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Role Of Construction Chemicals In Ensuring Durability of Concrete Structure

need of major repair and hundreds of crores of rupees is being spent on

restoration. The situation is not much different in other countries. Hence, there

is an not much different in other countries. Hence, there is an urgency to study

the causes of deterioration in concrete and the role of construction chemicals

in making new construction durable and in rehabilitating and construction

durable and rehabilitating and resurrecting structures whose durability is in

question.

So the chemical admixtures are used to modify the properties of

concrete or mortar to make them more suitable for the work at hand, or for

economy, or for such other purposes as saving energy.

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2. PERMEABILITY OF CONCRETE

If concrete is impermeable, corrosive agents cannot penetrate

and attack it. Concrete basically has two types of pores, which determine

permeability. These are capillary pores (with a diameter varying between 0.01

to 10 micron) in the cement, paste which coats the aggregates and larger micro

voids, between 1 mm to 10 mm, which are caused by faulty compaction of

fresh concrete.

When voids are interconnected because of their larger number

and size a continuous link is formed, which makes the concrete permeable.

FACTOR'S CONTROLLING PERMEABILITY

There are three major factors which determine the permeability

in concrete.

(a) Water cement ration,

(b) Compaction and curing.

fig.1. Each factor is equally important, if one of these factors is not controlled,

the result will be increase, in permeability.

It can be shown that permeability increases as water cement

ration increase. Fig.2. Portrays the relationship. Typically, at a water cement

ratio of around 0.4, permeability is practically nill.

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3. TYPES OF ADMIXTURES

Admixtures can act to reduce water cement ratio while

maintaining work ability which is essential for good compaction. Therefore,

work ability is a major criteria for ensuring impermeability in concrete.

Admixtures are used to modify the properties of fresh concrete, mortar, and

grout.

TABLE 2 : TYPES OF ADMIXTURES

Chemical admixture Miscellaneous admixtures

Non-water reducing

Accelerators

Retarders

:

: Air entraining agents

: Integral water proofers

Water reducers Normalplasticizers

Accelerating

plasticizers

Retarding

:

: Pumping aids:

: Bonding agents.

:

: Gas forming.

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plasticizers : Expansion producing.

High range water Normal

reducer.superplasticizers

Retarding

Superplastic

izers

:

: Corrosion inhibiting

: Fungicides: Air detraining

: Flocculating

: Pigments

: Mortar plasticisers

: Grout admixtures

WATER REDUCTION CAPACITY OF ADMIXTURES

Minimum reduction in water for different types of admixtures.

These values are given below in Table 3.

TABLE 3 : WATER REDUCTION FOR DIFFERENT TYPES OF ADMIXTURES.

Category of admixture Water reduction at normal dosage, percentage

Minimum BS: 5057

requirement

Actual in practice

Normal plasticisers 8 8 to 15

Accelerating plasticisers 8 8 to 12Retarding plasticisers 8 8 to 16

Air entraining agents - 2 to 4

Entraining agents - 8 to 12

Normal 16 16 to 35

Superplasticisers

Retarding 16 16 to 30

Superplasticisers

PERMEABILITY REDUCED BY SUPERPLASTICISERS

As per tests were carried out to determine the effect of

superplasticisers on water permeability 150 mm size cubes water stored for 28

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day's in lime - saturated water at 230C and subjected to water pressure on one

face.

Definition of Admixture

In general, an admixture is defined as a material other than

water, aggregate and Portland cement that is added to concrete immediately

before or during its mixing". It was established that, these substances usually,

added in comparatively small quantities, for this reason they have been called

as admixture.

Why is admixture used ?

Over decades, attempts have been made to obtain concrete with

certain desired characteristics such as high compressive strength, high

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workability, high performance and durability parameters to meet the

requirement of complexity of modern structures. To achieve the improved

properties, the use of cementitious/chemical admixture as fourth ingredient

proved to be essential and changes microstructure of concrete depends upon

the quantity of admixture added to concrete. The properties commonly

modified are the heat of hydration, accelerate or retard setting time,

workability, water reduction, dispersion and air-entrainment, impermeability

and durability factors. Admixtures certainly enhance the properties of

concrete and it is humorously suggested that "admixtures are to concrete as

cosmetics to a woman".

Type of Admixture

The present day concrete of the incorporated with an admixture

is modify one or more properties at free of hardened state and are broadly

classified as follows :

Chemical admixtures - Accelerators, Retarders, Water-reducing agents and

Superplasticizers.

Mineral admixtures - Diatomacco earth, Volcanic glass. Calcined clays on

Shales as natural minerals and Fly-as Blast-furnace slag, Silica fume and R

husk bye-product mineral admixture.

Miscellaneous admixtures - Air entraining and Water proofing agents.

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Selection and specific application Selection

Admixtures shall be selected carefully to alter the concrete

properties to the requirement of job at site and shall be used judiciously

according to specification and method of application to avoid adverse effect

on concrete properties at fresh and hardened strata. After selecting the

product, one should carefully choose the supplier, who can supply quality

product, timely service and at competitive price. The compare shall be

reputed one and time tested the business, shall possess the staff with efficient

and professional experience who can guide on effective application/use of

admixture in right way. The admixture shall be supplied with test certificate,

manufacturing date and its chemical composition, shall comply specifications

given by the authorities.

Specific application

The following chemical admixture commonly used for specific

purpose and are explained in detail;

i) Accelerators : Admixtures which are used to speed up the initial set of

concrete is called an accelerator. The advantage of these admixtures are either

to increase the rate of hydration of cement or to shorten setting time results in

early strength development, removal of shuttering, reduction of curing period

and specially when concrete used in low temperature and marine construction.

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The common accelerator is Calcium chloride and rarely Tri-

ethanolamine, Carbonates, Silicates etc., used. However the use of Calcium

chloride is not permitted in Pre-stressed concrete whereas in other concrete it

is restricted to 1.5% by eight of cement content.

Mechanism : According to investigations, the essence of hardening

intensification is CaCl2 as a catalyst acts on hydration of C S results in

increase the rate of setting and strength development. It also established from

the figure 1 that the CaCl2 accelerate the setting time considerably.

(ii) Retarders: The function of retarded is to delay or extend the setting time

of cement paste in concrete. These are helpful for concrete that has to be

transported to long distance in transit mixers and helpful in placing the

concrete at high temperatures, specially used as grouting admixture and water

reducers results in increase of strength and durability.

The commonly known retards are Calcium Ligno-sulphonates

and Carbohydrates derivatives used in fraction of percent by weight of

cement.

Mechanism : The mechanism of set retards is based on absorption. The large

admixture anions and molecules are absorbed on the surface of cement

particles, which hinders further reactions between cement and water i.e.

retards setting. Later as a result of the reaction between the organic salts and

C3A for cement, the former are removed from liquid phase of system, thus

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eliminating further retardation. The figure 2 shows the effect of retards on

setting.

(iii) Water-reducing admixture (WRA) :

The water reducing admixture are group of products which

posses concrete of a given workability as measured by slump or compaction

factor at a lower water-cement ratio than the control concrete.

The commonly used admixtures are Ligno-sulphonates and

hydrocarbolic acid salts.

Mechanism : The principal role on mechanism of water reductions and set

retardation of admixtures are usually composed of long-chain organic

molecules and that are hydrophobic (not wetting) at one end and hydrophilic

(readily wet) at the other. Such molecules tend to become concentrated and

form a film at the interface between two immiscible phases such as cement

and water, and alter the physio-chemical forces acting at this interface. The

presence of such admixture in a fresh concrete results in

(i) a reduction of the interfacial tension.

(ii) an increase in the electro kinetic potentials and

(iii) protection sheath of water dipoles around each particles i.e. mobility of

fresh mix becomes greater, partly because of reduction in inter-particle forces

and partly because of water freed from the restraining influence of the highly

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flocculated system which is now available to lubricate the mixture. Hence less

water is required to achieve given consistency.

(iv) High range water-reducing agents (HRWA) : These are the second

generation admixture and also called as Superplasticizers. These are synthetic

chemical products made from organic sulphonates of type RSO3, where R is

complex organic group of higher molecular weight produced under carefully

controlled condition :

The commonly used superplasticizer are as follows :

i) Sulphonated melamine formaldehyde condensate (S M F C)

ii) Sulphonated napthalene formaldehyde condensate (S N F C)

iii) Modified ligno-sulphonates and other sulphonic esters, acids etc.,

Mechanism : The H R W A consists off very large molecules normally

anionic in nature, are thought to be absorbed on to the cement particles

become negatively charged and subsequently dispersed in the water, similar to

the action of WRA. However the H R W A produce a much higher degree of

dispersion and do not lower the surface tension of water significantly. The

figure 3 shows the mechanism of Superplasticizer with cement and water.

iv) Air Entraining agents : These are generally used to improve workability,

ease of placing, increased durability, better resistance to frost action and

reduction in bleeding.

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The common Air-Entraining agents are natural wood resins,

neutralized vinsol resins, polyethelene oxide polymers and sulphonated

compounds.

Mechanism : These are anionic, because the hydrocarbon structures contain

negatively charged hydrophilic groups, such as COO, SO3 and OSO so that

large anions are released in water. Conversely, if the hydrocarbon ion is

positively charged, the compound is cation active or cationic. In other words,

anionic surface active agents produce bubbles that are negatively charged,

cationic charged cause bubbles to be positively charged, surface active agents

of all classes can cause air entrainment in concrete, but their efficiency and

characteristics of air-void system vary widely.

General Tests on Admixture

Normally the admixture are not tested at site and generally used

based on the guidelines given by manufacturers. However, it is very essential

to ascertain the suitability of admixture with the ingredients used such as

cement, aggregates etc. in concrete. The following tests must be carried out

before using the admixture.

i) Compatibility test - March cone test.

ii) Consistency/Workability - Slump cone or Compaction factor test.

iii) Setting time - Concrete Penetrometer test.

iv) Flow test - Flow table test

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For the large and off-shore structures one should ensure the Choloride and

Sulphate cement of admixture.

Quality Requirement of Admixture

When the admixtures are said to be compatible with concrete, it

should meet the following quality requirement;

i) Characteristics of admixture : The data sheet shall give the characteristic

details such as type of admixtures, available forms, basic material used, details

on dosage and its application methods, precaution to be taken and compliance

with specified standards.

ii) Chemical composition : This is an important parameter and manufacturer

shall furnish details of suitability of admixture with cement available in

market and other ingredients in different environment condition. The

chemical composition such as chloride and soluble sulphate content of

admixture shall comply with specification given by BIS and other

organisation.

iii) Solid content : The solid content will determine the concentration and

efficiency of admixture. Higher the solid contents higher the efficiency and

require less amount of admixture to alter the properties of concrete.

iv) Specific gravity : The consistency of admixture mainly depends on its

specific gravity and depends on solid content. If the specific gravity changes,

the consistency of concrete mix will vary.

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v) Molecular weight : Higher the molecular weight higher the efficiency

when it is used in concrete.

vi) Dosage/Mode of application :

Details of dosage and application methods shall be furnished by

manufacturer for all admixtures.

vii) Compatibility details : Basic compatible details, possible compatibility

problems due to different type of cement and their effects on water demand or

water absorption etc., shall be furnished.

viii) The admixture should not change the hydration process of cement paste

to convert into solid mass and it should not contain high chloride, which will

corrode steel.

ix) Air entrain in the concrete should not exceed 1% unless otherwise

specified.

Adverse effects due to improper application :

Admixtures are used extensively to produce high workable, high

strength high performance and highly durable concrete with minimum cost.

However, these admixtures are not used judiciously and with the poor

knowledge of admixture among engineers at site results in the following

adverse effect on concrete.

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Rapid slum loss : This effect general observed in rich mixes with higher

cement content and it can be reduced by adding booster dosages at different

intervals.

Severe segregation/bleeding : This is generally observed in lean mixes with

low cement content and depends on dosage of admixture. This can be

minimized either by reducing admixture dosage or by increasing content of

fine in the concrete.

Over retardation : This effect a noticed when the admixture is added beyond

the specified dosage and it would effect the construction schedule, result in

low strength development at early age. However ultimate strength of the

concrete remains same.

Plastic shrinkage : This is general observed in large floor slabs of this

sections and due to excess evaporator of water from the surface of the concrete

at high temperatures are continuous breezing. However the plastic shrinkage

cracks are determental to structures.

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Effect of CaCl2 on setting time of OPC

4. ROLE OF ADMIXTURES

Admixtures are used to modify properties of fresh concrete,

mortar and grout so as to.

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(1) Increase workability without increasing water content or decrease the

water content at the same workability.

(2) Retard or accelerate time of initial setting.

(3) Reduced or prevent settlement or create slight expansion,

(4) Modify the rate and or capacity for bleeding.

(5) Reduced segregation.

(6) Improve pumpability, and

(7) Reduced the rate of slump loss.

Admixtures are also used to modify properties of hardened

concrete, mortar and grout so as to

(1) Retard or reduce heat evolution during early hardening.

(2) Accelerate the rate of strength development at early ages.

(3) Increase strength (compressive, tensile, or Flexural, increase durability or

resistance to servers conditions of exposure, including application of deicing

salts.

(4) Decrease permeability of concrete.

(5) Control expansion caused by the reaction of alkalies with certain aggregate

constituents.

(6) Increase bond between concrete and steel reinforcement.

(7) Increase bond between existing and concrete.

(8) Improve impact resistance and abrasion resistance.

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(9) Inhibit corrosion embedded metal and

(10) Produced coloured concrete or mortar.

CONCRETE ADMIXTURES

Fairmate Chemicals, subsidiary of Fairmate Group of companies

dealing in the marketing of chemicals since last Eighteen Years and is engaged

in the Marketing and Manufacturing of speciality construction chemicals and

ready to use products in collaboration of M/s Resin Building Products Ltd.,

U.K. and M/s Morton Chemicals USA. M/s Resin Building Products the

major Principals are one of the pioneers in the technology of Resin Based

Products, and have been in this field for more then two decades. Morton

Chemicals USA are the pioneers in bringing the Poly sulphide based products

in the field of Civil Engineering applications and one of the few companies all

the world manufacturing the basic Poly sulphides.

Fairmate Chemicals in collaborations with M/s RBP US & M/s

Mortons Chemicals USA, has been in the manufacturing & Marketing of High

Quality Construction Chemicals. Fairmate Chemicals to keep ahead in the

competition market has opted for ISO 9002 since its existence as a

Manufacturer and is opting for ISO 14000 in short time.

In the range of Construction Chemicals the Groups of products

offered.

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1. Admixtures

2. Cementitious & Epoxy Grouts

3. Water Proofing Systems

4. Heavy duty Industrial Floors & screeds

5. Prepacked Concrete & Mortar

6. Protective Coatings.

The following section describes the Range of Admixtures

offered by the company.

Fairmate Chemicals has brought new range of Admixtures based

on Naphthalene Formaldehyde & range of admixture based as Acrylic

Polymers to Produce Ultra High Strength, free flowing concrete with or

without Retardation. Products have two ranges the Faircrete-Range, the

Range of Normal high performance Plasticisers & Fairflorange, the range of

high performance Super Plasticisers. In both the ranges the plasticisers

containing retarders are named under Faircrete R range and super plasticisers

are named under Fairflo R range.

Range of plasticiser containing Faircrete N the best seller in

Normal Plasticiser which works excellent for High slump concrete up to 350

kg of cement for normal concrete, for longer retention Faircrete HP is offered

and for retention and retardation application up to 350 kg cement/m3 of

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concrete Faircrete R2 is offered. The above are conforming to ASTM-C494

Type A&D.

In high rang water reducing types, Fairflo we offer Fairflo which

is excellent product for retention of slump for up to 90 minutes without

introducing any retardation if concrete temperature is controlled within 30-

350C.

Further in the range of Accelerators and product offered are

Faircrete NC non-chloride, high performance liquid accelerator for all

Reinforced concrete. Spraycrete a powder accelerator for spray concrete and

Guniting Faircrete a chloride based liquid accelerator offered specifically for

Hollow block construction for faster setting and strength development, less

curing & better finishes. A specialised Air entraining agent Fairmin is offered

for production lightweight concrete.

For Mortar, Fairplast IP, a power admixture is offered which

help increasing the pot life of Mortar reduces dropping of Mortar and

increases the yield of Mortar.

Faircrete RMW, a waterproofing admixture is specially offered

for the waterproofing of all type of concrete floors and slabs.

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ADMIXTURES AND FIBRES FOR IMPROVED CONCRETE

For Roads And Bridges

This article is intended to specifically highlight the conditions of

building roads and the role of speciality chemical admixtures, which facilitate

the construction of highways in adverse conditions.

Concrete Pavement

Construction Condition

It is very difficult to generalise the site conditions for the

construction of a highway since the conditions depend on the terrain

environment and size of the project, which varies from place to place and

project to project.

But more often the conditions affecting tile manufacturing and

performance of wet concrete on site can be summerised below.

Location of concrete manufacturing unit with respect to minimum lead.

Difference in the day and night temperatures and humidity.

The total length of construction defining the increase in lead and lead

time.

The casting method and quantity of concrete consumed per hour

defining the size of manufacturing unit, medium of transportation and

the loading and unloading time (cum/min).

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All the above factors point towards the unique quality of

concrete required.

To be manufactured with following characteristics.

Highly cohesive mix- to enable heavy vibrations for

compactions by paving machine.

Low initial slump- To enable concrete to be carried in dumper

vehicles which will also help fast loading and unloading. Transit mixers with

rotating drum are not capable of delivering more than 1 cum per minute

whereas the consumption of a mechanical paving machine is of the order of

1.6 to 2.0 cum. per minute.

Long retention time- to enable long lead distances to be comfortably

handled. This is the issue of pavement quality concrete since in the

construction of road the casting site changes continuously whereas the

site of production of concrete is fixed.

Minimising the water loss of concrete and lowering tile development of

shrinkage cracks.

The above characteristics make the use of plasticising, water

reducing and admixtures essential.

Fairmate has developed a special admixture (FAIRFLO R13)

meeting all above requirements with further benefits of lowering the initial

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heat of hydration of cement and to hold the water for a longer time, thus

reducing the plastic shrinkage cracks.

Bridges, Culverts And Other Structures On Road

The quantity of structural concrete consumed per minute is not

high since the casting mechanism is manual and the sites are in restricted areas

many a times requiring high slump concrete.

Characteristics of structural concrete required are:

- High initial slump

- Long retention

- Pumpability at the end of retention period.

The special admixture has extensively been used with slight

modification in the control mix to give floatable concrete after 60 minutes and

90 minutes.

Concrete Admixtures with New Concepts

The construction industry has continued to become more

international as the economic climate of the construction industry has declined

in most western countries, so has the need to be involved in overseas contracts

become more important. Many more Engineers are finding themselves

grappling with products, standards and specifications which emanate from

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other countries and working in climatic conditions which make Concrete

Admixtures not only desirable, but necessary.

Also there arc multiple reasons affecting strength and durability

of concrete. Right from the stage of mixing of its constituents, placing into

forms, curing, handling and during service life concrete has some limitations.

Mostly to the requirement of work site, high early strength, retardation,

acceleration and denser quality of concrete etc is necessary. To prepare a mix

for such requirement without affecting the basic concrete properties and

imparting strength and durability, admixtures are required.

In order to take "care" of these specific requirements Apple

Chemic has Admixtures:

1. AC-Plast-BV: Lignosuphonate based chloride free liquid Plasticizer

cum water reducing admixture for achieving impermeable and

improved strength concrete confirming of relevant DIN, BS, IS: 9103:

1979 and ASTM-C-494 specifications. Use of product results in

cement saving. Useful in structural and mass concrete for water

retaining, hydraulic and sewerage structures. Dosage: 0.15 to 0.3%.

2. AC-MENT-BV: Naphthalene Formaldehyde based high early strength

universal liquid Super Plasticizer for producing flowable & pumpable

mix conforming to ASTM-C-494 Type G,IS: 9103 Concrete placing at

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difficult & large places with ease is possible. Dosage (a) Flow concrete

1 to 1.50% (b) Early strength 1.5 to 3%.

3. AC. SUPERPLAST (FF) : Melamine Formaldehyde based liquid super

plasticiser for prestressed and precast concrete confirming to ASTM-

C-194, Type F, BS: 5075 Part III and IS: 9103-1979, Dosage (a) flow

concrete 0.8% to 1.6% (b) High early strength 1.50 to 3%.

4. AC-PLAST-N- High performance liquid Waterproofer for all types of

water retaining structures for all concrete grades, mortars & plasters.

Confirming to ASTM-C-494 IS:2645 and IS:9103-1979. Dosage-0.3%

to 0.5%.

5. AC-RETARD- Retarding liquid Superplasticizer. Delays initial setting

& makes concrete flowable. Useful in hot climate confirming to

ASTMC-494-Typc D& IS:9103: 1979. Dosage 0.3% to 0.5%.

6. AC-IMPRO-Integral Waterproofer for all cement based works

confirming to IS:2645:1979 in powder & liquid form. Dosage : @ 2%

7. AC-SET-FAST- Liquid Accelerator gives rapid strength to

concrete/mortars suitable for all cement grades. Dosage-Depends on

reduction in setting time required.

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A Novel Admixture-KR-2 Emulsion

It is well known that the properties of the cement can be altered

by using suitable additives. These additives are known as admixtures and are

materials used in used in cement mortar and cement concrete lo improve or

impart some of its properties.

They are defined as material, other than cement, water and

aggregate, that are used as an ingredients of concrete and are added to the

batch immediately before or during mixing. A proper use of admixtures offers

certain beneficial effects to concrete, improved quality, acceleration or

retardation of setting time, enhanced frost and surface resistance, control of

strength development, improved workability, and enhanced finishability.

The use of these admixtures and additives has been a matter of

controversy and several technologists have discouraged the use of these

admixtures. But there are many on the contrary, who highly commend and

foster the use and development of admixtures as they impart many desirable

characteristics and effect economy in concrete construction.

There are large number of proprietary products available in the

market with their effects described but the full details of the action of these

additives, known as admixtures are yet to be determined and the performance

of the admixtures should be carefully checked before use.

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Admixtures are classified according to the purpose for which

they are used in concrete, (1) Accelerating admixtures (Calcium Chloride) (2)

Retarding admixtures (3) Water reducing admixtures and also the so called

superplasticizers.

There are other additives like air entrainment admixtures etc.

there exist additives for other purposes also such as water proofing and

fungicidal action etc., but it may be noted that these are not sufficiently

standardized. Here it suffices to say that waterproofing admixtures (Calcium,

Ammonium Stearate, Butyl Stearate, Calcium Oleate etc.) are supposed to

repel water by an electrostatic charge which they form after reacting with

calcium ions on the walls of the capillaries in the hydrated cement paste. It is

doubtful whether this effect persists over long periods.

For fungicidal purposes, Copper Sulphate and

Pentachlorophenol have been suggested. These also control the growth of

algae or lichen on hardened concrete but again their effectiveness is lost with

time. Needless to say toxic admixtures should not be used.

To understand the present status of admixtures, it would be

appropriate to quote from "Properties of Concrete by A.M. Neville".

"An important feature of majority of admixtures for concrete is

that they are used primarily on the basis of experience or adhoc tests. The

theoretical information

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on a scientific basis is generally not available to permit a reliable quantitative

prediction of behaviour in concrete under the various possible circumstances.

This is due to the marketing of admixtures largely as proprietary products. In

view of the above, it is important that admixtures should be used judiciously

and will proper instructions, because of these different views and difficulties

faced by the users.

Tech-dry (India) Pvt. Ltd; has develop a novel Emulsion-KR2 which has not

chemical admixtures are added concrete in a small amount mainly the

entrainment of air, reduction of water or cement content, plasticization of the

concrete mixtures, or control of setting time and based on that they are divided

in the following categories.

Air-Entrainment

Water-Reducing

Set-Retarding

Accelerating

Superplasticizers

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However, EMULSION-KR2 emulsion solvent-free aqueous organic copoly

water based emulsion. This unit Emulsion creates hydrophobicity in pores and

capillaries and therefore evaporation is slow and the water already present

enables the hydration. Because of its unique ability to create this

hydrophobacity. It reduces the water absorption by 80% besides increases the

compressive and flexural strength.

Description

Emulsion KR-2 is designed to be unit as an admixture during in-

placing manufacture of slow slump, cementitious containing blocks products

as admixture in ready-mix-concrete freshly made concrete and MORTOR

FOR PLASTE.

1. When EMULSION-KR2 incorporated into low slum cementitious products

such as imitant stone blocks and pavers, the permeability to water and the

occurrence of unsighted efflorescence is dramatically reduced. Additionally,

the 28 day compressive strength and transverse breaking by the strength

increased by up to 50%.

Superment-F10: A Revolution in Dry Mortar industry

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Building Materials technology is changing rapidly with the

development of new innovative materials. Concrete is no longer a mixture of

one, two and three shovels of cement, sand and coarse aggregate respectively.

It has matured enough to lead us into the 21st century.

Dry mortar is one of the major parts of that revolutionary

change. The concept includes

a) Gypsum and gypsum hydrated lime mortars.

b) Cement and cement hydrated lime mortars.

Such mortars based on mineral or binder combinations can be grouped into

Self-leveling floor screeds Repairs. External paints. Grouts Injection mortars,

Underwater concrete Depending on the applications, such blends require

adjustment to their characteristic properties like Consistency, Flowability,

Strength, Surface hardness etc.

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Superment - industrially called Superment-F10, is a powder admixture based

on water soluble melamine polymer. Superment-F10 makes it possible to

formulate tailor made dry mortar products ready for use on the building site

requiring only the addition of water. When water is added to the dry mortar,

Superment-F10 goes into solution with the other binders and the dispersing

effect of polymer can be used to obtain the required consistency or reduce the

water demand and of course both characteristics at the same time Superment-

F10 can also be used to increase properties and stability towards segregation,

increased adhesion or wear resistance.

1. Self leveling floor screeds

Floor screeds are in most cases based on high alumina cement,

which combined with gypsum results in a reduced shrinkage and a high degree

of chemical water binding. With Superment-F10 combined with set

regulation chemicals, resin copolymer, filler and suspension additives, it has

been possible to develop many different

floor screed products which fulfill very high quality requirements such as

hardness, evenness, low emission, etc.

2. Repairs

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With concrete structures built 30 years ago becoming weak.

repairs to protect these structures have become increasingly important. There

are repair products with different applications and different properties such as

consistency, setting time, strength, wear resistance, etc. With Superment-F10,

it is possible to adapt and even increase the properties of these products.

3. Cement Based Paints For External Use

A plastered facade with a cement based paint in pleasant color

gives a classic and elegant appearance. Cement based powder paints for

external use often contains coloring pigments, copolymers and fillers. The use

of Superment-F10 enables the effective dispersion, a reduction of water

content and an increase of coloring effect. It enables better utilization of the

pigments and the cements, thereby also enabling the reduction in the quantities

of these additives.

4. Grout

The need for grout exists when there is built up in different

ways. There are products with different levels and times of expansion.

Common points between all the types of grout are the need for high early and

final strength, a low water-cement ratio and an ability to flow and fill under

difficult conditions.

Superment-F10 is excellent for formulating this type of grout

and gives all the required properties.

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5. Injection Mortar

When there arc sonic cracks in rocks, in concrete or in soil to

stabilize, it is possible to inject different types of grouts. The most common

type is cement slurry but because of the settlement and requirement for good

flow with a low water demand, it is necessary to modify the grout. The

excellent water reduction effect of Superment-F10 can be used to give very

good flow even with very low water/cement ratio.

6. Underwater Concrete

For underwater concrete , it is important to design the concrete

very carefully to minimize the risk of separation and wash out the cement

paste in the water. The use of micro-silica and of the water reducing admixture

increase the properties but to ensure that the concrete can be used in an

optimal water, it is often advised to add a stabilizing agent. More-ever for

underwater concrete, it is necessary that the cement has a good flow since

manual finishing is impossible.

Thanks to Superment-F10, there are many possibilities to

formulate admixtures with all necessary properties combined in one product.

5. COST ASPECT

Through diffusion coefficients in concrete do not follow linear

relationships, by using curve fitting techniques. It can be shown that in the

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given situation the life of a concrete structure, say for example, a bridge which

would normally have lasted a period of 25 years, would have an extra span of

10 year. The cost of using construction chemicals as admixtures, sealants,

curing membranes and protective coatings, in comparison to the extra lease of

life is insignificant.

6. CONCLUSION

Admixtures, sealants and curing membranes could be used to

ensure structural curability despite the higher initial costs. These initial costs

would be more than compensated several times over by the enhance life of the

structure. In aggressive environments it may be prudent to go in for

appropriate protective coating. The argument about cost versus enhanced life,

equally holds here as well.

7. REFERENCES

1. Concrete Technology

- By Mr. M.S. Shetty

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2. Soil Mechanics & Foundation Engg.

- By Dr. K.R. Arora

- Dr. B.C.Punmia

3. Constructional Material

Jer. 2000, vol. 6

4. M/S Fairmate Chemicals Pvt. Ltd.

E-mail: [email protected]

7314245 admixtures

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