The Development And Application Of High-performance Accelerator For Shotcrete

View the present situation of the big rebound and the poor durability of theshotcrete in China, on reading a large number of domestic and foreign patents andliteratures and using chemical modification, organic and inorganic compositetechnology, we successfully developed two used in shotcrete as quick-setting, lowcorrosion and low springback of high performance liquid accelerator. Based on theaccelerating agent modification application experimental study, and finally by usingXRD and SEM modern microscopic analysis methods for its mechanism is discussed.The development of the high-performance Accelerator:(1) The low alkali liquid accelerator: First to determine the optimal dosage ofcomponents accelerator for liquor by orthogonal test. Aluminum sulfate content was46%, Alcohol amine content was4%,Sodium fluoride content was4%, The calciumnitrate content was9%.Then introduce the calcium formate, Its content is0.5%~1%,Itis used as early strength components. Also adding0.2%~0.3%of polyacrylamide, It isused as a viscosifier. The last low alkaline liquid accelerator was got. The acceleratorwas a red-brown transparent liquid, of which the solid content was42%, the alkalicontent was less than3%.(2) The alkali liquid accelerator: First to determine the optimal dosage ofcomponents accelerator for liquor by orthogonal test. Aluminum sulfate content was50%, Hydroxy carboxylic acid content was1%, Alcohol amine content was7%,Polyhydric alcohol content was8%. Then introduce the phosphate, Its content is1%~2%,It is used as stabilizer. Also adding0.2%~0.3%of polyacrylamide, It is used as aviscosifier. The alkali liquid accelerator was got. The accelerator was light greentransparent liquid, of which the solid content was44%.The performance experimental study showed that: the adjustability with differentbrands of ordinary portland cement was good; and the compatibility with naphthaleneseries superplasticizer and polycarboxylic type superplasticizer, basically met therequirements, and when they were combined to use, the introduction of superplasticizerwould affect the procoagulant effect of the accelerator, but an appropriate increase in thedosage of the accelerator or decrease in cement ratio could ensure the procoagulant effect of the accelerator. The time of introduction would significantly affect itsaccelerating effect. In the engineering construction, jet construction should be made assoon as possible after mixing with water, so as not to affect its accelerating effect.Concrete field spraying testing determined that the optimum wet sprayed concretesand ratio ranged from50%to55%; maximum aggregate size ranged from13.2mm to16mm; mixing highly active mineral admixtures had an effect on shotcrete suppressionresilience and the improvement of bond strength with the rock.By means of XRD and SEM modern microscopic analysis methods foraccelerating mechanism study found: Different from traditional alkaline acceleratingagent action mechanism, The two kinds of liquid accelerator is by accelerating C3Ahydration and shorten the induction period of or eliminate C3S to achieve rapid settingand the early strength of concrete.