The rheological performance of wet-process sprayed mortars

Mix design and fresh properties for high-performance printing concrete

“…Earlier research concerning this ability referred to the pumping and spraying of concrete [3,4,7], but the fresh concrete exits the system as a particle stream, not an extrusion. Extruding concrete to build components has been mentioned in previous research [8][9][10][11] but a suitable test method to evaluate this ability of concrete has not been described.…”

“…Such methods have their own difficulties (especially in calibration) and cannot be conducted in-situ. Austin et al [3,4,7] adopted a shear vane apparatus (originally for measuring the shear strength of soils) to measure the workability of concrete. This approach was adopted because it derives a relevant, scientific rheological parameter (unlike, say slump) and can also evaluate the workability at various points in the production process including the mixer and container [7].…”

“…A pumpable sprayed mortar [3] and a commercial pre-packaged mortar [19] are also shown for comparison. The percentage passing 0.6 mm was over 95% for all mixes, whilst the reference sprayable mixes were in the range of 83 -90%.…”

“…Sprayed concrete [3,4] is another approach to making concrete components usually using a backing material (natural, like rock, or man-made) to eliminate temporary formwork. The mix proportions are designed for a minimum voids by a grading with the largest size particles filled with particles of the next size fraction down, and so on.…”

Low-volume wet-process sprayed concrete: hardened properties

“…The rheological performance of wet-sprayed mortars has also been investigated by the authors 3,4 . However, the concrete's hardened properties are of equal importance, so that a durable and long-lasting repair can be obtained, and it is these properties that this paper will investigate.…”