Experimental investigations on the influence of nozzle travel speed and height on the mechanical properties of 3D printed concrete
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摘要: 为研究喷嘴行进速度、喷嘴高度等打印参数对3D打印混凝土力学性能的影响,制备了相同配合比的浇筑试块和不同打印参数组合下的打印试块,通过混凝土立方体抗压试验、棱柱体轴心抗压试验和立方体劈裂抗拉试验,考察了其受力破坏过程和破坏形态,分析了喷嘴行进速度、喷嘴高度对3D打印混凝土力学性能的影响,得到了3D打印混凝土轴心受压应力-应变曲线,建立了3D打印混凝土各强度之间的关系。结果表明:3D打印混凝土立方体抗压强度、轴心抗压强度、劈裂抗拉强度均随喷嘴行进速度的加快、喷嘴高度的升高而降低,且喷嘴高度对强度的不利影响强于喷嘴行进速度;在较优打印参数组合下,打印试块的抗压强度高于浇筑试块,但因打印试块存在层间粘结弱面,其劈裂断面在其层间界面处,致使断面明显平滑,劈裂抗拉强度低于浇筑试块;通过回归分析,建立了3D打印混凝土各强度与打印参数间的函数关系及轴心抗压强度、劈裂抗拉强度与立方体抗压强度之间的换算关系。Abstract: In order to study the influence of printed parameters such as nozzle travel speed and nozzle height on the mechanical properties of 3D printed concrete (3D PC), the same mix proportion of cast test blocks and printed test blocks with different printed parameters were prepared. Through concrete cubic compressive test, prismatic axial compressive test and cubic splitting tensile test, the failure process and failure mode were investigated, the influence of nozzle travel speed and nozzle height on the mechanical properties of 3D PC were analyzed, the axial compression stress-strain curve of 3D PC was obtained, and the relationships between the strengths of 3D PC were established. The results show that the cubic compressive strength, axial compressive strength and splitting tensile strength of 3D PC decrease with the acceleration of nozzle travel speed and the increase of nozzle height, and the adverse effect of nozzle height on strengths is stronger than that of nozzle travel speed. Under the optimal combination of printed parameters, the compressive strength of printed test block is higher than that of cast test block. However, due to the weak interlayer bonding surface of printed test block, the splitting section is at the interlayer interface, resulting in an obvious smooth section, and the splitting tensile strength is lower than that of cast test block. Through regression analysis, the functional relationships between the strengths of 3D PC and printed parameters, as well as the conversion relationships between axial compressive strength, splitting tensile strength and cubic compressive strength were established.
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图 9 3D打印混凝土强度与打印参数的关系
Figure 9. Relationship between strength of 3D printed concrete and printed parameters
v/v0—Nozzle relative travel speed; h/h0—Nozzle relative height; $ {\eta _{{f_{{\text{cu}}}}}} $—Change rate of cubic compressive strength of 3D printed concrete comparedto cast concrete; $ {\eta _{{f_{\text{c}}}}} $—Change rate of axial compressive strength of 3D printed concrete compared to cast concrete; $ {\eta _{{f_{\text{t}}}}} $—Change rate of splittingtensile strength of 3D printed concrete compared to cast concrete
表 1 3D打印混凝土配合比
Table 1. Mix proportion of 3D printed concrete
wt% P·O42.5 R·SAC42.5 Sand PCE HPMC GF Water 0.8 0.2 1.25 0.25 0.15 0.5 0.35 Notes: P·O42.5—Ordinary portland cement; R·SAC42.5—Sulpho-aluminate early-strength cement; PCE—Polycarboxylic acid superplasticizer; HPMC—Hydroxypropyl methyl cellulose; GF—Glass fiber. 表 2 3D打印混凝土各项力学性能指标
Table 2. Mechanical property indexes of 3D printed concrete
Sample $ {f_{{\text{cu}}}}/{\text{MPa}} $ $ {f_{\text{c}}}/{\text{MPa}} $ $ {f_{\text{t}}}/{\text{MPa}} $ $ {\varepsilon _{\text{0}}}/{10^{_{ - 3}}} $ $ {E_{\text{c}}}/{\text{GPa}} $ fc/fcu ft/fcu 110-14 45.64 35.79 2.58 2.26 15.77 0.78 0.06 110-17 43.59 33.97 2.35 2.31 14.96 0.78 0.05 110-20 39.86 30.10 2.06 1.82 14.26 0.76 0.05 120-14 44.21 33.52 2.51 2.96 16.02 0.76 0.06 120-17 42.90 30.91 2.29 2.50 14.16 0.72 0.05 120-20 37.98 27.15 1.93 1.94 15.14 0.71 0.05 130-14 43.99 32.51 2.37 2.60 15.61 0.74 0.05 130-17 41.37 28.34 2.11 1.73 14.50 0.69 0.05 130-20 35.24 25.90 1.68 2.63 14.02 0.73 0.05 140-14 42.84 31.61 2.28 2.67 14.63 0.74 0.05 140-17 39.45 27.06 1.80 2.95 16.25 0.69 0.05 140-20 33.78 23.93 1.49 2.31 13.44 0.71 0.04 150-14 41.59 30.58 1.99 2.66 14.30 0.74 0.05 150-17 38.09 26.75 1.65 2.73 13.67 0.70 0.04 150-20 31.10 21.52 1.15 2.33 12.59 0.69 0.04 Cast 42.82 34.03 3.04 2.18 16.52 0.79 0.07 Notes: $ {f_{{\text{cu}}}} $—Cubic compressive strength; $ {f_{\text{c}}} $—Axial compressive strength; $ {f_{\text{t}}} $—Splitting tensile strength; $ {\varepsilon _{\text{0}}} $—Peak strain; $ {E_{\text{c}}} $—Elastic modulus. -
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