Laboratory Test Of Salt Extraction By Poulticing On The Earthen Sites In Northwest Arid Area Of China

The most applied intervention to avoid the salt weathering which the earthen structures are suffering in the northwest arid area of China is consolidating the destroyed area by chemical or physical methods. Meanwhile, the preventive interventions have not been studied.This study is based on the European salt reduction method on brick and stone heritages. A kind of method named desalination is chosen as a preventive intervention according to the current situation of the earthen structures in northwest arid area of China. The laboratory test study and its results are as following:(1) We choose the salt reduction materials for this test based on the desalinating principle, commonly used materials and its research tendency.(2) The properties of the selected materials are investigated and the results show that the water absorption property of bentonite is better than that of fine-grained soil, but its dry time is longer, and the retain moisture is7%less. The desorption speed of BC1000cellulose is faster than that of common cellulose, and its dry time is shorter too. The weight of common cellulose is2.4times heavier than that of BC1000cellulose when they absorb the same amount of water.(3) Based on the properties of the tested materials, six groups of materials are chosen to reduce the salt of reshaped block for twice. The result showed that the desalination efficiency from high to low for the first time is:fine-grained soil and common cellulose, X60, bentonite and common cellulose, fine-grained soil and BC1000cellulose, bentonite, BC1000cellulose and sponge. And the second time result of it is X60, fine-grained soil, BC1000cellulose, bentonite, BC1000cellulose, fine-grained soil, common cellulose, sponge, bentonite and common cellulose.(4) Water permeability study is also investigated to assist and supply the desalination test. By conducting the water permeability test, we can observe the process of water transport during the desalting. And we have precisely measured the water effective permeate depth and the ideal prewet water amount of the six groups during the twice desalination tests.