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Uttorkning av lågcementbetong

Andersson, Axel LU and Jonasson, Elias LU (2024) In 0349-4969 VBKL01 20241
Division of Structural Engineering
Abstract
New laws and environmental certifications are being introduced today to reduce the
environmental impact of the construction industry. From 2022 onwards, environmental
declarations have been required for new buildings with a construction area of more than
100 m2
in order to control the environmental impact of a building. Cement production
accounts for a large proportion of carbon dioxide emissions during construction, and
35% of carbon dioxide emissions from cement production come from the calcination of
limestone. To reduce the environmental impact of the construction sector, cement
consumption must be reduced, which could be done by using low-cement concrete.
The drying time of concrete is a crucial factor in the... (More)
New laws and environmental certifications are being introduced today to reduce the
environmental impact of the construction industry. From 2022 onwards, environmental
declarations have been required for new buildings with a construction area of more than
100 m2
in order to control the environmental impact of a building. Cement production
accounts for a large proportion of carbon dioxide emissions during construction, and
35% of carbon dioxide emissions from cement production come from the calcination of
limestone. To reduce the environmental impact of the construction sector, cement
consumption must be reduced, which could be done by using low-cement concrete.
The drying time of concrete is a crucial factor in the construction process and has a
major impact on the total construction time. The aim of this thesis is therefore to
investigate the drying of low-cement concrete and compare it with the drying time of
traditional concrete.
Five different types of cement mortar and three different types of concrete were used to
investigate the drying time. Cement mortar consists of cement, sand and water, and in
some cases, finely ground limestone flour, so called filler. Concrete consists of cement
mortar, aggregate and water. In one case, the concrete was produced by infiltrating a
bed of coarse gravel with a flowable cement mortar. This type of concrete was called
cement-bound-makadam.
The drying time was analyzed by continuous weight measurements of soaked mortar
slabs of size 40x40x4 mm and soaked concrete prisms of size 100x200x400 mm, when
these were allowed to dry in an environment with different relative humidity. The
results of the measurements show that concrete with a lower cement content tends to
dry out faster than traditional concrete, despite a higher initial moisture content. This is
explained by the fact that concrete with a low cement content has coarser pores, which
facilitates drying through capillary moisture transport through vapor diffusion. An
additional contributing factor to the faster drying of low-cement concrete may be that
limestone flour has been used to compensate for the reduced cement content. The
addition of clayey fine material could have had the opposite effect, but this issue has
not been studied in this thesis. Within the framework of the thesis simplified analyzes
of the expected drying times of concrete prisms have also been carried out. The
analyzes also indicate that concrete prisms with a low cement content dry faster than
traditional concrete, but the results are subject to great uncertainty. (Less)
Popular Abstract (Swedish)
Nya lagar och miljöcertifieringar införs idag för att minska byggindustrins miljö- och
klimatpåverkan. Från och med 2022 har krav ställts på klimatdeklaration av
nybyggnationer med en byggnadsarea större än 100 m2
för att kontrollera hur stor
klimatpåverkan en byggnad har. Cementproduktionen står för en stor del av
byggindustrins koldioxidutsläpp, vilket gör att byggindustrins koldioxidutsläpp
väsentligt kan minskas genom en mer rationell användning av cement, till exempel
genom att i större utsträckning använda betong med låg cementhalt.
Uttorkningstiden för betong är en avgörande faktor i byggprocessen och har en stor
påverkan på den totala byggtiden. Syftet med detta kandidatarbete är därför att
undersöka uttorkningen... (More)
Nya lagar och miljöcertifieringar införs idag för att minska byggindustrins miljö- och
klimatpåverkan. Från och med 2022 har krav ställts på klimatdeklaration av
nybyggnationer med en byggnadsarea större än 100 m2
för att kontrollera hur stor
klimatpåverkan en byggnad har. Cementproduktionen står för en stor del av
byggindustrins koldioxidutsläpp, vilket gör att byggindustrins koldioxidutsläpp
väsentligt kan minskas genom en mer rationell användning av cement, till exempel
genom att i större utsträckning använda betong med låg cementhalt.
Uttorkningstiden för betong är en avgörande faktor i byggprocessen och har en stor
påverkan på den totala byggtiden. Syftet med detta kandidatarbete är därför att
undersöka uttorkningen för cementsnål betong och ställa mot uttorkningstiden för
traditionell betong.
Fem olika sorters cementbruk och tre olika sorters betong har använts till undersökning
av uttorkningstid. Cementbruk består av cement, sand och vatten, och i förekommande
fall finmalt kalkstensmjöl, så kallad filler. Betong består av cementbruk, stenmaterial
och vatten. I ett fall har betongen tillverkats genom att infiltrera en bädd av grov
makadam med ett lättflytande cementbruk. Den här typen av betong kallas för
cementbunden makadam.
Uttorkningstiden har studerats genom kontinuerliga viktmätningar av blötlagda
bruksskivor med storleken 40x40x4 mm och blötlagda betongprismor med storleken
100x200x400 mm, när dessa fick torka i miljö med olika relativ fuktighet. Resultatet
av mätningarna visar att betong med lägre cementhalt har en tendens att torka ut
snabbare än traditionell betong, trots högre initial fukthalt. Detta förklaras av att betong
med låg cementhalt har grövre porer, vilket underlättar uttorkning genom kapillär
fukttransport. Kapillär fukttransport sker mycket fortare än fukttransport genom
ångdiffusion. En ytterligare bidragande orsak till den snabbare uttorkningen hos betong
med låg cementhalt kan vara att kalkstensmjöl har använts för att kompensera för det
minskade cementinnehållet. Tillsats av lerhaltigt finmaterial kunde ha medfört en
motsatt effekt men frågan har inte studerats inom kandidatarbetet. Inom ramen för
kandidatarbetet har även förenklade analyser gjorts av förväntade uttorkningstider hos
betongprismor. Även analyserna pekar mot att betongprismorna med låg cementhalt
torkar snabbare än traditionell betong men resultaten är behäftade med stora
osäkerheter. (Less)
Please use this url to cite or link to this publication:
author
Andersson, Axel LU and Jonasson, Elias LU
supervisor
organization
alternative title
Drying out of low-cement concrete
course
VBKL01 20241
year
type
M2 - Bachelor Degree
subject
publication/series
0349-4969
report number
5301
other publication id
LUTVDG/TVBK-24/5301-SE
language
Swedish
additional info
Handledare: Miklos Molnar och Mohammad Kahangi
Examinator: Eva Frühwald Hansson
id
9170649
date added to LUP
2024-08-19 14:15:27
date last changed
2024-08-19 14:26:33
@misc{9170649,
  abstract     = {{New laws and environmental certifications are being introduced today to reduce the 
environmental impact of the construction industry. From 2022 onwards, environmental 
declarations have been required for new buildings with a construction area of more than 
100 m2
in order to control the environmental impact of a building. Cement production 
accounts for a large proportion of carbon dioxide emissions during construction, and 
35% of carbon dioxide emissions from cement production come from the calcination of 
limestone. To reduce the environmental impact of the construction sector, cement 
consumption must be reduced, which could be done by using low-cement concrete.
The drying time of concrete is a crucial factor in the construction process and has a 
major impact on the total construction time. The aim of this thesis is therefore to 
investigate the drying of low-cement concrete and compare it with the drying time of 
traditional concrete.
Five different types of cement mortar and three different types of concrete were used to 
investigate the drying time. Cement mortar consists of cement, sand and water, and in 
some cases, finely ground limestone flour, so called filler. Concrete consists of cement 
mortar, aggregate and water. In one case, the concrete was produced by infiltrating a 
bed of coarse gravel with a flowable cement mortar. This type of concrete was called 
cement-bound-makadam.
The drying time was analyzed by continuous weight measurements of soaked mortar 
slabs of size 40x40x4 mm and soaked concrete prisms of size 100x200x400 mm, when 
these were allowed to dry in an environment with different relative humidity. The 
results of the measurements show that concrete with a lower cement content tends to 
dry out faster than traditional concrete, despite a higher initial moisture content. This is 
explained by the fact that concrete with a low cement content has coarser pores, which 
facilitates drying through capillary moisture transport through vapor diffusion. An 
additional contributing factor to the faster drying of low-cement concrete may be that 
limestone flour has been used to compensate for the reduced cement content. The 
addition of clayey fine material could have had the opposite effect, but this issue has 
not been studied in this thesis. Within the framework of the thesis simplified analyzes 
of the expected drying times of concrete prisms have also been carried out. The 
analyzes also indicate that concrete prisms with a low cement content dry faster than 
traditional concrete, but the results are subject to great uncertainty.}},
  author       = {{Andersson, Axel and Jonasson, Elias}},
  language     = {{swe}},
  note         = {{Student Paper}},
  series       = {{0349-4969}},
  title        = {{Uttorkning av lågcementbetong}},
  year         = {{2024}},
}