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Concrete

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Welcome to howtocivil .In this article, I will discuss on concrete definition, types, function, Ingredients, grade, manufacture and curing time and everything you need to know about concrete. Hope you enjoy this article.

Concrete Definition

Concrete can be defined as the composite material composed of the binding medium such as the mixture of cement, water and different fine and coarse aggregates. Many people do consider the cement as the concrete, but cement is just a part of concrete.  Concrete structures have been built around the world are subject to a wide range of different conditions of use and acquaintance to environmental conditions comprising erosion, weather, and pollution.

All environmental conditions found concrete as the long-lasting and the best binding material. Beside of whatever the conditions might be, concrete is expected to provide satisfactory performance for the wholeness of their service life with very little care.I think you understand,what is concrete now .If you then you continue reading to next topic  ” Concrete ingredients or what concrete made of”.

Concrete ingredients Or what concrete made of

What makes the monster so much rigid, long-lasting and powerful enough to support every condition? To answer this, one has to look into the ingredients of concrete. This composite material is composed of varies ingredients. The properties and functions of this binding material depend upon its constituents. If the constituents have more strength, then concrete will be more sustainable.  Have a look at concrete ingredients:

Concrete = Filler (Aggregates)+ Binder (Cement)+Water +Admixture (Optional)

Binding materials

In concrete, Portland cement is generally used. It gives strength and its selection is a function of concrete durability and functioning. According to the American Society for Testing and Materials (ASTM) there are five types of cement, but in manufacturing of concrete Type I. Type III cement is used maximum time.

Aggregate

The aggregates usually comprise 75% volume of the concrete. This percentage might give you the importance of these aggregates.  One must be very careful in the selection of aggregates because the property of aggregates is basically the property of concrete.  These are the granular material such as the sand, gravel, crushed stone or iron-blast furnace slag. Fine aggregate is usually the sand and all other materials that pass through sieve #4 [0.187 in. (4.75 mm). On the other hand, coarse aggregates are the stones, gravel and all other material that is retained on the #4 sieve.

Water

Water is one of the most important ingredient of concrete. Because of water, the hardening of concrete through process call hydration happens. When you going to make concrete you need to use pure water otherwise it can make weak concrete,also make a disturbance in the hydration process. You should also consider the water-cement ratio,too much water reduces concrete strength and too title water will make concrete unworkable.

Admixtures

Admixtures are added to give extra power and increase toughness, resistance, rigidness of the concrete. There are admixtures that reduce the viscosity, increase the resistance. Some have the ability to delay the setting time when necessary

Strength of concrete:

Strength of concrete can be known by knowing the compressive strength of this material.The compressive strength of any material is the property of a material to withstand against the provided load without any blows or crushes.

Concrete compressive strength varies from 15Mpa to 35Mpa and it depends upon several factors like water-cement ratio, types of admixtures used, type of aggregate uses, and type of cement used. Test on strengths revealed that concrete by using good materials have 69Mpa strength at 28 days.

Curing time of concrete:

Curing of concrete is defined as the process of preserving the wetness and temperature circumstances of concrete for hydration response to normally so that concrete develops hardened properties over time. The main components which need to be taken care of curing are moisture, heat and time during curing the process.

If curing is not done, there is the chance of building cracks in the concrete. However, 28 days are considered to be the best curing time for the 100% strength of concrete. Concrete develops 69Mpa strength on its 28 days after manufacturing.

Curing TimeStrength (%)
1Day16%
2Days40%
7 Days60%
14Days89%
28Days99.9%

 

Types of concrete:

There is various type of concrete available in the market based on its functionality, strength and structure. For the construction purposes, if someone go to the market to buy the concrete for his/her building-it is available in the two forms:

  • Normal mix concrete
  • Design mix concrete.

However, on the base of material used and the construction required and design purpose there are also further three types of concrete.

  • Plane cement concrete
  • Reinforced Cement concrete
  • Pre-stress Cement Concrete

According to binding Material concrete can be classified as

  • Cement concrete
  • Lime Concrete

Based on Weight, Concrete can be classified into 4 categories they are

  • Ultra-Light Weight Concrete
  • Light Weight Concrete
  • Normal Weight Concrete
  • Heavy Weight Concrete

Based on Strength, Concrete can also be classified into Four Categories

  • Low-strength concrete
  • Moderate-strength concrete
  • High-strength concrete
  • compressive strength
  • Ultra high-strength concrete

Based On Additives

  • Normal concrete
  • Fiber Reinforced Concrete
  • Polyumer concrete
  • Ready-Mix Concrete
  • Green Concrete
  • High-Performance Concrete
  • Ultra-High Performance Concrete
  • Rapid Strength Concrete
  • Shrinkage Compensating Concrete
  • Fibre-Reinforced Concrete
  • Asphalt Concrete
  • Polymer Concrete
  • Gypsum Concrete
  • Vacuum Concrete

 

Normal mix concrete:

It is a concrete which is prepared according to the specific considerations of design. Common ingredients used here is cement, water, and aggregate. Setting time could be varied from 20 to 80 minutes. If one looks at 28 days formula for concrete, it provides more than 80% strength to concrete which should be more than 95%.

Design mix concrete:

Concrete is not prepared on hit and trial basis. Ingredients’ ratio is carefully selected after doing a lab test. After performing a different test on the different proportions of material, the best design is selected. Design mix or simply mix designs are prepared according to the strength required for the structure.

Plane concrete construction:

In-plane concrete, there will be no reinforcement. The most common ingredients; cement, aggregate, and water is mixed with proportion 1:2:4 respectively. In an area where less tensile strength is required like pavement and the other small building, plane concrete construction is usually used.

Reinforced concrete construction:

A Mixture of cement, send, coarse aggregate and water with reinforcement is known as Reinforced concrete construction. Here the tensile strength of the structure increases. It is used as a building substantial for nearly all types of buildings such as inhabited concrete buildings, engineering structures, dams, roads, tunnels, multi-story buildings, towers, channels, sidewalks, and superhighways.

Cost of Concrete

Cost of concrete depends upon several factors like quality of material used in concrete, local prices of binding material like cement, and the area for which concrete required. But the thumb rule is that the cost of concrete is $108 per cubic yard. Pouring concrete ranges in price from $8 to $18 per square foot.

Weight of concrete

Unit weight of the concrete varies depending upon the basic constituents used in the manufacturing of concrete. Quantity and thickness of the aggregate, the water and cement content matters the most in determining the unit weight of concrete. Apart from this, 1 cubic meter of concrete weighs 2400 kg.

Advantages  of concrete:

  • Ingredients are easily available
  • Concrete can easily handled and molder to any desired shape .
  • Easy to  transported from the place of mixing to place of casting
  • The monolithic character of concrete gives it better appearance and much rigidity to the structure.
  • The property of concrete to possess high compressive strength makes a concrete structure more
  • Economical than a steel structure.
  • More Economical
  • Ability to be cast
  • More Energy Efficient
  • Excellent Resistance to Water
  • High-Temperature Resistance
  • Fire Resistance
  • Aesthetic Properties
  • Ability to Consume waste
  • Ability to work with reinforcing Steel

 

Disadvantages of concrete:

  • Low Tensile Strength
  • Lower Ductility (Brittle)
  • Volume Instability
  • Formwork is needed
  • Low Toughness
  • Long Curing Time
  • concrete is required to be reinforced to avoid cracks
  • Due to drying shrinkage and moisture expansion concrete may crack

 

Properties of concrete

Freshly mixed concrete should have following properties

  • workability
  • segrefation
  • bleeding
  • Harsh

In the harden state of concrete ,should have following properties

  • Strenth
  • Durability
  • Impermeability
  • shrinkage
  • creep
  • Thermal expansion
  • Modulus of Elasticity

Factors affecting the performance of concrete fresh concrete

  • Cement
  • Aggregates
  • Water cement ration
  • Mixing of concrete
  • Transporting
  • Placing
  • Compacting hardened conrete
  • Curing

Tests Of concrete

Tests on Fresh Concrete

  • Vee-bee consistometer test
  • Compaction factor Test
  • Slump test
  • Air content
  • Setting Time
  • Segregation resistance
  • Unit weight
  • Wet analysis
  • Temperature
  • Heat generation
  • Bleeding

Tests on Hardened Concrete

  • Compressive strength
  • Tensile strength
  • Modulus of elasticity
  • Permeability Test

Other quality tests are conducted to test the following

  • Modulus of rupture
  • Density
  • Shrinkage
  • Creep
  • Freeze/thaw resistance
  • Resistance to aggressive chemicals
  • Resistance to abrasion
  • Bond to reinforcement
  • Absorption

 

Bottom Line:

Concrete proves to be a very good binding material. Its strength can be increased by adding proper ratio of admixtures. 28 days are the best curing time for the concrete where it gives the optimum strength i-e 100%. Its variability in types depending upon its use in the construction makes it versatile and usable.

Note: I collected the data from my old notes, I performed varies test in my Uni-life on making concrete by adding some admixtures like ash. I used some reading from that data. Advantages and disadvantages are common I knew it. I was well aware about types and its ingredients.

Glass Fiber Reinforced Concrete

Glass fiber reinforced concrete is an engineered material composed of the same ingredients required in the production of the concrete with the addition of the reinforcement of glass fiber in the concrete. GFRC comprises tiny discrete fibers that are consistently spread and haphazardly oriented. Initially, the use of glass fiber in the concrete was threatened because of the alkaline nature of both made it difficult to exist again the corrosion. The problem was solved by the use of anti-alkaline glass fiber.

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Glass fiber reinforced concrete (GFRC) is a material that is building a substantial influence on the economics, technology, and aesthetics of the building industry worldwide for over 40 years. GFRC is one of the most multipurpose structure tools obtainable to architects and engineers Compared to old concrete, it has composite properties because of its unusual structure. Diverse constraints in the GFRC such as water-cement ratio, porosity, composite density, inter filler content, fiber content, orientation and length influence properties and behavior of GFRC as well as the accuracy of production method.

Properties of Glass Fiber Reinforced Concrete

The properties of Glass Fiber Reinforced Concrete are dependent on the structure of the composite. The properties of the GFRC are the function of the concrete and anti-alkaline fiber used for the preparation. And then one needs to study the interaction of both-glass fiber and concrete. So, the structural properties of GFRC are all about the concert and fiber.

Glass Fiber Reinforced Concrete
Glass Fiber Reinforced Concrete
  • For the concrete, Glass fiber reinforced concrete mortars are typically applied in the thin pane which is working mainly for covering. In these applications, the fibers act as the primary reinforcement and their content is usually in the range of 5–15 % by volume.
  • For the fibers, there are two types of reinforcing; 3D and 2D. In the 2d GFRC, the level of fiber reinforcing is very incompetent, demanding very high loads of fibers. Naturally, only about 15 % of the fibers are leaning correctly. In 2d GFRC, The fibers are oriented haphazardly within a thin plane. As the fibers are scattered into the forms, they lay flat, settling to the shape of the form.

Glass Fiber Reinforced Concrete

The effect on the mechanical properties of the concrete after the reinforcement of fiberglass can be categorized and summarized as shown in the table below.

No#Mechanical propertiesChange
1Compressive StrengthDue to reinforcement of fiber in the concrete, compressive strength increase.
2Modulus of ElasticityNo important effect of use GFRC.
3Stress–Strain CurveHighly effected
4Flexural StrengthGlass fiber increases the flexural strength of concrete.

 

The effect of the glass fiber reinforcement concrete on the physical properties of the structure is also undeniable.

No#Physical propertiesEffects/ Change
1CreepThe chances of cracking increases.
2PorosityThere are several micro-pores in the concrete. Special consideration must be applied during reinforcement of the fiber
3Chloride Penetration ResistanceIncrease in the fiber content increases the chlorine resistance.
4Electrical ResistivityCan decrease.

 

Ingredients of Glass Fiber Reinforced concrete

Glass Fiber Reinforced Concrete

Glass Fiber Reinforced concrete has the reinforcement of the glass fiber in the concrete. Glass Fiber Reinforced Concrete is, well, pretty much exactly what it sounds like: concrete reinforced with glass fibers. As in most composite ingredients, the fiber elements in GFRC can be wisely oriented, or casually distributed, in the solid matrix. So for the preparation of the GFRC, one has to start from the preparation of the concrete, and after there will be the spray of glass fiber on it. For the concrete, cement, sand or other aggregate and water is required. The fiber for the concrete is added about 4% to 6% by weight.

Glass Fiber Reinforced Concrete

Applications of Glass Fiber Reinforced

Glass Fiber Reinforced concrete has been using in the various fields of life including industrial, medical textile, manufacturing, and building industry. GFRC has compound properties as paralleled to old concrete, because of its special structure. As a result of the structural properties, it has appropriate decoration, sturdy and durable structure. Moreover, because of being fast to connect and easy to handle and transport, it provides low cost.

concrete glass fibers

It scatters or absorbs sound and it is environmentally friendly Can be used for the noise control, GFRC can be used as the noise barrier; thick fiberglass in the concrete does not allow the noise to pass through it. In the Architectural industry, GFRC panels provide good aesthetics and high resistance to weathering and the fire and therefore very much suitable for the durability of the structures. Complex freeform architecture is one of the most striking trends in contemporary architecture. More resistance of the GFRC to the strains makes it usable in the interior of the houses.

Advantage of GFRC

  • GFRC’s service life is higher than traditional concrete
  • High–efficiency.
  • Environmentally–friendly,
  •  Cost–effective and building technology.
  • Flame resistant.
  • Resistant to strains
  • Resistant to fire
  • GFRC does not require any extra reinforcement.
  • 50–70 % lighter than traditional concrete

Disadvantages of GFRC

  • It is difficult to self–mix (requirement of special material)
  • Its cost is higher than that of traditional concrete.
  • Ductility is not available in the GFRC.

Video Of making GFRC-Glass Fiber Reinforced Concrete

 

GFRC is one of the most multipurpose structure materials accessible to architects and engineers. It has added meaningfully to the economics, technology, and aesthetics of the building industry. Glass fiber reinforcement in the concrete makes it versatile in the use.

The use of GFRC is not new; its demand is increasing day by day. Sharing the good information is the virtue so keep sharing it.

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Spalling Concrete: Spalling Concrete Causes ,prevention and Repair

Reference and Related Research:

1.Kim, Junhee & You, Young-Chan. (2015). Composite Behavior of a Novel Insulated Concrete Sandwich Wall Panel Reinforced with GFRP Shear Grids: Effects of Insulation Types. Materials. 8. 899-913. 10.3390/ma8030899.

2.Harle, Shrikant. (2014). COMPARISON OF GLASS FIBER REINFORCED CONCRETE & GEOPOLYMER CONCRETE WITH GLASS FIBER REINFORCEMENT. International Journal of Research in Engineering and Technology. 03. 263-265. 10.15623/ijret.2014.0301045.

3.https://www.slideshare.net/bhavinshah80/glass-fiber-reinforced-concrete-53784748

4.Toutanji, H. A., & Saafi, M. (2000). Flexural behavior of concrete beams reinforced with glass fiber-reinforced polymer (GFRP) bars. Structural Journal97(5), 712-719.

5.Beaudoin, J. J. (1990). Handbook of fiber-reinforced concrete. Principles, properties, developments and applications.

6.Benmokrane, B., Wang, P., Ton-That, T. M., Rahman, H., & Robert, J. F. (2002). Durability of glass fiber-reinforced polymer reinforcing bars in concrete environment. Journal of Composites for Construction6(3), 143-153.

7.De Luca, A., Matta, F., & Nanni, A. (2010). Behavior of full-scale glass fiber-reinforced polymer reinforced concrete columns under axial load. ACI Structural Journal107(5), 589.

8.Shah, S. P., Ludirdja, D., Daniel, J. I., & Mobasher, B. (1988). Toughness-durability of glass fiber reinforced concrete systems. ACI Materials journal85(5), 352-360.

9.Kizilkanat, A. B., Kabay, N., Akyüncü, V., Chowdhury, S., & Akça, A. H. (2015). Mechanical properties and fracture behavior of basalt and glass fiber reinforced concrete: An experimental study. Construction and Building Materials100, 218-224.

10.https://journals.sagepub.com/doi/10.1177/0731684405058273

11.https://www.rnbco.org/glass-fiber-reinforced-concrete-gfrc/

 

 

What is spalling concrete ?

The word Spalling comes from spall means flakes of the material that are wrecked off of a larger solid body. When a source of the mixture, water enters into the solid structure at the foundation of concrete structure, it starts leaching deeper and deeper, causes the formation of cracks in the structure. The idea of spalling can be explained by the well-known phenomenon known as rusting. In rusting, there is oxidation reaction between air and the surface of the metal. Due to the presence of moisture in the air, the metal starts rusting. In the same way different atmospheric conditions like moisture content, increase in temperature, corrosion involves in the formation of the spalling of concrete.

spalling concrete
spalling concrete

There are different misconceptions in people regarding spalling of concrete- water could be the main culprit of spalling concrete. As concrete has three basic components: cement, aggregate, and water. The third ingredient, water sometimes added too much during the preparation of concrete which can cause spalling  .

Likewise, Corrosion of the reinforcement steel is the most common cause of spalling and excruciating in big concrete constructions. Steel reinforcement is castoff in concrete to provide strength to a material. The process known as the carbonation-natural deterioration process causes the reinforcement steel bars present in the concrete structure to corrode, which ultimately produces the flakes-spalling.

Spalling Concrete Causes

Before knowing about causes of spalling concrete, one should know that Spalling is disruption of the concrete exterior which frequently spreads to the top coatings of reinforcing steel. Spalls might be 150 mm in diameter and 25mm in depth. Here are some leading causes of spalling Concrete :

spalling concrete

1-    CORROSION OF EMBEDDED METALS:

As described earlier, steel uses for the reinforcement, so the corrosion of the steel and other embedded material cause the deterioration of the concrete. When steel rusts, the resultant corrosion occupies a larger volume than the steel. This expansion makes tensile stresses in the concrete, which can ultimately cause cracking.

2-    Exposure of reinforced concrete to chloride ions:

Exposure of reinforced concrete to chloride ions is another primary reason for the spalling deterioration of the concrete. The chances of spalling increase as the number of chlorine increases. If moisture is present at the threshold limit of chlorine, it causes series spalling-deterioration. The invasion of chloride ions into reinforced concrete can cause steel corrosion if oxygen and moisture are also available to sustain the reaction. Chlorides melted in water can infuse over complete concrete or spread the steel through cracks.

3-    Natural deterioration- Carbonation:

A slow process which occurs when carbon dioxide from the air enters the concrete and counters with hydroxides, such as calcium hydroxide, to form carbonates. So, spalling after a period of more than fifty years is due to the carbonation process.

4-    FREEZE-THAW DETERIORATION:

Water being the important constituent of the concrete plays a very curious role in the spalling also. If water freezes, it can expand by about 9%. As the water in humid concrete freezes, it yields pressure in the capillaries and pores of the concrete. If the pressure surpasses the tensile power of the concrete, the cavity will dilate and break.

5-    Expansion of the aggregates:

Expansion of the aggregate happens when it absorbs too much water. In this condition aggregates cannot accommodate in the prevailing weather conditions. As every material have its own water absorbing capacity, if it exceeds a certain limit it can be hazardous. So far, in all cases the main cause or leading cause of the deterioration and spalling is the water content.

6-    Chemical Attack:

Chemical attack can also deteriorate the concrete, the exposure of concrete to different environmental conditions like acid rain have series effects on the concrete. Acids in the acidic rain react with the surface of the structure and can produce spalling to high quality concrete. Apart from this Sulfate attack have also devastating impacts. Thaumasite may form in the sulfate outbreak in humid circumstances at temperatures typically between 0°C and 10°C (32°F to 50°F).

7-    Exposure to heat and fire:

Concrete can withstand every atmospheric condition but when it exposed to high heat and fire, sometimes, it can cause spalling. Scientists are now working to minimize the effects of heat and fire on the concrete. Here again, the role of admixture is very important. The admixture should be chosen with high resistant to heat and fire.

Disadvantage of spalling concrete

Spalling of concrete can be a series headache for the building owner. It takes years to collect money for some people to prepare homes, but this spalling can have diverse effects on the structure of the building, the structure can fall down- create a serious economic burden. If the average life of the concrete is 80-100 years, then due to spalling it can reduce to 50 years. So spalling concrete can decrease the half-life of the structure.

 

How to prevent spalling concrete

1-    Ingredients should be properly mixed.

2-    Selection of aggregate should be optimized.

3-    Can be escaped if the concrete is managed wisely.

4-    Give distinct care to the ends and corners of bare concrete.

5-    Spalling, judges earlier can tackle easily.

6-    Corrosion of fixed metals in concrete can be significantly minimized by placing crack-free concrete with low absorptivity and adequate concrete cove.

Spalling concrete repairs

spalling concrete repairs

As this article describes the causes of spalling of concrete, here we will tail about the repair steps. As thumb rule is to do remedy steps as one notice the spalling. To convey the fruitful repair, confirm that you eliminate the concrete about 1.5 inches profound. You should then fresh and eliminate the wreckage earlier the repair begins. The embedded steel, if suffering from corrosion should also be cleaned by different chemicals. One should ensure that new binding material should possess the same properties as of existing concrete. Apply of cement overly is also the best idea if spalling is on the horizontal surface.

Spalling concrete repairs Video

 

 

 

 

 

Spalling no doubt is an eye irritating process, but by applying some common rules and knowing the facts and causes of spalling, it can effectively reduce. Spalling can be natural and man-made; there are the prevention and repair steps which should be followed.

Reference :

http://flexkrete.com/concrete-repair/long-term-spalling-concrete-repair/

https://www.hdb.gov.sg/cs/infoweb/spalling-concrete

https://www.researchgate.net/figure/Typical-damage-a-concrete-spalling-b-buckling-of-steel-cross-bracing-and-c_fig2_251993179

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