Initial Review

7/31/2019 Initial Review

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Initial Review

Project brief and objectives

The ingression of sulfates and chlorides along with carbonation of concrete can lead to the

deterioration of the concrete as well as corrosion of the steel (Figure 1). The current European(EN206) and American (ACI 318) standards provide guidelines for combating each of these

deterioration mechanisms individually but numerous scenarios where two or more of these

mechanisms may occur simultaneously exist (Table 1 and Table 2); and these scenarios are not

specifically accounted for in the codes.

Figure 1 - Occurrences of deterioration mechanisms (adapted from Tilly, 2007)

By considering the actions of theses mechanisms, both individually and in combination, this project

will seek to provide guidance for combating multi mode deterioration. This concept is to be explored

in concretes manufactured with a combination of cementitious materials including OPC, GGBS, PFA

and micro silica.

The primary aim of this project is to develop a comprehensive understanding of the boundaries in

which deterioration of concrete can occur when exposed to carbonation and chloride and sulphate

ions along with an understanding the mechanisms and interactions involved. The following

objectives have been identified in order to satisfy the main aim of this project:

To increase the depth of understanding of single mode deterioration

Determine an accelerated testing regime that accurately reflects natural exposure regimes

To determine the mechanisms and effects of combined modes on deterioration

To run natural testing to validate data obtained from accelerated testing

Use data obtained from the testing to develop multiple mode deterioration models

Develop guidelines to compliment the current standards

AAR

Frost

Cracking

Faulty

Construction

Wear

Other

Corrosion -

Carbonation and

Chloride


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Methodology

To achieve these objectives, the potential scenarios illustrated in Figure 2 will be considered in more

detail with testing designed to accelerate the deterioration process in each of the seven possible

exposure scenarios.

Methods to accelerate these mechanisms will be used such as: increasing temperature,

concentration or pressure which are applicable for accelerating all mechanisms; increasing crystal

pressure through wetting and drying cycles and ionic migration applicable for chlorides and sulfates;

and increasing surface area to volume ratios used for accelerating sulfate attack.

A site for natural exposure will also need to be chosen and the accelerated tests correlated to

represent the conditions experienced at the site.

With the deterioration accelerated, it will be quantified using a combination of tests to account for

different variables. SEM, XRD, XRF, ICP, pH monitoring, pore fluid extraction, resistivity, strength and

permeability testing will be used to determine the extent of the deterioration and the interaction of

the mechanisms.

Progress to date

Literature review of knowledge gap

o Research by CONREPNET (Figure 1) has highlighted that over half of all concrete

deterioration is caused by the corrosion of steel.

o By considering the exposure regimes set out in EN 206, the scenarios where two or

more exposure regimes may occur have been considered to assess the feasibility of

the testing (Table 1).

Figure 2 - Representation of deterioration mechanisms and combinations


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o Four likely scenarios for combination have been chosen along with the three

individual deterioration modes

Literature review of mechanism

o Literature of laboratory work involving the interaction of two of the deleterious

substances together has been consulted to ensure the research remains relevant

and possible.

o Literature regarding the testing of sulfate attack has been consulted with shortfalls

in current testing noted.

Literature review of tests methods

o While the potential testing methods required for the monitoring of the interactions

has also been researched.

o Relevant testing techniques to assess the interaction of deterioration modes and

mechanisms have been investigated.

Project deliverables at the end of first year

Composition of solutions to reflect natural environments will be identified and used to

ensure that the accelerated testing methods will replicate the natural environment

Natural environment chosen to run in conjunction with and supply data to assess

accelerated tests

Testing regime to monitor progression of deterioration will be determined

Difficulties encountered

At this stage, the main difficulties of the project are yet to be encountered. However, difficulties inrecreating the natural environment in an accelerated manner are expected as are difficulties in

obtaining sufficient data from the natural environment within the time frame of the project.

Research training attended

Due to difficulties with the QSIS post graduate training page and a late start date, fewer courses

have been attended than hoped. However, more training sessions are booked for February and

March.

Postgrad Research Induction Workshop (Full day )

How to write a Literature Review (Half day 12th Jan 2011)

RefWorks (Half day 13th Jan 2011)


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Bar Schedule for first year

Projected Deliverables

Task OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP

Background Literature

Development of idea

Investigation of Testing

Mixing and casting

Carbonation testing

Chloride testing

Sulfate testing

Combined testing

Table 1 Potential exposure conditions in a marine environment according to BS EN206

Chlorides Sulfates Carbonation

XS1 (Airborne)

- XC3 (Moderate Humidity)

- XC4 (Cyclic wet and Dry)

XS2 (Submerged)

XA1 (Slightly aggressive) -

XA2 (Moderately aggressive) -

XS3 (Tidal/splash/spray)

XA1 (Slightly aggressive)XC3 (Moderate humidity)

XC4 (Cyclic wet and dry)

XA2 (Moderately aggressive)

XC3 (Moderate humidity)

XC4 (Cyclic wet and dry)

Table 2 - Potential exposure conditions from ACI 318

Corrosion Permeability Sulfate

C2 (Severe) P1 (Required)

S0 (Not applicable)

S1 (Moderate)


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Natural

Anal sis Modelling

Increased Temperature

Increased Concentration

Increased Crystal

Pressure

Increased Surface

Area

Increased Pressure

Ionic migration

Accelerated

CO2 Cl-

SO4

Exposure Conditions

Single Combined

CO2 Cl-

SO4 Cl-& CO2 Cl

-& SO4 All 3

EN206 Table 1 / ACI 318 Table 4.2.1 Gap in Knowledge

Measurements

SEM, XRF, ICP, XRD, pH Monitoring, Pore Fluid, Resistivity, Strength, Permeability

Phenolphthalein Profiling

Ex ansion

Carbonation Chloride Sulfate

Documents

Initial Review