Recovery And Simulation Of Lime Crack-sealer Of Historic Buildings In Shanghai

Because of the non-renewable nature, people have paid more and more attention to the historic buildings in Shanghai. Their intangible assets are not only the material and human resources while building or maintenance, but also the cultural values which were formed with the time passed. In fact, the essence of protecting and repair these architectural heritages is a continuation of the construction of life. "The Protection Ordinance of Historical and Cultural Character Areas and Excellent Historical Buildings in Shanghai" was adopted in July 2000 and formally implemented in January 2003, which clear the protection of historical and cultural character areas. Through the development since reform and opening, we have made remarkable achievements on infrastructure and protection of historic buildings in Shanghai Bund Area. However, there are some problems: first, the advantages of the historic buildings have not been fully developed; second, historic preservation efforts are lacked; third, the infrastructure is still weak; forth, the authenticity of some important historic buildings was destroyed and last the function replacement of the buildings is facing obstacles. Though the maintenance and protection are carrying on, but because of the protection concepts, maintenance processes and material selection errors, historic buildings have been damaged unrecovered.The aim of this study is, firstly, to solve the historical crack-sealer selection problem of Amps Matheson in Block No.174 Huangpu District, Shanghai. According to the wet chemistry and modern testing methods, we recovered the historic lime crack-sealer and designed simulated crack-sealer on the basic of the recovery ratio. Under the influence of recycled materials adding different additives, we decided the ratio of simulated lime crack-sealer.Through the experimental design, we test and verified the accuracy of the results of German wet chemical methods for different material types and different aggregate size of the historical material. The study found that aggregate size played little effects on the results of wet chemical methods, but there was a larger difference from design to calculation of wet-chemical methods for different substrate historic materials. The experiment result of calcareous materials recovery was about the same with experimental design, but for the cement-based materials, there was a great difference.The study recovered the ratio of the historical crack-sealer. The experimental results showed that there were a lot of bonding agent materials and a small amount of water-based materials and the binder content was about 78%; the proportion of sand gray was over 4:1; the hydraulicity material component was 6%. Through X-Ray diffraction analysis, we found that historical materials primarily contained calcium carbonate and silica, which was formed through long-term carbonation of calcium hydroxide. By granularity analysis and water absorption experiment, the results showed that the material was with high water absorption and particle size smaller after a long period of weathering. Therefore, it is difficult to simulate the particle size of the historical materials, so we should adjust the aggregate size of crack-sealer on site in practical applications. We Added 8% ramie in the aggregate, which not only simulated the historical crack-sealer, but also increased the strength of the materials.Modern architecture crack-sealer mainly contains cement, inorganic fiber, organic fiber, powder, fillers, organic hydrophobic agents, air leading water-reducing agent, water-retaining agent and so on, which all affect the pointing performance of material, such as the compressive strength, flexural strength, water resistance, adhesive strength, seepage water, antifreeze and construction of nature. Wall crack-sealer should have the following properties: a. The bond is good and the crack-sealer must be able to work closely with the brick and no cracks. b. The materials must be well hydrophobic, durability, and grade high impermeability and can effectively prevent water leakage. c. As the wall pointing operations during the construction is of a vertical direction, which is more difficult and complex than the horizontal direction of the roof, therefore, to meet the material properties of the premise, the materials must to be easy construction.Lime crack-sealer usually use hydrated lime. There are food grade and industrial grade two kinds of lime as raw materials. Through the properties of the materials testing and molding observation, we found that food-grade lime samples are better performance and smooth surface. Though the latter intensity had a little improvement, the water absorption is too high. So we use food grade lime in this study and the proportion of sand gray (lime quality: the quality of aggregate) was 4:1. Adding cement to the crack-sealer played an obvious effect on material properties, which can significantly increase the later strength of lime-pointing agent. Different types of cement have different influence on simulated crack-sealer. According to material performance testing, the final choice was to add 7% P.O52.5. We use molding ceramic materials testing machine to simulate the crack-sealer forming.Different additives improve the performance of lime crack-sealer, such as the early strength of lime-pointing agent and post-strength, lower water absorption, reducing the volume shrinkage and so on. We determine the optimal adding amount of different additives through the experiments: 1.0% FD40, 2.0% 5010N, 0.1% 9010; 1.0% early strength agent, 0.1% F10, and 0.2% 8034H. In active volcanic ash, activity silica and alumina reacted with calcium hydroxide and rigid aluminum / calcium silicate with the water-cement material properties, which played a certain role in material-enhanced. According to production experience, we added 10% activity volcanic ash.Color simulation is very important for simulated lime materials. In the study, we use industrial color toner, which play a role in regulating crack-sealer and better co-ordination body with the floor to achieve uniformity. According to the experimental results and the contrast with historical crack-sealer, we added the color red for the addition of 4.0% and 4.0% in powder yellow powder in Amps Matheson historical materials.Through the performance testing of optimization simulated lime crack-sealer, the experimental results show that compressive strength has been to meet the needs of practical application and the water absorption decreased clearly. The materials occurs cracking phenomenon at secondary forming division after freeze-thaw cycle. If the sample can be a shape, we can avoid serious cracking. Observing the samples after freeze-thaw cycles by SEM, we found that the density of materials decreased and the combined between particles of different materials became poor. The group study is for the historic buildings in Shanghai, according to local climatic conditions, so optimized materials can meet the construction requirements.The historical lime crack-sealer simulation and enhance mechanism: Calcium hydroxide slowly carbonate into the calcium. During the process of carbonization, calcium form dense particles with other materials and generate colloid hydrated aluminum/ calcium silicate. Organic fiber and colloidal substances make these particles a close connection, increase the strength of simulatd materials, reduce the water absorption of materials and decrease the volume expansion.