Epoxy is a system based on a combination of RESINS & HARDENERS. On mixing ,the resins and hardeners chemically react to form a homogeneous rigid plastic material. The final product has good adhesive properties to bond well irrespective of the surface where it is applied. Epoxy floors are very strong , abrasion resistant and inert and can resist heavy traffic . The reason for this, is that epoxy flooring proves to last many years, and offers a durable, smooth, easy to clean, water impermeable and high-performance floor surface that is able to resist heavy loads.That is why epoxy floor is used in industrial facilities , sports complex, hospitals ,commercial areas etc.
THE TYPES OF EPOXY FLOORING A ) SELF LEVELLING EPOXY
SELF LEVELLING EPOXY
Self-levelling epoxy is applied over new, old, cracked, or damaged concrete floors to create a smooth, durable, and a levelled texture on the surface of the floor. Self-levelling epoxy floors comes with different colours and it can be used in commercial, industrial, and residential spaces. Upon application the epoxy resin coating forms a smooth and level texture on the surface of the floor .The resin has a tendency to “self-level” unlike applying the coating with a roller. The self levelling epoxy shall be used as flooring and floor coatings.
EPOXY MORTAR FLOORS
This flooring option is the most stringent epoxy floor system available for use. This epoxy floor is made up of 100% solid epoxies and graded or quartz sand. Mortar systems are ideal for floors that has to be highly chemically-resistant and has to negotiate a great deal of impact. This epoxy mortar can also be used to repair cracks and level a pitted floor prior to the application of self levelling epoxy floorings.
QUARTZ FILLED EPOXY FLOORS
Quartz epoxy flooring is a combination of a high-performance epoxy polymer resin and stained quartz grains. Normally 150 micron to 2 mm quartz sand is used in this type of flooring. This epoxy is used for decorative spaces that require sanitary and slip-resistant properties.
ANTISTATIC EPOXY FLOORS (ESDFLOORS)
ANTI STATIC EPOXY FLOOR
This is also called ESD floorings (Electro static Dissipate). For taking care of static hazards anti-static epoxy floors are applied.This epoxy floor typically holds a conductive compound that accumulates static electricity that dissipates any potential discharge. An anti-static solution is a highly recommended epoxy floor for spaces that contain flammable materials. This type of flooring is commonly used in electronic, chemical, or pharmaceutical manufacturing facilities, healthcare facilities, or any spaces that use flammable gases or liquids that bring a risk of combustible dust buildup.
EPOXY FLAKE FLOORS
EPOXY FLAKE FLOORS
This type of epoxy floor contains colored flake materials that are inserted in the epoxy to create a vibrant, multi-hued look. The flakes not only offer a seamless look but also provides each surface with subtle grooves to reduce any slips and falls. Epoxy flake floors come in an infinite variety of sizes, colors, styles, and textures that is customizable for any space. and used in sports venues , showrooms etc.
A false ceiling that uses metals either in the form GALVANISED IRON, STEEL OR ALUMINIUM is called metal false ceiling. Metal false ceilings are hard and durable and very easy to install. The ceilings are plank type (linear pattern) or grid type. These ceiling tiles can be removed and refixed easily after maintenance .These ceilings are economical and maintenance is very low.The self life of the metal ceilings are high compared with other false ceilings. For more details about false ceiling material types, refer our earlier article ” Materials for false ceiling – Top 7 false ceiling materials.
WHAT ARE THE DIFFERENT TYPE OF METAL FALSE CEILINGS?
a) Metal ceiling lay in type
b) Metal ceiling clip in type
c) Metal ceiling plank type
d) Open cell type
c) linear pattern C shape, U shape, R shape panels, 150 F panels
d) customise ceiling panels.
e) plain & perforated patterns
The thickness of a metal false ceiling mostly ranges from 0.4 mm to 1 mm. Thickness more than 1 mm is also available . The metal false ceiling is available in GALVANISED IRON , ALUMINIUM & STEEL types and the surface coating shall powder coated type which is used in aluminium and coil coated type used in steel false ceilings. The tiles used for metal false ceiling shall be square type or plank type or perforated type.
Following are the commonly used types of metal false ceiling.
In these type of ceilings the tiles are laid over a T grid (as shown in fig) which is hanged to the ceiling using hangers/ wires 3 to 4 mm thick. The tiles used can either be plain type or perforated type. The size of grids normally used shall be 600×600 mm. In this type of false ceiling the grids are exposed and can be seen from outside. Tiles are simply placed on a T-shaped runner (ref fig), generally between 10 and 25mm, and can be easily installed and can be demounted as individual tiles during maintenance of services like AC, fire fighting,electrical etc.
T grids for Tile Laying
This ceiling system comprises of Galvanized steel /Aluminium lay in tiles ( 600 mm x 600 mm) are manufactured out of 0.50-1 mm thick polyester coil coated steel 120 gsm zinc coating or powder coated with 50 microns polyester paint. Aluminium tiles are manufactured out of 0.70mm – 1 mm thick aluminium sheets and are powder coated using polyester paint 50 micron thick. The lay in tiles used can be plain tiles or perforated tiles. The perforations depend on the client requirement and manufacturer specifications.
Grid system for lay in tiles
Advantages of lay in tile Lay-in tiles are easy to remove and flexible for services related to electrical, fire ,plumbing and air conditioning facilities concealed in the false ceiling etc. They are also the easiest to move around when renovating and shifting office spaces.Installation and maintenance is very easy.The tile can be removed and remounted without any skilled assistance.The material is very durable and moisture and fire resistant.
In the clip-in system, ceiling tiles clip into the suspended runner. Due to their washability clip-in tiles see consistent use in industrial and commercial uses. Ceiling tiles clip on to the suspended grid and therefore conceal the grid from view. Manufacturers have their own unique clip-in systems that match their boards but generally they all consist of a spring tee runner from which boards clip on to.
Clip in tile grid system
This ceiling system comprises of Galvanized steel /Aluminium lay in tiles ( 600 mm x 600 mm) are manufactured out of 0.50/1mm mm thick polyester coil coated steel 120 gsm zinc coating or powder coated with 50 microns polyester paint. Aluminium tiles are manufactured out of 0.70mm-1 mm thick aluminium sheets with powder coated 50 microns polyester paint. The CLIP IN TILES used can be plain tiles or perforated tiles. The perforations depend on the client requirement and manufacturer specifications.
Conclusion
Metal false ceiling systems are durable and long lasting when compared with any other ceiling. They are easy to install and maintain and a very preferred choice for industrial, commercial and residential areas.
<p value="<amp-fit-text layout="fixed-height" min-font-size="6" max-font-size="72" height="80"><strong><span class="has-inline-color has-vivid-red-color">WHAT DO YOU MEAN BY CONCRETE?</span></strong>WHAT DO YOU MEAN BY CONCRETE?
<p class="has-text-align-justify" style="font-size:17px" value="<amp-fit-text layout="fixed-height" min-font-size="6" max-font-size="72" height="80"><strong>Concrete </strong>is a composite material, which is produced from a mixture of cement, aggregates (coarse & fine), water and sometimes admixtures in required proportions. These mixture consolidates in course of time to form a dense mass called concrete.Concrete is a composite material, which is produced from a mixture of cement, aggregates (coarse & fine), water and sometimes admixtures in required proportions. These mixture consolidates in course of time to form a dense mass called concrete.
INGREDIENTS OF CONCRETE
a) CEMENT
b) COARSE AGGREGATE
c) FINE AGGREGATE
d) WATER
e) ADMIXTURE
f ) AIR
WHY QUALITY CONTROL OF CONCRETE IS IMPORTANT ?
<p class="has-text-align-justify" style="font-size:17px" value="<amp-fit-text layout="fixed-height" min-font-size="6" max-font-size="72" height="80">Concrete is designed for a particular strength and the total structural stability is dependent on a good quality concrete. and that is why quality control is one of the most important aspects taken into account during the production of concrete . A little variation in water to cement ratio, ingredient proportioning, increase in slump etc will have a major impact on the desired strength of the structure which in turn affects the structural stability.Concrete is designed for a particular strength and the total structural stability is dependent on a good quality concrete. and that is why quality control is one of the most important aspects taken into account during the production of concrete . A little variation in water to cement ratio, ingredient proportioning, increase in slump etc will have a major impact on the desired strength of the structure which in turn affects the structural stability.
The quality control of concrete is done in three stages
a) Production stage ( On fresh concrete before placing)
b) Hardened stage ( hardened concrete specimens)
c) On structures ( tests done on the structures )
TESTS TO BE DONE ON FRESH CONCRETE
a) SLUMP TEST
b) Compaction Factor test
c) Vee- Bee Test
d) k slump test
e) Kelly ball test
f ) Flow table test
TESTS TO BE DONE ON HARDENED CONCRETE
a) COMPRESSIVE STRENGTH TEST (CUBE TEST)
b) WATER PERMEABILITY TEST
c) WATER ABSORPTION TEST
NON DESTRUCTIVE TESTS ON STRUCTURES
a) REBOUND HAMMER
b) UPV TEST
CONCRETE CORE TEST
SLUMP TEST
WHAT IS A SLUMP TEST?
Slump cone test is to determine the workability or consistency of a concrete mix prepared at the laboratory . Slump test shall be done on fresh concrete immediately after production at the batching plant to ensure the workability is in line with the design mix requirements and also at the pour point immediately after releasing from the transit mixture.
HOW DO YOU DO A SLUMP TEST (AS PER IS 1199:1959 REAFFIRMED 2013)
The nominal size of the aggregate shall be less than 38 mm . The cone has 20cm bottom diameter and 10 cm top diameter. The height of the cone is 30 mm. It consists of a 16 mm tamping rod having a length of 600 mm
The mould shall be filled in four layers, each approximately one-quarter of the height of the mould. Each layer shall be tamped with twenty-five strokes of the rounded end of the tamping rod. The cone is removed gently and the decrease in the height of concrete is the slump of concrete.
The slump tolerance shall be +/- 25 mm . If a design mix recommends a slump of 100 mm it cant go beyond 125 mm and go below 75 mm.
Concrete is the most widely used building material in the world. Concrete is perfectly inert, and has exceptional durability without the need for special maintenance.Concrete is basically a mixture of Portland Cement, water and aggregates comprising sand and gravel or crushed stone. In traditional construction sites, each of these materials is procured separately and mixed in specified proportions at site to make concrete. Ready mix concrete refers to a concrete manufactured from a batching plant according to customer/clients requirements & approved Design Mix and conveyed to the site in a ready to use condition. The concrete is conveyed through transit mixers of capacity ranging from 3 cum to 10 cum and more. 6 cum trucks are most commonly used. Batching plants are available in a wide range of capacities and types. ranging from 10 cum per hour to 125 cum/hr and some manufactures have much higher capacity plants.Most commonly used capacities are 30 cum, and 60 cum.
MAJOR CONSUMERS OF READY MIX CONCRETE
a) BIG CONSTRUCTION COMPANIES
They have there own batching plant set up along with expertise for installation, operation and maintaining it. These are used for there own use in construction sites depending on the feasibility in terms of space,quantity and economy.These plants are site specific and no commercial selling may not be permitted.
They setup there own plant in a specified location with all arrangements for stocking raw materials and commercially manufacture the materials as per customer/ client requirements.
COMMON METHODS USED FOR CONVEYING RMC
a) Transit mixed or truck mixed concrete
b) Shrink mixed concrete
c) Central mixed concrete.
a) Transit mixed concrete
The materials are batched at a central plant and are thoroughly mixed in the truck in transition. Transit-mixing separate water from the cement and aggregates and allows the concrete to be mixed instantly before using at the job site, Frequently partial mixing happens in transit and remaining mixing shall be done at site just before casting. This avoids slump loss, segregation, premature hardening, delays due to traffic jams, pouring delays due to equipment failure etc. The main disadvantage is the truck capacity is less compared to the one carrying fully mixed RMC.
b) Shrink mixed concrete
In shrink-mixed concrete, concrete is partially mixed at the plant to reduce or shrink the volume of the mixture and mixing is completed in transit or at the jobsite. The disadvantage is that concrete that has been remixed tends to set more rapidly than concrete mixed only once.
c) Central mixed concrete
The concrete is batched and completely mixed in a stationary mixer at the plant site before discharging it into the truck mixers. This can enhance the quality of concrete and cater higher production requirements.
HOW RMC IS MANUFACTURED
Ready mix concrete is manufactured from a centralised plant having facilities for storage of raw materials, Lab for inspection of raw material quality and concrete quality, having a series of batching plant/plants of different capacities etc.
RMC PLANT
The raw materials are checked to ensure compliance with relevant Indian standards so that there shall no be any quality issues to the end product. The raw materials are stored in separate areas on a firm ground. The RMC plant uses there In house design mixes most to the time. Customisation can also be done with the help of quality engineers. The design mixes are done in a way to give maximum quality with economy.
RAW MATERIAL BIN OF RMC PLANT
The running time, distance covered, initial settling time, slump etc are controlled using addition of special admixtures(mineral and chemical) etc without hampering the concrete strength. RMC is a totally controlled concrete having high work efficiency.
The raw materials stored shall be conveyed to the mixing drum using conveyor belts or bucket elevator. Cement is stored in silos also are conveyed using screw conveyors attached to the batching plants.
VIDEO SHOWING THE MIXING METHOD OF RMC
Once the weight of all material types meets the needs of specific amounts, the door of the weighing hopper is opened automatically. The materials will then be mixed by a concrete mixer. Once the setting time is over, the loading door of the concrete mixer opens and the concrete flows into a transit mixer.
WHAT ARE THE ADVANTAGES OF READ MIX CONCRETE
a) Uses the updated technology in proportioning, mixing and conveying and hence RMC plants can maintain excellent quality.
b) Transportation and placing is very easy. Once the concrete transit mixers reaches site concrete placing can commence immediately through concrete pumps, concrete buckets or boom placers.
c) As the concrete production and mixing is done in another place the site will be free form noise and dust pollution and free from raw material and cement trucks.
d) By using RMC the construction speed can be enhanced and schedule delays can be avoided upto an extent.
c) The concrete produced from RMC plants can be customised as per the client/ customer requirements.
d) RMC plants are a great relief when the site do not have sufficient spaces for stocking of raw materials and locating a batching plant with its raw material bins. RMC plants can cater any quantity of concrete starting from small residences to big construction sites.
e) Onsite wastage of raw materials and concrete can be eliminated by using Ready mix concrete.
d) Labour required for production of concrete and manpower for operation and running of batching plant & its associated machinery can be eliminated .
WHAT ARE THE DISADVANTAGES OF RMC
a) Requires huge investment to set an RMC plant.
b) Labour force shall be ready to place the concrete as and when it comes
c) Unforeseen delays and traffic jam leads to concrete rejection.
d) A very efficient and effective transporting system has to be maintained.
e) Quality has to be checked at site as per is standards on fresh concrete and also on hardened specimen.
f) Very effective quality system to be maintained for adjusting the setting time and slump according to the time of transit.
g) For residential construction the customer may not get a better idea of the quality of concrete due to lack of site testing facilities.
h) There are problems due to discrepancies in quantities which cant be convinced properly to the RMC vendors.
Green walls are independent vertical structures attached to the wall provided with a medium for plants and attached built-in irrigation systems. We are living in a polluted environment, hence it is advisable to maintain trees and plants that purify the air and makes us free, fresh and energetic. This article is about green walls and their healing benefits.
The green walls are the best option to make us feel close to nature. The concept of Green walls is getting popular nowadays. It was earlier confined to commercial and residential establishments. They are slowly getting into the residential atmosphere as an architectural concept. Surprisingly the green walls are much more than a back to nature architectural concept.
WHAT ARE GREEN WALLS?
Green walls consist of plants grown in a medium and placed on horizontal walls using a framing system. The system members are assembled structurally and fixed to the wall. The system includes both automatic and manual watering facilities.
Plants naturally take in carbon dioxide and absorb pollutants and then expel fresh, clean oxygen. Green walls make us happier and energetic with their close to natural abilities. They can lift our moods and help us to forget the feel of a busy urban atmosphere. It is a proven fact that nature can heal a lot of human behaviourism like anxiety, depression, aggression stress, mental fatigue etc. Ashrams built across the world are full of greenery and are the best destinations for healing minds.
Architectural and visual appeal
They are visually appealing and give an entirely different feel from the conventional interiors. The space looks bright, charming and pleasing due to the presence of living walls.
Indoor green walls system
Energy efficiency
The outdoor green walls are energy efficient as they can reduce the heat transmission to the interiors in areas where they are exposed to direct sunlight. The transpiration process of plants can reduce indoor heat to an extent and function as an energy-efficient solution. Transpiration is a process in which the plants release water in the form of moisture or water vapour.
Acoustic properties of green walls
Vertical gardens have good acoustic properties. Indoor vertical gardens absorb high-frequency noises.
Improving air quality
Environmental pollution is the biggest challenge we are facing nowadays due to industrialisation. Being close to nature can reverse the urbanisation effect to some extent. Apart from the action of photosynthesis plants are known to absorb poisonous gases by purifying the air. Studies show that they can reduce harmful pollutants to an extent of about 25-30 %.
Recreating eco systems.
The vertical gardens can recreate a missing natural ecosystem in the urban areas.
natural ecosystem
Biophilic effects ( productivity increase) of Green walls
Being close to plants can have a positive impact on an individual’s well being. Studies have shown that even seeing nature while working can increase job satisfaction. The installation of a green wall also makes the employees feel at ease with the companies commitment to maintaining a healthy work environment. By spending about 8 -12 hours in offices people develop a lot of discomforts due to inadequate ventilation, chemical indoor pollutants etc. Vertical gardens reduces such discomforts to an extent.
working environment
Leeds certification
Green walls are an internationally recognised green building certification (LEEDS) system. They help in transforming the design, construction and operation of buildings. Vertical gardens can secure LEEDS points due to their eco-sensitive and sustainable solutions in terms of water usage and environmentally friendly qualities. The LEEDS certification tends to increase the property values too. For more details about LEEDS certification refer the article “LEED certification India- A comprehensive guide”
Living walls contain a large number of plants placed horizontally in a relatively small area. This can provide the maximum benefit, as they are installed using minimal floor space.
INDOOR AND OUT DOOR GREEN WALLS
OUT DOOR WALLS
Outdoor living walls are visual elements and the plants chosen are to be in line with the prevailing climatic conditions of that area. The plants have to look good, absorb rainwater, insulate buildings and have to be cost-effective.
Outdoor vertical Garden
INDOOR WALLS
Unlike outdoor plants, indoor plants have space restrictions, size restrictions and species restrictions. The plant choice will be limited to indoor plants with air purification abilities. This system is suited to be fixed lengthwise than height wise for easy maintenance.
Hence it can be concluded that green walls are not a mere architectural concept for visual appealing , but an environmental friendly, sustainable, energy efficient, accounting option which can give mental peace, and feel the nurturing of nature.
The prestressing in Prestressed concrete is done by inducing predetermined compressive stresses to concrete by tensioning the steel, before subjecting it to service loads. In prestressed Concrete the stress developed during the service stage is countered by the already induced compressive stresses. Prestressing is a combination of the high-strength compressive properties of concrete with the high tensile strength of steel. This article is about prestressing in prestressed concrete, different methods of prestressing, and how prestressing works.
Prestressing in Prestressed concrete
Concrete got excellent properties, making them the most preferred material for structural members, but has its weakness too. Let us consider two cases where a concrete beam is subjected to loads.
CASE 1 ( PLAIN CEMENT CONCRETE BEAM ON LOADS)
CASE 2 (REINFORCEMENT CEMENT CONCRETE ON LOADS)
Plain Cement Concrete Beam on Loads
Let us consider a Plain Cement Concrete (PCC) beam subjected to loads as shown in Fig. The beam bends and cracks are developed in the tensile zone. This confirms that the concrete is very weak in tension and strong in compression.
Beam subjected to loads
Reinforced Cement Concrete beam on loads
Consider a reinforced Cement Concrete beam subjected to loads as shown in fig. In this case, the beam will not bend or cracks. This is due to the presence of reinforcement steel in the tensile zone. The reinforcement steel takes care of the tensile loads and prevents the member from cracking.
RCC beam subjected to loads
In this case, the RCC beam with steel behaves as a composite member. Concrete’s poor tensile strength and ductility are countered by the reinforcement steel having high tensile strength and ductility.
Significance of Prestressed Concrete
Even though concrete owes the property of good compressive strength, it has the following disadvantages.
Tensile strength is weak
Brittle
Non ductile
A good designer anticipates the areas of failure and designs the structure to overcome them. The design developed through this method is optimised. The Design is based on Design criteria ( Goal of the design). Each design should satisfy the design criteria of ultimate strength and Serviceability.
Let us go through the details of Ultimate strength and Serviceability
Ultimate strength
In this design Criteria, the structures are designed on ultimate strength and will not collapse even in the worst condition. For example, if the proposed structure for a bridge can handle a load of traffic without a collapse then it satisfies the Design criteria of ultimate strength.
Serviceability
The structures are to be checked for serviceability conditions like stability analysis, deflection checks, etc. In the service stage if the structure tends to deflect on moments, then the serviceability criteria is not satisfied.
Let us analysis the impact of service loads on RCC structure like a bridge.
Deflection of steel structures
Deflection On Service loads
The figure presents what happens when an RCC structure is subjected to service loads. The moments cause the structure to deflect. The ductile reinforcement elongates to negotiate the loads. However concrete with poor tensile strength fails on tensile loads and develops cracks.
Beam subjected to loads
Cracks developed on deflection
The cracks absorb moisture and gradually rust the reinforcement steel. This leads to spalling of concrete and initiates an ultimate collapse of the structure. Prestressed concrete is introduced to minimise deflection cracks, for increasing the strength of members. Prestressing gives the designers, the flexibility of optimising the design while negotiating large spans.
PRESTRESSED CONCRETE
Prestressed concrete
Prestressing is a method of inducing Compressive stress into a structural member by tensioning the steel, before subjecting to service loads.
The figure below explains how an RCC member subjected to loads deflects and gets cracked
Deflection and cracks on service loads
Principle of Prestressed Concrete
In prestressed concrete, the steel/tendons are stretched along the axis before pouring concrete as shown in fig. The tendons are released once the concrete reaches the desired strength. On detaching, the tendons induce compressive stresses in the structural member.
Mechanism of Prestressed Concrete
The compressive stress induced in the structural member on releasing the tensioned steel, counterbalances the compression arose due to loads applied in the service stage. In prestressed concrete, tensioning of steel initiates negative deflections in the member. These defections balance the compressive stress due to service loads and prevent the concrete from cracking.
Prestressed bridge on service Loads – No deflection
Prestressing method provides the designers with the much-needed flexibility in designing large spanned structures. Whereas deriving economical and optimised designs in RCC seems difficult.
Method of Prestressed Concrete
Prestressing is done in two methods
Pre-tensioning Method
Post – tensioning Method
Pre tensioning Method
In Pre tensioning method, the tendons are stretched before pouring the concrete. Once the concrete attains the desired strength the tendons are released. After releasing the tendon the structure is subjected to service loads. The High-strength steel tendons are placed between two abutments/buttress. The tendons are stretched around 70% of their ultimate strength or as per design requirements. Concrete is poured with Tendons kept stretched. The tendons are released once the concrete attains its desired strength. On release, the steel tries to regain its original length due to its high ductility. During this process, the tensile stress in steel is converted to compressive stress in concrete and thereby initiates a negative deflection. These compressive stresses induced in the structural member counters the compressive stress in the service stage.
Pre tension bed and process
The post-tensioning method is for precast girders of bridge spans, metro lines, flyovers, railway sleepers, piles, and prefabricated elements subjected to heavy loads. The structures are prestressed in the prestressing yards, conveyed, and lifted for erection at the site.
The post-tensioned structures have size limitations as they have to be carried from fabrication yard to site and erected at the site.
Post-Tensioning Method
In the post-tensioning method tendons are tensioned, once the concrete attains design strength. For this purpose, ducts or profiles are strategically placed within the concrete during casting.
Once the concrete hardens and attains design strength, the tendons are inserted through the already placed ducts or profiles. The tendons are tensioned using jacks as per design requirements. On completion of post-tensioning works, the structure is released for service loads.
Post tensioning system
In bonded type post-tensioning, the tendons are grouted with special grouts after tensioning. In unbounded type, tendon grouting is not necessary.
Post-tensioning is done at the site and not in the fabrication yard like a pre-tensioning system. The post-tensioning method is used in viaducts, segmental construction of large bridge spans, large slabs, reservoirs, big silos of cement plants, coal washeries, etc
What are tendons?
Tendons consist of single wires, multi-wire strands or threaded bars that are most commonly made from high-tensile steels, carbon fiber or aramid fiber.
vin civilworld 