Title of Invention

A PROCESS FOR THE PRODUCTION OF NATURAL RUBBER LOTEX BASED CEMENT CONCRETE.

Abstract A process for production of natural rubber latex based cement concrete by mixing natural rubber latex (NRL) solution and a non-ionic surfactant such as poly-oxy nonyl phenol ether, adding to the solution an anti-foaming agent such as silicone t- emulsion, adding cement to water under constant stirring to obtain a cement slurry, adding to the cement slurry the resultant NRL solution prepared under constant stirring to obtain a cement - NRL slurry, mixing fine and/or coarse aggregates such as sand and/or crushed hard rocks and the cement - NRL slurry prepared to obtain an uniform mix, pouring the mix obtained into moulds and covering the said mould for a period of about 24 hours with a covering sheet being selected from a group consisting of polyethylene, rubber sheet and wet gunny cloth, curing of mould as obtained with moist water for a period about 5 days and further curing of moist water cured mould as obtained with air curing for a period of about 21 days to obtain the natural rubber latex based cement concrete (NR-LMCC). The natural rubber latex based cement concrete provide good protection to steel reinforcement against corrosion and is also useful for repair of distressed concrete structure.
Full Text The present invention relates to a process for the production of Natural Rubber Latex based Cement Concrete.
Latex Modified Cement Concretes (LMCCs) contain latex solution besides conventional ingredients such as ordinary Portland cement (OPC ), sand, and aggregates. They are used in civil engineering applications because of their superiority to conventional cement concretes in respect of durability characteristics, while matching them in mechanical and other strength properties.
A patent search made using the key words - latex, modified, cement, and concrete, yielded no references on the process of producing cement based concrete using natural rubber latex (NRL), whereas several patents were listed related to use of synthetic rubber latex. The ingredients mentioned in the processes of the patents on synthetic latex based concrete, are different from the controlling ingredients utilized in the process of the present invention of natural rubber latex based cement concretes.
The direct use of natural rubber latex (NRL) in cement concrete, without any modification is observed to cause formation of agglomerates of cement, thereby preventing good dispersion of cement particles in cement concrete. Moreover, the NRL gets coagulated in the presence of cement particles. Thus, cement concrete produced using the NRL without any modification suffers from the drawbacks of lack of cohesiveness and insufficient workability.

The main objective of the present invention is to provide a process for the production of natural rubber latex based cement concrete (LMCC), which successfully surmounts the problem of coagulation of latex usually associated with cement matrices which leads to insufficient workability of the concrete mix.
Accordingly, the present invention provides a process for production of natural rubber latex based cement concrete which comprises :
a) mixing natural rubber latex (NRL) solution and a non-ionic surfactant such as
poly-oxy nonyl phenol ether, adding to the solution an anti-foaming agent
such as silicone emulsion,
b) adding cement to water under constant stirring to obtain a cement slurry,
adding to the cement slurry the resultant NRL solution prepared in step (a)
under constant stirring to obtain a cement - NRL slurry,
c) mixing fine and/or coarse aggregates such as sand and/or crushed hard
rocks and the cement - NRL slurry prepared in step (b) to obtain an uniform
mix,
d) pouring the mix obtained in step ( c) into moulds and covering the said mould
for a period of about 24 hours with a covering sheet being selected from a
group consisting of polyethylene, rubber sheet and wet gunny cloth,
e) curing of mould as obtained in step (d) with moist water for a period about 5
days,
f) further curing of moist water cured mould as obtained in step (e) with air
curing for a period of about 21 days to obtain the natural rubber latex based
cement concrete (NR-LMCC).
In an embodiment of the present invention the non ionic surfactant such as poly-oxynonyl phenol ether added to the NRL solution may be in the range of 2.5% to 3.5% of the polymeric solids of NRL solution.

In an another embodiment of the present invention the anti-foaming agent such as silicone
emulsion added to the NRL solution may be in the range of 1.5 % to 2.5 % of the
polymeric solids of NRL solution.
In yet another embodiment of the present invention the cement used may be such as
ordinary Portland cement, sulphate resisting cement, Portland Pozzolana cement.
In still another embodiment of the present invention the water used may be potable water .
In another embodiment of the present invention the fine aggregates used may be such as
natural river sand with a fineness modulus in the range of 2.2 to 3.2 and the coarse
aggregates used may be crushed hard rock such as granite with the maximum size of
aggregate in the range of 10 mm to 12.5 mm.
In yet another embodiment of the present invention the ingredients maybe mixed in the following proportions:
1 part by weight of cement: 1 to 3 parts by weight of sand : 0 to 4 parts by weight of coarse aggregate : 0.05 to 0.20 parts by weight of polymeric solids of the NRL : 0.30 to 0.50 part by weight of water, for producing mortar / concrete.
In still another embodiment the curing may be effected in the following manner :
a) covering the moulds for a minimum of around 24 hours by a polyethylene/rubber
sheet / wet gunny cloth and
b) moist / water curing for a minimum of around 5 days and
c) ambient air curing for a further preferred minimum period of around 21 days.

The present invention has been achieved using the following scientific considerations:
The coagulating tendency of Natural rubber latex in the presence of cement concrete is prevented / delayed by use of suitable surfactants so that the latex particles do no coalesce atleast till the completion of pouring and compaction of the cement concrete in the moulds
The addition of surfactant to avoid coagulation causes entrainment of excess amount of air in the cement concrete which reduces the strength of concrete and hence, a suitable de-entraining or anti-foaming chemical is added to the latex.
The curing of latex modified cement concrete essentially consists of :
Moist curing period, so that the cement hydrates and develops sufficient strength. Air drying period, so that the moisture/water in the latex solution is removed / reduced such that the polymeric solid particles of latex coalesce to form a continuous polymeric film inside the cement concrete. The period for the above two modes of curing needed to be properly determined so that both the hydration of cement and coalescence of latex solids occur in the latex modified cement concrete.
The following examples are given by way of illustration of the process of the present invention and should not be construed to limit the scope of the present invention.
Example 1
Ordinary Portland Cement 20 kg
Natural River Sand 40 kg
Natural Rubber Latex 3.3 litres

Free water added 6 litres
Silicone Emulsion 3 3.0 ml
Poly-Oxy Nonyl Phenol Ether 66 ml
Using the above ingredients natural rubber latex based cement mortar was prepared by
(a) mixing natural rubber latex (NRL) solution and non-ionic surfactant poly-oxy
nonyl phenol ether, adding to the solution anti-foaming agent silicone emulsion;
(b) adding cement to water under constant stirring to obtain a cement slurry, adding
to the cement slurry the resultant NRL solution prepared in step (a) under constant
stirring to obtain a cement - NRL slurry ;
(c) mixing sand and the cement -NRL slurry prepared in step (b) to obtain an
uniform mix ;
(d) pouring the mix obtained in step (c) into moulds, as desired, followed by
compacting and curing.
The mix so obtained is cohesive and does not have coagulation of latex, thereby demonstrating the novelty of the invention. After the curing period of 28 days [1 day in mould under covered conditions + 5 days in water + 21 days in air curing by storing in the ambient conditions ], the test results obtained are:
28 days Compressive strength 25.3 MPa
28 days Split tensile strength 2.5 MPa

28 days Flexural strength 2.8 MPa
28 days modulus of elasticity 20.9 GPa
Germann water permeability (steady state) 0.043 mm3/s
Capillary suction resistance number 7.5
Chloride penetration 9.8 mm at 90 days
Carbonation depth 3 mm
Abrasion depth 1.5 mm
Impact resistance 140 Joules.
Example 2
Ordinary Portland Cement 12kg
Natural River Sand 18kg
Crushed Hard Rock (Granite) 36 kg
10 mm to 12 mm size
Natural Rubber Latex 3 litres
Free water added 6 litres
Silicone Emulsion 30 ml
Poly-Oxy Nonyl Phenol Ether 60 ml

Using the above ingredients natural rubber latex based cement concrete was prepared by
(a) mixing natural rubber latex (NRL) solution and non-ionic surfactant poly-oxy
nonyl phenol ether, adding to the solution anti-foaming agent silicone emulsion ;
(b) adding cement to water under constant stirring to obtain a cement slurry, adding
to the cement slurry the resultant NRL solution prepared in step (a) under constant
stirring to obtain a cement - NRL slurry ;
(c) mixing sand , crushed rocks and the cement -NRL slurry prepared in step (b) to
obtain an uniform mix ;
(d) pouring the mix obtained in step (c) into moulds, as desired, followed by
compacting and curing.
The mix so obtained is cohesive and does not have coagulation of latex, thereby demonstrating the novelty of the invention. After the curing period of 28 days [1 day in mould under covered conditions + 5 days in water + 21 days in air curing by storing in the ambient conditions ], the test results obtained are:
28 days Compressive strength 30.3 MPa
28 days Split tensile strength 3.12 MPa
28 days Flexural strength 4.90 MPa
28 days modulus of elasticity 32.3 GPa
Germann water permeability (steady state) 0.074 mm3/s
Capillary suction resistance number 8.5

Chloride penetration 8.0 mm at 60 days
Carbonation depth 2.5 mm
Abrasion depth 1.1 mm
Impact resistance 400 Joules.
The main advantages of the present invention are:
1. The Natural Rubber Latex based Cement Concrete (NR-LMCC) described in the
present invention have improved impermeability characteristics over conventional
cement concretes with reference to intrusion of moisture, water, oxygen, carbon
dioxide and chloride ions. Therefore, they could be expected to provide good
protection to steel reinforcement against corrosion, particularly in severe
environmental conditions such as coastal regions.
2. Though LMCCs based on synthetic latexes are available, those latexes are based on
petroleum which is a non-renewable source. Hence, natural rubber latex based
concretes, developed in the present invention, would be preferable as they utilize
latexes derived from rubber plants. Thus LMCCs based on NRL are eco-friendly and
sustainable development of these materials can be planned.
3. The modulus of elasticity of NR-LMCCs is of the same order as that of conventional
concrete and their bond with conventional cement concrete is also good. Therefore
NR-LMCCs are compatible with conventional cement concrete and can be used for
the repair of distressed concrete structures.

4. The impact and abrasion resistance of NR-LMCCs are higher than that of conventional concretes. Hence, they can be used in applications such as overlay material for bridge decks, factory floors and airport pavements.



We claim :
1. A process for production of natural rubber latex based cement concrete which comprises:
a) mixing natural rubber latex (NRL) solution and a non-ionic surfactant such as
poly-oxy nonyl phenol ether in a ratio of about 50:1 , adding to the solution
an anti-foaming agent such as silicone emulsion,
b) adding cement to water under constant stirring to obtain a cement slurry,
adding to the cement slurry the resultant NRL solution prepared in step (a)
under constant stirring to obtain a cement - NRL slurry,
c) mixing fine and/or coarse aggregates such as sand and/or crushed hard
rocks and the cement - NRL slurry prepared in step (b) to obtain an uniform
mix,
d) pouring the mix obtained in step (c) into moulds and covering the said mould
for a period of about 24 hours with a covering sheet being selected from
a group consisting of polyethylene, rubber sheet and wet gunny cloth,
e) curing of mould as obtained in step (d) with moist water for a period about 5
days,

f) further curing of moist water cured mould as obtained in step (e) with air curing for a period of about 21 days to obtain the natural rubber latex based cement concrete (NR-LMCC).
2. A process as claimed in claim 1 wherein the non ionic surfactant used is such
as poly-oxy nonyl phenol ether added to the NRL solution in the range of 2.5%
to 3.5% of the polymeric solids of NRL solution.
3. A process as claimed in claims 1-2 wherein the anti-foaming agent used is such
as silicone emulsion added to the NRL solution in the range of 1.5% to 2.5% of
the polymeric solids of NRL solution.
4. A process as claimed in claims 1-3 wherein the cement used is such as ordinary
Portland cement, sulphate resisting cement, Portland Pozzolana cement.
5. A process as claimed in claims 1-4 wherein the water used is potable water.
6. A process as claimed in claims 1-5 wherein the fine aggregates used is such as
natural river sand with a fineness modulus in the range of 2.2 to 3.2 and the
coarse aggregates used is crushed hard rock such as granite with the maximum
size of aggregate in the range of 10 mm to 12.5 mm.
7. A process for production of natural rubber latex based cement concrete
substantially as herein described with reference to the examples.

Documents:

2514-del-1998-abstract.pdf

2514-del-1998-claims.pdf

2514-del-1998-correspondence-others.pdf

2514-del-1998-correspondence-po.pdf

2514-del-1998-description (complete).pdf

2514-del-1998-form-1.pdf

2514-del-1998-form-19.pdf

2514-DEL-1998-Form-3.pdf


Patent Number 215196
Indian Patent Application Number 2514/DEL/1998
PG Journal Number 10/2008
Publication Date 07-Mar-2008
Grant Date 21-Feb-2008
Date of Filing 26-Aug-1998
Name of Patentee COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH
Applicant Address RAFI MARG, NEW DELHI-110001, INDIA.
Inventors:
# Inventor's Name Inventor's Address
1 NIRMALAKUMAR PARSHWANATH RAJAMANE SCIENTISTS OF STRUCTURAL ENGINEERING RESEARCH CENTRE, CSIR CAMPUS, TARAMANI, MADRAS-600113
2 MEYAPPAN NEELAMEGAM SCIENTISTS OF STRUCTURAL ENGINEERING RESEARCH CENTRE, CSIR CAMPUS, TARAMANI, MADRAS-600113
3 JAMBOOR KRISHNAMURTHI DATTATREYA SCIENTISTS OF STRUCTURAL ENGINEERING RESEARCH CENTRE, CSIR CAMPUS, TARAMANI, MADRAS-600113
4 JOLLY ANNIE PETER SCIENTISTS OF STRUCTURAL ENGINEERING RESEARCH CENTRE, CSIR CAMPUS, TARAMANI, MADRAS-600113
5 SESHADRI GOPALKRISHNAN SCIENTISTS OF STRUCTURAL ENGINEERING RESEARCH CENTRE, CSIR CAMPUS, TARAMANI, MADRAS-600113
PCT International Classification Number C08C 9/18
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA