Concrete repairs

civil techniques

Concrete Hacking Procedure

abbu riyaz 7 Aug, 2023

The Concrete Hacking Procedure discuss in this post. The Concrete hacking performs in a specific way in a proper procedure. Hacking executes manually with the help of hacking chisel and hammer. It executes mechanically using grinding machines with the concrete cutting blades. This performs by making a very small groves on the RCC Structures.

Concrete Hacking is a process of making smooth surface rough. It makes on the surface of concrete to provide a strong bond for the plastering. As the finishing surface of concrete is smooth, the plaster wont sticks to it. To create a strong mechanical bonding between them, this process of hacking in concrete performs.

Hacking performs mostly in Reinforced Cement Concrete structures like, the Roof Slab at the bottom of slab. This creates a strong mechanical bonding between the chemicals and the mortar in RCC members on plastering. It sticks strongly and gives a long and durable life to the concrete structures and protects them.

Concrete Hacking Procedure

Concrete hacking performs in a specific way in a proper procedure. Concrete Hacking carries out after removing the shuttering of Reinforced Cement Concrete structures. After De-shuttering the RCC members cures properly to attain its strength. And hacking executes after two to three days from the date of casting, before it attains its harder state.

The surface of concrete surface cleans for shuttering oil, excess slurry, dust, supporting wood materials and other loose particles. Hacking performs on the surface of concrete structures manually with hacking chisel and hammers only on its faces. This should not carries out on the corners as it affects the strength of the concrete structure.

This performs at a depth of two to five millimeter groves in the concrete surface. The length of hacking groves in concrete surface is twenty five millimeters. And hacking performs in a same consecutive lines in a pattern.

This pattern performs in a zigzag series opposite ways. This zigzag series of hacking is known as cross stitching method way of hacking in the concrete surfaces. After this the concrete structure cleans thoroughly and left for curing to attain its design strength. And then plastering performs above the concrete structure.

civil techniques

Concrete Hacking Properties

abbu riyaz 3 Aug, 2023

Concrete Hacking Properties discuss in this post. Concrete Hacking is a process of making smooth surface rough. It makes on surface of concrete to provide a strong bond for plastering. As the finishing surface of concrete is smooth, plaster wont sticks to it. To create a strong mechanical bonding between them, this process of hacking in concrete performs.

Concrete Hacking carries out after removing the shuttering of Reinforced Cement Concrete structures. After De-shuttering the RCC members cures properly to attain its strength. And hacking executes after two to three days from the date of casting, before it attains its harder state. This helps to hold mortar with plastering in walls, tile works.

Concrete Hacking Properties

Hacking executes manually with the help of hacking chisel and hacking hammer. It executes mechanically using grinding machines with concrete cutting blades.This performs by making a very small groves on RCC Structures.

The depth of the groves in concrete surface is two to five millimeters. The length of hacking groves in concrete surface is twenty five millimeters. And hacking performs in a same consecutive lines in a pattern. This pattern performs in a zigzag series opposite ways. This zigzag series of hacking is known as cross stitching method way of hacking in the concrete surfaces.

Hacking performs mostly in Reinforced Cement Concrete structures like, Roof Slab at the bottom of slab. And specially in the Walls and roof slabs of underground tanks, sumps for the purpose of water proofing and plastering. This creates a strong mechanical bonding between chemicals, mortar in RCC members on plastering. It sticks strongly and gives a long and durable life to concrete structures and protects them.

civil techniques

Concrete Hacking

abbu riyaz 1 May, 2023

Concrete Hacking is a process of making smooth surface rough. It makes on surface of concrete to provide a strong bond for plastering. As the finishing surface of concrete is smooth, plaster wont sticks to it. To create a strong mechanical bonding between them, this process of hacking in concrete performs. This makes on surfaces of beam, column and roof slabs for plastering. And helps to hold mortar with plastering in walls, tile works.

Concrete Hacking

This carries manually and mechanically. Hacking performs on places where plastering carries out. This creates a mechanical bonding between RCC members and Cementous plastering mortar which applies directly on the surfaces.

The surface of RCC structure where the walls to constructs hacks properly before starting with brick or block work. This makes a strong connection between RCC structure and walls. And mainly in plastering of roof ceilings in super structures.

civil techniques

Uses of Chicken Mesh in Plastering

abbu riyaz 1 May, 2023

Uses of Chicken Mesh in Plastering discusses in this post. Chicken Mesh in Plastering uses to prevent cracks. Concretes have a property of expansion and contraction. It expands in heat and contract on cooling. The gap between RCC Structures and walls joint fills with fixing Chicken Mesh before plastering. It fixes on the connection surface of columns, beams and walls.

In Construction of RCC structures, after casting of columns, beams and slab, the walls raises. Brickwork or Block-work makes to fill space in-between columns, beams and slabs in outer sides. And to make all kinds of partition walls inside buildings. After brick or block work, plastering works performs. The column sides touching walls hacks properly. Hacking is a process of making smooth concrete surface rough. This provides a strong bonding between RCC surfaces, walls and Plastering.

This mesh is hexagonal in shape. And possess a structure of honeycomb. This property makes it strong. And it gives a long life. It is a made of galvanized iron. This manufactures in coils. It cuts in running maters as per length requires. And minimum 100 mm in width.

It prevents the development of cracks between wall, column, beam joints and junctions. This reduces the chances of cracks occurring in walls in future. And it acts like reinforcement use in concrete. It makes the plastering strong at joints and junctions.

Uses of Chicken Mesh in Plastering

Chicken mesh uses in interior plastering. This uses maximum in interiors because of major pipelines for electrical conduits and water lines comes in interior walls. It Prevents the cracks occurring because of electrical conduits laying inside wall by grove cutting. The miss handling of switchboards cause electrical conduit damages resulting in formation of cracks on walls.

And all waterlines going inside these walls makes little vibrations because of water pressure. The miss handling of water taps causes water pipe lines damages resulting in formation of cracks on walls. And it uses if the plastering thickness is more than 15 Cm. It is not uses in plastering lesser than 15 Cm. Because it causes hair cracks if the thickness of plastering is less.

In exterior plastering this chicken mesh is not used. It has a chance of creating rust in it. If any rust forms in it, then the plastering will fall. It is only supposed to fix the mesh only if the thickness of plastering more than 20 mm. This chicken wire mesh is flexible in structure.

This makes it ideal for using in curves and all kinds of plastering.

civil techniques

Chicken Mesh Properties

abbu riyaz 1 May, 2023

Chicken Mesh Properties discusses in this post. In Construction of RCC structures, after casting of columns, beams and slab, the walls raises. Brickwork or Block work makes to fill space in-between columns, beams and slabs in outer sides. And to make all kinds of partition walls inside buildings. After brick or block work, plastering works performs.

Concretes have a property of expansion and contraction. It expands in heat and contract on cooling. The gap between RCC Structures and walls joint fills with fixing Chicken Mesh before plastering. It fixes on the connection surface of columns, beams and walls.

This reduces the chances of cracks occurring in walls in future. And it acts like reinforcement use in concrete. It makes the plastering strong at joints and junctions.

This uses maximum in interiors because of major pipelines for electrical conduits and water lines comes in interior walls. It Prevents the cracks occurring because of electrical conduits laying inside wall by grove cutting. The miss handling of switchboards cause electrical conduit damages resulting in formation of cracks on walls.

And all waterlines going inside these walls makes little vibrations because of water pressure. And miss handling of water taps causes water pipe lines damages resulting in formation of cracks on walls.

Chicken Mesh Properties

This Chicken mesh is hexagonal in shape. And possess a structure of honeycomb. This property makes it strong. And it gives a long life. It is a made of galvanized iron.

This manufactures in coils. It cuts in running maters as per length requires. And minimum 100 mm in width. If this cuts in one place while placing or after plastering, it wont make any damages in plastering. This chicken wire mesh is flexible in structure. This makes it ideal for using in curves and all kinds of plastering. This is available in Rolls of bundles. The Length is of about 10 m to 100 m. And as per usages / require length. It has a width of 1 meter to 2.5 meter. And it possess various gauges.

It is available in different materials like, in Ms and galvanized iron. The mesh size also varies. And it is available in different wire diameters. The gaps between hexagonal wire mesh varies. It varies from 13 mm to 50 mm.

civil techniques

Chicken Mesh in Plastering

abbu riyaz 1 May, 2023

Chicken Mesh in Plastering uses to prevent cracks. Concretes have a property of expansion and contraction. It expands in heat and contract on cooling. The gap between RCC Structures and walls joint fills with fixing Chicken Mesh before plastering. It fixes on the connection surface of columns, beams and walls.

In Construction of RCC structures, after casting of columns, beams and slab, the walls raises. Brickwork or Block work makes to fill space in-between columns, beams and slabs in outer sides. And to make all kinds of partition walls inside buildings. After brick or block work, plastering works performs. The column sides touching walls hacks properly. Hacking is a process of making smooth concrete surface rough. This provides a strong bonding between RCC surfaces, walls and Plastering.

Chicken Mesh in Plastering

Chicken mesh uses in interior plastering. This uses maximum in interiors because of pipelines for electrical conduits and water lines comes in interior walls. It Prevents the cracks occurring because of electrical conduits laying inside wall by grove cutting. The miss handling of switchboards cause electrical conduit damages resulting in formation of cracks on walls.

And all waterlines going inside these walls makes little vibrations because of water pressure. The miss handling of water taps and fittings causes water pipe lines damages resulting in formation of cracks on walls.

And it uses if the plastering thickness is more than 15 Cm. It is not uses in plastering lesser than 15 Cm. Because it causes hair cracks if the thickness of plastering is less.

civil techniques

Concrete Manufacturing Process

abbu riyaz 1 May, 2023

Concrete Manufacturing Process consists of many stages. The Concrete mix for delivery from a plant instead of mixing on the job site. The concrete mixes, transports and delivers to a construction site to place in formworks for construction. And to form various structures, like a column, beam, slab, etc.

Concrete Manufacturing Process

The main Concrete Manufacturing Process is as follows

Batching
Mixing
Transporting
Placing
Compacting
Curing

1. Batching

It is the main thing in the Concrete Manufacturing Process. The measurement of materials like aggregates, cement, water necessary for preparing different grades of concrete is Batching. It is by two processes. One is volume and other is weight batching. The volume batching is by mixing materials with its volume. And weight batching is by the self-weight ratio of materials. It has ratios according to standard codes. Some of the different grades of concrete are M10, M20, M25, M30.

2. Mixing

Mixing is to produce uniform, high-quality concrete. The mixing equipment is capable of effective concrete material. Separate paste mix shows the mixing of cement and water into a paste before combines with aggregates. This increase the compressive strength of concrete. This paste mix in high-speed, shear-type mixer at a water-cement ratio of 0.30 to 0.45 by mass. The premix paste blends with aggregates. The remaining batch water and final mix complete in a rotating concrete mixing equipment.

3. Transporting

Transporting concrete require great care. After mixing, the concrete transports to site. The mixing carries near the construction site. A bucket, ropeway, belt conveyor use to transport concrete. Readymix conveyor trucks use mostly in the modern construction times. The concrete transporting by conveyor truck has time limits. The concrete transporting by trucks reach the construction plant early.

4. Placing

Concrete to place in a good manner. It places without segregation to reach maximum efficiency. The concrete not to pour over a height of 1.5m. As the height of pouring concrete increases, it leads to separation of aggregates and cement paste. It causes segregation of concrete and causes honeycomb. Many concrete placing equipment use in modern construction times. some of the equipment are concrete pumps and boom lifts. Concrete pumps are normal pumps with joints to connect and remove according to needs.

Boom lifts are concrete pumps with movable arms. With the help of movable arm, a concrete place easily at heights and corners which is difficult with the normal pump.

5. Curing

Curing is to provide best strength and hardness to concrete. It is the next step after placing of concrete. Curing helps concrete to gain strength early. The concrete requires a moist and wet environment to gain full strength. Proper curing of concrete leads to increase the strength of concrete. And prevent cracking at surface dries. Avoid freezing and overheating of concrete to gain its full strength.

civil techniques

Concrete in construction Field

abbu riyaz 1 May, 2023

Concrete in construction Field is a mixture of paste and aggregates. It composes of fly ash, fine and coarse aggregate, water and chemicals. The fine aggregates are sand and coarse aggregates are gravel. By hydration, the paste hardens and gains strength to form the concrete.

Concrete in construction Field

Concrete is soft in newly mix, strong at hardens. Hence concrete uses to build bridges, superhighways, houses, and dams.

There are some important factors involve in the manufacturing process of concrete. They are

Proportioning
water-cement ratio
Ingredients
Hydration
Placement
Curing and
Special techniques

1. Proportioning

Proportioning and mixing are the main things in making a strong concrete. so choose the materials carefully. The mixture that does not have enough paste to fill the gaps between the aggregates is difficult to place. And produce rough surfaces. A mixture of a high cement paste is easy to place. And produce a smooth surface.

2. water-cement ratio

The quality of the paste determines the character of the concrete. The strength of the paste depends on the ratio of water to cement. It is the weight of the mixing water divided by the weight of the cement. High-quality concrete produces by lowering the water-cement ratio without losing the workability of fresh concrete. And allowing it to properly place and cure.

A properly design mixture possesses desire workability for the fresh concrete and the long-life and strength of the concrete.

3. Ingredients

Natural water drinkable and has no bad taste or smell used as mixing water for concrete. Impurities in mixing water affect setting time and strength. It causes efflorescence, staining, corrosion of reinforcement, and reduce lifetime. Drinking water suitable for mixing concrete and aggregates are to choose properly.

The aggregates to be clean and free from matter that affects the quality of the concrete.

4. Hydration

Aggregates, water, and the cement combine, the mixture hardens. By hydration, the paste hardens and get the strength to form concrete. During this reaction, a node forms on the surface of each cement particle. The node grows and expands until it links up with nodes from other cement particles.

5. Placement

The concrete thoroughly mixes and workable is places in forms before the mixture becomes too stiff. At placement, the concrete compact within the forms to reduce honeycombs.

For slabs, concrete makes ideal to stand until the surface moisture film disappears. A wood or metal hand float uses to smooth off the concrete. Floating produces an even, but slightly rough, texture that has good slip resistance. And use as a final finish for exterior slabs. If smooth, hard, dense surface requires, floating follows by steel trowels.

6. Curing

The curing begins after the exposed surfaces of the concrete have hardened sufficiently to resist damage. Curing ensures the continued hydration of the cement. So that the concrete continues to gain strength. Concrete surfaces cure by sprinkling with water fog. Other curing methods prevent evaporation of the water by sealing the surface with special sprays called curing compounds.

7. Special techniques

It uses for curing concrete during cold or hot weather to protect the concrete. The longer the concrete is wet, the stronger it becomes. The rate of hardening depends upon the composition, fineness of the cement, mix proportions, moisture, and temperature. Concrete continues to get stronger as it gets older. Most of the hydration and strength gain take place within the first month of concrete’s life cycle.

civil techniques

Soil Nailing

abbu riyaz 1 May, 2023

Soil nailing is a construction technique to reinforce soil to make it stable and strong. Soil nailing technique uses for slopes and excavations alongside highways, railway lines. It uses for, excavations, retaining walls slopes, to make it more strong and stable.

The soil reinforces with slender elements like reinforcing bars name as nails. These reinforcing bars install into pre-drill holes and grouts. The nails install at an inclination of ten to twenty degrees with vertical reinforcement.

Soil Nailing employes when requiring slopes for excavation cannot provide due to space constraints. And employes in the construction of retaining wall. It is an alternative to retaining wall structures.

At excavation, the shotcrete, concrete and grouting materials apply to the excavation face to grout the reinforcing steel and nails. It provides stability to the steep soil slope.

Types of Soil Nailing:

There are various types of soil nailing techniques:

Grouted Soil Nailing
Driven Nails
Self-drilling Soil Nail
Jet Grouted Soil Nail
Launched Soil Nail

1. Grouted Soil Nailing

In this type, the holes drills in walls or slope face and nails inserts in the pre-drill holes. These holes fill with grouting materials like concrete and shotcrete.

2. Driven Nails:

Driven nailing use for temporary stabilization of soil slopes. In this method, the nails drive in the slope face at the time of excavation. This method is very fast. It does not provide corrosion protection to the reinforcement steel and nails.

3. Self-drilling Soil Nail:

In this method, the hollow bars use. Hollow bars drills into the slope surface and grout inject simultaneously during the drilling process. This method of soil nailing is faster than grout nailing. This method provides more corrosion resistance to nails than driven nails.

4. Jet Grouted Soil Nail:

In this method, jets use for eroding the soil for creating holes in the slope surface. Steel bars install in this hole and grouts with concrete. It provides good corrosion protection for the steel bars and nails.

5. Launched Soil Nail:

In this method, the steel bars force into the soil with high speed using compressed air mechanism. The installation of soil nails is fast. And control over the length of bar penetrating the ground is difficult.

civil techniques

Causes of Cracks in concrete structures

abbu riyaz 1 May, 2023

Causes of Cracks in concrete structures

There are many Causes of Cracks in concrete structures, they are

Thermal movement
The permeability of concrete.
Corrosion of Reinforcement
Creep
Moisture Movement
Structural design and specifications
Poor Construction practices.
Improper maintenance

1.Thermal movement

All materials expand on heating and contract on cooling. The thermal movement depends on temperature variations, dimensions, a coefficient of thermal expansion and physical properties of materials. The external exposed to direct solar radiation and the roof subject to thermal variation is liable to cracking.

Remedial Measures:

Thermal joints avoid by expansion joints, control joints and slip joints.

2.The Permeability of concrete

Concrete permeability controls by factors like water-cement ratio, water hydration, curing, air voids, micro-cracks and continues exposure to thermal variations.

3.Corrosion of Reinforcement

Concrete provides protection to reinforcing steel. Steel will not corrode as concrete around it is impervious. And does not allow moisture or chlorides to penetrate within the coverage area. A properly designed and constructed concrete is initially water-tight. The reinforcement steel protects by a physical barrier of the concrete cover having low permeability and high density.

Remedial Measures:

Increase the concrete cover with proper materials like plastic, concrete, readymade cover blocks, etc., instead of using stones and wood pieces. Increased concrete cover over the reinforcing bar reduces corrosion.

use concrete with low permeability.

4.Creep

Concrete subjected to loading exhibits a slow time-dependent deformation known as creep. Creep increases with increase in water and cement content, water-cement ratio and temperature. It decreases with increase in humidity of surrounding atmosphere and age of material at the time of loading. Use of admixtures and pozzolanas in concrete increases creep. Amount of creep in steel increases with rising in temperature.

5.Moisture Movement

Shrinkage occurs in all building materials that are cement/lime based. Heavy aggregate concrete shows less shrinkage than lightweight aggregate concrete.

Materials with pores in the structure in the form of intermolecular space expand on absorbing moisture and shrink on drying. These movements are cyclic in nature and causes by increase or decrease in inter pore pressure with moisture changes.

Remedial Measures:

Shrinkage cracks in masonry minimize by avoiding the use of rich cement mortar in masonry.

Plastering of masonry after proper curing.

6.Structural design and specifications

Cracks in concrete forms due to poor structural design and specifications. At the starting of design first, consider the environmental conditions existing around the building site. It is important to determine the type of foundations, the type of concrete materials use in concrete. And the grade of concrete depending on chemicals present in groundwater and subsoil. Closely spaced of reinforcement steel bars due to inadequate detailing causes segregation.

precautions while designing

specification for concrete materials and concrete.

Proper quality and thickness of concrete cover around the reinforcement steel.

proper reinforcement layout and detailing

7.Poor Construction practices

Construction should design and supervise only by civil engineers or persons having proper knowledge and experience in construction practices. People without construction knowledge are engaging nowadays to supervise construction works and to carry out construction works.

Lack of good construction practices due to ignorance, carelessness, greed or negligence.

For a healthy building, it is necessary to ensure good quality materials selection and good construction practices.

Some of the main causes for poor construction practices

Using poor quality materials
improper selection of materials
cheap and nonstandard materials
improper concrete mix
Inadequate control on various steps of concrete products such as batching, mixing, transporting, placing, finishing and curing
Inadequate quality control and supervision causing large voids(honeycomb)
Improper construction joints between
Addition of excess water in concrete and mortar mixes.
Poor quality of plumbing and sanitation materials and practices.

8.improper Maintenance

Buildings should maintain at regular interval of time properly to avoid damages. Attend Leakages as earliest as possible before corrosion of steel inside concrete starts. The external painting of the building helps in protecting the building against moisture and other chemical attacks. Necessary water-proofing and protective coating on reinforcement steel or concrete.

civil techniques

Steel corrosion control methods

abbu riyaz 30 Apr, 2023

Steel Corrosion control methods are essential to prevent damage and the failure of structures. 40% of failure of structures are by corrosion of inner steel. Steel corrosion control methods carry mostly in the structure that locates in coastal areas. And steel structures like tower transmission lines, cell phone towers, etc.

There are many causes of corrosion. It relates to the quality of concrete and quality of construction. The first step in corrosion of steel is to provide good quality of concrete. The quality of concrete materials, mixing and compaction and workmanship help to control the steel corrosion.

Quality in construction reduces corrosion. There are various methods, they are

Steel corrosion control methods

Cement-Polymer Composite Coated Rebars (CPCC)
Fusion Bonded Epoxy Coated Rebars (FBEC)
Corrosion Resistant Steel Deformed Rebars (CRSD)

1. CPCC

It set in concrete surrounds by an alkaline medium. A cement base coating is more useful for steel corrosion control. Apply two coats of cement polymer on rebar.

Products in CPCC are:

De-rusting Solution
Alkaline Powder
Phosphating Jelly
Inhibitor Solution
Sealing Solution

2. FBEC

It produces from 100% solid finely ground fuse powder particles. At heating, it melts to form an adherent film. There is no primer film provide in FBEC rebars. It makes a medium of weakness in the path of a bond between rebar and concrete.

Epoxy coats the rebar by

Melts
Flows
Gels
Cures
Cools
Stick to coat

3. CRSD

Corrosion begins with the formation of an initial layer of rust. On common rust on normal rebars, the CRSD rust is self-renewing. The protective oxide is fine texture, tightly stick and a barrier to moisture, oxygen, carbon dioxide, Sulphur dioxide. And chloride prevents corrosion.

Use corrosion resistance bars to prevent corrosion of concrete structures, damage, and failure of structures. This increases the strength and lifespan of structures.

civil techniques

Plastic Formwork Types

abbu riyaz 30 Apr, 2023

There are different Plastic Formwork types use in the construction of structures.

Plastic formworks for concrete construction is to hold freshly place concrete in a correct position. And to gain strength. With the help of formworks, concrete easily makes into various shapes and size.

There is different material uses to make formworks. Mainly timber and steel. Plastic gives a number of advantage, compares to other materials, like durability, cost-effectiveness, and flexibility.

Plastic Formwork Types

There are Different Plastic Formwork types.

Siscon

It is a type of plastic forms uses to construct various structural elements. Like walls, columns, and slabs.

Formworks for Walls

It is for the construction of boundary walls, retaining walls, shear walls. And for rainwater drains, storm drains and irrigation canals.

1. Corner wall formwork

It uses in the construction of corner walls. It makes with simple joints. And fewer supports.

2. Junction wall Plastic formwork

It uses in the construction of junction walls. It is easy to handle.

3. Intersection wall plastic formwork

It uses in the construction of intersection walls. And easy to fix and remove.

Plastic Formworks for Column

It manufactures from specific grade plastic. Other materials do not stick to it. And no chemical reactions occur between concrete and the plastic form. And no patch forms on the surface of the concrete.

1. Nova Plastic Formwork System

It produces from the composite plastic material. And use in salt and fresh water.

2. Moladi Formwork

It is lightweight and reusable. It makes to handle bad qualities. And problems relates to formworks.

Objectives of Formworks

It needs attention to avoid damages. The formwork design and construction are controls by three principles:

1. Safety

It depends on the strength of formwork. Life of labors and public might be in danger if the formwork does not has strength.

2. Quality

Concrete shape accuracy. And the quality of a final surface of the concrete.

3. Economy

It is highly economical.

Advantages of Formworks

Water resistant
Recyclable
Cost-effective
Labor and
Eco-friendly
Low maintenance