Research On The Prepartion And Properties Of Machine Sprayed Mortar

Mortar of machine spraying changed the traditional manual process because of the construction of high efficiency, good quality, cost saving and many other advantages. But mechanical spraying technology puts forward higher requirements on water retention, bonding strength, hardening strength and rheological properties, it's great significantly to study the effects of each component on performance of mortar and prepare the mortar mixing rate suit for mechanical spraying technology.In the paper, cellulose ethers, redispersible powder, mineral admixtures were studied on the performance of machine spraying mortar and the performance included water retention, flexural strength, compressive strength and bonding strength and so on. The type of material and content were determined and excellent performance machine spraying mortar prepared by orthogonal test. The rheological properties are further analyzed and evaluated by using the rheometer.The results indicated that: between the two kinds of cellulose ethers, HPMC is more conducive to improving the water retention properties of mortar and its water retention is more than 90% when content is 0.15%, But HPMC would reduce the mechanical properties of mortar, the compressive strength decreased by 20%~35% when content was 0.05%. The results showed that 100Pa·HPMC mortar was suitable as water retention agent. The flexibility and tensile bond strength of mortar were improved by adding the powder which J2 and J3 were recommended. Fly ash was beneficial to improve the water retention performance and workability but which would decrease the strength. The rate of water retention was improved and reached 92.8% when the content of slag is 40%. The 28 days strength of mortar would increased and then decreased by increase the slag replacement level. The rate of water retention was improved by 8% when the content of limestone was 20%. Limestone powder could significantly improve the strength of mortar and the compressive strength of powder 1 and powder 2 improved by 31.2% and 36.9% respectively. The best ratio of mortar was 0.05% A + 1.5% B +10 % C + 15% D + 14% E.The rheological properties of fresh mortar influenced by water-cement ratio, HPMC content, pre-sterring time and testing time. The yield stress and plastic viscosity of fresh mortar gradually decreased with the increase of water-cement ratio. The viscosity of cellulose ether did not affect the rheological properties of mortar. The yield stress of mortar increased and then decreased, the plastic viscosity decreased and then increased with the increase of HPMC. The yield stress and plastic viscosity gradually decreased with the increase of stirring time. The yield stress increased gradually by increasing test time.