Abstract
In this paper, fly ash, ladle furnace slag and limestone filler were utilized in concrete used as material for additive manufacturing (3D printing). Fly ash and ladle furnace slag were used as a replacement of cement (30% wt.) and limestone filler as a replacement of siliceous aggregates (50% wt.). Workability of fresh concretes that contained these by-products was measured 0, 15 and 30 minutes after mixing. Three different workability tests were conducted and compared: flow table, ICAR rheometer and an experimental method that measures the electric power consumption of the motor that rotates the screw extruder. Workability parameters that were measured were evaluated regarding printability of mixtures. Density, ultrasonic pulse velocity, compressive and flexural strength were measured on hardened concrete. Additionally, relative likelihood of cracking of different concrete mixtures was estimated by performing restrained shrinkage test (ASTM C1581). Results showed that use of fly ash or ladle furnace slag as binder, and limestone filler as aggregate decreases slightly the mechanical properties of concrete but improve its durability regarding cracking potential. Monitoring of electric power consumption of screw extruder motor was found to be an effective method for measuring easily real-time workability and define if a mixture is printable or not.
Highlights
3-D printing technology is an additive manufacturing technique in which a structure is built layer by layer with various printing materials, based on a three dimensional (3D) model data
Power consumption is decreased and this can be attributed to the fact that higher quantity of cement renders to lower quantity of aggregate in a given volume of concrete and less friction induced by the aggregates in the moving parts of the screw extruder
Mixtures with Fly Ash (FA) seem to lose more rapidly workability compared to mixtures with cement or cement and Ladle Furnace Slag (LFS) as binder
Summary
3-D printing technology is an additive manufacturing technique in which a structure is built layer by layer with various printing materials, based on a three dimensional (3D) model data. Fresh concrete properties were estimated using a rotational rheometer [22,23] and the flow table test according to EN 1015-3 [24] These tests were conducted 0, 15 and 30 min after mixing in order to determine the rate of which the workability is lost for the given 3D printing system and materials. Performing of these tests requires extracting an adequate quantity of the material from the printing system and results are obtained after the test is completed For this reason, a new method was implemented in order to estimate real-time workability of fresh concrete during printing by recording real time energy consumption of screw extruder motor.
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