Research On The Preparation And Properties Of Hydraulic Lime

Architectural heritage protection and adaptability use is the important subject of urban development in our country, the ancient city wall in China has a long history and numerous, but because of natural disaster and man-made destruction, many of the ancient city wall is on the verge of destruction, people need to repair urgently and reasonably. During the repair of the ancient city wall, now generally to use modern cement based materials for processing, but much scientific research has proved that modern cement based materials and the building of the ancient with wood and brick as the main material, there are inadaptability in physical and chemistry characteristics. The cementitious materials used in most of China’s ancient city wall is lime. In America and europe, all of the masonry monuments, also adopt lime-based material for protecting. Based on this situation, the hydraulic lime as a new material for historic buildings protection is becoming more and more important.In this study, according to EN-459, adopt the mixed way with various raw materials for preparing hydraulic lime.The study of water absorption, coefficient of softness, compressive and flexural strength, drying shrinkage with different water-binder ratio, quality ratio of lime-white cement-calcium carbonate powder-slag powder was carried out. The results show that the optimum mixture ratio of L1, Lime:white cement:calcium carbonate powder:slag powder=27:36:27:10. The mortar fluidity was 185mm, the 28d compressive strength reached 7.31MPa, and the softening coefficient was 0.66. On this basis, the physical and mechanical properties, early drying shrinkage (28d) with different content of Aluminum additives, polypropylene fiber and sepiolite velvet were investigated. The results show that the strength increase 19.4% more than the benchmark mix, early drying shrinkage reduce by 33%; polypropylene fiber into the mortar has little effect on early drying shrinkage, for the mortar with 1‰,2‰ and 3‰ Polypropylene fiber, their strength increase by 20%,21.9% and 21.9% respectively; And drying shrinkage increase 16%-32%, compressive strength decrease first and then increase with the increase of sepiolite velvet.Carbonation test of hydraulic lime was studied; The shear bond strength and tensile bond strength of hydraulic lime was studied respectively. Among them, the shear bond strength of the benchmark is 0.186 MPa, higher than traditional cement mortar and lime mortar, which are 0.069MPa,0.022MPa, and the tensile bond strength is 0.114MPa. The results show that the hydraulic lime prepared could satisfy the requirement of "reversible" for the ancient city wall restoration.In addition, According to the concrete durability test methods, the durability include freezing and thawing environment, sulfate and sulfate-dry wet cycle immersion were studied by hydraulic lime. The results show that compared with the traditional lime mortar (carbonization), the durability of hydraulic lime is better. The addition of polypropylene fiber significantly improves the frost resistance; Aluminum sulfate incorporation improves the resistance to sulfate attack, but poor frost resistance.Finally, this paper which using scanning electron microscope (SEM), XRD, mercury injection method (MIP) technology to analysis the microstructure and organization morphology, hydration products and the pore structure of hydraulic lime; And the early hydration process and microstructure formation of hydraulic lime was studied by hydration heat test.