{"title":"Flexural and fracture performance of fiber reinforced self compacting alkali activated concrete– A DOE approach","authors":"","doi":"10.1016/j.tafmec.2024.104630","DOIUrl":null,"url":null,"abstract":"<div><p>Owing to their much-reduced carbon footprint and lower embodied energy, compared to conventional Portland Cement (OPC-based) Concrete mixes, Alkali Activated Concrete (AAC) mixes represent a pivotal advancement towards achieving sustainability goals. The fracture properties were investigated using Three-Point Bending Tests (3-PBT) under the mode I failure mechanism. This study utilises Taguchi analysis to analyse and optimise Self-Compacting Alkali-Activated Concrete (SAAC), focusing mainly on its flexural strength and fracture characteristics. An L-16 orthogonal array of experiments with three input parameters − replacement of Blast Furnace Slag (BFS) with Fly ash (FA) (0 %, 30 %, 40 %, and 50 %), Steel Fibers (SF) volume content (0 %, 0.25 %, 0.5 % and 0.75 %) and Notch to Depth (a<sub>0</sub>/d) ratio (0.2,0.3,0.4 and 0.5), at four levels each, was adopted. The Work of Fracture Method (WFM) and Double K Fracture Criterion (DKFC) were utilised to determine the Fracture Energy (G<sub>F</sub>) and fracture toughness, respectively. The results obtained from all the sixteen mixes showed that the F0-S0.75-N0.5 mix demonstrated better values in several parameters, such as flexural strength of 7.82 MPa,<span><math><mrow><mspace></mspace><msubsup><mtext>K</mtext><mrow><mtext>IC</mtext></mrow><mtext>ini</mtext></msubsup></mrow></math></span> of 0.928 MPa√m, <span><math><mrow><msubsup><mrow><mspace></mspace><mtext>K</mtext></mrow><mrow><mtext>IC</mtext></mrow><mtext>uns</mtext></msubsup></mrow></math></span> of 6.99 MPa√m and <span><math><mrow><msubsup><mtext>K</mtext><mrow><mtext>IC</mtext></mrow><mtext>ini</mtext></msubsup></mrow></math></span>/ <span><math><mrow><msubsup><mtext>K</mtext><mrow><mtext>IC</mtext></mrow><mtext>uns</mtext></msubsup></mrow></math></span> of 0.133. A maximum G<sub>F</sub> of 2350 N/m was obtained with F50-S0.75-N0.2 mix. However, all the inferior values of these parameters were observed with F50-S0-N0.5 mix, which recorded a flexural strength of 4.90 MPa, <span><math><mrow><msubsup><mtext>K</mtext><mrow><mtext>IC</mtext></mrow><mtext>ini</mtext></msubsup></mrow></math></span> of 0.612 MPa√m,<span><math><mrow><msubsup><mrow><mspace></mspace><mtext>K</mtext></mrow><mrow><mtext>IC</mtext></mrow><mtext>uns</mtext></msubsup></mrow></math></span> of 1.16 MPa√m, <span><math><mrow><msubsup><mtext>K</mtext><mrow><mtext>IC</mtext></mrow><mtext>ini</mtext></msubsup></mrow></math></span>/ <span><math><mrow><msubsup><mtext>K</mtext><mrow><mtext>IC</mtext></mrow><mtext>uns</mtext></msubsup></mrow></math></span> of 0.528 and G<sub>F</sub> of 125 N/m. Through Taguchi analysis, the optimal combination for flexural strength was identified as FA 0 %, SF 0.75 %, and a<sub>0</sub>/d 0.5 and for both Initial Fracture Toughness (<span><math><mrow><msubsup><mtext>K</mtext><mrow><mtext>IC</mtext></mrow><mtext>ini</mtext></msubsup></mrow></math></span>) and Unstable Fracture Toughness (<span><math><mrow><msubsup><mtext>K</mtext><mrow><mtext>IC</mtext></mrow><mrow><mtext>un</mtext><mtext>s</mtext></mrow></msubsup></mrow></math></span>) at FA 0 %, SF 0.75 % and a<sub>0</sub>/d 0.4. For both the ratio of initial to unstable fracture toughness (<span><math><mrow><msubsup><mtext>K</mtext><mrow><mtext>IC</mtext></mrow><mtext>ini</mtext></msubsup></mrow></math></span>/ <span><math><mrow><msubsup><mtext>K</mtext><mrow><mtext>IC</mtext></mrow><mrow><mtext>un</mtext><mtext>s</mtext></mrow></msubsup></mrow></math></span>) and fracture energy (G<sub>F</sub>), the optimum combination was FA 0 %, SF 0.75 % and a<sub>0</sub>/d 0.2. Furthermore, the results indicate that FA significantly influences <span><math><mrow><msubsup><mtext>K</mtext><mrow><mtext>IC</mtext></mrow><mtext>ini</mtext></msubsup></mrow></math></span>, while SF predominantly affects all other parameters. The predictive performance of the regression equations demonstrates good agreement with experimental outcomes.</p></div>","PeriodicalId":22879,"journal":{"name":"Theoretical and Applied Fracture Mechanics","volume":null,"pages":null},"PeriodicalIF":5.0000,"publicationDate":"2024-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Theoretical and Applied Fracture Mechanics","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S016784422400380X","RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENGINEERING, MECHANICAL","Score":null,"Total":0}
引用次数: 0
Abstract
Owing to their much-reduced carbon footprint and lower embodied energy, compared to conventional Portland Cement (OPC-based) Concrete mixes, Alkali Activated Concrete (AAC) mixes represent a pivotal advancement towards achieving sustainability goals. The fracture properties were investigated using Three-Point Bending Tests (3-PBT) under the mode I failure mechanism. This study utilises Taguchi analysis to analyse and optimise Self-Compacting Alkali-Activated Concrete (SAAC), focusing mainly on its flexural strength and fracture characteristics. An L-16 orthogonal array of experiments with three input parameters − replacement of Blast Furnace Slag (BFS) with Fly ash (FA) (0 %, 30 %, 40 %, and 50 %), Steel Fibers (SF) volume content (0 %, 0.25 %, 0.5 % and 0.75 %) and Notch to Depth (a0/d) ratio (0.2,0.3,0.4 and 0.5), at four levels each, was adopted. The Work of Fracture Method (WFM) and Double K Fracture Criterion (DKFC) were utilised to determine the Fracture Energy (GF) and fracture toughness, respectively. The results obtained from all the sixteen mixes showed that the F0-S0.75-N0.5 mix demonstrated better values in several parameters, such as flexural strength of 7.82 MPa, of 0.928 MPa√m, of 6.99 MPa√m and / of 0.133. A maximum GF of 2350 N/m was obtained with F50-S0.75-N0.2 mix. However, all the inferior values of these parameters were observed with F50-S0-N0.5 mix, which recorded a flexural strength of 4.90 MPa, of 0.612 MPa√m, of 1.16 MPa√m, / of 0.528 and GF of 125 N/m. Through Taguchi analysis, the optimal combination for flexural strength was identified as FA 0 %, SF 0.75 %, and a0/d 0.5 and for both Initial Fracture Toughness () and Unstable Fracture Toughness () at FA 0 %, SF 0.75 % and a0/d 0.4. For both the ratio of initial to unstable fracture toughness (/ ) and fracture energy (GF), the optimum combination was FA 0 %, SF 0.75 % and a0/d 0.2. Furthermore, the results indicate that FA significantly influences , while SF predominantly affects all other parameters. The predictive performance of the regression equations demonstrates good agreement with experimental outcomes.
期刊介绍:
Theoretical and Applied Fracture Mechanics'' aims & scopes have been re-designed to cover both the theoretical, applied, and numerical aspects associated with those cracking related phenomena taking place, at a micro-, meso-, and macroscopic level, in materials/components/structures of any kind.
The journal aims to cover the cracking/mechanical behaviour of materials/components/structures in those situations involving both time-independent and time-dependent system of external forces/moments (such as, for instance, quasi-static, impulsive, impact, blasting, creep, contact, and fatigue loading). Since, under the above circumstances, the mechanical behaviour of cracked materials/components/structures is also affected by the environmental conditions, the journal would consider also those theoretical/experimental research works investigating the effect of external variables such as, for instance, the effect of corrosive environments as well as of high/low-temperature.