civil techniques

Repairing Concrete Column Cracks and Damages

abbu riyaz 30 Apr, 2023

Repairing concrete column cracks and damages is essential. The column concrete damages are becoming critical in mass structures like shopping malls, commercial buildings. To carry out the column repair identify the axial dead load, live load, and horizontal load.

Repairing concrete columns are two category

Surface or cosmetic – covers local deterioration
structural repair – strengthens the affected columns.

Repairing Concrete Methods for cracks and damages

1. Unloading Columns

unloading the column is necessary. Entire cross-section of the repair column is capable of carrying the reintroduce design load. Without unloading, new repair does not carry any load. Drying shrinkage of new material reduces the share of the load.

2. Redistribution of the Load

In corrosion of reinforcement and concrete deterioration, Redistribute a load of column concrete with alternative supports for repair.

3. Supplemental Reinforcing Steel

The supplemental vertical bar to fix outside the original cage with extra ties. Provide adequate cover and Place Apartment’s bars outside the tie bars to increase column dimensions. Use Hairpin ties, of stainless steel laterally to support the supplemental bars. Column ties cannot disturb at the repair of the longitudinal bars as it causes buckling.

4. Concrete Removal

Remove concrete within a column cage and unload the column. If not, the longitudinal bars are buckle and compression failure of column take place.

5. Corroded Reinforcing Steel

It’s not necessary to remove the corrode reinforcing bar with the reduce cross-sectional area if the loss is supplement with additional reinforcing bars. The partially corrode reinforcing bars are thoroughly clean by sandblasting to obtain the bare metal. The bars with excessive corrosion is replacing with fresh reinforcement having full laps on both sides.

6. Corroded Ties

Replace the corrode ties by adding stainless steel hairpin ties that are anchor into the concrete. It is often necessary to deposit extra material around columns to provide an adequate cover over the supplemental ties.

7. Low-strength Concrete

Where the concrete strength is low, resulting in insufficient load-carrying capacity, several alternatives are available:

Shore the column and remove and replace the in-place concrete.
Shore column and increase the size of the column to reduce bending stresses, and increase confinement on placed weak concrete.
Wrap the column with carbon- or glass-reinforced plastic.
Install a supplemental column.

civil techniques

Corrosion protection

abbu riyaz 30 Apr, 2023

Corrosion protection of underwater pile is essential in aqua construction. Eliminating this corrosion problem is very hard, the corrosion is control by using corrosion protection methods.

Corrosion Protection Methods for Underwater Piles

Protective Coatings for Underwater Piles

Protective coating for underwater piles is necessary as it causes corrosion of piles. The Corrosion protection of underwater pile methods provides a great solution to corrosion of underwater piles.

The surface of pile comes in contact with water, corrosion in piles forms. To protect the piles from coming in contact with water, the pile is cover with non-porous material which is anti-corrosive. There is some non-corrosive chemical materials use in corrosion of underwater piles. Several chemical coating uses for corrosion protection.

The different types of coatings employes for underwater piles are mention below:

High build Epoxy coatings
Zinc Rich epoxy primer
FRP composites
Inorganic zinc silicate primers

1. High Build Epoxy Coatings

These epoxy coatings are abrasion and chemical resistant. These epoxy coatings provide a high level of service and more tolerant ambient weather conditions. And most effective in maintaining the damage area and breakdown of a coating system.

2. Zinc Rich Epoxy Primers

Zinc Rich epoxy primer is a mixture of Inorganic Zinc Silicates Primer and High Build Epoxy Coating. It provides a high level of service and more tolerant ambient weather conditions. And most effective in maintaining the damage area and breakdown of a coating system.

3. Application of FRP Composites for Corrosion Protection of Underwater Piles

FRP a mix of wet concrete is economic to repair on substructure parts. Repair of this parts requires the enlargement to accommodate new ties. Completely corroded part of the elements should remove by using FRP.

spreading of corrosion to other piles are protect by FRP. The aesthetics of FRP repair is one of its unheralded benefits.

4. Inorganic Zinc Silicates Primers

The structure below the splash zone always immerse in water are commonly not coat with cathodic protective layers. There are numerous types of anti-corrosive pigment primers in which inorganic zinc silicate is the best. It arrests rust creep or undercutting of the coating surrounding.

civil techniques

Methods of Ground Water Control in Excavations

abbu riyaz 30 Apr, 2023

The Methods of Ground Water Control in Excavations explains in this post. These techniques use to prevent groundwater entering into construction like, piling for bridges, tunneling, marine structures, underground structures. The groundwater causes extreme geotechnical problems in excavations like sand running for most of the construction projects. These issues caused by groundwater increase construction budget and extend construction time.

Methods of Ground Water Control in Excavations

There are two major Methods of Ground Water Control in Excavation explains as follows,

Pumping technique
exclusion technique

1. Pumping technique

It is highly expensive by Utilization of large capacity pumps which are not economical to consider in the critical situations.

2. Exclusion Methods to Control Ground Water in Excavations

There is a number of techniques by which groundwater exclusion are obtaining:

Forming impervious barriers

Chemical consolidation for controlling groundwater in excavation

Groundwater control by compressed air

Freezing groundwater control.

In these, we provide methods to prevent groundwater entering in construction by using Forming impervious barriers.

3. Forming impervious barriers

In this technique, permeability reduces by creating an impervious barrier.

An impervious barrier with lower end close by expandable plug & upper end seals on the surface drives into the soil. And grout is force into the pipe and drive out the plug and wide fissures with grout.

Application

Drill a hole in advance, insert a lance for grouting to carry out by a bottom-up method or top-down method.
Gout upper part by a lance inserted into the hole. After its setting time grout lower part of the pipe.
After grouting, preventing groundwater from entering into the excavation of piling, the normal procedure implies out for constructions.

Chemical consolidation for controlling groundwater in excavation

Chemical consolidation method is suitable for sandy gravels and fine grading sands. The most usual chemical material used for chemical consolidation is the sodium silicate.

Control Ground Water in Excavation by Compressed Air Method

There are several factors that motivate the application of compressed air to control groundwater in excavations. Compress air techniques are for controlling groundwater in excavations of tunnels and shafts.

civil techniques

Structural strengthening

abbu riyaz 30 Apr, 2023

Structural strengthening of concrete structures considers when the existing structure damages. And alteration of the structure is to make due to which the structure fail to serve its purpose.

Before strengthening all failure modes should Identify. Strengthening a structure for flexure lead to shear failure instead of giving the desired increased load-bearing capacity. It identifies that not only the failure mode of the strengthening member is important. If a critical member in a structure is strengthening, another member becomes the critical one. Because of change stiffness in an undetermined structural system, the whole structure investigates. This strengthening designs with consideration to minimizing the maintenance and repairs.

THE NEED OF STRUCTURAL STRENGTHENING

Load increases due to higher live loads, increased wheel loads, installations of heavy machinery, or vibrations.
Damage to structural parts due to fire damage, corrosion of steel reinforcement, and/or impact of vehicles.
Improvements in suitability for use due to a limitation of deflections, reduction of stress in steel reinforcement. And the reduction of crack widths.
Modification of structural system due to an elimination of walls columns and openings cut through slabs.
Errors in planning or construction due to insufficient design dimensions or insufficient reinforcing steel.

Methods of Strengthening

1. Strengthening a slab by increasing its depth from top

2. Strengthening a slab by increasing its depth from the bottom

Procedure for strengthening

Remove the concrete cover.
Clean the reinforcing steel bars using a wire brush or a sand compressor.
Coat the steel bars with an epoxy material that prevent corrosion
Install a new steel mesh, designed according to the requirements.
Install the new reinforcing steel mesh. Fix it vertical to the slab of the roof and horizontally to the surrounding beams, using steel dowels.
Coat the concrete surface with an appropriate epoxy material that guarantees the bond between the old and new concrete.
Pour concrete before the epoxy dries to the required thickness. Add materials that lower the shrinkage to the concrete.

civil techniques

Grouting techniques

abbu riyaz 30 Apr, 2023

Grouting techniques use to prevent water leakage in massive and other water retaining systems. Underground structures like tunnels, hydroelectric power plants, storage caverns etc are always expensive to build. And have a major value to the society. As infrastructures, they are directly responsible for wealth creation and development, to the need for better and constant maintenance.

Grouting works are a significant part of these important projects, mainly in:

Consolidation & strengthening weak soil during tunneling excavation
curtain grouting for concrete and earth dams
ground settlement control
waterproofing of existing structures
preventing the spreading of hazardous contaminants
foundation plate formation
re-opening of old dams and tunnels

Today the range of products and techniques available for injection is quite wide.

Grouting technique helps people to design. And application phases to choose easy and the best system to solve the specific problems.

Grouting Methods

There are two main grouting methods. They are,

Grouts based on types of cement
Grouts based on chemical product

These procedures for grouting makes with great care. The entire grouting process to carry out in a controlled environment. This makes a strong bond between the materials with concrete.

1. Grouts based on types of cement

PCM – pure cement mixes, consisting of cement and water.

ACM – Admixed cement mixes, composed of cement, water, plasticisers or superplasticizers.

ADCM – Additive cement mixes, composed of an admixed cement mix plus clays.

2. Grouts based on chemical products

SG – Silicate Gels, A solution of sodium silicate in aqueous solution with a reagent.

PH – Phenolic resins, an aqueous solution cured with strong acidic or alkaline hardeners, according to resin type.

OM – Organomineral resins, modified silicate reacts with isocyanate to form a tough material with very high adhesive strength.

PU – Polyurethane, polyol, and isocyanate react forming a high strength adhesive material.

EP – Epoxies, resins, react to form a tough non-foaming material.

Advantages of grouting techniques

Low priced materials
Easy to apply
High penetration capacity
Fast setting times
High capacity for energy absorption (PU)
Non-washable

civil techniques

EXPANSION JOINTS

abbu riyaz 30 Apr, 2023

The usage of EXPANSION JOINTS discuss and explains in this post. This is the main member in the construction of a bridge. A bridge constructs with many major components like, the pile foundations, pile caps, columns, beams, decks, etc,. The top slab of bridge known as decks. These decks constructs at specific lengths with small gaps at specific intervals between them. These gaps provides for these concrete slab decks to expand and contract. This implements to avoid crack formations and spreading of cracks to other deck slabs. This causes by the temperature change, drying shrinkage, live load etc. These gaps seals with elastic sealants. These sealants are elastic members provides ways for concrete to is expansion and contractions in changing environments.

This expansion joint damages among bridge members causes by the increase of traffic load, improper installation, and careless repairs,etc. It causes a bad ride, accidents leads to traffic. And the frequent repair causes the heavy traffics. This increases the maintenance cost of bridges.

EXPANSION JOINS

The gaps seals with the watertight elastomeric profiles. It allows enough vertical movement to permit bearing replacement, without the need to dismantle the bridge expansion joint.

The method of using copper plates employs. And this method is cost-effective. This provide long-life, compare to other systems.

Its done by replacing an elastic system with the pre-fabricated copper plates. These designs as per requirements for bridge decks. And inserts into expansion joints. And provides a free way to concrete for its expansion and the contraction.

The Advantages

Some of the major advantages explains as follows,

This system stands a change of temperature, contraction, and cliff of concrete.
Provides smooth movement in deck slab roads.
Not necessary to remove the entire expansion joint.
This reduces the time for repairing works.
Reduces the maintenance.
Highly economical.
This system will easily apply on existing bridges according to their types.