Study On The Erosion Resistance Effect And Mechanism Of Deposition On The Rammed Earth Surface

Fujian Tulou is often considered as the representative of the rammed earth buildings.After suffering the erosion of wind-driven rain,the rammed earth wall has gone through different degrees of damage.the protection problem is quite serious.Microbial Induced Calcite Precipitation,as one of the research hotspots of microbial geotechnical engineering,is eco-friendly in environment,straightforward in mechanism and convenient in operation and good in tolerance.Research indicates that this kind of technical application has a outstanding protective effect in brick masonry ancient architectural relics and concrete surface protection.Not only does it not change the original appearance of the surface,but it also greatly reduces the surface water absorption.As for the Fujian Tulou,the durability of the rammed earth wall depends on its water tolerance.the water resistance of the wall depends on the waterproofing performance of the rammed earth wall.This research attempts to apply MICP to the deposition of rammed earth wall surface for the first time.It is a beneficial exploration for the protection technology of Fujian earth building.Firstly,this thesis has a good knowledge of the bacterial growth rhythm and the most suitable conditions and duration of bacteria by selecting,activating and preserving.Secondly,under the condition of vitro,it analyzes that the impact on the urease activity of the reactants(bacteria,urea the Ca²⁺),products?NH₄⁺?,and responsive environment?p H and temperature?and that the concentrations of bacteria and mixture influence on the productivity and crystal form of calcium carbonic.Then,we investigate Fujian Tulou in Yongding District,conclude and analyze the diseases of the rammed earth wall.And also,we use the new soil which got from the local area to measure basic physical properties.Next,we finish the preparation,curing and carbonization of triaxial soil sample and determination of unconfined compressive strength.Last but not least,we deposit on the surfaces of samples by brushing.According to the analysis of color difference,the observation of the surfaces of scanning electron microscopy and the experiments of water tolerance?wettability,water absorption with and without osmotic pressure?,breathability and durability,we can make an comprehensive evaluation about deposition effects and analyze the influence of bacteria and mixture concentrations.This thesis draws the following conclusions:?1?By using MICP can we neglect the effects of using shelling-out deposition to the color difference of sample surface.?2?The concentrations of bacteria play an major role in deposition effects.The higher the concentration of bacteria,the weaker the inhibitory effect of Ca²⁺on urease activity.The higher concentration the bacteria have,the better effects the deposition has.?3?higher mixture concentrations and the better deposition effects.But bacteria concentrations should be limited less than 1.5M.The concentrations of the mixture are largely influenced by the bacteria concentration.?4?After deposition,if we get better water tolerance,we will get better durability.?5?When the concentration of bacteria is 10⁹cells/ml and the concentration of the mixture is1.5M,the coating effect is best.As the concentration of bacteria continues to increase,the effect of coating may be better,but the extent of improvement and cost issues are worth considering.