green concrete

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A TECHNICAL PAPER ON Submited By: ANSARI NURALAM M.H. GOKULE SAGAR D. B.E. (Civil) B.E. (Civil) E-MAIL: [email protected] 1

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Green concrete

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A TECHNICAL PAPER ON

Submited By:

ANSARI NURALAM M.H. GOKULE SAGAR D.

B.E. (Civil) B.E. (Civil) E-MAIL: [email protected]

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INDEX

CHAPTER NO. PAGE NO.

1) INTRODUCTION…………………………………………………………01

2) HISTORY OF GREEN CONCRETE……………………………………02

3) PROPERTIES OF GREEN LIGHTWEIGHT AGGREGATES………03

4) SUITABILITY OF GREEN CONCRETE IN BUILDINGS…………..04

5) DEVELOPMENT OF GREEN CEMENT ……………………………..05

6) GREEN CEMENT WITH REDUCED ENV. IMPACT……………….06

7) PRODUCTION OF GREEN CONCRETE……………………………. 06

8) TYPES OF GREEN CONCRETE……………………………………….07

9) ADVANTAGES …………………………………………………………..07

10) LIMITATIONS……………………………………………………………08

11) APPLICATION OF GREEN CONCRETE……………………………..08

12) SCOPE IN INDIA…………………………………………………………09

13) CONCLUSION…………………………………………………………....10

14) REFERRANCES………………………………………………………....10

INTRODUCTION2

Concrete is one of the most widely used man-made building materials in the world. Compared to other building material concrete has numerous advantages such as abundant resources, easy operation, steady mechanical properties, durability, low cost, of production. These characteristics enable concrete to be widely employed in the field of civil bridges, roads, hydraulic structures, Underground Ocean and military engineering. Despite such advantages concrete has some disadvantages such as high energy and raw material consumption & environmental pollution etc. which tends to serious effects on the image of the concrete as a sustainable material. In this respect professor WA proposed the concept of “GREEN CONCRETE” in 1997. He proposed that ‘GC’ should meet three requirements, very low energy & resource consumption, no environmental pollution & sustainable development. After that ‘GC’ was developed and applied rapidly , where as to data understanding of GC still stay at the qualitative level rather than at the level of quantitative evaluation. In ceramic industries about 30% of the production goes as waste due to manufacturing flaws. This waste is not utilized in any form, adding up day by day and occupies more area of the industry. So industries are in pressure to find a disposal system for this waste. These ceramic wastes are durable, hard & almost inert to normal chemicals. The mechanical properties of the coarse aggregates from these wastes are well within the range of the properties of concrete-making aggregates. The concrete made with this industries waste is eco-friendly and so it is called as “Green concrete”. It is also possible to use residual products –thus reducing the need to landfill these materials – while still maintaining a high quality concrete. This is the background for the Danish centre. The goal of the centre is to reduce the environmental impacts of the concrete through the development of new resource –saving binder system and increased recycling and energy recovery of waste materials. The solution for environmental problem is not to replace with other material but to reduce the environmental impact of the concrete &cement. Even small reduction of the environmental impact per tonne of concrete will result in large environmental benefits because of vast amount of concrete produce today. The potential environmental benefits to society of being able to build with green concrete are huge. During last few decades, society has become aware of the problem associated with land filling of the residual product and limits, restrictions, and taxes have been imposed. As several residual products have properties suited for concrete production, there is large potential to increase material recycling by investigating the possible use of these for concrete production. Building materials with reduced environmental impact are often less expensive to produce. The other name for green concrete is resource saving structures means structure with reduced environmental impact as regards, for example energy saving, reduced in CO2 emission , waste water. It is very cheap to produce because waste products are used. Since foe producing 1 tonne of cement/concrete about 0.1 tonne o CO2 emission is taking place. “Green concrete is the concrete in which concrete with minimal clinker content &with green types of cement &binders. Concrete with inorganic residual products &industrial waste is eco-friendly so it is called Green concrete.”

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HISTORY OF GREEN CONCRETE

By volume alone, concrete is the world’s most important construction material. Concrete is an artificial rock composed of aggregates, water and cement. The raw materials are readily available. By reinforcing the concrete with steel, a uniquely strong and durable material is obtained which in terms of shape and size can be designed almost at will by architects and civil engineers. Annually, approximately 5 km3 is used for construction world-wide. In Denmark alone, 8,000,000 t of concrete is produced annually. This corresponds to 1.5 t of concrete per capita annually. Concrete is an environmentally friendly material and the overall impact on the environment per ton of concrete is limited (1). The CO2 emission related to concrete production, i.e. primarily from cement production, is between 0.1 and 0.2 t per tonne of produced concrete. However, the absolute figures for the environmental impact are quite significant, due to the large amounts of cement and concrete produced. From cement and concrete production a total quantity of CO2 of 800,000-1,600,000 t per year is emitted. This corresponds to approximately 2 % of Denmark’s total CO2 emission.The solution to this environmental problem is not to replace concrete with other materials but to reduce the environmental impact of concrete and cement. Again, even a small reduction of the environmental impact per tonne of concrete will result in large environmental benefits because of the vast amount of concrete produced today. The potential environmental benefit to society of being able to build with green concrete is huge. It is realistic to assume that technology can be developed which can halve the CO2 emission related to concrete production. With the large consumption of concrete this will potentially reduce Denmark’s CO2 emission by as much as 1 %. Concrete can also be the solution to environmental problems other than those related to CO2 emission. It may be possible to use residual products from other industries in the concrete production while still maintaining a high concrete quality. During the last few decades, society has become aware of the problems associated with landfilling of residual products, and limits, restrictions and taxes have been imposed. As several residual products have properties suited for concrete production, there is a large potential to increase material recycling by investigating the possible use of these for concrete production. When assessing the environmental compatibility of concrete it is essential to consider all life cycle phases – and not only the environmental impacts associated with the production and use of the material itself. In Northern Europe only a very minor part of the environmental impact associated with buildings and structures originates from the production and use of the building materials themselves. It has been calculated that the energy consumption needed to produce a reinforced concrete office or residential building is 500 MJ per m3 space. Over a 50-year lifespan, however, 15,000 MJ per m3 space will be used for heating and electricity consumption. In other words, only 3% of the total energy consumed during the life of the building come from the concrete and other building materials used in its construction. This study points to durability and insulation as key parameters to be considered if real environmental improvements are to be achieved. Even taking these considerations into account, it is still important to reduce the environmental impact of the materials themselves, not least, because environmental improvement is a competitive parameter. Building materials with reduced environmental impact are often less expensive to produce. Furthermore, environmental performance is increasingly taken into account in tenders. The material with the best environmental parameters is the most likely to be used. Life cycle inventories of concrete-based products show that the concrete mixture Proportions have a major influence on the total life cycle impact. Combined with reducing the environmental impact of the constituent materials, improved mixture design may result in concrete with significantly improved performance. to reduce the CO2 emission by 21% of the 1990 level before 2012 as agreed to at the Kyoto conference. It is also possible to use residual products – thus reducing the need to landfill these materials – while still maintaining a high concrete quality.

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PROPERTIES OF GREEN LIGHTWEIGHTAGGREGATE CONCRETE

With increasing concern over the excessive exploitation of natural aggregates, synthetic lightweight aggregate produced from environmental waste is a viable new source of structural aggregate material. The uses of structural grade lightweight concrete reduce considerably the self-load of a structure and permit larger precast units to be handled. Water absorption of the green aggregate is large but the crushing strength of the resulting concrete can be high. The 28-day cube compressive strength of the resulting lightweight aggregate concrete with density of 1590 kg/m3 and respective strength of 34 MPa.Most of normal weight aggregate of normal weight concrete is natural stone such as limestone and granite. With the amount of concrete used keeps increasing, natural environment and resources are excessively exploited. Synthetic lightweight aggregate produced from environmental waste, like fly ash, is a viable new source of structural aggregate material. The use of lightweight concrete permits greater design flexibility and substantial cost savings, reducing dead load, improved cyclic loading structural response, longer spans, better fire ratings, thinner sections, smaller size structural members, less reinforcing steel, and lower foundation costs [1-3]. Weight of lightweight concrete is typically 25% to 35% lighter but its strengths is comparable to normal weight concrete. The aggregate is reinforced with a PFA rich surface coating applied at a later stage of firing. 2. Laboratory tests and Results2.1. Characteristics of the aggregateThe quality of the green aggregate [in terms of crushing strength] was specified by a crushing strength test based on GB2842-81 (China Standard). The strength as measured by compressing the aggregate in a steel cylinder through a prescribed distance of 20 mm is 3.8 MPa. Results of the sieve analysis and water absorption of the aggregate at different time are given in Table 1.

Recycled concrete ruble – from Waste to a viable construction

Section of light aggregates Highly workable fresh concrete

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Bonding between the steel bars and the lightweight concrete

2. Test results:

The successful application of structural lightweight aggregate demonstrated that lightweight used for precast structural elements can be used in building construction to increase the speed of construction, enhance green construction environment such as reducing the wet trade on site and keep dust level at construction site to the minimum.

SUITABILITY OF GREEN CONCRETE IN BUILDINGS

The following advantages are concluded for using lightweight green concrete in Prefabrication in building;1) Reduce the dead weight of a facade from 5 tons to about 3.5 tons.Reduce crane age load, allow handling, lifting flexibility with lighter weight.Good thermal and fire resistance, sound insulation than the traditionalgranite rock.Allow design and construction flexibility for larger prefabrication modules.Allow maintenance flexibility with replaceable modules.Factory production of module enhances quality of product.Enhance speed of construction, shorten overall construction period.Enhance green building construction, minimize wet trade on site.Improve damping resistance of building.Utilization of PFA in aggregate production resolves the waste disposalproblems of ash and reduce the production cost of concrete.

DEVELOPMENT OF “GREEN” CEMENT FOR

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SUSTAINABLE CONCRETE

A research project was conducted to develop “green” cement for sustainable concrete using cement kiln dust (CKD) and Class F fly ash (FA). In the project, effects of mechanical, chemical and thermal activations on strength and other properties of CKD-FA binders were investigated. Different CKD-fly ash combinations, grinding equipment and methods, chemical additions, and elevated curing temperatures were considered. The set time, heat of hydration, and strength of CKD-fly ash pastes were evaluated. The hydration products and microstructure of the binder pastes were studied. The results indicate that when blend proportion and activation are properly applied, the binder made with CKD and fly ash will have satisfactory strength and performance, which provides potential applications for the new cementitious product.1. IntroductionPortland cement concrete is the most widely used construction material in the world. Each year, the concrete industry produces approximate 12 billion tons of concrete and uses about 1.6 billion tons of portland cement worldwide. In addition to consuming considerable amounts of nature materials (limestone and sand) and energy, producing each ton of Portland cement releases one ton of carbon dioxide (CO2) into the environment. Concerns for the sustainable development in the cement and concrete industries are increasingly addressed [1, 2.].One of the immerging concrete technologies for sustainable development is to use “Green” materials for construction. The “green” materials are considered as materials that use less natural resource and energy and generate less CO2. They are durable and recyclable and require less maintenance [3]. The purpose of the present research was to develop non-clinker “green” cement using two industry wastes: cement kiln dust (CKD) and fly ash (FA). CKD contains partially calcined materials with some hydraulic and cementitious Properties. It also has high alkali, chloride, and sulfate content, which may cause problems in cement performance. FA is mainly composed of vitrified (amorphous) alumina-silicate melts in addition to a small amount of crystalline minerals, such as quartz, mullite, mica etc. Due to the high degree of polymerization at which tetrahedral silicate is bridged with oxygen, most fly ashes, especially Class F FA, react with water very slowly at a room temperature. Some research has indicated that, if the two materials are appropriately blended, the alkalis from CKD may activate hydration of FA, and the blends may create a cementitious material in which the waste material deficiencies will be converted into benefits [4,5]. In the present research, different activation methods were employed to activate hydration of CKD-FA binders. The effects of raw material characteristics, blend proportions, and activation methods on the binder performance were investigated. Some of the results are presented below.2. Experimental Work2.1. Materials and proportionsTable 1 provides the chemical compositions of CKDs and fly ashes used, where Type I ordinary portland cement (OPC) is listed as a reference. CKD 1 and FA 1 were used for chemical and thermal activation studies with a CKD 1:FA1 ratio of 50:50. CKD 2 and FA 2 were used for mechanical activation (grinding) study with a CKD2:FA2 ratio of 35:65. The median particle size (50% passing) of OPC, CKD 1, FA 1, CKD 2 and FA 2 are 25, 53, 10, 8, and 30 microns, respectively.Table 1: Chemical composition of cementitious materials (% by weight)

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2.2. Activation methodsThree activation methods are used for accelerating CKD-FA binder hydration: chemical, thermal, and mechanical activations. In addition, 2% and 5% (by weight of binder) of NaOH was added into the CKD-FA binder systems for chemical activation. Curing temperatures of 38C and 50C were considered for thermal activation and the results were compared with that from curing temperature of 24C. Different grinding regimes were selected for mechanical activation, and they were(1) Simple blending (B), (2) ball mill grinding (G), (3) vibratory mill grinding, and (4) combined grinding using ball and vibratory mill grinding (C). Grinding aid (A) and high-speed mixing (H) were also applied.

GREEN CEMENT WITH REDUCED ENVIRONMENTAL IMPACT

So-called “mineralized” cement is being tested in one of the centre projects. The cement is based on an intermediate product, clinker, which is produced with minor additions of mineralizes (CaSO4 and CaF2) to the kiln resulting in a 5% reduction in energy consumption and a 5-10% increase in 28-day strength of the cement. The higher strength enables the cement content to be reduced, resulting in a further total energy reduction per m3 concrete without compromising concrete strength and durability. Further reductions in the clinker content in concrete have been achieved by the successful introduction of high-strength limestone cement based on mineralised clinker. The filler content of this cement is 14%. The new Portland limestone cement has significantly higher early as well as late strengths (EN 196 mortar 1 and 28-day strengths of 27 and 66 MPa respectively). This enables it to be used in applications such as in the precast industry, where high early strengths are a requirement, without having to increase the cement content That this has proved possible is due to the synergetic effect of combining clinker mineralized by CaF2 and SO3 with finely divided limestone filler, that results in much higher strengths than would normally be expected. Aalborg Portland aims to substitute at least 1/3 of the fossil fuel with CO2 neutral alternative fuels in its largest kiln. This will be achieved by processing combustible waste into an alternative fuel, which can be used in cement production. When the developments now in progress are completed, the CO2 emission from combustion of fuel in cement production is expected to be reduced to less than 2/3 of its original level.

PRODUCTION OF GREEN CONCRETE

Development projects in the research project; green concrete is examined in different ways:1. To minimise the clinker content (i.e. by replacing cement with fly ash, micro silica in larger amounts than are allowed today, or by using extended cement, i.e. lime stone filler cement)2. To develop new green cements and binding materials (i.e. by increasing the use of alternative raw materials and alternative fuels, and by developing/improving cement with low energy consumption). 3. Concrete with inorganic residual products (stone dust, crushed concrete as aggregate in quantities and for areas that are not allowed today) and cement stabilized foundation with waste incinerator, slag and low quality fly ash.4. To increase the use of conventional residual products, i.e. fly ash.

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TYPES OF GREEN CONCRETE

The concrete types selected for testing are shown below for concrete in passive (P) and aggressive (A) environmental class, respectively. It can be seen that the four principles of producing green concrete are combined in order to achieve the most environmentally friendly concrete. All the concrete types fulfils the technical goals are as follows;PR Reference concreteP2 50% fly ash and 10% kiln dust of powderP3 17% sewage sludge incineration ash of powderP5 Concrete slurryP6 100% stone dust of sandP7 30% fly ash from bio fuels of powderAR Reference concreteA0 Cement with reduced environmental impactA1 40% fly ash of powder and cement with reduced environmental impactA3 10% sewage sludge incineration ash of powder and cement with reduced environmental impact.A5 Concrete slurryA6 50% stone dust of sand

ADVANTAGES OF GREEN CONCRETE

Reduction of the concrete industry's CO2-emmision by 30 %.Increased concrete industry's use of waste products by 20%.Reduction of the concrete industry's use of non-renewal fuels.NO environmental pollution and sustainable development.5)The recycling quality of green concrete must not be less compared to existing Concretes types.The production of green concrete must not reduce the recycling applicability of the discharge water.No increased noise & dust emission.8) Green concrete requires less maintenance and repairs.9) By using stainless steel in green concrete instead of black reinforcement so corroding action is less.10) It is more durable.11) Corrosion resistant.12) By using the light weight aggregates self weight of structures can be reduced.13) Energy saving material.14) Green concrete having better workability than conventional concrete.15) Compressive strength behaviour of ceracrete with water cement ratio is similar to conventional concrete.16) Flexural strength of green concrete is almost equal to that of conventional concrete.17) Use of concrete industries own residual products.18) Less expensive to produce it.19) At least 20% of the concrete shall be residual products used as aggregates.20) Good thermal resistant and fire resistant. 21) Good sound insulation than traditional concrete.22) Improve damping resistant of buildings.

LIMITATIONS OF GREEN CONCRETE

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1) The focus of this technology is mainly based on co2 reduction, while whole environmental impact should be covered and accordingly investigations should not only made in the field of concrete but also structures build with it.

2) The research & development works are solely based on environmental goals. While, some consideration need to be given to the market condition which limits the cost of the products in terms of technology.

3) Green concrete does not fulfill the requirement of existing standards also according to structures of least importance.

APPLICATION OF GREEN CONCRETE

Concrete & fire Green concrete dam

SCOPE IN INDIA

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“Green concrete” is a revolutionary topic in the history of concrete industry. This was first invented in Denmark in the year 1998 by Dr.WG. it does not took, long time to be carried in India because highest problem of Indian industries to dispose of their waste by economical way is under research. The main emphasis is given by this technology on reduction of co2 content in the environment produced during manufacturing process of cement, concrete& other main stream materials.Some industries in Denmark producing Green concrete have pointed out that reduction in production cost often go hand in hand with reduction in pollution.From view point green concrete is not only promising from environment aspect but also economic aspects. Green concrete can replace traditional concrete in various parameters like, Binders – cement content in concrete can be effectively minimized by substituting parts of cement by pozzolonic materials for example, fly ash, silicon, microsilica, residual products of electricity & production of silicon respectively. Stones dust – it is residual products of crushing plant & expected to replace part of sand. Concrete slurry – it is the residual product of concrete manufacturing i.e. washing of mixtures & other equipments. It is recycled in the form of dry powder & can exchange marginal amount of binder.Investigation have shown co2 emission can be reduced up to 21 to 30% and one more significant change by using crush asphalt as part of aggregates can eliminates development of macro cracks in the foundations.So definitely it can be proved potential environmental benefits to society of being able to build with the green concrete is huge & gives a most economical way of disposing of Indian industrial wastes. By giving a look to the success of Green concrete in foreign countries, Indians also took various projects of producing green concrete under hand at various places, Mumbai, Delhi, etc.

CONCLUSION

Green concrete having reduced environmental impact with reduction of the concrete industries co2 –emissions by 30%. By using 40% fly ash of powder and cement with reduced environmental impact. Therefore reduced environmental pollution. Green concrete is

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having good thermal and fire resistant. Also having good sound insulation in comparison with traditional concrete. In this concrete recycling use of waste material such as ceramic wastes, aggregates, so increased concrete industry’s use of waste products by 20%.hence green concrete consumes less energy and becomes economical. Developing country like India second rank is given to construction development, which uses concrete in large amount & at the same time produces waste in the form of concrete material. So use of product like green concrete in future will not only reduce the emission of co2 in environment but also economical to produce.

REFERRNCES

Journals:

1. Indian concrete journal volume 77 -January -2003-N0.-1

2. Green concrete using industrial wastes. Proceedings, National

conferences on advances in building materials. Vellore Institutes of

technology, Vellore.

3. Devdas Manoharan.P , Senthamarai.R.M. Concrete using ceramic

insulators scraps as coarse aggregates. Proceedings, 6th

International conferences on conc. Tech, Amman, Jordan.

4. Galvind, Munch-Petersen, “Green concrete” structural concrete.

Websites:

1. http://www.greenconcrete.dk/

2. http://www.dundee.dc-uk/

3. http://www.diamondbidewarehouse.com/green concrete.html.

4. http://www.gronbeton.dk/

5. http://www.ctre.iastate.edu/index.html.

6. http://www.is/ncr/publication/doc-24-3.pdf

7. http://www.metrokc.gov/procure/green /conc.htm.

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