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Chloride profiling in marine concrete - methods and tools for sampling

Wall, Henrik LU (2007)
Abstract (Swedish)
Popular Abstract in Swedish

Detta projekt fokuserar på hur man på bästa sätt bestämmer kloridprofiler i marina betongkonstruktioner. När borrmjöl från provtagning på marina betongkonstruktioner analyseras, är det inte ovanligt att de olika kloridprofilerna varierar oerhört mycket även om provtagningspunkterna ligger mycket nära varandra inom ett område med till synes homogen betong. Syftet med projektet har varit att hitta förklaringar till de extrema variationer i kloridinnehåll som beskrivits ovan, samt att hitta undersökningsmetoder som minskar dessa variationer.



Laboratoriestudierna har bestått i provtagningar på en betongplatta som har stått helt nedsänkt i saltlösning en längre tid i laboratorium.... (More)
Popular Abstract in Swedish

Detta projekt fokuserar på hur man på bästa sätt bestämmer kloridprofiler i marina betongkonstruktioner. När borrmjöl från provtagning på marina betongkonstruktioner analyseras, är det inte ovanligt att de olika kloridprofilerna varierar oerhört mycket även om provtagningspunkterna ligger mycket nära varandra inom ett område med till synes homogen betong. Syftet med projektet har varit att hitta förklaringar till de extrema variationer i kloridinnehåll som beskrivits ovan, samt att hitta undersökningsmetoder som minskar dessa variationer.



Laboratoriestudierna har bestått i provtagningar på en betongplatta som har stått helt nedsänkt i saltlösning en längre tid i laboratorium. Provtagningarna på denna platta har dels utförts genom uttagning av borrmjöl samt genom kärnborrning med 100 mm kärnor. Borrmjölet har tagits ut med borr av olika storlek för att kunna se om borrdiametern inverkade på resultatet vad gäller spridningen i kloridinnehåll. De kloridprofiler som erhållits från kärnorna har använts som referens för alla borrmjölsprover. Studien visar att svarvning av kärnor är det absolut bästa sättet att ta prover på, med hänsyn till spridning i kloridinnehåll. Studien visar också att om mindre borrdiametrar används vid uppsamling av borrmjöl, så skall detta borrmjöl tas som blandprov från ett flertal intilliggande borrhål. Oavsett hur proverna tas så skall analysen av dessa också inkludera cementinnehållet i proverna. Att redovisa resultaten som klorid i förhållande till cementinnehåll ger mindre variationer mellan proverna jämfört med om kloridinnehållet bara bestäms som andel av själva provet.



Under projektets gång har två fältstudier utförts, en i Trelleborgs hamn och en i Malmö oljehamn, båda i södra delen av Sverige. Fältstudien i Trelleborgs hamn har omfattat en inventering av alla kajkonstruktionerna i hamnen, en klimatstudie över området med avseende på vindhastighet och vindriktning samt vattenstånd och temperatur följt av en mer detaljerad undersökning med provborrningar i en utvald kaj. Studien visar att

exponeringen av betongkonstruktionerna ut mot öppet hav klart påverkar kloridupptagningen i konstruktionerna mer än den förhärskande vindriktningen.



Även fältstudien i Malmö oljehamn visar samma resultat. Slutsatsen av dessa studier är att betongprover tas från konstruktioner i marin miljö så är det viktigt att inte bara studera den omgivande miljön såsom den förhärskande vindriktningen utan att även ta hänsyn till hur konstruktionen eller konstruktionsdelen är exponerad för öppet hav.



Studierna i laboratoriet visar också att om möjligheten finns så skall provtagningen genomföras genom att ta borrkärnor, eftersom resultaten av kloridanalyserna uppvisar minst spridning med denna metod. Om det inte är möjligt att ta ut kärnor, så är minsta rekommendabla borrdiameter 20 mm.



Laboratoriestudierna visar att när så små borrdiametrar som 8 mm används, så måste proverna tas ut som samlingsprover från flera närliggande

borrhål för att minimera spridningen i kloridinnehåll. Oavsett hur proverna tas ut så skall även cementinnehållet i provet analyseras samtidigt. Eftersom svensk ballast normalt utgörs av kristallint urberg och således inte binder klorider till sig, så kan spridningen i kloridinnehåll mellan olika provtagningspunkter minimeras genom att redovisa kloridinnehållet i vikts-% av cementinnehållet. (Less)
Abstract
This project focuses on how to determine the chloride content in concrete structures exposed to marine environment in an accurate way. When analyzing dust from dry drilling in concrete, it is very often a fact that the chloride profiles show extensive variations even if the sampling has been performed within a very concentrated area with the sampling points close to each other. Several authors have observed this phenomenon in earlier research and some of these are referred to in this thesis.



The aim of this project has been to find reasons to these extensive variations and to find inspection methods that decrease the variations. Both laboratory studies and field studies have been performed within the line of this work.... (More)
This project focuses on how to determine the chloride content in concrete structures exposed to marine environment in an accurate way. When analyzing dust from dry drilling in concrete, it is very often a fact that the chloride profiles show extensive variations even if the sampling has been performed within a very concentrated area with the sampling points close to each other. Several authors have observed this phenomenon in earlier research and some of these are referred to in this thesis.



The aim of this project has been to find reasons to these extensive variations and to find inspection methods that decrease the variations. Both laboratory studies and field studies have been performed within the line of this work. The laboratory study has consisted of concrete sampling by dry drilling and by profile grinding 100 mm cores on a concrete slab that had been submerged in saline water in the laboratory. The chloride profiles from the cores have been used as a reference to all other samples collected on the slab.



The study shows that profile grinding of cores is the most accurate method to perform sampling on concrete with the purpose of analyzing the chloride content, and that when using small bore diameters the sampling should be performed as mixed samples from several bore holes. In all cases, samples should not only be analyzed for chloride but also for binder content. The results from the dry drilling in laboratory shows that the binder content becomes over estimated in the dust samples compared to the analyzed cores on

the same concrete slab. This means that the analyzed dust samples seams to contain a higher chloride content than the cores analyzed by profile grinding. This phenomenon became obvious when simulating chloride profiles using data from EPMA. Most probably the drilling follows an easy path between the large aggregate particles.



One field study has been performed in the port of Trelleborg in southern Sweden and another one in the port of Malmö, also in southern Sweden within some 50 km distance but facing the open sea in different directions. The field study in Trelleborg has consisted of an inventory of existing concrete structures in the harbour and climate studies of the wind and temperature in the area followed by a more detailed inspection including

sampling on selected parts of a quay. This study shows that the exposure to open sea clearly influences the chloride content in concrete structures exposed to marine environment more than the main wind direction. The field study in the port of Malmö also confirms this finding.



The conclusions of this work is that when sampling concrete on structures in marine environment it is important not only to study the surrounding

environmental loads such as the dominating wind direction, but also the exposure of the structure to the open sea which has shown to be of great importance in the field studies. If it is possible, the sampling should be performed by profile grinding cores. The studies in the laboratory have shown that sampling cores gives small variations in the analyzed chloride content. If dry drilling is used, the diameter of the drill bit should not be smaller than 20 mm. In all cases the analyzes should include the binder content, since it is the binder who contains chlorides. Presenting the chloride content in % by binder content has been shown to give the smallest variations in this study. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Thesis
publication status
published
subject
keywords
klorider, betong, provtagning, concrete, sampling, chloride
pages
80 pages
publisher
Division of Building Materials, LTH, Lund University
external identifiers
  • other:TVBM-3138
language
English
LU publication?
yes
id
12927eef-a301-45a8-a69a-972947379fd4 (old id 633704)
date added to LUP
2007-12-02 10:49:49
date last changed
2016-09-19 08:44:59
@misc{12927eef-a301-45a8-a69a-972947379fd4,
  abstract     = {This project focuses on how to determine the chloride content in concrete structures exposed to marine environment in an accurate way. When analyzing dust from dry drilling in concrete, it is very often a fact that the chloride profiles show extensive variations even if the sampling has been performed within a very concentrated area with the sampling points close to each other. Several authors have observed this phenomenon in earlier research and some of these are referred to in this thesis. <br/><br>
<br/><br>
The aim of this project has been to find reasons to these extensive variations and to find inspection methods that decrease the variations. Both laboratory studies and field studies have been performed within the line of this work. The laboratory study has consisted of concrete sampling by dry drilling and by profile grinding 100 mm cores on a concrete slab that had been submerged in saline water in the laboratory. The chloride profiles from the cores have been used as a reference to all other samples collected on the slab.<br/><br>
<br/><br>
The study shows that profile grinding of cores is the most accurate method to perform sampling on concrete with the purpose of analyzing the chloride content, and that when using small bore diameters the sampling should be performed as mixed samples from several bore holes. In all cases, samples should not only be analyzed for chloride but also for binder content. The results from the dry drilling in laboratory shows that the binder content becomes over estimated in the dust samples compared to the analyzed cores on<br/><br>
the same concrete slab. This means that the analyzed dust samples seams to contain a higher chloride content than the cores analyzed by profile grinding. This phenomenon became obvious when simulating chloride profiles using data from EPMA. Most probably the drilling follows an easy path between the large aggregate particles.<br/><br>
<br/><br>
One field study has been performed in the port of Trelleborg in southern Sweden and another one in the port of Malmö, also in southern Sweden within some 50 km distance but facing the open sea in different directions. The field study in Trelleborg has consisted of an inventory of existing concrete structures in the harbour and climate studies of the wind and temperature in the area followed by a more detailed inspection including<br/><br>
sampling on selected parts of a quay. This study shows that the exposure to open sea clearly influences the chloride content in concrete structures exposed to marine environment more than the main wind direction. The field study in the port of Malmö also confirms this finding. <br/><br>
<br/><br>
The conclusions of this work is that when sampling concrete on structures in marine environment it is important not only to study the surrounding<br/><br>
environmental loads such as the dominating wind direction, but also the exposure of the structure to the open sea which has shown to be of great importance in the field studies. If it is possible, the sampling should be performed by profile grinding cores. The studies in the laboratory have shown that sampling cores gives small variations in the analyzed chloride content. If dry drilling is used, the diameter of the drill bit should not be smaller than 20 mm. In all cases the analyzes should include the binder content, since it is the binder who contains chlorides. Presenting the chloride content in % by binder content has been shown to give the smallest variations in this study.},
  author       = {Wall, Henrik},
  keyword      = {klorider,betong,provtagning,concrete,sampling,chloride},
  language     = {eng},
  note         = {Licentiate Thesis},
  pages        = {80},
  publisher    = {Division of Building Materials, LTH, Lund University},
  title        = {Chloride profiling in marine concrete - methods and tools for sampling},
  year         = {2007},
}