CEMENT SURFACE FINISHES

Post 543  by Gautam Shah

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This blog >>   was originally published 15 June 2015 at http://talking-interior-design.blogspot.in/
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Cement surface finishes occur in three different conditions:

1 Finishes generated over the cast cement products,

2 Rendered finishes of cements,

3 Cement coatings’ finishes.

The major problem with cement finishes is the consistency of colour over the surface. Other problems happen due to differences in application (casting, rendering or coating), mixing water content and quality and curing processes. The colour differences arise due to many reasons: ingredients used in cement manufacturing, particulate size and its distribution, size and colour quality, proportionate quantity of other ingredients, quality-conditioning additives and mixing procedures.

Centrifuge Cast cement concrete pods on Sea face at Mumbai, India

Cement cast products are plain or steel reinforced structures, pre cast blocks, units, etc. A cement finish of a cast product emerges due to the form-work, compaction, level of vibration (causing aeration), proportion of water and technique of casting (towards gravity, centrifugal or centripetal, short or long depth fall).

Cracks in Cement plaster due to uneven mixing of ingredients

Cement Concrete Surfaces can have finishes depending on several factors, such as:

1 Form work surface, joints and continuity, use of a release agent, absorbency of the form work surface and setting or hardening enhancer and retarders used.

2 Concrete mix proportions, ingredients’ colour, size, and texture (lighter toned aggregates and sands produce light-coloured concrete (colour of cement is variable not only from plant to plant but often batch to batch). Degree of mixing and air entrapment affect the colour. Free lime in water creates a soapy foam which also affects the colour.

3 Insufficient or uneven curing affects the hydration and eventually the colour of the concrete.

4 Inadequate vibration causes minor pockets of air bubbles, which affects the texture.

Weathered Cement Concrete at Sanskar Kendra by Le Corbusier Ahmedabad India

Rendered finishes of cement include plasters, sprays, guniting, masonry pointing, screeds and daubing. These are comparatively of thinner mass. The compaction, if any is part of the application or rendering-levelling by trowels, plasters boards, etc. For rendered finish the surface quality is fairly consistent for small-extent surfaces. For very large surfaces, such as multi-storeyed buildings, the surface differences are noticeable. These anomalies can be reduced by dividing the surface with wide intervening elements of different colour, texture, projections or depressions. Same technique is used for pointing to the masonry faces of stones or bricks. Pointing is designed to enhance the joints’ pattern, as strongly horizontal, vertical, or both. The joint is usually of a contrasting colour and of finer texture, then the main material surface. A raked joint or protruding joint looks much darker than a flushed joint or flat joint.

Masonry bricks of Cement with Fly-ash

Cement is used for creating in-situ and precast floor blocks. Use of fine sands increases the air entraining effect and reduces the work-ability. Angular or flaky sands are difficult to use in sand face plasters.

The mixed mortars are affected by the colour of the aggregates. So it is very difficult to produce a perfectly white marble mosaic tile or washed chips’ plaster unless only pure white aggregates are used. Cement and aggregate flooring such as IPS – Indian Patent Stone, Red Madras floor and Ironite (cast iron milling waste) are all affected by the colour of the constituents. coloured mortars have pigments of iron oxides (black, red and yellow). Green, blue and other colours (though not sun fast or long lasting) are achieved by use of chrome pigments.

Cement pointing over brick masonry

For vertical and ceiling surfaces ziki plaster formed with marble dust containing substantial amounts of fine mica and talc. Similarly pearl glow and a smooth surface can be achieved by including sea shell dust. Slow setting and engravable cement mortars require high workability, are achieved by addition of fully calcined gypsum or lime containing such compounds.

Cement coatings’ finishes are in the form of cement paints and high viscosity or bodied rendering formulations. Cement paints have limited life of 3-5 monsoons and re-applicability of 5-7 coatings. Cement paints are alkaline materials and applied on similar substrates, and as a result the colour range is mostly of Oxides colours. Some blues and greens of darker range are available. The chief problem is the process of adding the water, which creates flocculation and aerated mass. Next problem is application on a dried out substrates with chances of poor adhesion and difficult brushing. Rendering formulations have high viscosity, and the success usage relies more on the craft of application.

White cement + Marble chips Terrazzo

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Cement Surface Finishes have few basic problems:

fine hair cracks

honey comb voids

unbounded loose particles

foreign particles stuck on the surface

foreign particles deposited on the surface.

washable salts leached out from the surface

salts and compounds formed over the surface by the constituents of the environment

mould and fungi type bacterial growth

disengagements from the substrate -peel off.

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MEANING of CRAFT – 3

Post 542  by Gautam Shah

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Craft processes have been closely linked to exploration of materials with hands or manual operations. Use of tools as reach-extension of hands is considered nominal. Equipments where manually manipulable are accepted, but any process operative on auto corrective feed-forward or feedback is challenged [1]. The skill of making things by hands (including with tools) evolves with experience. And as a result the product is continuously improvised. Every item crafted with hand and (non automatic) tools, is a unique piece. So are the intentions for good design and material manipulation with hand, sufficient to deliver a ‘craft’?

Lijiang, Yunnan, China: Exhibition of copper smith works Wikipedia image Attribution (required by the license) © CEphoto, Uwe Aranas / CC-BY-SA-3.0

If the crafts evolve with the exploration of materials, where does it start? Craft’s person has to procure materials that are substantially processed, and proceed from there on. In a modern world, craftspeople start their work with industrially re-composed and synthesized products. These materials till 1960s came along with specifications of quality and sometimes suggestive conditions for their use. But over the last few decades such specifications have been found to be very restrictive and futile. New modes by International standards Organization, ISO allows manufacturers to offer details on how the material-product is made, and the ‘quality culture’ the manufacturers follow. Further exploration of the same is left to the individual person, who may use it for a non traditional purpose.

Handicraft_shop,_on_Janpath,_New_Delhi

Craft was also considered a pastime or a hobby. The terms a crafts-man or a crafts-woman, were long replaced by term artisan or crafts-people. The craft products missed this personal expression when materials from unknown places and in substantially processed form began to be used. The hands on materials, approach which was considered to be the basis of creative human expression began to be irrelevant. Craft was considered a reflection of a localized tradition, matured over a period. This was seen through the motifs, patterns other abstractions. The personalized expression when unique in content and high in abstractions became an art form. An artefact (Early 19th : from Latin arte by or using art‘ + factumsomething made‘) is a crafted item that has the essence of art.

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Crafts have been called handiwork or handicrafts. This raises the question, Are products created using hands but by automated tools and equipments really crafts? Products whose formation is not exclusively dependent on fixed dies, jigs, fixtures, and other standard devices, has a greater scope of being continuously improvised. This cannot happen in a continuous line-production but in a single item production or a batch-based system. Line production does not allow human expression as reflected in some course corrections. This began to be seen when factories sponsored by royalties and big business group began to produce crafts-works. These sponsors established production centres that have produced some excellent crafted works.

Wedgewood pottery Wikipedia image by Author Kpjas

Craftsmen till about middle ages were tied to a location and the guild. The guilds, protected as well as encouraged the crafts, by restricting new entrants, conditions of practicing the crafts and in few instances facilitating the raw materials. Factories of later periods enticed the protected crafts persons to move out of the restrictive and monopolistic guild environment. Craft products were not known by the craftsperson, the town or region, but by the production factories. The craftspeople were distanced from the user-clients and social connoisseurs of their skills.

Wood Block printing William Morris 1873 Wikipedia image

The factories supported innovative production processes that included partial automation. The factories subscribed to new designs for inclusion into now their standardized products. They offered large number of identical items like ceramics, vessels, utensils, tapestries, fabrics, furniture items, etc. with coordinated designs, patterns, or colour schemes. The crafts of the post middle ages began to reflect the style of the production centre.

Loan 74, f. Front Cover

The detachment of craft from material handling processes had already emerged before the onset of industrial age. The practical involvement hand with the material had now terminated. The craft factories were overwhelming involved with design. The new class of designers were only perfunctorily connected to the artisans. The semblance of human expression in unique creations, began to diffuse when large number of products arrived from automated industrial production. The Arts and Crafts movement emerged from exposition of ornate and artificial artefacts that disrespected the materials, at the Great exhibition of 1851. It sought to reform the design.

A_bullock_cart_in_Bombay_in_the_1870s

[1] In India Khadi (hand spun & hand woven) fabric is accepted as a craft product. The process is now being challenged by manual-machines as well powered machine spinning devices (called Amber Charkha). The raw material was mainly cotton (but occasionally silk, jute and wool). But now polyester fibres are being mixed with the raw material, resulting in better fiber strength, wear-ability, fineness and economics of costing. To complicate the scene further, since 1950s auto spun fibres are woven on hand-looms (manually operated weaving looms). So should these be a craft-product? Another variant, a Power-loom uses auto-machine spun fibres over automated looms (of simplistic design compared to air-jet and other weaving devices). The controversies of technological involvement occur for all types of products or artefacts.

Amber Charkha India, Automated spinning machine Wikipedia image by Author Sailee5

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PEWTER

Post 541  -by Gautam Shah

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Pewter Teapots

Pewter Mugs

Pewter is a metal alloy with Tin as the chief constituent. Pewter denotes a vast array of alloy-compositions of many different metals in various measures. Pewter metal of the ancient times contained about 70% Tin and 30% Lead. Both were known as distinct metals since 3000 BC. (Tin shows a chemical similarity to the periodic table group-14 element -the lead). Pewter has been preferred material for craft and utility items, mainly due to its low melting temperature, and the fine finish, it offered. Pewter with high lead content, offered a shining but tarnishing black metal that darkened further on aging. Primitive pewter with lead was hazardous for food storage. And as a result the composition pewter has seen many changes, with efforts directed towards eliminating the lead.

 

Pewter Tableware

Pewter Napkin Rings Flickr image by Didriks

Pewter as craft material offered certain advantages such as: low melting point, malleability, ductility, easy workability and highly crystalline silvery-white surface. Pewter can be crafted by cold-working, as it does not cause hardening like other metals, which often requires annealing. Pewter items are usually cast, and then further finished by hammering, turning on a lathe, burnishing, and sometimes engraving. Pewter alloys were rolled into sheets from cast blobs. Such sheets could be shaped, deformed, spun and welded with tin. The presence of tin provides affinity to all embellishing crafts metals like brass, gold, silver, etc.

Detail on a pewter fork handle from Norway, showing three scenes: King Olaf II of Norway, his men, and a Viking ship Wikipedia image by Author Goldenrowley

Pewter Continental Dollar, 1776 (proposed)

Romans used pewter utilities like cups, plates, dishes, etc. and medallions, rings, armlets, etc. But the use diminished due to lead poisoning. Use of tin with natural ‘impurities’ like bismuth, antimony, copper and silver was known but not clearly understood. Pewter utilities never formed cooking vessels as tin and lead had low softening point of temperature, besides an increased health hazard of lead. Pewter, in spite of its easy workability was primarily a utilitarian metal, and less exploited for its ornamental capacity. Pewter work finished like silver, and was passed off as silver. It was used where precious metal items were too expensive and theft prone. In the 11th C poor churches began to use pewter in place of silver items. Lower classes across Europe, were still using it for eating and drinking. Trade guilds in the 12th C in France and elsewhere began to control the constituents of pewter.

Components and products of pewter manufacture Wikipedia image

By 15th C, the Worshipful Company of Pewterers began to standardize pewter. The first, known as ‘fine metal’, with tin and copper, was marked for tableware. The second, known as ‘trifling metal or trifle’, with fine metal and 4% lead, was designated for holloware. The third, known as ‘lay or ley metal’, with 15% of lead, was meant for non food or drink utilities.

Rockport Pewtersmith Wikipedia image

Modern pewter is without any lead, but with about 91% tin, 7.5 % antimony, and 1.5% copper. Alloying materials like antimony and bismuth make it more durable. The surface of modern pewter is bluish white with soft satin to high sheen finish. It resists tarnishing, while retaining its colour and finish. Without any lead, it is safe for food and drinks. Britannia metal consists of tin, antimony, and copper.

Teapot, Britannia metal, Wikipedia image by Author Daderot

Pewter items are cast, moulded, pressure die-cast or shaped. Pewter was fashioned by hammering (workers called Sadware men) or by casting (workers called Hollow-ware men). Pewter wares were earlier cast in metal moulds, but now Silicon, Teflon and rubber moulds are for mass production. Few items are painted, enamelled, gilded, and inlaid or embellished with other metals and materials. Pewter was the chief tableware until the making of porcelain. Pewter items include household goods, (porringer, plates, tea sets, dishes, basins, spoons, measures, flagons, communion cups, teapots, sugar bowls, beer steins, and cream jugs), candlesticks bases, church vessels, snuffboxes, personal adornments, organ pipes dishes, statuettes and figurines, game medals and presentations, aircraft and other models (replica), coins, support or inner structures for gold-silver presentation items.

Pewter manufacturing Wikipedia image

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IRON MAKING

Post 540 — by Gautam Shah

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640px-Ahnighito_AMNH,_34_tons_meteorite

576px-Willamette_Meteorite_AMNH

First iron used by ancient people was of a meteoric source, an iron alloy with nickel. This was used for everal millenniums before the actual iron age. It was a natural Iron in metallic state and so required no smelting of ores. This nearly pure iron is softer than bronze, and therefore tools formed of it had soft wearing edge.

445px-QtubIronPillar

Primitive age iron was smelted by mixing iron ore with charcoal, and burning in bloomeries, a type of furnaces where bellows were used to force in the air. The carbon monoxide produced by the burning charcoal, reduced the iron oxide ore to metallic iron. The apparatus, however, did not achieve a temperature of 1540° C, to completely melt the iron. The metal collected in the bottom of the furnace remained as a spongy non homogeneous mass or bloom. It had high proportion of intermingled slag. The blooms were repeatedly heated, beaten and folded to remove the slag. This produced wrought iron (=worked iron), a malleable, but fairly soft material. Iron age Irons were not castable products but required hot forming (forging). This was mainly due to inability to fully melt the material. Hot forming was a labourious process, requiring skill and experience. In comparison to bronze, iron ore was procurable everywhere and cheaper to process.

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Wrought iron shows high resistance to corrosion due to the trapped slag in the metal. The presence of slag in the iron helps fusion joining by hammering or forging. Wrought iron is no longer produced commercially, because low-carbon steel is less expensive and is of more uniform quality. Wrought iron, however, is still produced for certain craft-based uses such as making intricate craft objects balustrades, gates, garden accessories, etc.

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Simulated form of wrought iron is made by melting scrap mild steel in small furnaces, blowing air through the melt to remove carbon, and pouring the molten metal into a ladle containing molten slag, which is usually prepared by melting iron ore, mill scale, and sand together. When the molten iron carrying a large amount of gas in solution, is poured into the molten slag (kept at a lower temperature than iron), the metal solidifies almost instantly, releasing the dissolved gas. The force exerted by the gas shatters the metal into minute particles that are heavier than the slag and settle at the bottom of the ladle, agglomerating into a spongy mass.

Silla iron armor, en:Three Kingdoms of Korea, 3rd century Wikipedia image

It was Chinese (1200 BC or earlier) who designed kilns that could raise the temperature for iron making. These kilns, used upgraded coal and had high volume air supply for efficient burning. Chinese were able to melt the Iron and cast it into desired forms. Casting was less labourious, and allowed multiple items with same die form. It was accurate than forging each piece. Chinese smiths melted wrought iron and cast iron together to produce steel -a material of controlled carbon content. The process was called ‘harmonizing the hard and the soft’. This was widely used for casting cooking pots and iron statuettes. A cast iron is harder than wrought iron, but maintains the cutting edge.

Casting pig iron, Iroquois smelter, Chicago, between 1890 and 1901. Wikipedia image

Perhaps as early as 500 BC, although certainly by 200 AD, high quality steel was also produced in southern India by the crucible technique. In this system, high-purity wrought iron, charcoal, and glass were mixed in a crucible and heated until the iron melted and absorbed the carbon.

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Columns_of_the_Grand_Palais,_Paris_13_November_2016

Carbon content of iron is a major factor that creates harder material. It was necessary to absorb more carbon in the iron. This required higher ratio of fuel to ore, and push in a lot more volume of air. The strength of iron begins to increase with carbon contents of 0.5 percent. To heat treat iron a carbon content of 1.2% was necessary. Wrought iron which contained less than this proportion had no qualitative effect due to heat treatments. A higher carbon content creates a brittle material but allows heat hardening. ‘Iron hardening by quenching was not practised because it made iron very brittle, unless followed by tempering, or reheating at a lower temperature, to restore toughness’. Simple fire, 600-700° C, based technique of repeated cold forging and annealing was used.

cast iron columns line the Albert Dock’s quayside Wikipedia image

In the pre-Christian portion of the period, the first important steel production was started in India, using a process called Wootz steel. It was prepared as sponge (porous) iron. This was hammered while hot to expel slag, broken into smaller pieces, and placed with wood chips in clay containers, and heated. On melting, an iron composition containing 1 to 1.6% carbon was produced. The pieces were reheated to form articles that required a hard body and sharp edge. Such steel products were exported to Middle East and other countries. It was known as Faulad (Persian). (Faulad or wootz steel has a Kannada term, ukku, a Language of Indian region of Karnataka).

Elevator screen from the Chicago Stock Exchange cast iron electroplated with copper. Wikipedia image by Joe Mabel

431px-Nef_du_Grand_Palais_(détails),_juin_2018_(17)

Nowadays commercial steel plants produce ingots or pig iron. It has very limited use. It goes to casting foundries or to steel mills. At both the places it is remelted to reduce its carbon content and for allying by adding various elements such as manganese and nickel. Often scrap steels are also added for the same purposes.

Melting points for various forms of Irons

Iron, Wrought     1482 – 1593

Iron, Gray Cast   1127 – 1204

Iron, Ductile       1149

Steel, Carbon      1425 – 1540

Steel, Stainless   1510

Le_Grand_Palais_depuis_le_pont_Alexandre_III_à_Paris

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BUILDING CLIMATE

Post 539  –by Gautam Shah

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1024px-Bahay_Kubo_Iao_Valley_Maui_Hawaii

A building is affected by various aspects of the climate, which are, mainly external to it. A building as a shell modulates the climate, and creates an improvised climatic (interior environment) not only within it, but over the vicinity. Modern buildings have systems that consume energy to provide lighting, ventilation, cooling, heating, conveyance, and various types of kinetic power. Operations of such systems affect the environmental conditions of the building and the surroundings. Occupants of the building are also active energy processors, and leave their imprint in the place of inhabitation.

Gangtok Author Thebrowniris

Building level climate is formed by following factors:

            1.         Climate of the region

            2.         Climate at the location

            3.         Building structure or shell

Ideally a building design should begin with the climate of the region and its location related variant. A building shell is formed of many materials and form-compositions. The materials due to their constitution and forms of composition offer a complex but unique set of interactions with the various climatic aspects.

Kerala courtyard with planter Wikipedia image by Author User: Soumyavn

As a design, the tasks are scheduled and located through appropriate orientation, and so are expected to benefit from the climate. Specific activities are spatially designated and timed in the sections of the building for their density of occupancy in terms of humans, facilities and amenities. These activities, however, often stretch beyond their nominally defined space, overrun the schedules, and have varied levels of occupancy. The adequacy of a building for the climate and possible environmental comfort is thus an averaged experience.

Wikipedia image by Author Baycrest (“CC-BY-SA-2.5”)

In dense urban localities the site size, shape and the predefined exposure due to the surroundings, all constrain perfectly oriented planning. The interrelationship between sections and linkages add to the contradictions. From a climate point of view, a building shell behaves like a biological entity, that is in a continuous process of achieving equilibrium. But the permanency of the site size, shape and predefined exposure, limit the climatic adjustments. There are two sets variable factors that require climatic management: the externally, the unpredictability of climate, and internally changing task profiles, related space occupancy, and time scheduling. The variable factors cannot always be managed in the size, shape and form of the building form, however, amenities, and facilities mitigate the situation.

Tagore

At an extreme level, with the use of ‘universal services’ (central air conditioning, auto ventilation, etc.) environmentally consistency is achieved for the entire building shell. In another approach, relocatable amenities and facilities, help time+space shifting of tasks. Designers also use materials and techniques of composition to make energy exchange favourable. The techniques include architectonic features such as parapets, barricades, curbs, chowks, cutouts, ventilators, ducts, chimneys, shafts projections, chhajjas, balconies, galleries, canopies, and textured surfaces. Landscape features like slopes, hills, mounds, gorges, valleys, water bodies, shrubs, plants, shrubs, hedges, groves etc. are used for the same purpose. The success of a climatic design depends on how the active and passive means can hasten, delay, curtail or terminate some of the environmental processes.

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Indian Library Calcutta India, Wikipedia image by Author njanam92

Some of the problems that designers face while designing with the climate are:

1 Building is often required to be located in a climate region that is essentially inappropriate for the intended activity. A dehydration plant to be located in tropical rain forest area.

2 A building consists of several sub units (limbs), some of which will have either inferior or superior climatic orientation. Placement of parking on a west side of a building / bedroom on a windward side.

3 Environmental requirements are often so exact or acute that traditional climate modulation techniques like building shape, materials, orientation etc. is inadequate.

4 Activities within a building cannot be located permanently, because there are many hourly, daily and seasonal variations in a climate.

5 An activity though accurately located in a building, may last longer than the affective duration of the particular type of climate in that section.

6 Activities often require specific climate conditions, but whose occurrence is not easily predictable.

7 Some activities cannot be relocated to new areas to suit the hourly or seasonal changes in a climate, because the amenities with which they flourish are fixed.

17th-century qasbah in the Skoura palm grove in Morocco is built with the traditional pisé, also known as pisé de terre, or rammed earth. Flickr image by Maureen (https://www.flickr.com/photos/amerune/)

Old Town Homes Flensburg Baltic Sea Architecture

Old Town Homes Flensburg Baltic Sea Architecture

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