Abstract
The mix proportioning of extrusion-based 3D-printed cementitious material should balance printability and hardened properties. This paper investigated the effects of three key mix proportion parameters of 3D-printed alkali-activated fly ash/slag (3D-AAFS) mortar, i.e., the sand to binder (s/b) ratio, fly ash/ground granulated blast-furnace slag (FA/GGBS) ratio, and silicate modulus (Ms) of the activator, on extrudability, buildability, interlayer strength, and drying shrinkage. The results showed that the loss of extrudability and the development of buildability were accelerated by increasing the s/b ratio, decreasing the FA/GGBS ratio, or using a lower Ms activator. A rise in the s/b ratio improved the interlayer strength and reduces the drying shrinkage. Although increasing the FA/GGBS mass ratio from 1 to 3 led to a reduction of 35% in the interlayer bond strength, it decreased the shrinkage strain by half. A larger silicate modulus was beneficial to the interlayer bond strength, but it made shrinkage more serious. Moreover, a simple centroid design method was developed for optimizing the mix proportion of 3D-AAFS mortar to simultaneously meet the requirements of printability and hardened properties.
Highlights
3D printing, known as additive manufacturing, is an emerging technology to produce well-designed 3D products in the absence of formwork [1,2]
For a full understanding of the relationship between the composition of 3D-printed alkali-activated fly ash/slag (3D-AAFS) mortar and its properties, this study comprehensively investigated the influences of the sand-to-binder ratio, the relative proportion of FA-ground granulated blast furnace slag powder (GGBS) precursors, and the silicate modulus of the activator on the printability, interlayer bond strength, and volume stability of 3D-AAFS mortar for the first time
The following conclusions can be summarized from the presented findings: (1) The composition of alkali-activated fly ash/slag (AAFS) mortar exerts a tremendous
Summary
Rheological tests were performed by a Rheolab QC rheometer (Anton Paar, Grazw, t.%). ST22-4 V-40-SN20452, and the height and width of each blade were 40.00 mm and 22.00 mm, respePct1iv-Se1ly-.MD0uring th2e5.t0est, the25te.0mpera5tu0r.e0 was kept1at 25 ◦C us1i.n0g a water 0bath. PT3h-eS0p.r8o-cMed0ure of4t1h.7e dyna1m3.i9c yield44st.4ress test c3onsisted of0p.8reshearing0at 100 s−1 3.5 for 6P01s-S, 1re-sMti0n.g5 for 1525s.,0ramp2in5g.0up fro5m0.00 to 100 s1−1 in 60 s, s1topping f0o.r530 s, and 3.5 ramping down from 100 to 0 s−1 in 60 s. 22.2.2.2..RShtaetoilcogTeicsatl Tests for AAFS Mortar BRefhoereoltohegisctaatlicteysietsldwsheeraer pteesrt,fothremseadmpblye waaRs hpereoslhaebarQedCatrh10e0osm−e1tfeorr 6(A0 snttoonreaPcahar, Graz aAcuonstsriisate)nwt iinthitiaalcsytalitned[6r3ic].aTl hgeeotemstewtrays oruf n41a.t9a4cmonmstainntisnhneearr rdaitaemofe0te.0r2. Ts−h1efotyrp6e0 so,f rotato twheaps eSaTk2v2a-l4ueVo-4f0t-hSeNm2e0a4s5u2r,edansdhetahresthreesigshwtaasnddenwoitdedthasoftheeascthatbiclaydieeldwsetrreess4.0.T0h0emm and test was repeated every 5 min until the yield stress reached the upper limit value of the 22.00 mm, respectively. The temperature was kept at 25 °C using a wate bath
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