| Bonding mortar based on Super-thin Thermal Insulation Plate (STP) is the most important part of the STP external thermal insulating system. It plays a key role in improving the durability of the system. In order to overcome the disadvantages of traditional binding mortar, such as low bond strength、poor workability、poor durability and so on, this paper made a study on the law of various material factors composed of bonding mortar which influence mortar performance through a large number of experiments. It mainly analyzed the types and the adding ratio of the redispersible emulsion powder which influence bond property of bonding mortar. Taking cost-effective to improve cohesive force and flexibility of the bonding mortar as a breakthrough point, this paper has developed a fine performance bonding mortar suitable for STP. And it has obtained results that optimized bonding mortar can be able to adapt to the complex environmental conditions through a comprehensive performance testing of bonding mortar. At last, hydration mechanism of bonding mortar was studied and analyzed on the micro-level. It revealed the modification mechanism of polymer on bonding mortar by analyzing the effects of polymer on hydration products. These achievements provide a theoretical basis for the promotion and application of bonding mortar.First, this paper used low alkalinity CSA cement which has three strength grades including32.5,42.5and52.5to prepare bonding mortar. Bond strength and the ratio of compressive strength to flexural strength of bonding mortar comprehensively considered, this paper chose42.5strength grade as the cementitious material. Bonding mortar which is prepared of two mesh number40-70and70-120quartz sand mixed according to the ratio of2:1has a better water retention. This bonding mortar has maximum tensile bond strength with STP board and flexibility is also relatively best. Bonding mortar which is prepared of methylcellulose ether that has100000Pa-s viscosity has relatively minimum of14days the ratio of compressive strength to flexural strength, and the water retentivity is also higher.The mixing amount of the redispersible emulsion powder must not be too high because it is very expensive. But the mixing amount of the powder can not be less in order to ensure the bond strength of bonding mortar. This paper selected five redispersible emulsion powder, and made a study on the performance of bonding mortar by changing the dosage of the powder. The results show that the optimum mix amount of Wacker4023N powder is2.8%. The optimum mix amount of Wacker5010N powder is3.0%. The optimum mix amount of Ashland N2098powder is2.6%. The optimum mix amount of Tai Wan Da Lian DA-1220powder is2.4%. The optimum mix amount of Gomes6070powder is about3.2%.This paper made a study on the effects of water reducing agent on the performance of bonding mortar by considering whether to remove naphthalene superplasticizer. The results show that water reducing agent has no effect on the bond strength of bonding mortar. When the mixing amount of water reducing agent is reduced, flexibility of bonding mortar which is prepared of Wacker4023N powder and Ashland N2098powder become poor. Flexibility of bonding mortar which is prepared of Wacker5010N powder and Gomes6070powder become good. However, flexibility can meet the requirements without water reducing agent for Tai Wan Da Lian powder.This paper made a study on comprehensive performance of bonding mortar selecting each of a group of excellent performance mortar from each mortar which is prepared of redispersible emulsion powder. These performance include workability, bond strength, flexibility, shrinkage resistance and frost resistance. The paper analyzed the results and contrasted with ordinary mortar. The results show that the performance of bonding mortar has improved largely compared with ordinary mortar.Finally, this paper made a study on microscopic analysis and modification mechanism of bonding mortar by SEM. After28days hydration, the network structure of the polymer can be seen clearly from specimen pictures which have been corroded. The polymer can change the hydration products of cement, cement paste morphology within the mortar and bonding interface between paste and aggregate on the micro-level. Thus it can improve the workability and mechanical performance of bonding mortar. |
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