Ehitusinseneriõppe lõputöö
Maaehituse õppekavalKäesolevas magistritöös uuriti tagastatud vedela betooni taaskasutamist uue betoonisegu
koostamisel. Töö annab ülevaate taaskasutamisest nii Eestis kui ka mujal maailmas. Üha
rohkem on üle maailma hakatud pooldama ja tegelema taaskasutamisega, kuna toorainetena
kasutatavaid loodusvarasid ei jätku lõpmatuseni. Betoon on maailmas ka enim kasutatav
ehitusmaterjal ja enimkasutatud ressurss vee järel. Tagastatud betoon on segu, mis tuuakse
betooniveokitega tehasesse tagasi ja nimetatakse üleliigseks materjaliks. Töö eesmärk on
uurida betoonisegusid, mis sisaldavad tagastatud betooni.
Magistritöös uuriti erinevaid betoonisegusid, mis sisaldasid 0%, 20%, 40% ja 60%
taaskasutatavat seisvat betooni. Uuriti betoonisegude omadusi, nagu survetugevus,
töödeldavus, lisatud vee mõju, õhusisaldust ning tsemendi tardumisaega. Kivistunud
betooni puhul võrreldi survetugevust valmis segatud ja aeglaselt tarduvas betoonis, mis on
segatud uuesti ringlusse võetud betooniga.
Katseteks kasutati kahte erineva tugevusklassiga betooni ning selgus, et teatud kogus
betoonisegust on võimalik asendada taaskasutatava betooniga. Paremad tulemused saadi
betooni tugevusklassiga C35/45, kus vajaliku tugevuse saavutasid kõik katsekehad. Tund
aega seisnud taaskasutatav betoon (segus 60%) oli segatud värske betooniga (segus 40%)
ning peale 28 päeva saadi keskmiseks survetugevuseks 48,71 MPa. Kaks tundi seisnud
taaskasutatav betoon (segus 40%) segati värske betooniga (segus 60%) ning keskmiseks
survetugevuseks saadi 49,08 MPa. Kolm tundi seisnud taaskasutatav betoon (segus 20%)
segati värske betooniga (segus 80%) ning keskmiseks survetugevuseks saadi 50,79 MPa.
Tugevama tugevusega (C50/60) betoonil tuleb kasutada väiksem kogus taaskasutatavat
betoonisegu. Tund aega seisnud taaskasutatav betoon (segus 60%) oli segatud värske
betooniga (segus 40%) ning peale 28 päeva saadi keskmiseks survetugevuseks 57,76 MPa.
Kaks tundi seisnud taaskasutatav betoon (segus 40%) segati värske betooniga (segus 60%)
ning keskmiseks survetugevuseks saadi 55,14 MPa. Kolm tundi seisnud taaskasutatav
betoon (segus 20%) segati värske betooniga (segus 80%) ning keskmiseks survetugevuseks
saadi 61,47 MPa.
Katsete põhjal saab järeldada, et kolm tundi seisnud betooni on võimalik kasutada kogu
tema olekus uuesti värske betooni koostamisel. Asendades 20% värsket betooni
taaskasutatava betooniga saab vajaliku survetugevuse kätte.
Edaspidi tuleks täiendavalt uurida, milline on taaskasutatava betoonisegu külmakindlus.In this master's thesis, the reuse of returned liquid concrete in the making of a new concrete
mix was investigated. The work provides an overview of reuse both in Estonia and
elsewhere in the world. There is growing support around the world and deal with recovery
because resources do not last indefinitely. Concrete is also the most used building material
and resource after water in the world. Returned concrete is a mixture that is brought back
to the factory by concrete trucks and is called surplus material. The aim of the work is to
study concrete mixtures that contain returned concrete.
In the master's thesis, different concrete mixtures were studied, which contained 0%, 20%,
40% and 60% recyclable standing concrete. In the case of hardened concrete, the
compressive strength was compared in ready-mixed and slow-setting concrete mixed with
recycled concrete. The concrete mixtures were studied with Abrams cone, added water, air
content in the concrete, compressive strength and setting time of the cement.
Two different strength classes of concrete were used for the experiments and it was found
that a certain amount of concrete mix can be replaced by recycled concrete. Better results
were obtained with a lower strength class (C35/45), where the required strength was
achieved by all test specimens. The recyclable concrete (in the mixture 60%) that had been
standing for one hour, was mixed with fresh concrete (in the mixture 40%) and after 28
days the average compressive strength was 48,71 MPa. After two hours the recycled
concrete (in the mixture 40%) was mixed with fresh concrete (in the mixture 60%) and the
average compressive strength was 49,08 MPa. After three hours the recycled concrete (in
the mixture 20%) was mixed with fresh concrete (in the mixture 80%) and the average
compressive strength was 50,79 MPa. For stronger strength (C50/60) concrete, a smaller
amount of reusable concrete mix must be used. The recycled concrete (60% in the mix) that
had been standing for one hour was mixed with fresh concrete (40% in the mix) and after
28 days the average compressive strength was 57.76 MPa. After two hours, the recycled
concrete (in the mixture 40%) was mixed with fresh concrete (in the mixture 60%) and the
average compressive strength was 55,14 MPa. After three hours the recycled concrete (in
the mixture 20%) was mixed with fresh concrete (in the mixture 80%) and the average
compressive strength was 61,47 MPa.
From the tests, it can be concluded that the concrete, which has been standing for three
hours, can be used in its entire state in the preparation of fresh concrete. By replacing 20%
of fresh concrete with recycled concrete, the required compressive strength is obtained.
The frost resistance of the recycled concrete mix should be further investigated in the future
