Title Sastav betona za 3D printanje
Title (english) Concrete mix design for 3D printing
Author Lucija Ricov
Mentor Ivana Banjad Pečur (mentor)
Committee member Ivana Banjad Pečur (predsjednik povjerenstva)
Committee member Bojan Milovanović (član povjerenstva)
Committee member Marijan Skazlić (član povjerenstva)
Granter University of Zagreb Faculty of Civil Engineering (Materials) Zagreb
Defense date and country 2020-09-24, Croatia
Scientific / art field, discipline and subdiscipline TECHNICAL SCIENCES Civil Engineering
Abstract Zbog potrebe za sve bržim i automatiziranim radom, u suvremenom graditeljstvu sve više se razvija, i sve više područja zahvaća nova mogućnost ugradnje betona pomoću 3D printanja. Tehnologija 3D printanja zahtjeva stroge kriterije za svojstva u svježem i očvrsnulom stanju, koja uvjetuju i izbor komponenti i sastav betona. Razvoju betona za 3D printanje najviše su pridonijela postignuća na području samozbijajućeg betona i mokrog postupka izvedbe mlaznog betona. Najveće promjene koje ova tehnologija donosi su ugradnja betona bez oplate i bez vibriranja ugrađenog betona. Pripremljena mješavina betona se kroz sustav cijevi transportira pod pritiskom pumpe do mlaznice na glavi printera kroz koju se istiskuju tanke, kontinuirane betonske niti koje zajedno tvore betonske slojeve, koji tvore čitavi betonski element. Zbog svoje specifičnosti, ovakva tehnologija donosi i neka nova svojstva i metode ispitivanja istih. Svojstva koja mješavina svježeg betona za 3D printanje mora zadovoljiti su sposobnost transporta kroz sustav cijevi i istiskivanja kroz mlaznicu, sposobnost građenja velikog broja slojeva bez značajnijih deformacija te dostatno vrijeme vezivanja za proces printanja uz dobru obradivost za vrijeme cijelog procesa. Optimalna mješavina betona koja zadovoljava u pogledu navedenih svojstava, kvalitetna izvedba procesa printanja i njega ugrađenog betona, trebala bi zadovoljiti i zahtjeve za svojstva u očvrsnulom stanju, a to su visoka tlačna čvrstoća i čvrstoća na savijanje, vlačna čvrstoća u pogledu čvrste i kvalitetne veze između slojeva i minimiziranje skupljanja uslijed sušenja kao kritičnog svojstva betona za 3D printanje s obzirom da beton očvršćava bez oplate. Brojna istraživanja znanstvenika iz područja građevinarstva tijekom zadnjih desetljeća donijela su važne smjernice za projektiranje sastava betona za 3D printanje. Ustanovljeno je da je za postizanje zahtijevanih svojstava potrebno maksimalno zrno riječnog agregata 2 mm, zamjena dijela cementa mineralnim dodacima kao što je leteći pepeo za poboljšanje obradivosti i silicijska prašina za povećanje granice tečenja bez utjecaja na viskoznost, doziranje superplastifikatora za smanjenje vodovezivnog omjera i postizanje dostatne obradivosti i usporivača vezivanja za postizanje protočnosti za vrijeme cijelog procesa printanja, upotreba vlakana za povećanje čvrstoće na kidanje i na savijanje te ubrzivača vezivanja na mlaznici za kontrolu polaganja betona. Optimalna mješavina mora zadovoljiti stroge kriterije tlačne čvrstoće od 100 MPa i čvrstoće na savijanje od 12 MPa u starosti od 28 dana. U radu je opisan tijek projektiranja sastava betona za 3D printanje, metode ispitivanja relevantnih svojstava te postignuta svojstva za beton ugrađen tehnologijom 3D printanja.
Abstract (english) Due to the need for faster and more automated work, modern construction is increasingly developing, and more and more areas are affected by the new possibility of concrete installation using 3D printing. 3D printing technology requires strict criteria for fresh and hardened properties, which condition both the selection of components and mix design for 3D printing concrete. The development of concrete for 3D printing was mostly influenced by the achievements in the area of self-compacting concrete and wet process of the performance of jet concrete. The greatest changes this technology brings are the installation of concrete without formwork and without vibration of built-in concrete. The prepared concrete mix is transported through the pipe system under pump pressure to the printer head nozzle through which thin continuous concrete fibres are extruded, forming together concrete layers, forming the entire concrete element. Due to its specificity, this technology brings some new characteristic and methods of testing them. Properties that the mix of fresh concrete for 3D printing must meet the ability to transport through the pipe system and to be extruded through the nozzle, buildability of a large number of layers without significant deformations, and sufficient open time for printing process with good workability. An optimum mix of concrete satisfying the before mentioned fresh properties, good quality performance and proper curing method should provide also hardened properties, which are high compressive and flexural strength, tensile strength in terms of firm and high quality bond between the layers and minimisation of drying shrinkage which is critical feature of concrete for 3D printing, since concrete is hardened without framework. Numerous research by scientists in the field of construction over the past decades has brought important guidelines for the design of concrete for 3D printing. It has been established that to achieve the required properties, a maximum grain of the 2 mm river aggregate is required, a replacement of a part of cement with mineral additives such as fly ash to improve workability and silica fume to increase the yield stress without affecting viscosity, the dosage of superplasticiser for minimazing water-binder ratio and to achieve sufficient workability, and the dosage of retarder to achieve flowability throughout the printing process, the use of fibres to increase flexural and tensile strength, and accelerator to control setting of concrete by the nozzle. The optimum mixture must meet the strict compressive strength criteria of 100 MPa and flexural strength of 12 MPa at 28 days. This paper describes the course of mix design, the methods for testing relevant properties and the achieved properties for concrete installed with 3D printing technology.
Keywords
3D printanje
sastav betona
sposobnost istiskivanja
sposobnost građenja slojeva
vrijeme vezivanja
obradivost
čvrstoća
Keywords (english)
3D printing
concrete mix design
extrudability
buildability
open time
workability
strength
Language croatian
URN:NBN urn:nbn:hr:237:097473
Study programme Title: Civil Engineering; specializations in: Construction Management, Transportation Engineering, Geotechnical Engineering, Hydraulic Engineering, Structural Engineering, Construction Materials, Theory and Modeling of Structures Course: Construction Management Study programme type: university Study level: graduate Academic / professional title: magistar/magistra inženjer/inženjerka građevinarstva (magistar/magistra inženjer/inženjerka građevinarstva)
Type of resource Text
File origin Born digital
Access conditions Closed access
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Created on 2023-06-12 06:59:17