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Studies of moisture and alkalinity in self-levelling flooring compounds

Anderberg, Anders LU (2007) In Report TVBM 1025
Abstract (Swedish)
Popular Abstract in Swedish

<p>

Under de senaste decennierna har innemiljön och dess relation till hälsa rönt ett allt större intresse. En viktig aspekt i detta sammanhang har varit kopplingen mellan fukt i byggnader och hälsa.

<p>

Cementbaserade material innehåller ofta överskottsvatten ("byggfukt") när de gjuts då detta är nödvändigt för deras arbetbarhet och flytegenskaper. Förutom det höga vatteninnehållet är porlösningarna i dessa material oftast högalkaliska, d.v.s. de har höga pH. Höga fukttillstånd gynnar biologisk tillväxt och höga fukttillstånd i kombination med höga pH kan leda till kemiska nedbrytningsprocesser i andra material. Båda dessa fenomen kan påverka såväl... (More)
Popular Abstract in Swedish

<p>

Under de senaste decennierna har innemiljön och dess relation till hälsa rönt ett allt större intresse. En viktig aspekt i detta sammanhang har varit kopplingen mellan fukt i byggnader och hälsa.

<p>

Cementbaserade material innehåller ofta överskottsvatten ("byggfukt") när de gjuts då detta är nödvändigt för deras arbetbarhet och flytegenskaper. Förutom det höga vatteninnehållet är porlösningarna i dessa material oftast högalkaliska, d.v.s. de har höga pH. Höga fukttillstånd gynnar biologisk tillväxt och höga fukttillstånd i kombination med höga pH kan leda till kemiska nedbrytningsprocesser i andra material. Båda dessa fenomen kan påverka såväl innemiljön som den tekniska funktionen och utseendet av ett material.

<p>

Avjämningsmassor används för att skapa horisontella och jämna ytor i golvkonstruktioner innan ytbeläggningen påförs. Trots att avjämningsmassor används i stor omfattning finns det knappt några publicerade resultat som beskriver deras fuktegenskaper och alkaliska egenskaper. Denna studie syftar till att bestämma sådana egenskaper samt att öka förståelsen för hur avjämningsmassor fungerar i samverkan med andra material i golvkonstruktioner.

<p>

Många av de idag förekommande metoderna för bestämning av fuktegenskaper hos byggnadsmaterial är tidsödande och ej avsedda för avjämningsmassor. Nya metoder har därför tagits fram inom detta projekt, bl.a. en snabb mätmetod i vilken både sorptionsisotermen och diffusionskoefficienten bestäms.

<p>

Mätningar av kemisk bindning av vatten och fysikalisk bindning av vatten (sorptionsisotermen) samt mätningar av diffusionskoefficienter, ytavdunstninghastigheter och fuktflöden till en underliggande betong har utförts för att kunna studera uttorkningsförloppet hos avjämningsmassor samt för att kunna bedöma deras fuktnivåer i ett längre tidsperspektiv. Resultaten från dessa mätningar har utgjort grunden till en utorkningsmodell vilken sedan vidareutvecklades till ett datorbaserat simuleringsprogram som bedömer uttorkningstider och fuktnivåer på längre sikt i avjämningsmassor.

<p>

Mätningar visar att transport av hydroxidjoner mellan betong och avjämningsmassor och i avjämningsmassor sker mycket långsamt. Detta innebär att avjämningsmassor kan skydda golvbeläggningar och golvlim från en betongs höga alkalinitet.

<p>

Alkalisk nedbrytning av golvlim beror av pH (hydroxidjonkoncentrationen). Sekundära emissioner från golvkonstruktioner som uppkommer genom alkalisk hydrolys är därför direkt beroende av underlagsytans pH och transportegenskaper för hydroxidjoner. För högalkaliska underlagsytor som betong är därför karbonatisering nödvändig för att undvika nedbrytning av känsliga golvmaterial. Detta gäller inte för avjämningsmassor som har en

<p>

betydligt lägre pH. Karbonatisering ger vanligen endast ett tunt skikt av lägre pH i betongens yta. Det är därför osäkert huruvida detta skikt kan utgöra ett långsiktigt skydd för känsliga golvmaterial mot betongens i övrigt högalkaliska fukt. En avjämningsmassa får därför anses vara ett bättre alternativ i detta fall. (Less)
Abstract
<p>In recent decades there has been an increasing interest in the indoor environment and its connections with public health. One important topic discussed has been the relation between the moisture in buildings and health. <p>



Cementitious materials, when cast, contain excess water since this is necessary for workability and for flow properties. The pore solutions in cementitious materials, besides being high in water content, often have a high pH. High-moisture conditions can cause biological growth. A combination of high moisture conditions and high pH can also result in chemical degradation of other materials, affecting both indoor environment and the technical functioning and appearance of the materials... (More)
<p>In recent decades there has been an increasing interest in the indoor environment and its connections with public health. One important topic discussed has been the relation between the moisture in buildings and health. <p>



Cementitious materials, when cast, contain excess water since this is necessary for workability and for flow properties. The pore solutions in cementitious materials, besides being high in water content, often have a high pH. High-moisture conditions can cause biological growth. A combination of high moisture conditions and high pH can also result in chemical degradation of other materials, affecting both indoor environment and the technical functioning and appearance of the materials involved.

<p>

Self-levelling flooring compounds (SLCs) that provide smooth horizontal surfaces are used to level the substrates (mainly concrete slabs) before floor coverings are applied. Although such compounds are used extensively, only limited research on their moisture and alkali properties and their functioning in floor constructions has thus far been conducted. The aim of the present study was to investigate the moisture and alkali properties of SLCs and gain a better understanding of their interaction with other materials in floor constructions.

<p>

Many traditional methods of determining the moisture properties of building materials are time-consuming and are unsuitable for SLCs. Within the project, new methods, such as a rapid method for the simultaneous determination of both the moisture sorption isotherms and of diffusion coefficients, were developed.

<p>

Measurements were performed of such moisture properties as the chemical binding of water, the physical binding of it (the moisture sorption isotherm), moisture transport (diffusion), and the rate of surface evaporation and of moisture transport to a concrete substrate, with the aim of better understanding the drying behaviour involved and enabling predictions of the long-term moisture state of SLCs to be obtained. The results served as the basis for a drying model that was developed into a computer-based simulation programme for predicting drying times and long-term moisture states of SLCs.

<p>

Only very low rates for the transport of hydroxide ions from the concrete substrates to the SLCs and within SLCs were found to occur. This implies that SLCs can be used as barriers for protecting floor coverings and floor adhesives from the high pH of concrete.

<p>

The alkaline degradation of floor adhesives is dependent upon the pH (hydroxide ion concentration) in the zone of contact of the adhesives with the substrate. Secondary emissions from a floor construction due to alkaline degradation are thus dependent upon the pH-level and the transport of hydroxide ions in the substrate. For highly alkaline substrates, such as concrete, carbonation is essential for avoiding degradation of sensitive materials. This is not the case for SLCs that have considerably lower pH. The carbonated layer at the concrete surface may, however, due to its limited thickness, be unable to serve as a long-term protection in terms of secondary emissions. This is better provided by an SLC of lower alkalinity. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Dr. Hjorslev-Hansen, Morten, Danish Building Research Institute, Danmark
organization
publishing date
type
Thesis
publication status
published
subject
keywords
alkalinity, SLC, floor screed, moisture transport, self-levelling flooring compound, Material technology, diffusion coefficient, materialteknik, Materiallära, secondary emissions, sorption isotherm
in
Report TVBM 1025
pages
52 pages
publisher
Division of Building Materials, LTH, Lund University
defense location
Sal V:A, V-huset John Ericssons väg 1 Lunds Tekniska Högskola
defense date
2007-05-03 13:15
external identifiers
  • other:ISRN:LUTVDG/TVBM--00/1025--SE(1-47)
ISSN
0348-7911
ISBN
978-91-628-7146-8
language
English
LU publication?
yes
id
ea438de4-3bab-4fa4-b426-c80a63a58e23 (old id 548386)
date added to LUP
2009-11-09 11:10:32
date last changed
2016-09-19 08:44:53
@phdthesis{ea438de4-3bab-4fa4-b426-c80a63a58e23,
  abstract     = {&lt;p&gt;In recent decades there has been an increasing interest in the indoor environment and its connections with public health. One important topic discussed has been the relation between the moisture in buildings and health. &lt;p&gt;<br/><br>
<br/><br>
Cementitious materials, when cast, contain excess water since this is necessary for workability and for flow properties. The pore solutions in cementitious materials, besides being high in water content, often have a high pH. High-moisture conditions can cause biological growth. A combination of high moisture conditions and high pH can also result in chemical degradation of other materials, affecting both indoor environment and the technical functioning and appearance of the materials involved.<br/><br>
&lt;p&gt;<br/><br>
Self-levelling flooring compounds (SLCs) that provide smooth horizontal surfaces are used to level the substrates (mainly concrete slabs) before floor coverings are applied. Although such compounds are used extensively, only limited research on their moisture and alkali properties and their functioning in floor constructions has thus far been conducted. The aim of the present study was to investigate the moisture and alkali properties of SLCs and gain a better understanding of their interaction with other materials in floor constructions.<br/><br>
&lt;p&gt;<br/><br>
Many traditional methods of determining the moisture properties of building materials are time-consuming and are unsuitable for SLCs. Within the project, new methods, such as a rapid method for the simultaneous determination of both the moisture sorption isotherms and of diffusion coefficients, were developed.<br/><br>
&lt;p&gt;<br/><br>
Measurements were performed of such moisture properties as the chemical binding of water, the physical binding of it (the moisture sorption isotherm), moisture transport (diffusion), and the rate of surface evaporation and of moisture transport to a concrete substrate, with the aim of better understanding the drying behaviour involved and enabling predictions of the long-term moisture state of SLCs to be obtained. The results served as the basis for a drying model that was developed into a computer-based simulation programme for predicting drying times and long-term moisture states of SLCs.<br/><br>
&lt;p&gt;<br/><br>
Only very low rates for the transport of hydroxide ions from the concrete substrates to the SLCs and within SLCs were found to occur. This implies that SLCs can be used as barriers for protecting floor coverings and floor adhesives from the high pH of concrete.<br/><br>
&lt;p&gt;<br/><br>
The alkaline degradation of floor adhesives is dependent upon the pH (hydroxide ion concentration) in the zone of contact of the adhesives with the substrate. Secondary emissions from a floor construction due to alkaline degradation are thus dependent upon the pH-level and the transport of hydroxide ions in the substrate. For highly alkaline substrates, such as concrete, carbonation is essential for avoiding degradation of sensitive materials. This is not the case for SLCs that have considerably lower pH. The carbonated layer at the concrete surface may, however, due to its limited thickness, be unable to serve as a long-term protection in terms of secondary emissions. This is better provided by an SLC of lower alkalinity.},
  author       = {Anderberg, Anders},
  isbn         = {978-91-628-7146-8},
  issn         = {0348-7911},
  keyword      = {alkalinity,SLC,floor screed,moisture transport,self-levelling flooring compound,Material technology,diffusion coefficient,materialteknik,Materiallära,secondary emissions,sorption isotherm},
  language     = {eng},
  pages        = {52},
  publisher    = {Division of Building Materials, LTH, Lund University},
  school       = {Lund University},
  series       = {Report TVBM 1025},
  title        = {Studies of moisture and alkalinity in self-levelling flooring compounds},
  year         = {2007},
}