Study On The Drying Shrinkage Of Vitrified Microsphere Insulation Mortar

Vitrified microsphere insulation mortar is a kind of inorganic thermal insulation mortar which possess the feature of green environmental protection, admirable thermal insulation performance, excellent flame retardation propertie and high durability. At present, studies about the vitrified microsphere insulation mortar mainly concentrated on the mechanical and thermal properties, the studies concerning the shrinkage performance is comparatively rare. But the shrinkage is the main cause of cracking of insulation mortar. Once the insulation mortar crack, it will make the thermal insulation system leakage and the insulation performance of the insulation mortar decreased. And the leakage of water will exacerbate the cracking of insulation mortar and even make it burst off in the freezing and thawing cycles. In addition, the insulation mortar will be corroded by the gases such as SO 2 with water as the carrier, thus reduce its durability.First, paper study the influence of aggregate quantity of insulation mortar on the drying shrinkage and other performance. The results showed that when the dosage of vitrified microsphere is 40%, its dry density meet the requirement of II type insulation mortar, the thermal conductivity also meet the basic requirement, with good strength, and early drying shrinkage decrease in a certain extent compare to the insulation mortar which aggregate quantity is 30%. Therefore, 40% was chosen as the aggregate content of optimal ratio.Then paper study the effect of water to binder ratio on drying shrinkage and other properties of insulation mortar. Results show that when the water to binder ratio of vitrified microsphere insulation mortar is 1.4, the drying shr inkage is greatly decline, also has high compressive strength, lower dry density and suitable thermal conductivity compare to the insulation mortar which water to binder ratio is 1.5. And three indicators can all well meet the requirements of II type insulation mortar. So, 1.4 was chosen as the water to binder ratio of optimal ratio.Again paper study the effect of fly ash, polypropylene fiber, redispersible latex powder and air entraining agent on the drying shrinkage of vitrified microsphere insulation mortar. The results show that the drying shrinkage of insulation mortar decrease with the increase of the amount of fly ash. With the increase of the quantity of polypropylene fiber, the drying shrinkage of vitrified microsphere insulation mortar reduce quickly. With redispersible latex powder content increase, the dry ing shrinkage of insulation mortar decreased first and then increased, and when the content reaches 2%, the drying shrinkage is minimum. With the increase of the dosage of air entraining agent, the drying shrinkage of insulation mortar showed trend of increasing. And at the age of 7th days, the sequence of the influence of each factor on the drying shrinkage of insulation mortar from large to small in turn is: polypropylene fiber, air entraining agent, fly ash, redispersible latex powder. But at the rest of the time, sequence from large to small in turn is: air entraining agent, polypropylene fiber, fly ash, re dispersible latex powder.Finally, the A1B4C2D1 group with the minimum shrinkage in the table of orthogonal test was selected after a comprehensive consideration, and its performance is tested. The results show that the three most important indexes including dry density, compressive strength and thermal conductivity can meet the requirements of the specification for the II type insulation mortar.