A Concrete Mix Is Made Of 6 Parts Of Sand 5 Parts Of Cement And 4 Parts Of Stones: Fill & Download for Free

The natural earth track cannot withstand modern heavy traffic loads very satisfactorily because it lacks in strength and good riding surface. It is therefore, important to construct some structure in the form of pavements on the top of natural surface to enable it to support wheel load safety and to provide a good riding surface for a longer period.So properly constructed and maintained roads reduce the wear and tear of vehicles and also increase the speed of transportation. Therefore the construction of roads should be done properly according to the specification.1. Construction of Earth RoadsFirst of all sub-grade is prepared all the road surface is brought to the required camber and gradient.Then the surface is rolled properly and well wetted with water.Then a layer of about 10 cm thickness of graded soil is spread evenly.This layer of soil is rolled at optimum moisture content first with suitable roller and then finished with light roller.If a second layer is required to be laid, it should be laid in the same way as the first layer and rolled properly.Finally finished surface is watered for about 5 days for curing and no traffic is allowed in these days.2. Construction of Gravel RoadsFollowing steps are followed in the construction of gravel roads:First of all the sub-grade is prepared and the road surface is brought to the required camber and gradient. This prepared surface is then properly compacted.After compaction of the sub-grade, the mixture of gravel and clay is spread with more thickness at the center and less thickness towards the edges so that a required camber is provided. Clay in the mix acts as binder for gravel and sand.The gravel mix so spread is then compacted to the required camber. The size of gravel ranges between 6 mm to 35 mm. This surface is rolled with light roller till the required compaction is achieved.This compacted surface is then watered for 4 to 5 days for curing. During this period of curing traffic is not allowed to pass through the surface.After curing the road is opened to traffic but the water is sprinkled on the surface for further 10 to 15 days.Proper maintenance of the road surface should be done to keep it in working conditions for the traffic.3. Construction of Water Bound Macadam RoadsThe construction of water bound macadam roads we require course aggregates, screening and binding materials if necessary. Screening is used for filling voids in the aggregates. It is the residue of the same coarse aggregates. All these materials are stacked along the road side before its construction starts. The quantity of screening required per 100 sq.m of road surface is 30 cubic meter.The construction of water bound macadam roads is done in the following stages:Preparation of Sub-gradeAfter completing the earth work in embankment and cutting, the formation level is prepared. The Sub-grade is generally in the form of a trench having a thickness equal to the thickness of finished pavement. The sub-grade is prepared according to the camber and the grade of the road. It is then thoroughly compacted with road roller of weight not less than 8 tonnes. Before rolling, water is sprinkled on the sub-grade. Any low pot, if developed during rolling should be rectified and the surface brought to the required grade. If the soil is clayey, a layer of granular material like natural sand, moorum, gravel,literate or kankar should be spread with 10 to 15 cm thickness. Earthen Krebs along the road edge of 15 cm depth are also constructed to hold the road materials in proper position.Preparation of the Base Course of FoundationThe consists of 12 to 18 cm size boulder of broken pieces of stones, over burnt bricks, or brick soling. Care should be taken to keep minimum possible voids in hand packing of boulders. Voids are filled with small pieces of stones. The width of this course is kept 60 cm wider than the pavement width of road. The surface is then compacted with 10 tonne roller as the base course is laid with boulders.4. Construction of Bituminous RoadsFollowing types of bituminous roads are generally constructed:Surface painting roadSurface painting or surface dressing bituminous roads are used where traffic is small. For the construction of these roads, first water bound macadam road is constructed as described early. The surface is cleaned with wire brushes and brooms to make grooves in the joints of the surface. Then a layer of hot charcoal or asphalt is sprinkled over the surface. Over this layer, a layer of stone chippings is laid and rolled properly. This sets the aggregate into the binder. The thickness of this layer is between 2 to 3 cm. This surface dressing provides a thin, water proof and dustless surface of the road. About 2 kg of binder per sq.m. area of road surface is used and 1.8 to 2 cm of stone chipping are required per 100 sq.m. of the surface.In case of heavy traffic two layers or dressing are provided to the road surface. In second coat 1.5 kg of bitumen or tar is provided per sq meter of road surface.Bituminous Macadam roadThis type of road construction, the aggregates are spread in the prepared base. It is then rolled with roller and then the bituminous binder is sprayed on the surface which is penetrates to full or part depth of the compacted aggregate and thus binds them together.Bituminous Concrete roadsThese types of roads are used for heavy and mixed traffic. The base of this road is also water bound macadam. First of all the surface of water bound macadam is cleaned with wire brushes. Side Krebs of soil are formed to support the bituminous surfacing.The road metal of size of 6.3 mm is heated to a temperature of 180°. Then coarse sand of 1.3 mm size is also mixed in the road metal in the ratio of 1:2. Then bitumen or tar is heated at the same temperature as road metal mixed with road metal in a mixing plant. This hot mixture is spread on the cleaned surface of water bound macadam evenly and properly between the Kerbs in a thickness of 5 to 10 cm. This surface is then rolled with roller to proper camber and grade. Over this a sealing coat of coarse sand and bitumen is applied on this surface and surface is again rolled. This type of road surface provides a smooth surface and pleasant looking finish.Sheet Asphalt roadSheet asphalt provides a better type of surface. This type of road surface is applied to water bound macadam base or concrete base. It consists of 60 mm thick layer of asphaltic concrete over which 20 to 40 mm thick carpet of sand-bitumen-mix is laid.5. Construction of Cement Concrete RoadsThe cement concrete roads pavements may be constructed with or without sub-base. The concrete road slab perform the function of base course as well as wearing surface. The thickness of road slab varies between 15 to 20 cm depending upon the traffic load. For much heavy traffic loads reinforcement may be provided in the concrete road slab.Before laying the concrete slab, the sub-grade is prepared as usual. Then the cement concrete mix is laid in alternate panels, which are marked before laying the concrete. The panels may be kept 2.5 m to 3.5 m square. The completed surface of concrete slab is cured for 10 to 15 days before it is opened to traffic.

Scaffolding :Scaffolding is nothing but a fixed/movable platform which can be used for working at heights . They are usually used for activities such as plastering, painting, brick work at heights etc.There are various types of scaffolding :1. Tube and Coupler Scaffolding: Assembled using tubes and couplers at joints.2. Bamboo/Wooden Scaffold : It is made using bamboo materials. It is considered unfit for industrial use.3. Suspended Scaffold : It is used for cleaning glass at malls usually.Shuttering/Formworks can also be named based on the type of structural member construction such as slab formwork for use in slab, beam formwork, column formwork for use in beams and columns respectively etc.The construction of formwork takes time and involves expenditure upto 20 to 25% of the cost of the structure or even more. Design of these temporary structures are made to economic expenditure. The operation of removing the formwork is known as stripping. Stripped formwork can be reused. Reusable forms are known as panel forms and non-usable are called stationary forms.Timber is the most common material used for formwork. The disadvantage with timber formwork is that it will warp, swell and shrink. Application of water impermeable cost to the surface of wood mitigates these defects.A good formwork should satisfy the following requirements:1. It should be strong enough to withstand all types of dead and live loads.2. It should be rigidly constructed and efficiently propped and braced both horizontally and vertically, so as to retain its shape.3.The joints in the formwork should be tight against leakage of cement grout.4. Construction of formwork should permit removal of various parts in desired sequences without damage to the concrete.5.The material of the formwork should be cheap, easily available and should be suitable for reuse.6. The formwork should be set accurately to the desired line and levels should have plane surface.7. It should be as light as possible.8. The material of the formwork should not warp or get distorted when exposed to the elements.9. It should rest on firm base.Centering, or center is a type of falsework: the temporary structure upon which the stones of an arch or vault are laid during construction. Once the arch is complete, it supports itself, but until the keystone is inserted, it has no strength and needs the centring to keep the voussoirs in their correct relative positions. A simple centering without a truss is called a common centering. The cross piece connecting centering frames are called a lag or bolst.The centring is normally made of wood timbers, which was a relatively straightforward structure in a simple arch or vault, but with more complex shapes, involving double curvature, such as a small dome or the bottle-shaped flues of the kitchens of some Norman-period houses; clay or sand bound by a weak lime mortar mix could be used. The shaping of this sort of centring would probably be done by eye, perhaps with the help of a template and the stone or brick structure laid against it. On bigger work, like a 19th-century commercial pottery kiln, this was impractical. The structure would be built round a post acting as a datum, and each course of stonework would be set at a distance from the datum as measured by a stick or string.

The need for innovation in the construction industry has long been stressed from both within and outside the industry. Changes in global markets, increased customer expectations, and government pressure have all led to innovation becoming a key focus for the construction sector. There is increasing pressure on the construction industry to become more environ-mentally sustainable. As the construction industry is a major energy user as well as contributer to the greenhouse gas emissions and waste levels, the government is pushing hard to the construction sector to come up with more and more innovative technologies in concrete since concrete is the mother constituent of any construction.Developing and maintaining world’s infrastructure to meet the future demands of industrialized and developing countries has become necessary to economically grow and improve the quality of life. The quality and performance of concrete plays a key role for most of the infrastructure including commercial, industrial, residential and military structures, dams, power plants and transportation systems. Concrete is the single largest manufactured material in the world and accounts for more than 6 billion metric tons of materials annually. In United States, federal, state, and local governments have nearly $1.5 trillion dollars in investment in the U.S. civil infrastructure. The worldwide use of concrete materials accounts for nearly $780 billion in annual spending. The industrialized and developing world is facing the issues related to new construction as well as repair and rehabilitation of existing facilities. Rapid construction and long term durability are requirements on most projects. Initial and life-cycle costs play a major role in today’s infrastructure development. There have been number of notable advancements made in concrete technology in the last fifty years. Some of these advances have been incorporated in routine practices. But, in general, the state-of-practice has lagged far behind the state-of-art. This is particularly true for public sector projects. There is an increasing concern in most parts of the world that it takes unduly long time for successful concrete research products to be utilized in practice. Even though some advances have been made in quick implementation of new concrete technology, significant barriers to innovation and implementation remain. Continued coordination of ongoing inter- national research and educational pro-grams is needed.Numerous advances have been made in all areas of concrete technology including materials, mixture proportioning, recycling, structural design, durability requirements, testing and specifications. Throughout the world some progress has been achieved in utilizing these innovations but largely these re-main outside routine practice. The high performance concrete (HPC) for transportation structures, e.g., bridges and pavements, are gaining wider acceptability in routine practice. HPC provides enhanced strength and durability properties and contributes towards long lasting structures and pavements. The constructability can also be enhanced by proper mixture proportioning and testing. Most HPC mixture include re-cycled materials e.g. fly ash, ground granulated blast furnace slag (GGBFS), Metakaolin (MK) or silica fume. The use of recycled materials in construction is an issue of great importance in this century. Utilization of fly ash and GGBFS in concrete addresses this issue. The replacement of Portland cement by fly ash or GGBFS reduces the volumes of Portland cement used is a major benefit. The reduction of Portland cement production will reduce carbon dioxide (CO2) emissions, reduce energy consumption and reduce the rate of global warming. Utilization of fly ash and GGBFS usually provides cost savings as well as improved concrete properties. The case histories discussed demonstrate the practical uses of supplementary cementitious materials. fly ash, GGBFS and silica fume for various types of bridges and pavements in wide ranging environ- mental conditions. The successful utilization of supplementary cementitious materials requires proper mixture pro-portioning, testing, placement and curing. Lack of widespread transfer of developed and available new concrete technology is a major problem in most countries. The practicing engineer’s (user) involvement through re-search, development and technology transfer stages is a key to successful application of new concrete technology in routine design and practice. The past experience has shown that successful technology transfer occurs when there is a pressing national need, champions of technology are created, champion and organizations involved persist, practical demonstrations of technology are conducted to demonstrate benefits, and regulatory requirements are implemented. The new concrete technology must fulfill a need to be successful. The user’s (owner/designer/construction engineer) involvement is vital to success. The user starts and ends the techno-logy process. Examples of successful concrete technology transfer efforts are discussed.Some Emerging Trends and Innovations in Concrete1. Green Cements2. Blended Cements3. High Performance Concrete (HPC)4. Smart Concrete5. Self-Consolidating Concrete (SCC)6. Use of Recycled Tire Rubber in Concrete7. Smog Eating Concrete8. Reactive Powder Concrete (RPC)9. Translucent Concrete10. Pervious Concrete11. Low Temp. Concrete Admixture12. Prepacked Shotcrete Admixture13. Steel-Free Concrete Bridge Deck14. Pavemend – Rapid Repair Products15. Suntreat – Concrete Restoration & Protection System16. Precast Inverted T Beam17. Conductive Concrete18. Corrosion Inhibitors for Reinforced Concrete19. Shrinkage Reducing Admixture for Concrete20. Mellose non-dispersible Under-water Concrete AdmixtureGreen CementsResearch has been carried out to develop non-clinker “green” cement using two industry wastes: cement kiln dust (CKD) and fly ash (FA). CKD contains partially calcined materials with some hydraulic and cementitious properties. It also has high alkali, chloride, and sulfate content, which may cause problems in cement performance.Blended CementsAn important concept of concrete technology innovation is blended cements. It makes use of industry by pro-ducts like fly ash and blast furnace slag, which otherwise would have required land for its disposal. The concept also gives lesser natural lime stone and lesser emission of CO2 to atmosphere. Common ternary blends includes, 50% Portland cement + 30% slag cement + 20% fly ash, to improve concrete performance, qualify for tax credits with re-cycled content.High Performance Concrete (HPC)Normal Strength Concrete (NSC) is heavy and lacks the required work-ability in some large concrete structures, such as high-rise buildings, bridges, and structures under severe exposure conditions. By increasing concrete strength and performance, the required thickness of concrete members and the cost of concrete structures can both be reduced. In the U.S., a major move to-ward HPC is underway, especially in the manufacturing environment of precast concrete. A major demonstration precast concrete bridge is under construction in Texas. High Performance Concrete (HPC) is the latest development in concrete. It is not just High-Strength Concrete (HSC) and has replaced HSC developed in the early 1980’s. HPC can be defined as a concrete made with appropriate materials (superplasticizer, retarder, fly ash, blast furnace slag and silica fume) combined according to a selected mix design and properly mixed, transported, placed, consolidated, and cured to give excellent performance in some properties of concrete, such as high compressive strength, high density, low permeability and good resistance to certain forms of attack.Smart ConcreteConcrete has been widely used for many years as a composite material for various types of structures. One of the weaknesses of concrete is that it cannot withstand tension which can cause cracks easily. There has been a huge demand to monitor concrete structures cracking and preventing them from propagating further. These efforts are important for timely repair, safety and long-term durability of critical structures. Non-destructive evaluations, such as attaching or embedding sensors into structures, have been used in many ways to accommodate the demand, yet the tests are considered expensive. Smart concrete was developed by Dr. Deborah D.L. Chung from State University of New York at Buffalo. Smart concrete is reinforced by carbon fiber as much as 0.2% to 0.5% of volume to increase its sense ability to strain or stress while still has good mechanical properties. By adding small amount of short carbon fiber into concrete with a conventional concrete mixer, the electrical resistance of concrete increases in response to strain or stress. As the concrete is deformed or stressed, the contact between the fiber and cement matrix is affected, thereby affecting the volume electrical resistivity of the concrete. Strain is detected through measurement of the electrical resistance. So, the smart concrete has the ability to sense tiny structural flaws before they become significant, which could be used in monitoring the internal condition of structures and following an earthquake.Self-Consolidating Concrete (SCC)It has brought about “Revolution” in the precast industry. No compaction required in SCC still it results in no segregation and shows excellent flow-ability. It eliminates vibration and yields smooth surface finish with no voids.Use of Recycled Tire Rubber in ConcreteMore than 250 million scrap tires weighing more than 3 million tons are generated each year in the United States (Naik and Siddique 2002). This is considered as one of the major environ-mental challenges facing municipalities around the world because waste rubber is not easily biodegradable even after a long period of landfill treatment. One of the solutions suggested is the use of tire rubber particles as additives in cement-based materials.Smog Eating ConcreteCement treated with titanium oxide. Photocatalytic reaction with UV light takes place, it accelerates natural oxidation process and decomposes pollutants to clear air. The reaction prevents bacteria and dirt from accumulating on a surface. It is easily removed with water or rain and keep concrete clean and white.Reactive Powder Concrete (RPC)Reactive Powder Concrete is an ultra high-strength and high ductility composite material with advanced mechanical properties. Developed in the 1990s by Bouygues’ Laboratory in France. It consists of a special concrete where its micro structure is optimized by precise gradation of all particles in the mix to yield maximum density. It uses extensively the pozzolanic properties of highly refined silica fume and optimization of the Portland cement chemistry to produce the highest strength hydrates. RPC represents a new class of Portland cement-based material with compressive strengths in excess of 200 MPa range. By introducing fine steel fibers, RPC can achieve remarkable flexural strength up to 50 MPa. The material exhibits high ductility with typical values for energy absorption approaching those reserved for metals.Translucent ConcreteIt changes the perception of concrete’s opaque mass, it is prepared with optical glass fibers.Previous ConcreteIt possesses little or no sands and has open pore structure. It Reduces storm water run-off.Low Temperature Concrete AdmixturePerforming construction processes under the cold weather condition requires construction engineers to plan operations considering low temperature condition. Especially, since the quality of concrete is sensitive to temperature, costly cold weather protection has been required to prevent damage due to in-appropriate weather environment. Concrete admixtures, mostly chemically, interact with the constituents of concrete and affect the properties and characteristics of the fresh and hardened concrete and its durability. The purposes of the admixtures include water reduction, high strength, corrosion protection, crack control, finish enhancement, flowability, etc. One of the interesting and useful purposes is protection against freeze. Accelerating admixture is to increase the rate of early strengthdevelopment or to shorten the time of setting, or both. Some of these accelerating materials have properties effective to avoid free-zing. Pozzutec® 20+ developed by Master Builders, Inc. is a multicomponent, non-chloride, water reducing and accelerating admixture formulated to accelerate concrete setting time and increase early and ultimate strengths across a wide range of ambient temperatures.Prepacked Shotcrete AdmixtureOver the past 10 years, the wet shotcrete method has become increasingly used in the repair of vertical and over-head concrete surfaces. This is due, in part, to advances inmaterials such as the introduction of silica fume (microsilica), fibers and super-plasticizers, which not only make shotcrete easier to place, but also improve its durability. Batching all these materials in the right proportions with sand and cement can be difficult, so many manufacturers have developed pre-packed shotcrete repair mortars to which con-tractors add only water. The prepacked materials simplify batching and provide more consistent quality. But packaging all the dry materials increases their cost. Gemite Products Inc. Amherst, NY developed prepacked products (called “concentrates”), which include all the admixtures but require contractors to provide their own sand and cement. The material costs of concentrates mixed with sand and cement are considerably lower when compared with complete packaged systems, while maintaining the same quality.Steel-Free Concrete Bridge DeckSteel-free concrete replaces rein-forced concrete in bridge decks and similar structures in marine environments and in northern climates having snow and ice. It is to eliminate the source of deterioration, the steel reinforcing bars in slabs exposed to deicing salts. Eliminating corrosion makes concrete deck slabs virtually maintenance free, which makes life cycle costs of steel-free concrete decks much lower than reinforced concrete decks. Shear connectors make the steelfree concrete deck composite with the steel girders that support it. Top flanges of girders attempt to displace outward when a truck drives across the deck. External transverse steel straps below the bridge deck and between the bridge girders prevent this outward displacement by providing a lateral restraining force to the girder and concrete deck. In res-ponse, compressive membrane forces develop in the concrete deck. Ultimate load can be greater than the load at which the same deck would fail if it were reinforced conventionally. In fact, the tension capacity of the steel straps in the steel-free deck replaces conventional reinforcing steel. The external steel straps can be inspected and maintained in a similar fashion to steel girders.Status:Two versions are available:1. The cast-in-place version2. The pre-cast Arch Panel version.The cast-in-place deck slab is now in the Canadian Highway Bridge Design Code (CHBDC), currently in the press. Japan is reviewing the technology. Meet- ing with American Association State High- way Transportation Officials (AASHTO) Code Committee is in progress.Pavement – Rapid Repair ProductsRepair of concrete continues to be a major maintenance item in the budget of many agencies. There are many circumstances in which a rapid repair is highly desirable. Ceracrete Technologies, Inc. (CTI) is a Richmond, Virginia-based small business. CTI focuses on the manufacture of commercial products for construction applications using non- hazardous inorganic recovered raw materials to replace conventional virgin raw materials. Ceracrete technology is a chemical bonding process that uses very high percentages of coal ash, municipal solid waste ash, foundry sand residue, dredge material, flue gas desulferization by-products, etc. to create rapid concrete repair products. The initial Ceracrete rapid concrete repair product, PaveMend, reaches 3670 psi at one hour and 4400 psi at three hours, easily qualifying it as a very rapid pavement repair material. The twenty eight day comprehensive strength levels operate at around 6,000psi. This ge-nerally means that field users can mix, pour/place and open the area to traffic quickly without special curing or protection measures.Suntreat – Concrete Restoration & Protection SystemReinforcing steel corrosion is the most common cause of failure of concrete structures. Once started, rebar corrosion cannot be stopped by simply waterproofing the surface of the concrete. The corrosion process is influenced and promoted by penetration of air, water, chloride and an acid environment. Surtreat can be used to prevent contamination and decomposition of concrete surfaces in hostile, chloride and acid containing environments. Surtreat is a proprietary concrete restoration and protection system. The system includes sequential application of chemical treatments to improve the properties of the deteriorating concrete and protect new structures. Surtreat proprietary chemical formulations penetrate into the concrete microstructure in liquid and vapor state to combine with the cement phase of concrete and deposit on steel components. Surtreat increases the ability of concrete to resist deterioration by in-creasing compressive strength, reducing permeability, inhibiting corrosion of the reinforcing steel components and improving concrete’s resistance to acid attack. Surtreat is used in the widest variety of applications and every owner /manager/operator of structures that include concrete components can benefit from the installation of Surtreat. All tests were conducted at the NASA Kennedy Space Center laboratories and in compliance with applicable ASTM Standard Test Methods. The evaluation methods employed by NASA specialists included measurement of halfcell potential, corrosion current and polarization resistance. The most direct measure of the corrosion rate, polarization resistance was increased by 300% after application of Surtreat. Halfcell potential and corrosion current measurements also reflect a significant decline in corrosion rates after application of surtreat corrosion inhibitors.Precast Inverted T Beam:Current systems are either costly or time consuming to erect and have limitations. Cast-in-place slabs have become too expensive and time-consuming due to extensive field formwork. Precast solid slabs aren’t economical for spans longer than 9 meters. I-girders with concrete deck slab topping can span longer than other systems, but require field formwork and significantly higher clearance. The new precast concrete product for short to medium span bridges was developed by the University of Nebraska. The Nebraska Inverted Tee (IT) can span up to 26 meters with a total structural depth of 725 mm. Most U.S. highway bridges have short to medium span lengths. And most bridges needing rehabilitation or replacement are short-span. A recently developed type of pre-stressed concrete beam is helping slash 20% off the weight of a bridge being built in Florida between the cities of Boynton Beach and Ocean Ridge.Conductive Concrete:Concrete has been used for many years as a composite material that has excellent mechanical properties and durability for construction. However, concrete is a poor electrical conductor, especially under dry conditions. Concrete that is excellent in both mechanical and electrical conductivity properties may have important applications in the electrical, electronic, military and construction industry (e.g. for deicing road from snow). Traditional methods can warm roads, but installation cost is high and the procedure is complicated. The principle behind it is the use of cement to bind together electrically conductive materials such as carbon fiber, graphite and ‘coke breeze’ – a cheap by-product of steel production – to make a continuous network of conducting path- way. The design formulation is based on the ‘electrical percolation’ principle by which the composite conductivity increases dramatically by several orders of magnitude when the content of the conductive phase reaches a critical ‘threshold’ value. Further increases in the conductive phase content boost composite conductivity only slightly. The design specifies an amount just over the threshold content, assuring high conductivity and mechanical strength as well as good mixing conditions.Corrosion Inhibitors for Reinforced ConcreteSteel corrosion in reinforced concrete structures has been a major problem across World today. Steel-rein-forced concrete structures are continually subject to attack by corrosion brought on by naturally occurring environmental conditions such as carbonation and the introduction of chlorides from sources such as salt water, deicing salts, and accelerating admixtures. Corrosion inhibitors available in the market can be mixed with ready mixed concrete or applied over the old concrete greatly reduces the overall corrosion activity (up to 65% reduction). Such products normally do not affect the properties of hardened concrete, such as compressive strengths, permeability, etc. One demerit of such pro-ducts are that it reduces corrosion but cannot stop it. A combination of this product with other protective systems is required if the level of durability of the concrete structure needs to more than double.Shrinkage Reducing Admixture for ConcreteConcrete shrinkage cracking is a common problem in all types of concrete structures, especially for structures and environments where the cracks are prevalent and the repercussions are most severe. Examples of these are bridge decks, parking garages, marine structures, containment structures, and high performance floors. A liquid shrinkage reducing admixture for concrete, developed by Grace Construction Products and Arco Chemical Company, that reduces significantly the shrinkage during concrete drying and potentially reduces overall cracking over time. The product can be easily dissolved in concrete mix water or dispersed in concrete during mixing. The admixture works by reducing the surface tension of the water, decreasing the force pulling in on the walls of the pores, resulting in a reduction of the shrinkage strain.Mellose Non-dispersible Underwater Concrete AdmixtureMany under-water civil engineering structures are affected not only by the presence of water or salt but also by water pressure; flow of water, and by the different material’s density. These factors could cause cracks, corrosion, and dispersion of concrete particles. Mellose is a viscose agent based on under water Cellulose (Hydroxy Propyl Methyl Cellulose). It is commonly referred to as a self-leveling agent that increases viscosity when is dissolved in water. It can be also described as an anti-wash-out concrete or non-dispersible concrete mixture. When Mellose is added, it prevents the loss of cement in the mortar and the separation of the concrete particles due to its increased viscosity. It combines first with the water than with the cement and the other concrete particles.Benefits include: Mellose increases the viscosity of suspended concrete but decreases the viscosity of flowing con-crete. Therefore, it increases the work-ability of the concrete, while there is no separation of its aggregates. It prevents the segregation of aggregates as well as the bleeding when used for under water construction. The product comes in the form of a powder that is added as a concrete admixture.Barriers are: Mellosecan not be used with Naphtalene Sulphonate because of chemical reactions.ConclusionThe cement and concrete industry has some inherent problems that re-strict the rate of adoption of new technologies to meet these challenges. These include:– Expensive manufacturing infra-structure– Low margin product– Proliferation of formula based technical standards– Industry culture tied to the orthodox belief that “it has always been done this way”These excuses will not impress an institutional investor that has a myriad of investing opportunities to choose from and is ready to move millions of dollars of capital to anywhere in the world at the press of a button. Neither is a user trying to overcome a problem such as cement shrinkage or corrosion or a politician who is being pressured by community concern over environ-mental degradation going to be Interested in the problems of the industry. Cement manufacturers need to ask themselves the same questions.Cements and concretes are changing to better meet the needs of customers ahead of the competition. The construction industry is conservative and the changes have been slow, such as the increase in thealite/belite ratio over the last twenty years and the incorporation of supplementary cementitious materials and various fibres. Cements and concretes probably need to change much more quickly to meet the challenges of the future. Challenging the traditional construction paradigm is robotics. In the USA and elsewhere in the world researchers are looking at using robots to literally print buildings. It is all quite simple from a software, computer hardware and mechanical engineering point of view. The difficulty is in developing new construction materials with the right Bingham plastic rheology so they can be squeezed out like tooth-paste; yet retain their shape until hardened. The main inhibiters to evolution in the industry are the formula-based app-roach to standards which grew out of the industrial environment of the early twentieth century. Standards are important for society’s protection, but to allow creativity and innovation, standards would be a much better servant to society if they were performance-based rather than formula-based.Source - Masterbuilder