Microbial Biocementation Strength Control
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Solution Overview
Problem
Conventional methods using urease-producing bacteria to form mineral plugs in geological formations result in cements that are not strong enough for various applications and lack control over the process, leading to inconsistent results.
Innovation Solution
A method combining urease-producing microorganisms, urea, and calcium ions in a permeable starting material to produce high-strength cement through controlled calcite formation, achieving a urea hydrolysis rate of 0.5-50 mM/min and forming at least 33 g of calcite per liter, allowing for repeated applications and in situ cementation without disrupting the material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional cement is applied as a thick slurry, then it can provide structural strength, but it cannot be sprayed applied and cannot form cement at or below surface level while retaining porosity
Solution Approach 1:
The invention changes the physical and chemical parameters of the cement formulation by incorporating specific additives (superplasticizers, accelerators, retarders) and controlling water-to-cement ratios to enable spray application while maintaining strength. The cement composition is modified to achieve appropriate viscosity and setting characteristics for spray delivery systems.
Solution Approach 2:
The invention introduces spray delivery systems and intermediate carriers that facilitate the application of cement in spray form. These intermediaries enable the cement to be delivered as a fine mist or spray that can penetrate and form deposits at or below surface levels while maintaining the necessary structural properties.
2Quantity of substance
If urease producing bacteria are used to form mineral plugs, then porosity reduction is achieved, but the resulting cement strength is insufficient for various applications
Solution Approach 1:
The invention creates composite materials by combining biologically-formed mineral plugs with cementitious binders and additives. This composite approach integrates the porosity-reducing capability of bacterial mineral precipitation with the strength-providing properties of conventional cement, achieving both objectives simultaneously.
Solution Approach 2:
The invention merges two previously separate processes: microbial-induced calcium carbonate precipitation (MICP) and conventional cementation. By combining these processes into a unified treatment approach, the system achieves both the porosity reduction characteristic of biological plugging and the structural strength of cement-based materials.
3Strength
If conventional cement treatment methods are used, then cement strength can be achieved, but the process lacks control resulting in inconsistent results
Solution Approach 1:
The invention incorporates feedback mechanisms through controlled dosing of reactants (urea, calcium chloride, bacterial inoculums) based on monitored parameters such as pH, calcium carbonate precipitation rate, and moisture content. This feedback control enables consistent reproduction of desired cement strength and porosity characteristics.
Solution Approach 2:
The invention employs dynamic control of the cementation process by adjusting reaction conditions (temperature, moisture content, reactant concentrations, pH levels) during treatment. This dynamic approach allows optimization of both strength development and porosity control, producing consistent results across varying field conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method produces a high-strength cement with uniaxial compressive strength of 0.05-5 MPa, suitable for diverse applications including civil engineering, mining, and environmental uses, while maintaining the porosity of the starting material and allowing for controlled cementation.
Implementation Method 1
the enzymatic breakdown of urea by the urease enzyme
Implementation Method 2
urea hydrolysis rate, under standard conditions, of 0.5-50 mM urea hydrolysed.min-1
Implementation Method 3
Mineral plugs form as a result of precipitation caused by the increase in pH
Implementation Method 4
the production of relatively high levels of calcite in the starting material
Implementation Method 5
combining the starting material with effective amounts of (i) a urease producing micro-organism; (ii) urea; and (iii) calcium ions
Implementation Method 6
forming a high strength cement through the production of relatively high levels of calcite in the starting material
Data Source
AI summary
A method of forming a high strength cement in a permeable starting material, the method comprising the step of combining the starting material with effective amounts of (i) a urease producing micro-organism; (ii) urea; and (iii) calcium ions and wherein the effective amount of the urease producing organism provides a urea hydrolysis rate, under standard conditions, of 0.5-50 mM urea hydrolysed.min−1.