concrete mix more cohesive and less prone to segregation. RCH reduces plastic shrinkage and increases impact resistance and improves tensile strength of concrete. Results shows that the increase ratio of RCH decreases drying shrinkage in the concrete mix.

F) Resistance in thermal cracking:

Thermal cracking is a major problem in mass concrete during the initial stage. In some cases where higher cement content is specified to get either higher grade of concrete or durability, the heat of hydration becomes an important factor. RCH concrete has relatively lower heat of hydration as compared to normal concrete. This greatly reduces the risk of cracking in mass concrete applications. G) Protection from Sulphate attack:

Concrete structure exposed to sea water or sulphate bearing soils, sub-soils and ground waters may suffer deterioration during there service-life due to sulphate attack. The sulphate iron can react with calcium hydroxide and alumina - bearing phases hydrated cement. This leads to formation of expensive salts like calcium - sulpho - aluminate hydrate (Ettringite) and calcium sulphate (gypsum). This results in expansion, spalling, cracking and loss of strength of concrete. RCH resists the sulphate attack due to reduced pour size, decreases the permeability and lower the heat of hydration in concrete mix, so ingress of water carrying sulphate irons and other chemicals becomes more difficult.

H) Reduction in Alkali Silica reaction (ASR):

Some aggregates react with the alkali present in cement leading to expansion and therefore cracking to cause deterioration of concrete known as ASR. This reaction is more pronounced in structures in high humid environments; they include roads, bridge, piers, jetties, sea-wall and generally construction in the coastal region. The alkali content available in cement for such reaction is reduced due to partial replacement of cement with RCH. As a result, the refined micro-structure of concrete helps reducing moisture influence to cause ASR from the decreased built-up internal stress.

I) Effect of RCH on Corrosion of steel:

RCH is a non-corrosive material in both freezing and hot humid environment. Alkalinity in concrete is affected by the presence of moisture, oxygen, the chloride and the protective surrounding (matrix) and reduces effective coating of steel to cause its corrosion. Use of RCH causes sustained period of protection denser concrete matrix prevents ingress of chloride and others which are detrimental to concrete.

12. Important Technical advantages of RCH:

> Homogeneous Distribution:

The RCH, present close to surface, ensure an excellent metallic reinforcement at the joints of the segments.

> Multidirectional Reinforcement:

The RCH provide a resistance to stress in all directions.

> Excellent corrosion resistance:

The spalling risk of concrete is totally excluded.

> High abrasion resistance: RCH concrete gives maximum to abrasion, impact and high point loads, considerably extends the serviceable life of the concrete structure.

> High impact resistance:

The energy absorbed by the RCH concrete during impact is superior to the energy absorption of plain concrete.

> Excellent control of shrinkage cracks:

Uniform distribution of RCH throughout the mass of the concrete makes the concrete mix more cohesive and less prone to segregation, reduces plastic shrinkage. The increase ratio of RCH decreases drying shrinkage in the concrete mix.

> Reduction in construction time:

Use of RCH in concrete roads and other application reduces construction time in case of concrete pavements to permit rapid opening or re-opening of roads to traffic, without compromising long-life service ability.

13. General Advantages of RCH:

> Increase in compressive and flexural strength of concrete as well as its long term strengths.

> Reduction in heat of hydration resulting in lesser drying shrinkage as well as plastic shrinkage and minimizing thermal cracking.

> Increase in durability and anti-crack strength.

> Reduction in permeability due to the concrete becoming denser and increase in durability and better resistance to freezing and thawing.

> Improvement in abrasion, impact and fatigue resistance along with increased antiskid abrasion and resistance to chemicals.

> Improves ductility.

> Better resistance to sulphate, alkaline soils and sea water attack with no chloride contents.

> Increase in the life of structures (pavements) and other applications.

14. Applications of RCH concrete:

> Concrete pavements, airport runways, taxiways, aircraft hanger etc.

> Industrial floors, railways platforms, bridges, ammunition storages, depots, parking decks & multiple basements.

> Tunnel / Canal lining, harbor, mine linings, domes etc.

> Heavy pedestrian floor traffic areas such as civil centers-sports arenas. > Water dams, canals and other irrigation structures, sewage pipe & corrosion resistance structures

> Rock/slop stabilization, pre-cast & pre-stress products.

> Ship yards, Jetties, Seawalls, Piers birth & Bridge deck overlays.

> Ready-mix concrete plant. 15. Brief summary of the invention:

This research papers reviews the available literature on RCH and also presents the results of laboratory investigation & field applications comparing RCH with normal concrete. This research papers deals with an-experimental investigation on the physico-mechanical characteristics of High Performance Concrete (HPC) mixes with different replacement level of cement, Fly- Ash with RCH.

The development of RCH is based on the application of some basic principles to achieve enhanced homogeneity, very good Tensile strength, high compaction, high abrasion, high impact resistance, improved microstructure and high ductility. It could therefore, be a suitable choice for highways, road pavements, runways and other important applications. The planning for extended network of highways in India has been an impressive with majority of them being in concrete. This will enhance the use of concrete in pavements to be constructed in the coming years similar to those during the last decade. With higher strength properties, the initial cost will reduce the thickness of concrete pavements by adopting a rational design approach and the maintenance cost over its life span. RCH concrete could be important due to its higher compressive and flexural strengths along with the advantages in early stage. The concrete pavement currently designed for a 28 day flexural strength of 4-5 MPa; use of 10-15% RCH in the mix, flexural strength increases to as much as 10 MPa. There are two types of pavements adopted the world over to construct pucca roads, namely, the flexible pavements wherein bitumen is the binder and the rigid pavements in which cement is the binding material. In India, heavy transport vehicles are generally overloaded by anything between 50 to 80 percent, thus increasing their axle loads far beyond what the roads they use have been designed to withstand.

Concrete road (CC Pavement) is constructed on the basis on flexural strength as concrete is weak in tensile strength, reinforcement is provided to take care of tensile forces. This reinforcement has tendency to under go corrosion with result durability of RCC road is reduced to greater extensions as it is experienced in the construction of RCC road. Hence in the view of above facts we have developed Rock Concrete Hardener (RCH) to increases the flexural strength to the tune of 2 to 3 times by blending 10 to 15% of RCH by weight of cement & fly-ash, which eliminates the reinforcement or above increases the durability of the concrete roads. Road built from this material will not developed potholes or bend due to vehicle pressure.

A commercial and a laboratory investigation are comparing normal and RCH concrete leads to the following conclusions.

❖ A comparison of the measurements of the physical, mechanical and durability properties of normal & RCH concrete shows that RCH concrete possesses better strength (both compressive & flexural) and lower permeability compared to normal concrete.

❖ A major advantage of using metallic concrete hardener in concrete besides reducing permeability and increasing fatigue strength is that metallic concrete hardener improves the toughness or residual load carrying ability.

❖ The high makes concrete brittle so RCH are generally added to the concrete mix to enhance its ductility.

❖ It was observed that addition of RCH in concrete mix, reduction in water cementious material ratio, thus improving impermeability in concrete.

❖ Abrasion resistance is a function of the water - cement ratio (compressive strength) at the top surface of the concrete. RCH reduces water - cement ratio, improves the surface abrasion and reduces water absorption in concrete mix.

❖ RCH reduces plastic shrinkage, increases impact resistance and decreases drying shrinkage in concrete.

^♦♦^♦ Impact resistance of concrete also improves dramatically with the addition of metallic concrete hardener.

❖ RCH concrete has relatively lowers heat of hydration, as compared^" to normal concrete. This is greatly reduces the risk of cracking in mass concrete, it is very important in pavements and other applications.

❖ RCH resists the sulphate attack due to reduced pour size & permeability, and it's protecting against the attack from ingress of harmful sulphate salts in concrete.

❖ The alkali content available in cement for such reaction is reduced due to partially replacement of cement with RCH, as a result, the refined micro - structure of concrete helps reducing moisture influence to cause

♦♦^♦ RCH can be used a supplementary reinforcement of normal steel to decrease the crack, in plain concrete.

❖ RCH are added to concrete to provide better resistance against cracking and spalling due to thermal cycles and thermal shocks considerable increase of the life of concrete. 14. Research Significance and Conclusions:

Concrete made of RCH has excellent mechanical properties and durability characteristics better than OPC concrete. It is economical to provide a long term solution for the utilization.

RCH road should be considered as one of the preferable alternatives for highway construction in our country.

The tensile strength of the top course of road is an important factor in controlling cracks in a pavements, since the micro cracks produced in the material, it is necessary to design the concrete in such way that fewer initial thermal or shrinkage cracks occur. It was also found that subsequent deflection and bending are controlled.

The use of RCH concrete in rigid pavements and other applications, where design is based on the compressive and flexural strengths and other physical properties of concrete. It is conclude that the use of RCH enhances the flexural strength up to 200% compared to the normal concrete. Other applications such as dome structures, pre-cast or pre-stressed concrete structures such as transmission poles, railway slippers, and spun pipes.

RCH concrete also beneficial in enhancing service life and other desirable properties leading to maintenance-free (concrete) structures. Cost is always the criteria, but generally they turn out to be useful in light of some saving due to reduced use of cement. In case of RCH, the main advantage was to improve the performance even for surface, which may be important for some structures, such as pavements, runways, etc

Most notable among the improved mechanical characteristics of RCH concrete mix, compared to normal concrete mix, are its superior tensile strength, resistance to impact strength, improves the flexural fatigue strength, flexural toughness, shock resistance and static flexural strength.

Research reported here was carried out to in India to develop concrete as an economical material of construction to provide long-lasting, maintenance-free structures.

The construction facilities of the world have been deteriorating due to effect of the natural environment, excessive use behind the original design, aging of the material and general obsolescence. RCH concrete composites are almost ideal material for repair, rehabilitation, retrofit and renovation of the world's deteriorating infrastructure.

Claims

I claim:

1) A method of production of metallic iron concrete hardener. a. Selecting raw materials from ferrous and metallegical industries; b. Grading the above material at site; c. Sieving in a round rotary screen machine to remove the dust particles; d. Grinding the coarse material to a various mesh size; e. Removing the fine particles below the range by screening; f. Producing cement concrete with metallic iron concrete hardener; g. Testing the cement concrete for compressive strength and flexural strength; etc. h. Packing the metallic iron concrete hardener in HDPE bag for transportation.

2) A method of production of cement concrete containing metallic iron concrete hardener as claimed in claim (1) which contains several oxides components mainly of metallic iron.

3) A method of production of all types of cement concrete contain the metallic iron concrete hardener as claimed in claim 1 & 2 which contain metallic iron preferably oxide of FeO, Fe₂O₃ and Fe₃ O₄ etc.

4) The method as claimed in claim 1 to 3, wherein the iron metallic concrete hardener (RCH) used in cement concrete mix, proportion of RCH 2.5 % to 15.0 % or more percent by weight of cement, resulted higher values in both compressive and flexural strength as compared to normal concrete and better performance, for better performance designing the concrete mix proportion of various grades such as M-20 to M-75.

5) The process as claimed in claim 1 to 4, wherein the iron metallic concrete hardener (RCH) used in cement concrete mix, proportion of RCH 2.5 % to 15.0 % or more percent by weight of cement, to improves mechanical characteristics of RCH concrete mix, compared to normal concrete are its superior tensile strength, resistance to impact strength, improves the flexural toughness, shock resistance and static flexural strength, for better performance designing the concrete mix proportion of various grades such as M-20 to M-75 as per CL.9 6) The process is claimed wherein the iron metallic concrete hardener (RCH) used in cement concrete mix, proportion of RCH 2.5 % to 15.0 % or more percent by weight of cement, leads to increases the compressive strength is variable ranging from 30 to 70 % as per shown in Table -1, 2, 3, 4 & Figure - 1, 2, 3, 4 compared to normal concrete for a period of 3, 7 and 28 days as per CL.9.

7) The process as claimed in claim 6, for compressive strength wherein, with use of iron metallic concrete hardener (RCH) in concrete mix, proportion of RCH 2.5 % to 15.0 % or more percent by weight of cement, for better performance designing the concrete mix proportion of various grades such as M-20 to M-75.

8) The process is claimed wherein the iron metallic concrete hardener (RCH) used in cement concrete mix, proportion of RCH 2.5 % to 15.0 % or more percent by weight of cement, leads to increases the flexural strength by more then 100 % as per shown in Table - 5, 6, 7 & Figure - 5, 6, 7 compared to normal concrete for a period of 3, 7 and 28 days as per CL.10

9) The process as claimed in claim 8, for flexural strength wherein, with use of iron metallic concrete hardener (RCH) in cement concrete mix, in proportion of RCH 2.5 % to 15.0 % or more percent of by weight of cement, for better performance designing the concrete mix proportion of various grades such as M-20 to M-75 as per CL.10

10) The process is claimed in, with use of iron metallic concrete hardener (RCH) in cement concrete mix, in ratio of 10.0 % by weight of cement, improvement in flexural strength in both static and fatigue loading, load deflection curve for static loading at 28 days as per shown in Figure - 8, for better performance designing the concrete mix proportion of various grades such as M-20 to M-75.

11) The process is claimed wherein is that, with use of metallic concrete hardener (RCH) in cement concrete mix, proportion of RCH 2.5 % to 15.0 % or more percent by weight of cement, to improve the surface abrasion of concrete as per Table - 8 for better performance designing the concrete mix proportion of various grades such as M-20 to M- 75 as per CL. H(B). 12) The process is claimed wherein is that with use of metallic concrete hardener (RCH) in cement concrete mix, proportion of RCH 2.5 % to 15.0 % or more percent by weight cement, significant reduction in water absorption value in cement concrete as per Table-8 for better performance designing the concrete mix proportion of various grades such as M-20 to M-75 grade as per CL. ll(B).

13) The process claimed wherein, in cement concrete mix with metallic concrete hardener (RCH) in cement concrete mix, proportion of RCH 2.5 % to 15.0 % or more percent by weight of cement, permeability is reduced and ingress of moisture of cylindrical cement concrete sample under split tensile test as per CL. H(D).

14) The process as claimed in claim 1 to 13 wherein, with use of metallic concrete hardener (RCH) in cement concrete mix, proportion of RCH 2.5 % to 15.0 % or more percent by weight of cement, lowers the surface tension of water to make cement particles hydrophilic to control the setting of concrete as per CL.ll(C).

15) The process as claimed in claim 1 to 14 wherein, use of metallic concrete hardener (RCH) in cement concrete mix, proportion of RCH 2.5 % to 15.0 % or more percent by weight of cement, uniform distribution of RCH through out the mass of the concrete, makes the concrete mix more cohesive and less prone to segregation as per CL. H(E).

16) The process as claimed in claim 1 to 15 wherein, use of metallic concrete hardener (RCH) in cement concrete mix, proportion of RCH 2.5 % to 15.0 % or more percent by weight of cement, reduces plastic shrinkage and increases impact resistance and improves the tensile strength of the concrete as per CL. H(E).

17) The process claimed wherein, use of metallic concrete hardener (RCH) in cement concrete mix, proportion of RCH 2.5 % to 15.0 % or more percent by weight of cement, RCH concrete has relatively lowered heat of hydration as compared to normal concrete. This greatly advantages to reduce the risk of cracking in mass concrete application as per CL. H(F).

18) The process claimed wherein, use of metallic concrete hardener (RCH) in cement concrete mix, proportion of RCH 2.5 % to 15.0 % or more percent by weight of cement,