Hydrophobicity&Carbonation Protection Of Earthe Monument In Moist States

Earthen monuments are composed mainly of soil (rammed earthen, adobe, mud et al.) and classified to immovable earthen heritage. Nowadays, earthen monuments are classificated into the ones in arid and in humid weather condition according to the located climate or the800mm isohyet. Studies on earthen monuments in arid weather condition have been matured, but it is still at exploring stage for earthen monuments in humid weather condition. Earthen monuments in humid weather condition are easily to extinct in that of high rainfall and shallow groundwater condition. Therefore, it is an urgent responsibility to protect scientifically these earthen monuments.The conception of earthen monument in moist states is firstly proposed aiming at the natural phenomena of the earthen monuments that soil body has high water content but locates in arid weather condition. Furthermore, it puts forward the "environment" physical model and quantitative classification of earthen monument in moist states in view of environment structure theory.Water repellency soil theroy is introduced into earthen monument protection, and materials of tung oil and lime are selected theoretically to achieve the goal of hydrophobicity and carbonation protection.The archeological site of Da Bao'en Temple in Nanjing, Jiangsu province, China, is chosen as the research object. The failure patterns of the simulation underground palace from unearthing are compared and the relevant around hydrology-climate change are analyzed.Tests of atterberg limits, soil-water characteristic curve (SWCC), unsaturated permeability, shrinkage, water absorption and dcsorption, water repellency and stability in water are carried out for unsaturated characteristic, shrinkage disease and water stability protected requirement. Furthermore, the capillary water rise characteristics of untreated and treated soil are simulated and microstructures are obtained with the help of scanning electron microscope (SEM).The main research contents and results are as follows:(1) Definition of earthen monument in moist statesEnvironment structure of earthen monument includes climate environment, regional environment and underground environment, which can be characterized by damp coefficient, relative humidity (RH) and water content, respectively. Thus, earthen monument in moist states can be defined as the one has high water content. and can be further subdivided into four classfications:earthen monuments kept wet at huimd environment in humid areas, earthen monuments kept wet at humid environment but in arid areas, earthen monuments kept wet at arid environment but in humid areas, earthen monuments kept wet at arid environment in arid areas.(2) Selection of protected materialsTung oil is selected as one protected material draw lessons from water repellence of soil contaminated by oil. Meanwhile, lime is selected as the other protected material in view of antiseptic and structure stability. Hydrophobicity and carbonation protection is achieved by combining traditional material of tung oil and lime.(3) Diseases of earthen monument in humid statesDiseases of the simulation underground palace from unearthing (2009～2011) are studied. Rainfall and capillary water rise are the key factors for the unstability based on the changes of water content at different soil layers and its climatic environment.(4) Water absorption and desorption characters of untreated and treated soilChange in soil water content due to rainfall, groundwater lever elevation and air humidity variation is responsible for the soil structure deterioration. Specimens of earthen soil (US), tung oil treated soil (TS), lime treated soil (LS), tung oil and lime treated soil (TLS) are prepared at five levels of dry densities to cover the density variation measured from site investigation.Tung oil and lime treatment, alone or compound, increase the liquid limit and plastic limit of soil and decrease the plasticity index. US specimen has higher water retention in that the composition of hydrophilic minerals, but it is reduced by tung oil treatment. SWCCs of TLS specimen are a little stepper than that of LS specimen, but the whole change is gentle, especially at higher density.Saturated permeability coefficient of four soil specimens decrease with increasing of density. Tung oil and lime treatment can decrease permeability, especially the combine treatment, where the saturated permeability coefficient of treated soil is0.6time as that of earthen soil. The unsaturated permeability coefficients of US and TS specimen present gradient descending shape with the increasing of density, but it present right moving tendency to LS and TLS specimens. Generally, tung oil and lime treatment improve the stability of shrinkage and water absorption and liberation, equally important, the secondary shrinkage.(5) Water repellencyWater drop penetration time (WDPT), molarity of ethanol droplet (MED) and stability in water test are carried out to evaluate the water repellency in the long run. Water drop on tung oil and lime treated soil surface is different from earthen soil, where the formers tend to "balls up" into individual droplets and hardly infiltrate the interior and the latter spreads out and infiltrates quickly in10s. Earthen soil specimen disintegrate completely as soon as being immersed into water, Whereas, other three soil specimens can keep the original shapes, especially the TLS specimens, which are kept well the original shapes even after being immersed in water seven-days. Reduction in water absorption makes water menisci ineffective, and then prevents the destruction of soil. Therefore, decrease of wettability plays an important role on the water stability of soil.(6) Capillary water rise simulationOne-dimension mathematical modeling of capillary rise is built to studies the capillary height, rise process and water distribution at different soil lays for four soil specimens. Modified washburn equation is used to fit to obtain the balance height. tung oil and lime treatment has obvious retardation on capillary rise. Lime treatment is superior to water repellency in lower density, but it will be vanish gradually in higher density. Unite treatment with tung oil and lime can control well soil seepage.(7) Mechanism AnalysisTung oil film can well adapt to the contour and coated closely on soil particles. Calcium carbonate (CaCO3) formed by the carbonation reaction of lime can fill effectively the pores of soil and then improve the compactnes. As treated with both of tung oil and quicklime, there is a regulatory action on the carbonated reaction of calcium hydroxide (Ca(OH)2). Tung oil restricts the crystallization process of calcium carbonate (CaCO3), generates fine crystals, and then forms a firmer and closer structure. The interaction between tung oil and lime can be illustrated from the perspective of biomineralization, liposome changes the microenvironment of carbonated reaction by the way of enriching locally the ion of Ca2+, CO2-3and the hydrophobic chain of liposome restricts the growing of calcium carbonate(CaCO3).