Repair and Rehabilitation Distress In Structure Distress means

Repair and Rehabilitation

Distress In Structure Distress means Damage • Concrete may suffer distress or damage during its life period due to a number of reasons. Because of the varying conditions under which it is produced at various locations, the quality of concrete suffers occasionally either during production or during service conditions resulting in distress.

Distress In Structure Causes of distress of concrete Structural causes � Externally applied loads � Environmental loads � Accidents � Subsidence's, etc. � Error in design and detailing � Poor Construction practices � Construction Overloads � Drying Shrinkage � Thermal Stresses � Chemical Reactions � Weathering � Corrosion

Distress In Structure

In addition to the distress in hardened concrete, the plastic concrete may also suffer damage due to, � Plastic Shrinkage � Settlement Cracking � Early removal of formwork � Improper design of formwork.

Distress In Structure

Evaluation Procedure for Repair and Strengthening of Concrete Structures � Before finalizing any scheme for repairs and rehabilitation of a distressed concrete structure, the concerned engineer has to be fully aware of the causes of distress, extent of damage to the structure and the present condition of the concrete in the structure for repairs to be effective and lasting. �The extent of distress has to be categorized so that the repair schemes can be formulated according to the distress in a particular structural element. So that, pre-repair evaluation and assessment of a structure is pre-requisite for working out effective repair schemes.

Evaluation Procedure for Repair and Strengthening of Concrete Structures • Once the repairs have been carried out on a distressed structure, the post repair evaluation and assessment of the structure can be carried out for checking the efficacy of the repair. �The post repair assessment is a tool with the engineer to evaluate whether the parent material and the repair material have obtained bond or whether the cracks or the voids have been filled up by the grouting materials. �Thus, any scheme for effective repairs can be based on the pre-repair and post- repair evaluation of concrete structures

Tools for Evaluation of Concrete Structures The various tools available for evaluation of concrete structures are as follows: • Visual inspection and observations • Questioning of concerned personnel • Scrutiny of field data and records • Design Checks • Non- destructive testing (NDT) • Extraction of cores and testing • Supplementary laboratory techniques • Load testing of a structural member • The general approach adopted for pre-repair evaluation of distressed concrete structures is given below:

Visual Inspection and Observations �The first step in the process of evaluation of a distressed concrete structure is visual inspection and observations. �A through visual inspection leads to proper approach to be adopted during investigation. �It determines the number of field and laboratory tests required to be carried out.

Visual Inspection and Observations �Ambient conditions �Crack width and patterns �Spelling of Concrete � Color, texture and rust stains �Zinking of columns �Failure of beam-Column junctions. �Mal-functioning of machinery, structural components etc. � Condition of fixtures � Deposits/ splashes on structural components.

Questioning of Personnel/ Scrutiny of field Data and Records The questioning of personnel and the scrutiny of field data and records is carried out for the following: � Grade of concrete adopted �Cube test results �Type of material and sources �Constructional details �Environmental Conditions

Questioning of Personnel/ Scrutiny of field Data and Records �The Scrutiny of the grade of concrete and cube test results brings out adequacy of strength of concrete and the degree of quality control exercised during constructions. �The study of the type of materials used particularly cement, coarse aggregate, fine aggregate, additives etc. also focuses the direction of investigations. �The scrutiny of other constructional details e. g. removal of formwork, shifting of formwork for slip form construction, the height of pouring of concrete, use of compaction devices etc. are useful information for further investigation in many cases.

Questioning of Personnel/ Scrutiny of field Data and Records Scrutiny of field data and records: �Design checks: �Non-Destructive testing (NDT): Any visual inspection and scrutiny of the field data, the in-situ testing is carried as per the approach finalized.

Various in-situ non- destructive tests available are: �X-ray diffraction analysis �Differential thermal analysis �Chloride permeability test �Optical and Scanning microscopy �Chloride permeability test. �Compressive strength, density and modulus of elasticity determination on core samples, etc. �Load testing of a structural member �Extraction of Cores and testing

In addition to various in-situ tests carried out, it becomes necessary to support the findings with laboratory tests The laboratory tests generally adopted are: • Cement Content of Hardened Concrete • Chemical Analysis • Chlorides • Sulphates • p. H • Nitrates

Corrosion of Reinforcement in Concrete

Corrosion of Reinforcement in Concrete