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Advances in Construction Industry-An Overview

Improving Construction Efficiency & Productivity

The quality of life of every citizen relies in the quality of construction elements he experiences in his daily life-houses, office buildings, factories, shopping centres, hospitals, airports, universities, refineries, roads, bridges, power plants, water and sewer lines, and other infrastructure. These elements provide shelter, water, and power, and they support commerce, education, recreation, mobility, and connectivity.

The construction industry itself is a major generator of jobs and contributes an important component of the gross domestic product (GDP). We notice significant opportunities to improve construction efficiency and meeting other national challenges have been provided by the advancements in the technologies and that the awareness for properly implementing the same at large still is a challenge.

In the coming years, the Modular Construction Industry will attain prime significance as more and more customers are turning to modular for multi-story, steel framed structures, health care facilities, educational structures, and large scale military projects. Always known for its time saving advantages, modular is now being recognized for being a more resource-efficient, inherently greener process.

Based on the studies recently held, the construction industry has five key areas of utmost importance to be developed and addressed in the next two to ten years. 

• Widespread deployment and use of interoperable technology applications, also called Building Information Modelling (BIM).
• Improved job-site efficiency through more effective interfacing of people, processes, materials, equipment, and information.
• Greater use of prefabrication, preassembly, modularization, and off-site fabrication techniques and processes.
• Innovative, widespread use of demonstration installations.
• Effective performance measurement to drive efficiency and support innovation.

This article takes a comprehensive look upon the advances and emerging technologies that have tremendously influenced the construction industry in the last two decades. Contents have been arranged in parts as under; 

• Part 1- Advances in Concrete Technology
• Part 2- Role of Equipment in Construction
• Part 3- Emerging Technologies in Construction

PART 1- ADVANCES IN CONCRETE TECHNOLOGY

Concrete is the most widely used construction material in the world. Its consumption is around 20 billion tonnes annually which comes to around two tonnes per every living person. The reasons for such widespread use of concrete are its adaptability, durability, strength, availability and economy. Concrete is the only material which can be used everywhere; literally, from pavements to roofs. But the most sought after properties of concrete, viz., workability in the fresh state and strength and durability in the hardened state.

There have been a number of advances in new concrete technology in the past few years. There have been advancements made in almost all areas of concrete production including materials, recycling, mixture proportioning, durability, and environmental quality. The latest new concrete technology is beginning to gain acceptance in the industry. Some of the more interesting new concretes are called High performance concrete (HPC), Ultra High Performance Concrete, and Geopolymer Concrete, Smart Dynamic Concrete. They have significant advantages and little or no disadvantages when compared to standard concrete in use today.

IS456:2000 identifies three groups of concrete based on grades namely; Ordinary Concrete from M10 to M20; Standard Concrete from M25 to M60 and High Strength Concrete from M60 to M100; with a note to obtain special design parameters from standard published research works.

Application of HSC is primarily in aggressive environmental conditions for structural elements like columns in high rise buildings, bridge piers and so on. As the concrete technology advanced, it was felt that under such severe conditions, apart from strength considerations, concrete should be designed to have desired performance qualities and this gave rise to HPC-High Performance Concrete. Now-a-days, HSC and HPC have almost become synonymous terms.

Some of the advanced variants of concrete emerged as a result of continuous research is listed below. This article is not intended to give an elaborate description and details of each variant but, some of the important variants are touched upon briefly for the benefit of readers.

• High Strength Concrete (HSC)
• High Performance Concrete (HPC)
• Self Compacting Concrete (SCC)
• Pervious Concrete
• Light Weight Concrete (LWC)
• Fibre reinforced Concrete(FRC)
• Glass Fibre reinforced Concrete (GFRC)
• High Density Concrete (HDC)
• Smart Dynamic Concrete (SDC)
• Roller Compacted Concrete (RCC)
• Foam Concrete
• Under Water Concrete
• Acid Resistant Concrete (ARC)
• Geo Polymer Concrete (GPC)
• High Volume Flyash Concrete(HVFC)
• Self Healing Concrete (SHC)
• Decorative Concrete
• Translucent Concrete
• Vacuum Dewatered Concrete (VDC)
• Ultra Thin White Concrete.
• Recycled Concrete
• Green Concrete

High Performance Concrete (HPC)

HPC is a type of concrete meeting special performance requirements that cannot always be achieved by routinely using conventional constituents and normal mixing, placing and curing practices. HPC is a concrete mixture, which possess high durability and high strength when compared to conventional concrete. Any concrete which satisfies certain criteria proposed to overcome limitations of conventional concretes may be called High Performance Concrete. It may include concrete, which provides either substantially improved resistance to environmental influences or substantially increased structural capacity while maintaining adequate durability. It may also include concrete, which significantly reduces construction time to permit rapid opening or reopening of roads to traffic, without compromising long-term serviceability. Therefore it is not possible to provide a unique definition of High Performance Concrete without considering the performance requirements of the intended use of the concrete.

This concrete contains one or more of cementitious materials such as fly ash, Silica fume or ground granulated blast furnace slag and usually a super plasticizer. The term 'High Performance' is somewhat pretentious because the essential feature of this concrete is that its ingredients and proportions are specifically chosen so as to have particularly appropriate properties for the expected use of the structure such as high strength and low permeability. Hence High performance concrete is a special type of concrete in a sense. It comprises of the same materials as that of the conventional cement concrete. The use of some mineral and chemical admixtures like Silica fume and Super plasticizer enhance the strength, durability and workability qualities to a very high extent.

High Performance Concrete can be designed to give optimized performance characteristics for a given set of load, usage and exposure conditions consistent with the requirements of cost, service life and durability. The high performance concrete does not require special ingredients or special equipments except careful design and production. High performance concrete has several advantages like improved durability characteristics and much lesser micro cracking than normal strength concrete.

The direct advantage of HPC construction schedule is the early stripping of formwork. In addition, the greater stiffness and higher axial strength allows for the use of smaller columns in the construction. This will improve the construction schedule by reducing the amount of concrete that must be placed. These factors combined lead to construction elements of high economic efficiency, high utility and long-term engineering economy.

• Reduction of structural steel allows for greater flexibility in designing the shape and form of structural members.
• Superior ductility and energy absorption provided structural reliability under earthquakes.
• Reduction of structural steel allows numerous structural member shape and form freedom.
• Superior corrosion resistance.
• Concrete to be classified under HPC category, it should satisfy the following important criteria:
• Impermeability-Penetration of moisture is extremely harmful to the performance of concrete and in view of this, HPC to have a very low co-efficient of permeability in the range of 1x10^-14 m / sec.
• Volume Stability- High dimensional or Volume stability which depends on High Elastic modulus, low thermal strain, Low drying shrinkage and Low creep.
• All care as in the case of ordinary concrete should be taken in respect of transporting, mixing, compacting and curing.

Self-Compacting Concrete (SCC)

Self Compacting Concrete, also known as Self Consolidating Concrete, Self levelling Concrete, is the greatest discovery in the advancement of concrete technology in the last three decades. The guiding principle in SCC is that the sedimentation velocity of a particle is inversely proportional to the viscocity of the floating medium in which the particle exists. SCC should be able to Pass, Flow, fill and Stabilise.

Superplasticizers which help in water reduction and VMAs- Viscosity Modifying Agents which help in stabilising the concrete matrix along with other fines and mineral admixtures play vital role in the production of SCC. Compared to Normal concrete, SCC has less bleeding; lower drying shrinkage, higher bond strength with reinforcement, higher durability, lower permeability and uniform density.

SCC provides improvements in strength, density, durability, volume stability, and abrasion resistance. SCC is especially useful in confined zone where vibrating and compaction is difficult. The reduction in schedule is limited since a large portion of the schedule is still controlled by the time required to erect and remove formwork. Although the schedule reduction is limited, it is still sufficient that the reduction in labour costs overcomes the higher material costs. Self-Compacting concrete may be especially beneficial when used in combination with steel plate reinforced concrete structures, which requires a flowable concrete due to the complicated geometries.

Fibre Reinforced Concrete (FRC)

FRC is a concrete that includes fibrous substance that enhances its durability, ductility and structural strength. These fibres in FRC are homogeneously dispersed and randomly oriented providing a three dimensional stability. The use of randomly oriented and short fibres in order to improve the physical properties of a matrix is an age- old concept. For example, fibres made of straw or horse hair have been used to improve the properties of bricks for thousands of years. Most commonly used fibres in FRC are Steel and Synthetic. Fibres can be broadly classified as:

• Metallic fibres
• Polymeric fibres
• Mineral fibres
• Naturally occurring fibres

Metallic fibres are made of either steel or stainless steel. The polymeric fibres in use include acrylic, carbon, nylon, polyester, polyethylene and polypropylene fibres. Glass fibre is the predominantly used mineral fibre. Various types of organic and inorganic naturally occurring fibres such as cellulose are being used to reinforce the cement matrix.

Self-Compacting Concrete- Slump Testing	Fibres in Concrete

Following are a few pointers with respect to FRC.

• The presence of fibres at moderate volume fraction increases the modulus of rupture, fracture toughness, and impact resistance. These composites are used in construction methods such as shotcrete and in structures that require energy absorption capability, improved capacity against Delamination, Spalling, and Fatigue.
• The fibres used at high level fraction lead to strain hardening of the composites. Because of this improved behaviour, these composites are often referred as high-performance fibre-reinforced composites (HPFRC). In the last decade, even better composites were developed and are referred as ultra-high-performance fibre reinforced concretes (UHPFRC).
• The composite will carry increasing loads after the first cracking of the matrix if the pull-out resistance of the fibres at the first crack is greater than the load at first cracking;
• At the cracked section, the matrix does not resist any tension and the fibres carry the entire load taken by the composite.
• With an increasing load on the composite, the fibres will tend to transfer the additional stress to the matrix through bond stresses. This process of multiple cracking will continue until either fibres fail or the accumulated local de-bonding will lead to fibre pull-out.
• Since fibres impart considerable stability to a fresh concrete mass, the slump cone test is not a good index of workability. For example, introduction of 1.5 volume percent steel or glass fibres to a concrete with 200 mm of slump is likely to reduce the slump of the mixture to about 25 mm, but the placing ability of the concrete and its compactability under vibration may still be satisfactory.
• Ordinary glass fibre cannot be used in Portland cement mortars or concretes because of chemical attack by the alkaline cement paste.

Light weight Concrete

Lightweight concrete can be defined as a type of concrete which includes an expanding agent in that it increases the volume of the mixture while giving additional qualities such as nail ability and lessened the dead weight. It is lighter than the conventional concrete with a dry density of 300 kg/cum up to 1840 kg/cum; 87 to 23% lighter?

Light Weight Concrete Blocks

The strength of Lightweight concrete is roughly proportional to its weight and its resistance to weathering is about the same as that of ordinary concrete. Light weight concrete differs from heavy concrete by its use of naturally light weight materials (aggregates) such as pumice (volcanic stone) in place of the sand and gravel used in ordinary structural concrete mixes. There exists a whole range of light weight concretes "which have a density and compressive strength very similar to wood. They are easy to work with, can be nailed with ordinary nails, cut with a saw, drilled with wood working tools, and easily repaired. It is considered that ultra-light weight concrete is one of the most fundamental bulk building materials of the future.

Lightweight concretes can be categorised into three groups:

• No Fines Concrete
• Lightweight Aggregate Concrete and
• Foamed /Autoclaved Aerated Concrete (AAC).
• Lightweight aggregate concrete
• Lightweight aggregate concrete can be produced using a variety of lightweight aggregates. Lightweight aggregates originate from either:
• Natural materials, like volcanic pumice.
• The thermal treatment of natural raw materials like clay, slate or shale i.e. Leca.
• Manufacture from industrial by-products such as fly ash, i.e. Lytag.
• Processing of industrial by-products like FBA or slag.

The required properties of the lightweight concrete will have a bearing on the best type of lightweight aggregate to use. If little structural requirement, but high thermal insulation properties, are needed then a light, weak aggregate can be used. This will result in relatively low strength concrete.

Lightweight aggregate concretes can, however, be used for structural applications, with strengths equivalent to normal weight concrete.

Foamed Concrete

The benefits of using lightweight aggregate concrete include:

• Reduction in dead loads making savings in foundations and reinforcement.
• Improved thermal properties.
• Improved fire resistance.
• Savings in transporting and handling precast units on site.
• Reduction in formwork and propping.

Foamed concrete

Foamed concrete is a highly workable, low-density material which can incorporate up to 50 per cent entrained air. It is generally self-levelling, self-compacting and may be pumped. Foamed concrete is ideal for filling redundant voids such as disused fuel tanks, sewer systems, pipelines, and culverts - particularly where access is difficult. It is a recognised medium for the reinstatement of temporary road trenches. Good thermal insulation properties make foamed concrete also suitable for sub-screeds and filling under-floor voids.

Autoclaved aerated concrete (AAC)

AAC was first commercially produced in 1923 in Sweden. Since then, AAC construction systems such as masonry units, reinforced floor/roof and wall panels and lintels have been used on all continents and every climatic condition. AAC can also be sawn by hand, sculpted and penetrated by nails, screws and fixings.

Recycled Concrete

Concrete recycling is becoming an increasingly popular way to utilize aggregate left behind when structures or roadways are demolished. In the past, this rubble was disposed of in landfills, but with more attention being paid to environmental concerns, concrete recycling allows reuse of the rubble while also keeping construction costs down. (8) Concrete aggregate collected from demolition sites is put through a crushing machine.

Crushing facilities accept only uncontaminated concrete, which must be free of trash, wood, paper and other such materials. Metals such as rebar are accepted, since they can be removed with magnets and other sorting devices and melted down for recycling elsewhere. The remaining aggregate chunks are sorted by size. Larger chunks may go through the crusher again. After crushing has taken place, other particulates are filtered out through a variety of methods including hand-picking and water flotation.

Uses of recycled concrete

Recycled Concrete Used in Pedestrian Area

Smaller pieces of concrete are used as gravel for new construction projects. Sub-base gravel is laid down as the lowest layer in a road, with fresh concrete or asphalt poured over it. Crushed recycled concrete can also be used as the dry aggregate for brand new concrete if it is free of contaminants. Also, concrete pavements can be broken in place and used as a base layer for an asphalt pavement through a process called rubblization.

Larger pieces of crushed concrete, such as riprap, can be used for erosion control. With proper quality control at the crushing facility, well graded and aesthetically pleasing materials can be provided as a substitute for landscaping stone or mulch. Wire gabions (cages), can be filled with crushed concrete and stacked together to provide economical retaining walls. Stacked gabions are also used to build privacy screen walls.

Benefits of recycled concrete

There are a variety of benefits in recycling concrete rather than dumping it or burying it in a landfill.

• Keeping concrete debris out of landfills saves landfill space.
• Using recycled material as gravel reduces the need for gravel mining.
• Recycling one ton of cement could save 1,360 gallons (5.14 m3) water, 900 kg of CO₂.
• Using recycled concrete as the base material for roadways reduces the pollution involved in trucking material.

Admixtures

Admixtures are the materials other than the basic ingredients of concrete, cement, water, and aggregates. The use of admixture should offer an improvement not economically attainable by adjusting the proportions of cement and aggregates, and should not adversely affect any property of the concrete. An admixture should be employed only after an appropriate evaluation of its effects on the particular concrete under the conditions in which the concrete is intended to be used. It is often necessary to conduct tests on the representative samples of the materials for a particular job under simulated job conditions in order to obtain reliable information on the properties of concrete containing admixtures.⁽⁷⁾ Some of the important variants are;

Functions of Admixtures ⁽⁶⁾

The major reasons for using admixtures are:

• To reduce the cost of concrete construction
• To achieve certain properties in concrete more effectively than by other means
• To maintain the quality of concrete during the stages of mixing, transporting, placing, and curing in adverse weather conditions
• To overcome certain emergencies during concreting operations

Types of Admixtures ⁽⁹⁾

Fibres - FRC is exactly what it says, concrete containing fibres. Fibres are used to add strength to concrete, they are uniformly distributed and orientated at random to create a network of reinforcement and offer an alternative to steel reinforcement bars. There are two main types of fibre used today, steel and polypropylene (synthetic). Steel fibres are usually used to add strength to the concrete whilst polypropylene fibres increase pumpability over large distances and an increased resistance to fire.

Air Entrainments - Put simply, air entrainment is the addition of air to a concrete mix. Used primarily for freeze thaw protection. These bubbles in the concrete resulted in the very first air entrained concrete.

Accelerators - Is the practice of accelerating the standard set time of concrete. Adding sodium nitrate, calcium nitrite or calcium chloride to the cement are effective chemicals in this practice. However, it should be noted that adding calcium chloride into a concrete mix would cause problems by rusting the steel in reinforcement bars. When adding sodium top a mix it will increase the alkali content, which can compromise the concretes structural integrity.

Plasticisers and Superplasticisers - are essentially water reducers, with Superplasticisers being super high range water reducers. You would use this admixture to improve the workability of a concrete mix, particularly with high strength concretes. This is because high strength mixes have less water content, making them stiff and difficult to work. If this chemical sounds harsh on the environment you would be mistaken. The concrete industry uses a by-product of the paper industry, pop lignosulfonates. The products manufactured from the pop lignosulfonates are naphthalene and melamine.

Corrosion Inhibitors - increases the passivity of reinforcement and other metal materials within the concrete. Passivity is when a material becomes more resistant to environmental factors such as air or water, which can cause issues like rust that result in the compromised strength of the concrete. Corrosion inhibiting admixtures significantly reduce maintenance costs of reinforced concrete structures over the general service life of a structure.

Pumping Aids - are there to increase the pumpability of a concrete mix. This admixture acts as a lubricant to help concrete pumps cope with any issues that may arise during long distance pumping hauls. Problems can arise when poorly graded aggregates cause excessive friction by being flaky or elongated.

Most modern pumping aids are synthetic polymer based, more on specific modern types of pumping admixtures can be found here. Pumping aids are not just one-dimensional, they can also increase the workability of a concrete after travelling down a long pumping line.

Fly ash in concrete

Fly Ash is a by-product of the combustion of pulverized coal in electric power generation plants. When the pulverized coal is ignited in the combustion chamber, the carbon and volatile materials are burned off. However, some of the mineral impurities of clay, shale, feldspars, etc., are fused in suspension and carried out of the combustion chamber in the exhaust gases. As the exhaust gases cool, the fused materials solidify into spherical glassy particles called Fly Ash. ⁽¹²⁾

Fly Ash Concrete Blocks

The most prestigious projects of recent times have relied on fly ash concrete, including high-rise structures, dams, roads, nuclear power stations, bridges and tunnels. Indeed, it is hard to think about concrete construction without considering the use of fly ash. This has been based on sound engineering and economic benefits, although more recently the use of fly ash for improving durability has become an increasingly important consideration.⁽¹⁰⁾ Fly ash is a group of materials that can vary significantly in composition. It is residue left from burning coal, which is collected on an electrostatic precipitator or in a bag-house. It mixes with flue gases that result when powdered coal is used to produce electric power.

Most fly ash is pozzolonic, which means it's a siliceous or siliceous-and-aluminous material that reacts with calcium hydroxide to form cement. When Portland cement reacts with water, it produces a hydrated calcium silicate (CSH) and lime. Typically, fly ash is added to structural concrete at 15-35 percent by weight of the cement, but up to 70 percent is added for mass concrete used in dams, roller-compacted concrete pavements, and parking areas. Special care must be taken in selecting fly ash to ensure improved properties in concrete. (11)

Fly Ash Concrete - Testing

Advantages in Fresh Concrete

Since fly ash particles are spherical and in the same size range as Portland cement, a reduction in the amount of water needed for mixing and placing concrete can be obtained. In precast concrete, this can be translated into better workability, resulting in sharp and distinctive corners and edges with a better surface appearance. This also makes it easier to fill intricate shapes and patterns. Fly ash also benefits precast concrete by reducing permeability, which is the leading cause of premature failure. The use of fly ash can result in better workability, pumpability, cohesiveness, finish, ultimate strength, and durability. The fine particles in fly ash help to reduce bleeding and segregation and improve pumpability and finishing, especially in lean mixes. ⁽¹¹⁾

Advantages in Hardened Concrete

Strength in concrete depends on many factors, the most important of which is the ratio of water to cement. Good quality fly ash generally improves workability or at least produces the same workability with less water. The reduction in water leads to improved strength. Because some fly ash contains larger or less reactive particles than portland cement, significant hydration can continue for six months or longer, leading to much higher ultimate strength than concrete without fly ash.⁽¹¹)

General advantages of fly ash ⁽¹²⁾ 

• Fly Ash improves concrete workability and lowers water demand.
• Fly Ash generally exhibit less bleeding and segregation than plain concretes.
• Sulfate and Alkali Aggregate Resistance.
• Fly Ash has a lower heat of hydration.
• Fly Ash generally reduces the permeability and adsorption of concrete.
• Fly Ash is economical.

 Sustainable Concrete

Sustainability is important to the well-being of our planet, continued growth of a society, and human development. Environmental issues are playing an important role in the sustainable development of the cement and concrete industry. For example, if we run out of limestone, as it is predicted to happen in some places, then we cannot produce Portland cement; and, therefore, we cannot produce concrete and all the employment associated with the concrete industry goes out-of-business. ⁽¹⁴⁾ Concrete is one of the most widely used construction materials in the world. However, the production of Portland cement, an essential constituent of concrete, leads to the release of significant amounts of CO₂ , a greenhouse gas (GHG); production of one ton of Portland cement produces about one ton of CO₂ and other GHGs. The environmental issues associated with GHGs, in addition to natural resources issues, will play a leading role in the sustainable development of the cement and concrete industry during this century.⁽¹³⁾

Sustainable Concrete is a term given to a concrete that has had extra steps taken in the mix design and placement to insure a sustainable structure and a long life cycle with a low maintenance surface.

Environmental Criteria

For normal concrete, there is typically no consideration of the sustainable aspects when designing the material, as codes have not (until recently) contained specification of environmental or sustainable performance. Sustainable concrete should, therefore, be formed from the integration of sustainable knowledge and the traditional engineering knowledge.

The integration of sustainable knowledge will come from specification of sustainable performance for the concrete mixture; for example, specifying a certain level of CO₂ reduction will require inventory knowledge for calculating CO₂ emissions. Although sustainability contains a large number of aspects, it is most likely that the environmental performance will be considered more than others since current actions focus primarily on the environmental impact. Focusing on the environmental aspect only, most proposals for sustainable practice consider the reduction of CO₂ and the use of recycled and waste materials as the two primary environmental performances. Since Portland cement is the main source of CO₂, reduction scenarios typically focus on reducing the amount of Portland cement used in concrete, either by replacing cement with high volumes of fly ash (Malhotra, 1999) or utilizing super plasticizers to reduce the amount of mixing water and thus the amount of cement (Sakai, 2009). In the first case, fly ash acts as sustainable media, but in the second case there is no sustainable media; for both cases, the sustainable knowledge is CO₂ reduction, and engineering knowledge is then required to develop the proper mix proportions and procedures for producing concrete with the necessary performance.

 Decorative Concrete

Decorative concrete is the use of concrete as not simply a utilitarian medium for construction but as an aesthetic enhancement to a structure, while still serving its function as an integral part of the building itself such as floors, walls, driveways and patios. The transformation of concrete into decorative concrete is achieved through the use of a variety of materials that may be applied during the pouring process or after the concrete is cured, these materials and systems include stamped concrete, acid staining, decorative overlays, polished concrete, concrete countertops, vertical overlays.

Decorative Concrete designs are one of the hot new trends for concrete patios, concrete floors, entryways, countertops, pool decks and more. From expansive new homes with elaborate concrete driveways to budgeted one-room remodels showcasing a stunning, stained concrete floor, the attraction is continuing to grow when it comes to using concrete for decorating. Concrete is no longer plain, grey and boring, it is now thought of as a beautiful decorative element.

Decorative Concrete appears in myriad forms such as Stained Concrete, Stamped Concrete, Polished Concrete, Textured concrete, Coloured concrete etc.

Vacuum Dewatered Concrete

Floating Process

VDC is generally an application used extensively in concrete flooring options. Vacuum Dewatered Flooring, also known as VDF, is a special type of Flooring Technique to achieve High Strength, Durability, Longer Life, Better Finish and Faster Work. This type of floor is suitable for high abrasion & heavy traffic movement. The Vacuum Dewatered Flooring or VDF Flooring is a system for laying high quality concrete floors where the key is Dewatering of Concrete by Vacuum Process wherein surplus water from the concrete is removed immediately after placing and vibration, thereby reducing the water: cement ratio to the optimum level. Reduced water: cement ratio automatically leads to a noticeable improvement in almost each of the concrete properties.

Dewarting in Process	Decorative Concrete

VDF offers a solution to the problem of combining high workability with a minimum Water / Cement Ratio in case of freshly placed concrete. This is a process where excess water that is available for the workability is extracted from a certain depth of concrete by some mechanical means. The final water / Cement ratio before the concrete sets is thus reduced and as a result, controls the strength. It also imparts higher density, lower permeability, and greater durability with higher resistance to abrasion to the concrete placed with proper care and discipline.

Benefits & Features

• Increased Compressive strength by up to 60%  
• Reduced Cement consumption by 40% as no cement is required separately for finishing. 
• Increased Abrasion resistance by @ 60%
• Reduced Shrinkage.
• Minimizing dusting, crack formation
• Uniform homogeneous floor  with High flatness accuracy
• Increased wear resistance
• Earlier utilization and Reduced maintenance cost
• Lower water permeability due to increased density.
• Minimizes dry shrinkage and plastic shrinkage
• Controlled working Cycle
• Earlier start of finishing operation
• Fewer forms faster reutilization
• High early strength minimizes damage on newly cast floors

Roller Compacted Concrete (RCC)

As per ACI 207.5R-89, RCC is defined as concrete compacted by roller compaction. The concrete mixture in its unhardened state must support a roller while being compacted [using a roller, often a vibrating roller. Thus RCC differs from conventional concrete principally in its consistency requirement.

For effective consolidation, the concrete mixture must be dry enough to prevent sinking of the vibratory roller equipment but wet enough to permit adequate distribution of the binder mortar in concrete during the mixing and vibratory compaction operations.

Roller Compacted Concrete may be used in lieu of conventionally placed concrete in concrete gravity and arch-gravity dams. RCC can be placed as quickly as possible and its operations include as little manpower as possible.  RCC structures have been designed for a wide range of performance conditions, from low-strength more massive structures to high-strength less massive structures.

RCC has started its specialized applications in mainstream pavements such as Port, intermodal, and military facilities; parking, storage, and staging areas, streets, intersections, and low-speed roads. Now, RCC is used for any type of industrial or heavy-duty pavement. The reason is that it has the strength and performance of conventional concrete with the economy and simplicity of asphalt. Coupled with long service life and minimal maintenance, RCC's low initial cost adds up to economy and value.

The main characteristics like high strength, long-term durability and cost-effectiveness make RCC simple, fast, and economical. Roller Compacted Concrete pavements eliminate common and costly problems traditionally associated with asphalt pavements.

Mix Design

There currently exists several methods for proportioning RCC mixes for pavements; however, there is not one commonly accepted method. The main RCC proportioning methods include those based on concrete consistency testing, the solid suspension model, the optimal paste volume method, and soil compaction testing. Whichever method is employed, the goal is to produce an RCC mixture that has sufficient paste volume to coat the aggregates in the mix and to fill in the voids between them. Regardless of which proportioning method is used, it is important that an RCC mixture meet the following requirements: 

• The fine and coarse aggregates should be chosen to achieve the required density and to provide for a smooth, tight surface
• The moisture content should be such that the mix is dry enough to support the weight of a vibratory roller yet wet enough to ensure an even distribution of the cement paste
• The cementitious materials used should meet the required design strength requirements at minimal cost with sufficient paste volume.

Translucent Concrete

Innovations in the field of concrete to make it strong, durable, intelligent and beautiful have now reached new heights. The world's first media wall featuring light transmitting concrete has now been built in Aachen, Germany. The 30 meters wide and 4 meters high wall, which includes 136 panels was erected at the RWTH Aachen University campus, is now open to public.

This visual extravaganza designed by Aachen-based architects Carpus & Partner, establishes a new benchmark in the realm of intelligent and ventilated facades.

The world’s first media façade featuring LUCEM light transmitting concrete panels was unveiled on 6 December 2012. Concrete panels of size 150 cms x 50 cms containing optical fibres were used to build the wall façade. Each panel fitted with colour-changing technology, with the colours becoming brighter approximately one hour before sunset. The LED-panels are controlled using an internet-based DMX technology system, with each panel containing 3% optical fibres. The light panels are made with red, green and blue chips giving us an option to play with more than 16 million colours. Each individual panel can be controlled independently and thus making the entire façade, a large display screen.

According to LUCEM, the panels can have various application areas including 'facades, interior walls, claddings and flooring systems. There are currently three different types of LUCEM ®Lichbeton panels, which offer different effects and aesthetics for the user. With the LUCEM® Label panels, light transmitting fibres are arranged individually so that clients can display design logos, images, names, signatures and icons on the panels.

LUCEM® panels come in polished, sheen or matte surfaces and can be designed individually. The density of the form in which the fibers are placed creates a compelling visual aesthetic. There are three different types of LUCEM® Lichbeton panels that provide different aesthetics depending on the purpose. With LUCEM® Label panels, light transmitting fibers can be arranged individually so that clients can display design logos, images, names, signatures and icons on the panels.

Pervious Concrete

Pervious concrete is a special type of concrete with a high porocity used for concrete flat work. It allows water to pass through for drainage, yet it maintains its strength. Possible uses include pedestrian walkways, parking lots, drainage structures and lakeside homes.

Pervious Concrete, also known as no-fines or low fines concrete, pervious concrete is a mix of Portland cement, coarse aggregate, water and admixtures. Because there is little or no sand in the mix, the pore structure contains many voids that allow water and air to pass through. It typically has a voids content of 15% to 35%. This ensures that the concrete has the unique ability to allow storm water to pass through its mass into the ground underneath. Pervious concrete offers significant environmental benefits as it reduces the requirement for drainage facilities. Further it facilitates the recharge of ground water and the filtration process purifies the water as it percolates below.

Building owners are realizing better land utilization and LEED credits with pervious concrete parking lots. Pervious concrete applications can be used as an alternative to complex drainage systems and water retention areas reducing storm water runoff.

Ultra High Performance Concrete (UHPC)

First developed in the early 1990’s by Bouygue’s laboratory in France, UHPC (also called Reactive Powder Concrete  RPC) consists of a special concrete where its microstructure is optimized by precise gradation of all particles in the mix to yield maximum density. At the level of maximum compressive strength of concrete, the coarse aggregate becomes the weakest link in concrete. In order to increase the compressive strength of concrete even further, the only way is to remove the coarse aggregate. This philosophy has been employed in RPC. It is a material which can resist direct primary tensile stresses and having the potential to structurally compete with steel.

UHPC is a high-strength, ductile material formulated by combining Portland cement, silica fume, quartz flour, fine silica sand, high-range water reducer, water, and steel or organic fibres. The material provides compressive strengths up to 200 MPa and flexural strengths up to 50 MPa.

The materials are usually supplied in a three-component premix: powders (Portland cement, silica fume, quartz flour, and fine silica sand) pre-blended in bulk-bags; super-plasticizers; and organic fibres. The ductile behaviour of this material is a first for concrete, with the capacity to deform and support flexural and tensile loads, even after initial cracking. The use of this material for construction is simplified by the elimination of reinforcing steel and the ability of the material to be virtually self placing or dry cast.

The superior durability characteristics are due to a combination of fine powders selected for their grain size (max. size 600 microns) and chemical reactivity. The net effect is a maximum compactness and a small, disconnected pore structure leading to very low permeability and very high durability.

Self-curing Concrete

It is very well known that hydration of cement (which leads to gain of strength in concrete) occurs in the presence of moisture and to ensure the hydration of almost all particles of cement, it is essential to make available the moisture for a longer period. The mixing water tends to move from inside the body of concrete to the surface during hydration primarily due to the heat generated in the interior of concrete. Non availability of water may also lead to autogenous deformation and early micro-cracking.  Adding more water during mixing increases segregation, bleeding, porosity and reduces strength. Thus external curing is resorted to. Several methods like water ponding (where possible), covering with wet hessian/ gunny bags, plastic sheets, curing compounds etc., are used to  create a barrier for evaporation of water. It is known that in many cases the curing is not easy (viz. tall vertical surfaces, inaccessible places etc.) and in many other, curing is simply neglected leading to serious problems.

In order to mitigate this problem, efforts are on to find methods of reducing (if not avoiding) the necessity of external curing. This is being attempted by a process known as Internal Curing or Self Curing of concrete. ACI states, “Internal curing refers to the process by which the hydration of cement occurs because of the availability of additional internal water that is not part of the mixing water."  This is enabled by creating what can be called as internal reservoirs of water in the form of saturated porous aggregates (viz. light weight aggregates), superabsorbent polymers, saturated wood powders/fibres etc. Super absorbent polymers are a group of polymeric materials that have the ability to absorb a significant amount of liquid from the surroundings and to retain the liquid within their structure without dissolving. The most common application of these polymers is in super absorbent disposable diapers!

A few water-soluble chemicals (like polymeric glycols) are also available which can reduce the water evaporation from within the hydrating concrete creating self curing conditions.

Important applications of this concept of self curing would be concrete pavements, precast concrete operations, parking structures, bridges, projects where high performance/high strength concretes are used and architectural concretes. 

Self Healing Concrete

Autogenous healing is the natural process of crack repair that can occur in concrete in the presence of moisture, and the absence of tensile stress. The repair is enabled by a combination of mechanical blocking by particles carried into the crack with the water and the deposition of calcium carbonate from the cementitious material.

Autogenous healing has practical applications for closing dormant cracks in a moist environment, such as may be found in mass structures and in water retaining or watertight structures. It is said that cracks up to 0.2 mm wide will autogenously seal within 28 days; cracks up to 0.1 mm will seal within 14 days.

Victor Li's of Michigan University claims to have developed a self-healing concrete which is based on a material he came up with in 1990 called Engineered Cementitious Composite. He and En Hua Yang improved on this and came up with what is famously known as “bendable concrete”.  It has some of the same ingredients as Portland cement, except the coarser bits of the mix are replaced by microfibers. When the composite is stressed, it bends without fracturing. If it does crack, the cracks tend to be less than 50 microns wide--thinner than a human hair. These tiny cracks have the ability to heal themselves.

Some researchers have laced the concrete with bacteria spores that secrete calcium carbonate to fill the cracks and pores, while others embedded glass capillaries with a healing agent, but the process of filling the capillaries with the agent is long and tedious. Henk Jokers of Delft University of Technology in Delft, the Netherlands is trying packing the concrete with bacteria that use water and calcium lactate "food" to make calcite, natural cement. To keep the spores from activating in the wet concrete mix, and to keep them and their calcium lactate food from affecting the quality of the concrete, Jonkers and his colleagues first set both into ceramic pellets 2 to 4 millimetres wide and then added them to the concrete. Only when tiny cracks form in the concrete - opening up the pellets - and water seeps inside will the bacteria activate and begin to consume the food that has also been freed. As they feed, they combine the calcium with oxygen and carbon dioxide to form calcite – essentially pure limestone.

References:

• seminarprojects.com
• Reference: seminarprojects.com
• civil-resources.blogspot.in
• www.aggregateresearch.com
• www.concretecentre.com
• www.ce.memphis.edu
• theconstructor.org
• www.concreterecycling.org/
• www.readymixonline.co.uk
• www.indiamart.com
• precast.org
• www.ashgroveresources.com
• ascelibrary.org
• www4.uwm.edu
• management.kochi-tech.ac.jp
• wiki.answers.com
• Improving Construction Efficiency & Productivity With Modular Construction Modular Building Institute.
• Advances in Concrete Technology- Nayak and AK Jain
• Published articles in Built expressions

 PART 2- ROLE OF EQUIPMENT IN CONSTRUCTION

Indian construction industry being the second largest industry after agriculture has been contributing nearly 8 percent GDP over many years. This industry is also highly labour-intensive and provides direct and indirect employment to millions of people in the country. The thrust on infrastructure development and rapid urbanization are leading to high demand for real estate construction. Due to which, mechanization in construction industry has become inevitable in the present scenario. In the last few years, mechanization has grabbed a major attention!

Onsite mechanization in the last few years has taken construction to a new echelon all in all. A plethora of advantages the construction industry has witnessed with the adoption of mechanization. Speed of work has increased, the large quantity of material handling with equipments have paved in way to giving scope to larger size of the projects. High quality standards can be maintained with optimum use of material, manpower and finance and finally, less dependency on labour. 

Recent report by Synergy Property Development Services, a project management consultancy confirms that the labour shortage in the sector will drive the industry towards large-scale mechanisation, project management, and pre-cast or prefab technology and it is predicted that heavy equipment such as batching plants, tower cranes, hot plant mixers, earth moving equipment, stone-crushers, excavators, and soil compactors will come into demand in order to bring down construction times and, therefore, reduce cost overruns.

One reason why mechanisation has not been very widespread thus far is because of its high costs against the easy availability of cheap labour. However, as housing and infrastructure projects get larger, greener and more quality-conscious; and as project timeframes get tighter; manual labour is likely to be increasingly replaced by mechanisation and prefabrication. Metros now have skyscrapers while several thousand kilometres of expressways and highways are being laid across the country with foreign and public funding. All this requires sophisticated equipment both for construction and to meet project and quality deadlines.

Today's building construction projects are highly mechanized and becoming more so every day. With the growing industrialization of construction, there is a shift to offsite prefabrication of structural and finish elements that are then installed or assembled rather than produced on site. Consequently, production equipment is being replaced on the construction site by transportation equipment. Material handling and lifting equipment now dominates building construction sites more than ever before and constitutes the critical element in achieving productivity.

The mechanization has crept in all areas of construction such as highway projects, irrigation and power plants.  A whole variety of equipment is used at a construction site for various functions including material handling; concreting and horizontal movements are the main areas where mechanization has made a lot of difference. Some of them are heavy equipment that needs a specialist to operate them while some are simple utility equipment to make things easier.

Some of the equipments have truly made construction a truly mechanized process:

• Excavating and Earth-moving equipment
• Hauling equipment
• Hoisting equipment
• Conveying equipment
• Aggregate and concrete production equipment
• Pile-driving equipment
• Tunnelling and rock drilling equipment
• Pumping and dewatering equipment
• Excavating and Earth Moving Equipment

In any construction project, earth related operations can be listed as under;

Excavation, transportation of excavated earth, placement, compacting, leveling, dozing, grading and hauling are main process of any earth related operations would include. Back hoe, bulldozer, loaders and power shovels are commonly used excavating equipments.

The bulldozer is one of the most commonly used pieces of earthmoving equipment. It has a number of applications, from clearing and grubbing to site maintenance. In addition, there are several attachments that increase the versatility of the bulldozer. A bulldozer is a tractor that has a blade attached to its front. The tractor is mounted on either crawlers or wheels (actually, a wheel-mounted bulldozer is usually just a loader with a bulldozer blade attached, and is known as a Turner Dozer). Bulldozers are commonly classified based on these mountings.

Backhoes are typically used in trenching because they can excavate to a considerable depth below their base. This characteristic also makes them useful for work such as channel excavation, because the excavation can be done while the tractor remains on dry land. The backhoe, as equipment specialized in excavation consists of a boom, dipper stick, and bucket mounted on a tractor.

A loader is a heavy equipment machine often used in construction—to load material (such as asphalt, demolition debris, dirt, snow, feed, gravel, logs, raw minerals, recycled material, rock, sand, and woodchips) into or onto another type of machinery (such as a dump truck, conveyor belt, feed-hopper, or railcar).

Earth Compaction Equipment

Compaction equipment is used to increase the density of sub-base, base, and pavement materials. By applying weight to a material, the size of the spaces between individual particles will be decreased. This will result in a higher density for the material, which will make it more stable under a load.

Steel Wheel roller or smooth wheel roller come in handy for the compaction of sand, gravel and mixtures of sand and gravel. During compaction, material can accumulate on the surface of the steel wheel, possibly resulting in uneven compaction. To prevent this, rollers are equipped with scraper bars and sprinkler devices. Pneumatic-tire Rollers and Sheepsfoot Rollers are also widely used as earth compaction equipments.

Manually operated compactors are comparatively smaller equipments. They are used in areas where it is not possible to use a full size compactor. This includes applications such as compacting, compacting soil around a footing, or working in areas where large equipment might cause damage to adjacent structures or property.

Material handling equipments

Cranes that are categorized as material handling equipment reduced the dependency on labour in a big way. The efficiency, with which materials get handled on site and flow from one location to the next, plays a vital role in improving the productivity. The ability to handle construction material safely is vital to the proper functioning of any construction jobsite. Proper planning and identifying the mode of material transportation will not only reduce the risk factor but also increases the speed of construction.

Different types of equipment ranging from Tower Cranes to Lifting Hoists to simple site fabricated systems using electrically or mechanically operated winches can be adopted. They are frequently used for shifting of concrete, masonry blocks, labour, reinforcement and many other miscellaneous materials.

The construction equipment that falls under the term “cranes” represents a broad class of machines. The typical crane is used to lift and place loads. Modifications on the basic crane structure allow it to be used for other activities such as dredging and pile driving.

Pile driving equipment

A pile is a structural member that is driven into the ground to provide support for a structure. Piles are made from timber, concrete, or steel, and come in a variety of shapes and sizes. They can be driven into the ground vertically or at an angle. The material, size, and angle of the piles used on a Project are determined during the design phase. These characteristics will impact the type of pile driving equipment that the Contractor uses.

A kind of ground treatment for strengthening the ground soil and makes it capable of supporting the load of building is called piling. It involves the driving of pile into ground below the ground level. Generally, concrete piles, timber piles, steel piles and bored piles are used to make the soil stronger for holding the weight of a building. Piles are installed by a special pile driving device known as a pile hammer. These hammers come in different types that includes, Drop hammer, Single acting hammer, Double-acting hammer, Diesel hammer and Vibratory hammer

Hoisting Equipments

Big projects such as, construction of dams, industrial buildings etc. require extensive use of hoisting equipment. Hoisting equipment includes jacks, winches, chain hoists and cranes. Hoisting is a process of lifting a weight from one location and moving it to another location which is at a reasonable distance.

These equipments are used for lifting the loads, holding them in suspension during transfer from one place to other and placing them at designated location. Some of the commonly used equipments include:

• Pulleys
• Chain hoists
• Winches
• Cranes

Concrete Equipment

The role of concrete equipment plays a very vital role in the construction industry and they vary from simple 10/7 mixers to complicated, computerized batching plants. Hand fed tilting mixers, Loader fed tilting drum mixer, Reversing Drum mixers, Transit Mixers, Concrete dumpers, Concrete Pumps have been useful in the entire concrete production involves batching, mixing, handling and transportation, placing, finishing curing as per the desired specifications.

Bar Bending and Shearing Machines

The cutting and bending of steel is one of the most important activities in any kind of construction or infrastructure projects. This could be done on site manually or mechanically. In the traditional method of cutting and bending, there is a possibility of inaccuracies creeping in. This is avoided by using Cutting and Bending machines. Reinforcement bars of various diameters (ranging from 6 mm to 40 mm) are cut and bent as per the bar bending schedule. We find bending and cutting machines separately in the market while there are also machine performing dual duties. The machine usually consists of electrical panel board, limit switch, emergency stop and indicator. Different dies are provided for different sizes of bar. Skilled and trained operators are needed to operate these machines.

Conclusion

There are several other construction equipments used in the construction industry that are beneficial and help us in achieving optimum performance. The choice of using suitable machinery depends upon the awareness of availability of such machines in the market. Several tools like concrete chippers, hacking tools, grove cutting machines, shotcrete equipment, grouting pumps, wagon drilling equipment, Dewatering pumps etc to be considered while planning a fast track project.

At this juncture, India is on extensive road-building mode coupled with increasing labour shortage, strict project deadlines. There is a huge real estate demand due to rapid urbanization in recent years that has allowed to high demand for greater level of mechanization and quality in road construction and concrete segments. As a result of which, demand for sophisticated mechanization in these segments has increased substantially and the trend is likely to continue over the coming years too.

PART 3- EMERGING TECHNOLOGIES IN CONSTRUCTION

The rapid pace of urbanisation owing to the rural–urban migration is putting a strain on the urban infrastructure in cities. As urban development takes place, a growing concern for India’s urban planners is the massive urban housing shortage plaguing the country. But as things stand, affordable housing remains a challenging proposition for developers. Issues continue to persist in land availability and pricing, project approval processes and other areas which make low cost housing projects uneconomical for private developers.

With such an urgent need, construction industry is already stumbled with various impediments including unavailability of urban land, rising construction costs, lack of skilled manpower, financing constraints for low-income groups, archaic government laws and unclear guidelines. At the grass root level, even in the construction process itself has to brave certain challenges too--usage of traditional materials and dependence on manpower intensive traditional construction practices, which are slow and highly dependent on skilled labour workforce, which is already in scarce. Hence, to meet the massive housing shortage, the need has raised to adopt new construction methodologies such as monolithic construction, precast technology and pre-engineered buildings. These technologies are viable right from mass housing to natural disaster prone conditions of geographies. Leveraging innovative and low-cost technologies such as precast, monolithic construction and pre-engineered buildings builders can gain on higher efficiency and lower labour cost fronts. In Europe and Middle East, the use of these technologies have proven to be a major cost saving and man hours over conventional methods.

Monolithic Construction

In a scenario when developers are constantly exploring all possibilities to improve speed of construction to cater to the present and future housing requirement for the urban poor in India, Cast-in-Situ Monolithic Reinforced Concrete Construction has emerged as an advanced technology of the recent times. It provided an integrated solution to the problem of large-scale residential housing development. It is widely recognised as one of the most economically and technically feasible solutions to the prevailing problem of building cost-effective, durable and earth-quake-proof housing on a mass scale, quickly and effectively.

A Monolithic structure is one in which all the components of a building, like walls, slabs, staircases, sunshades etc. are cast together with a homogenous material –Concrete. This construction system uses a formwork system that allows the contractor to cast foundations, walls, and ceilings according to a pre-defined cycle. It combines the speed; quality and accuracy with the flexibility and economy of in-situ construction. The result is a reinforced concrete structure, the surfaces of which are of sufficiently high quality to require only minimal finishing for direct decoration.

Essentials of Monolithic Construction

There are two important factors. Well designed ready mix concrete to ensure desired strength for early deshuttering and a well designed formwork system to allow speedy handling. While a well designed ready mix concrete is achievable, the real challenge is to decide on a formwork systems available. The forms are lighter than most other formwork systems.

The wall forms can be removed within merely five to eight hours. Each set of forms can be used up to two hundred times, provided it is properly maintained and serviced. This cycle can be repeated following a thorough overhaul of the formwork components. These forms are of high strength and flexural rigidity fewer nuts and bolts are used to join the constituent parts of the formwork system.

The technology of monolithic construction can be nominally divided into 3 main stages:

• Assembly of special formwork forms, resembling the contours of future structural unit;
• Reinforcement installation;
• Concrete pouring.

After the concrete hardening a structural unit  is formed and all formwork elements are dismantled.

Advantages

• fast track construction
• variety of possibilities for architectural and planning concepts: creation of free layouts and designs with the broad spans and different ceiling heights;
• the walls executed on monolithic technology practically have no joints and, hence, there are no problems with junctions and  their hermetic sealing;
• good sound protection and thermal characteristics of buildings;
• erection of monolithic walls and overlapping of a smaller thickness reduces load on foundation and accordingly expenses for its erection;
• erection of buildings of different  functions and number of storeys as the frame of monolithic reinforced concrete resists heavy loads;
• Readily lends itself to quality control and assurance.
• Ensures a longer useful life.
• Costs substantially less than conventional methods.
• Easier cost control, and more accurate cost forecast

Precast Technology

Precast construction also known as mechanised construction started in India in early 1970s. Mass housing by precast construction was extensively practiced by Russia, Poland, Hungary, Germany etc., and was supported by the respective Governments. In Singapore, Hong Kong, China mass housing was promoted due to the benefits in speed of construction, limited skill requirement and high quality demand. In earlier days Indian government also supported many institutions and a few industries to design and develop precast products for housing. The popular precast building components developed were channel slabs, waffle slabs, light weight blocks, door frames, and architectural facades etc. Precast housing systems were not popularised due to high capital investment in manufacturing plant and lack logistics for lifting and transportation of elements and no unified approach on standardization of elements. The value engineering provided by mechanised speedy construction was never visualised as a major influencing parameter in awarding the contracts up to late 2010. Hence, not a few significant total precast building projects from architectural planning to total construction can be sighted in India. Currently some of the industries are producing the hollow core slabs, precast spun piles, wall units etc.

Pre-cast construction is gaining significance in Indian scenario in general and urban areas in particular. Pre-cast construction can be broadly classified in to three categories.

• Project Specific Pre-Cast
• General Pre-Cast for Sector Specific
• Precast for Non Structural Elements

While the first and last categories are very much prevalent in India for quite some time. The First Category is gaining more popularity with the rapid urban infrastructure growth in India.  The Non Structure Category is widely present but still to attract Major organized players. General Pre-Cast which is Sector Specific Such as Buildings, Power Distribution, Water Supply  etc., is available scattered in India.

Categories

Depending on the load-bearing structure, precast systems described can be divided into the following categories: Large-panel systems, Frame systems, Slab-column systems with walls  and, Mixed systems.

Large-Panel Systems

The designation “large-panel system” refers to multistory structures composed of large wall and floor concrete panels connected in the vertical and horizontal directions so that the wall panels enclose appropriate spaces for the rooms within a building. These panels form a box-like structure. Both vertical and horizontal panels resist gravity load.

Frame Systems

Precast frames can be constructed using either linear elements or spatial beam-column sub-assemblages. Precast beam-column sub-assemblages have the advantage that the connecting faces between the sub-assemblages can be placed away from the critical frame regions; however, linear elements are generally preferred because of the difficulties associated with forming, handling, and erecting spatial elements.

Slab-Column Systems with Shear Walls

These systems rely on shear walls to sustain lateral load effects, whereas the slab-column structure resists mainly gravity loads. There are two main systems in this category:

• Lift-slab system with walls

• Prestressed slab-column system

Architectural concrete

The architectural applications of precast concrete are extensive. With few limitations on shape and a wide range of finishes and mould textures at their disposal the designers can express their own style and give character to their designs. Architectural precast concrete is employed as decorative wall panels, window frames, stairs or feature walls (structural), non-structural wall panels, and in fact all exterior concrete that contributes to the visual effect of the building. This concrete can range from the lower cost plain panels to the more expensive textured or exposed aggregate faced units.

Sustainable Design

Precast concrete offers a number of benefits that make it environmentally friendly and also meet the goals of programs such as Leadership in Energy & Environmental Design. Precast concrete buildings can be designed for disassembly and adaptability, and are easily deconstructed for reuse at the end of a building’s life. Precast’s energy efficiency, reduction in materials, recyclability, reusability and ability for repurposing, along with minimal waste in the precast plant and on the jobsite, are keys to meeting environmental standards. In addition, with building codes requiring higher energy efficiency, integrated solutions using hollow core slabs for heating and cooling is a growing trend in building design that reduces energy consumption. With precast’s ability to aid in meeting LEED™ standards, other benefits such as thermal mass become more apparent to designers.

The use of fly ash, slag and other waste materials aid in reducing a buildings environmental footprint. Precast’s high durability produces buildings with a total service life that outpaces other systems or materials. Precast concrete demonstrates comparable environmental impact performance over alternative structures.

Why choose Precast

Before moving on to the crux of the advantages of choosing precast, is saving on the time aspect. This can be achieved with either on- or off-site construction providing the design team with a clear, well-organised production schedule for every project. Effective panelisation can also reduce material waste and save time.  Also, the production of precast concrete off-site, in a factory, means that construction sites are cleaner, quieter and safer. The installation of precast units is usually fast and efficient. Such efficiency helps to reduce the impact that construction has on surrounding areas. This social aspect of sustainability in precast is therefore a major benefit - helping to improve construction’s reputation with the public.

PEMB-Pre Engineered Metal Buildings

‘Pre-engineered Metal Building System-PEMBS’ is widely accepted across the globe as an efficient alternative to conventional buildings. It is the most affordable and flexible building system ideal for Industrial, Institutional or commercial application. The system offers excellent features such as speed, quality, strength and value making it the most preferred building system in the world.

All pre-engineered structures are designed structures, fabricated to conform to the specifications of the end user. The advantage of pre-engineered structures is that they are factory-built and designed to be erected in the shortest possible time. Each pre-engineered structure is shipped as a complete building kit including all the necessary materials and instructions to erect it. Technological advancements in design and construction mechanisation over the past few years have immensely contributed in achieving faster and safer completion of projects. Advent of Pre-engineered Buildings as a system is one such revolution. Though its origin can be traced back to 1960’s its potential has been felt only during the recent years. Pre-Engineered system of buildings use a combination of built-up sections providing basic steel frame work which subsequently are complimented with various options for covering roofs and walls. Roofs can be single skin sheeting with or without insulation and walls can be cladded or bricked. The concept is designed to provide a complete building envelope system which is air tight, energy efficient, optimum in weight and cost, and custom designed keeping the utilisation, a priority.

 Being a versatile building system, it can be fitted with different structural accessories including mezzanine floors, canopies, fascias, interior partitions etc and can be finished internally to serve any required function together with distinctive aesthetics architecturally. It is most suitable for any low-rise building and offers numerous benefits over conventional buildings.

Pre-engineered buildings are generally more advantageous in case of low rise buildings in terms of constructability, economy and ease of construction. However the maximum eave heights can go up to 25 to 30 metres. PEB system can be easily adopted in case of Warehouses, Factories, Workshops, Offices, Gas Stations, Vehicle Parking Sheds, Showrooms, Aircraft Hangars, Metro Stations, Schools, Recreational, Indoor Stadium Roofs, Outdoor Stadium Canopies, and Platform Shelters and many more such structures.

PEMB versatility

Time is the essence of any project and this is where PEMBs score over any other conventional building system. PEMBs have many advantages over conventional erection practices and are very well suited for a wide range of applications. These are faster to construct, are cost economical over life cycle as they are maintenance free, offer architectural flexibility, look pleasing. Pre Engineered Buildings are known for faster engineering and manufacturing of buildings, delivery and erection at sites. Though the time varies from project to project, typical time taken for completion of a regular size and complexity of project is 12-16 weeks. Due to low maintenance requirements, Life Cycle Cost of such buildings is typically lower than that of any other conventional Structure.

Pre-Engineered metal buildings use a predetermined inventory of raw materials that satisfy a wide range of structural and aesthetic requirements. The individual components required to make the PEMBs are pre-engineered with respect to their shapes, connection details and support arrangements. These results in faster design and detailing of the structure combined with speedy fabrication.

Primary Framing System

In conventional steel buildings, mill-produced hot rolled sections (beams and columns) are used. The size of each member is selected on the basis of the maximum internal stress in the member. The hot rolled section has a constant depth, many parts of the member (represented by the hatched area), in areas of low internal stresses, and are in excess of design requirements.

Frames of pre-engineered buildings are made from an extensive inventory of standard steel plates stocked to the Pre Engineered Building. Pre Engineered Building frames are normally tapered and often have flanges and webs of variable thickness along the individual members. The frame geometry matches the shape of the internal stress (bending moment) diagram thus optimizing material usage and reducing the total weight of the structure.

Secondary Framing System

Pre Engineered vs. Conventional

Pre engineered buildings are generally low rise buildings however the maximum eave height can go up to 25 to 30 meters. Low rise buildings are ideal for offices, houses, showrooms, shop fronts etc. The application of pre engineered buildings concept to low raise buildings is very economical and speedy. Buildings can be constructed in less than half the normal time especially when complemented with the other engineered sub systems.

Pre-Engineered Metal Buildings are making a great headway into Indian realty with ready to assemble knocked down sets. The demand for Pre-Engineered Metal Buildings is growing in all scales in India. The demand for construction attracts an investment of more than USD 500 billion in next few years. The Industry size of Pre-Engineered buildings is USD 0.38 billion and the current Pre-Engineered Metal Building manufacturing capacity is appox0.35 million tonnes per annum. The market potential for PEB is approx1.2 million tonnes per annum. The PEB industry in India is expected to grow, even considering the conservative estimate, at around 35% per annum.

Recapitulate

Emerging Technologies that can be adopted and shall find tremendous applicability in the times to come can be listed as under.

Construction

• Pre Engineered Buildings
• Pre-Cast Buildings
• Construction Equipment
• Fast Track Construction
• Tilt-up Construction
• Ground Freezing
• High Rise Buildings
• Soundless demolition Systems

New Generation Materials

• Bendable Concrete
•  Self Healing Concrete
•  Translucent Concrete
•  Electrified Wood
•  Bio Engineered Bricks
•  Sensitiles
•  Electrochromic Glass
•  Liquid Granite
•  Carbon Fibers
• Composites
•  Eco Bricks
•  Basalt Rods
•  Concrete Lumbers
•  Intelligent  Fixtures
•  Facades And Panels
•  Solar Films
•  Intelligent  Facades

Conclusion

Future Architects and Civil Engineers cannot restrict themselves just to the knowledge they have accumulated within four walls of a class room. They need to keep learning the Emerging Technologies and apply it on field. This presentation is an effort to make the readers stand face to face with the marvels of Emerging Construction Technologies. Opportunities to Civil engineers are galore.