Hardened Properties of 3D Printable Ultra-High Performance Fiber-Reinforced Concrete for Digital Construction Applications

3D Concrete Printing: A Systematic Review of Rheology, Mix Designs, Mechanical, Microstructural, and Durability Characteristics

“…The interface is the weakest point of printed concrete; therefore, it could not resist tensile stresses, and hence, flexural strength along the X -axis is lower. Figure 10 also indicates that flexural strength measured along the Y -axis has been observed to be higher than that of casted concrete [ 125 , 127 , 135 , 178 , 179 , 183 ] except Mechtcherine et al [ 1 ]. Mixed reports are available for the flexural strength along the Z -axis.…”

“…The frequent reported water-binder ratio lies within the range of 0.30–0.40, and the frequent sand-binder ratio lies within the range of 1.2–2.0. Researchers have also developed printable mixes with a high dosage of fibers to reinforce concrete [ 61 , 125 , 126 , 127 , 128 ]. Additional research is needed for optimizing fiber-reinforced printable concrete mixes such as engineered cementitious composites and ultra-high-performance fiber-reinforced concrete as the addition of fibers reduces the workability and has negative consequences upon the performance of concrete during pumping and extrusion steps.…”

“…A critical view of the data plotted in Figure 10 indicates two interesting pieces of evidence: first, the flexural strength of printed concrete along the X -axis has been reported lower than the flexural strength of casted concrete. Second, the flexural strength measured along the X -axis has also been reported lower than the flexural strength measured along the Y and Z axes [ 1 , 125 , 127 , 135 , 151 , 175 , 178 , 179 , 183 , 184 ]. This is due to the creation of tensile stresses between the extruded layers at the interface when flexural force applies along X -axis.…”

“…Mixed reports are available for the flexural strength along the Z -axis. Some studies have reported it to be lower than the flexural strength of casted concrete [ 1 , 142 , 165 , 180 , 184 ] while others have observed opposite results [ 61 , 125 , 127 , 135 , 175 , 178 , 183 , 187 ]. It is notable here that fiber-containing printable mixes [ 125 , 127 ] have always exhibited improved flexural strength along the Z -axis than the corresponding flexural strength of casted concrete.…”

“…Some studies have reported it to be lower than the flexural strength of casted concrete [ 1 , 142 , 165 , 180 , 184 ] while others have observed opposite results [ 61 , 125 , 127 , 135 , 175 , 178 , 183 , 187 ]. It is notable here that fiber-containing printable mixes [ 125 , 127 ] have always exhibited improved flexural strength along the Z -axis than the corresponding flexural strength of casted concrete. The increase in flexural performance of fiber-reinforced printable mixes has been associated with the alignment of the fibers along the printing direction at the extruding nozzle [ 61 ].…”