Synthesis and Characterization of Biocement using Bacteria, Cow urine, and Calcium ions refined from Limestone

Abstract

Biocement, a promising alternative cement made from micororgansisms is considered simpler and more eco-friendly in production process than conventional cement. In this study, a biocemented sand was produced by using locally available materials: activated sludge as a seed of bacteria, cow urine as a urea source and limestone as a soluble calcium ions source through microbially induced calcium carbonate precipitation method in a non-sterlized media. The presence and amount of bacterial biomass were determined qualitatively as the color of the solution chages from yellow to red and quantitativly through optical density and urease activty measurments. The improved geotechnical proerties as a function of calcium carbonate precipitates had been anylzed with their corresponding microstructural changes for the untreated sand (BCS-0), and that of treated sands (BCS-1), (BCS-2), (BCS-3) after two, four, and six times treatments respectivley. The thermal history of the limestone and the calium oxide had been analyzed by Thermogravimetric analysis in which decompostion had been observed at 700 0C and 420 0C respectively. The biocemented sand (BCS-3) had the higher geotecnical properties than the rest samples, which is 0.95MPa in unconfied compressive strength, 6.59×10-6 in permeablity, and 25 percent reduction in percentage pore space, this might be for this sample there was plenty time for the precipitates to form a stable and well crystaline structures between the sand grains.Biocement, A Promising Alternative Cement Made From Micororgansisms Is Considered Simpler And More Eco-Friendly In Production Process Than Conventional Cement. In This Study, A Biocemented Sand Was Produced By Using Locally Available Materials: Activated Sludge As A Seed Of Bacteria, Cow Urine As A Urea Source And Limestone As A Soluble Calcium Ions Source Through Microbially Induced Calcium Carbonate Precipitation Method In A Non-Sterlized Media. The Presence And Amount Of Bacterial Biomass Were Determined Qualitatively As The Color Of The Solution Chages From Yellow To Red And Quantitativly Through Optical Density And Urease Activty Measurments. The Improved Geotechnical Proerties As A Function Of Calcium Carbonate Precipitates Had Been Anylzed With Their Corresponding Microstructural Changes For The Untreated Sand (Bcs-0), And That Of Treated Sands (Bcs-1), (Bcs-2), (Bcs-3) After Two, Four, And Six Times Treatments Respectivley. The Thermal History Of The Limestone And The Calium Oxide Had Been Analyzed By Thermogravimetric Analysis In Which Decompostion Had Been Observed At 700 0c And 420 0c Respectively. The Biocemented Sand (Bcs-3) Had The Higher Geotecnical Properties Than The Rest Samples, Which Is 0.95mpa In Unconfied Compressive Strength, 6.59??10-6? In Permeablity, And 25 Percent Reduction In Percentage Pore Space,This Might Be For This Sample There Was Plenty Time For The Precipitates To Form A Stable And Well Crystaline Structures Between The Sand Grains.