CEN-391 Technical Communication

Local Material for Civil Infrastructure ProjectsAdarsh (14113004)

Abstract: This report deals with the contribution of local materials in civil infrastructure projects. Advantages of natural materials over the industrial materials have been discussed such as their contribution towards a sustainable environment, reduction in transportation costs and several other things. Different natural building technologies involving the use of local materials such as clay, timber, flyash, straw bale, stone, etc. have been discussed in this report. These materials can be used effectively in construction such as clay, timber, straw bales, etc. can be used to construct small structures, fly ash in embankments and road construction and several other uses.

Keywords: Adobe, Cob, Cordwood, Earthbag, Wattle and Daub

Introduction

Civil Engineering is considered to be the initial footsteps of mankind into the world of engineering. It keeps us overwhelmed by its astonishing outcomes. The development in the fields of structural, hydraulics, transportation, environmental and survey engineering has helped the people to have a safe place to live in, to travel with ease and get a sustainable environment.

All these things involved, the civil infrastructure projects incur huge costs and extensive use of materials such as cement, steel, composite material for road pavements, etc. The major problem related to these is that they involve huge costs in the project related to their production and transportation. Of course there is not a very great alternative to this, so it has to be fulfilled. But lately, considering the resources available and economically viable projects, natural or local materials

can be used effectively such as clay and sand, harvested wood, fly ash, etc.

Natural buildings mainly strive towards increasing environmental sustainability that include range of building systems and materials. Its basis is to lessen the environmental impacts of buildings and other supporting systems without compromising life and health. These natural buildings use abundantly available, recycled or reused materials. Also they rely on non-industrial, minimally processed and locally available materials.

FeaturesNatural or local materials have less energy embodied and less toxic than man-made materials. They require less processing and have very less impact on the environment. Also the products become more sustainable when they are incorporated into building materials.

Construction waste can also be reduced if use of natural materials is emphasised. For example, if we consider concrete, we can

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see how much of it goes waste regarding its handling, the time in which it should be used, etc. and several other factors. This results in a considerable amount of waste which needs to be dealt with properly and also there is wastage of money. On the other hand, less waste generation will be there in case of local materials because only that amount will be used that is required. Also some of the natural materials that are considered as waste such as harvested wood in forests, fly ash, etc. can be used in construction projects thereby reducing the waste.

Also the transportation cost can be reduced in case of local materials as it can be readily available as compared to the man-made or industrially produced materials.

MaterialsSome of the materials that can be used for natural building are clay, wood, straw (straw can be loosely defined to include any dried non-woody plant material such as palm fronds, reeds, etc.), fly-ash, rice-hulls, slag, wool, bamboo and stone. Variety of non-toxic recycled or reused materials are very common in natural buildings such as urbanite (salvaged chunks of used concrete), vehicle windscreens and other recycled glass.

Clay is abundantly available for many natural building techniques. Straw bales can be available seasonally from the farms. Bamboo can be a very effective material in constructing sustainable structures. Also fly-ash is being used nowadays in construction of roads and in embankments.

It is not always possible to use locally available materials but if used, should be done selectively and in a small volume.

Natural Building Techniques & TechnologiesAs we have already seen how locally available materials can be advantageous in the civil infrastructure projects, let us

discuss the technologies in which they can be used:

Adobe

It is one of the oldest building methods. Adobe is simply a mixture of clay and sand with water. For strengthening it, chopped straw or other fibres are added sometimes. The mixture is then dried in the desired shape. Usually it is used to form bricks that be stacked to form walls. Also, adobe can be plastered over with lime-based mixes for protection and appearance. It is not a good insulator hence insulators can be used preferably on the outside. However, thick traditional un-insulated adobe has proved to very effective in regions where weather conditions are not very harsh.

Fig 1. House constructed of bricks formed by adobe

Cob

The term cob is used to describe a monolithic building system based on a mixture of clay, sand, straw and earth. The construction uses no forms, bricks or wooden framework; it is built from the ground up. Cob is one of the simplest and least expensive building techniques available, though it is typically very labour-intensive. It can easily be shaped into any form owing to its versatility. Cob is generally associated with low-rise structures. Cob-like mixes are also used as plaster or filler in several methods of natural building, such as adobe, earth bags,

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timber frames, and straw bales. Earth is thus a primary ingredient of natural building.

Fig 2. A small Cob building

Cordwood

Cordwood construction is a term used for a natural building method in which short lengths of pieces of debarked tree are laid up crosswise with masonry or cob mixtures to build a wall. Cordwood masonry can be combined with other methods (e.g., rammed earth, cob or light clay) to produce attractive combinations. Cordwood masonry construction provides a relatively high thermal mass, which helps to minimise fluctuations in temperature.

Fig 3. A section of a Cordwood home

Earthbag

Earth is the most typical fill material used in bag-wall construction techniques. This building method uses stacked polypropylene or natural-fiber bags filled with earth or other mixes without a stabilizer such as portland cement, to form footings, foundations, walls and even domed roofs. Recently, this method has been gaining popularity as it facilitates self-contained, often free-form rammed-earth structures.

Since earth is a poor insulator, substitutes like pumice, rice-hulls, etc. are being utilised for their use in harsh weather conditions.

Fig 4. An Earthbag structure

Rammed Earth

Rammed earth is a wall system made of compacted earth, or another material that is compacted. It is extremely strong and durable. Quality rammed earth walls are dense, solid, and stone-like with great environmental benefits and superior low maintenance characteristics. Rammed earth walls are formed in place by pounding damp sub-soil (containing sand, clay and sometimes gravel) into movable, reusable forms with manual or machine-powered tampers.

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Fig 5. Multi-coloured rammed earth wall

Stone

Stone has been used as a building material for thousands of years and is recognized as a material of great durability. They form freestanding structures such as field walls, bridges and buildings that use irregularly shaped stones carefully selected and placed so that they fit closely together without slipping. Stone is a highly durable, low maintenance building material with high thermal mass. It is versatile, available in many shapes, sizes, colours and textures, and can be used for floors, walls, arches and roofs.

Fig 6. A Stone structure

Straw bale

Grasses and straw have been in use in a range of ways in building since pre-history around the world. Straw bale building

typically consists of stacking a series of rows of bales (often in running-bond) on a raised footing or foundation, with a moisture barrier between. Bale walls are often tied together with pins of bamboo or wood, or with surface wire meshes, and then plastered with either lime-based formulations or earth/clay renders. Basic bale-building method is now increasingly being extended to bound modules of other often-recycled materials, including tire-bales, as well as those of cardboard, paper, plastics and used carpeting, and to bag-contained "bales" of wood-chips, rice-hulls, etc.

Fig 7. A straw bale structure

Timber frame

The basic elements of this technique are joint timbers, clay walls and thatch roofs. These structures are mostly common in the European countries. Timber frame structures are frequently used in combination with other natural building techniques, such as cob, straw bale, or cordwood/masonry.

Fig 8. A timber frame structure

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Wattle and Daub

Wattles are made from flexible wood or fibres and are woven loosely to create an underlying structure for a wall. Plaster is then daubed onto the wattle to finish the wall and provide thermal mass. Straw wattle is a better-insulated variation where clay-embedded long straw fibres are woven around light-weight uprights and then plastered.

Wool Bricks

These bricks are exactly what the name suggests. By addition of wool and some natural polymer, their strengths are increased by about 37% as compared to the other bricks. They also dry hard, reducing the embodied energy as they don’t need to be fired like traditional bricks.

Fig 9. Wool Bricks

Uses of Flyash

Flyash can be used in the cement mixture as a substitute to Portland cement and sand, in the embankments or structural fills, waste stabilisation and solidification, as a subbase material for roads and in the bricks as a substitute material.

ConclusionFrom the content above we have seen various kinds of construction technologies being used involving the use of naturally or locally occurring materials. They can be used in small quantities in large scale

projects which can result in a considerable reduction in the cost of the project. Also they can be a great alternative to the industrial materials in small projects. The way in which they prove to be sustainable to the environment, it can be a better choice to use these materials in the civil infrastructure projects.

ReferencesKim J., Graves J., “Sustainable Architecture Module:

Qualities, Use, and Examples of Sustainable Building Materials.” (1998). Sustainable Architecture Module: Qualities, Use, and Examples of Sustainable Building Materials, National Pollution Prevention Center for Higher Education, 430 E. University Ave., Ann Arbor, <http://www.umich.edu/~nppcpub/resources/compendia/archpdfs/archsbmintro.pdf> (Oct. 16, 2016).

“Natural building.” (n.d.). Wikipedia, Wikimedia Foundation, <https://en.wikipedia.org/wiki/natural_building> (Oct. 16, 2016).

By lining the trench with 2. (2010). “Natural Building Materials, Techniques & Technologies at Dancing Rabbit.” Dancing Rabbit Ecovillage, <http://www.dancingrabbit.org/about-dancing-rabbit-ecovillage/eco-living/building/natural-building/> (Oct. 16, 2016).

“Five Sustainable Building Materials that Could Transform Construction.” (2010). This Big City Comments, Joe Peach, <http://thisbigcity.net/five-sustainable-building-materials-that-could-transform-construction/> (Oct. 16, 2016).

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