Fast-Setting Flowable Fill Composition for Low-Strength Trench Repair
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Solution Overview
Problem
Traditional Portland cement-sand Controlled Low Strength Materials (CLSM) take too long to set and produce significant bleed water, making it difficult to apply asphalt patches quickly and leading to increased compressive strength that complicates future excavation.
Innovation Solution
A composition comprising 60-90% aggregate, 3-25% Portland cement, 0.25-8% accelerant, and 8-35% water, with sodium bicarbonate as an accelerant, to achieve fast-setting flowable fill with reduced bleed water and lower compressive strength for easy excavation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If accelerants are used to decrease set time of cement, then set time is reduced, but compressive strength increases
Solution Approach 1:
The patent changes the chemical parameters of the cement mixture by incorporating specific accelerants (sodium bicarbonate, calcium chloride, non-chloride accelerator) at controlled dosages (0.25-8% by weight). These parameter changes enable the cement to set faster while the aggregate composition and water-cement ratio are adjusted to control the final compressive strength within the desired range.
Solution Approach 2:
The invention creates a composite material system combining Portland cement (3-25% by weight) with accelerants and aggregate (60-90% by weight). This composite approach allows the cementitious matrix to gain strength quickly from the accelerants while the aggregate provides structural framework that limits overall compressive strength development, resolving the contradiction between fast setting and controlled strength.
2Strength
If traditional Portland cement-sand CLSM is used, then compressive strength is controlled, but set time is too long and bleed water is significant
Solution Approach 1:
The patent modifies the traditional CLSM composition by changing the cement content (3-25% by weight), adding accelerants (0.25-8% by weight), and adjusting water content (8-35% by weight). These parameter changes reduce set time from 8-24 hours to a faster setting period while controlling bleed water through optimized water-cement ratio and accelerant selection.
Solution Approach 2:
The accelerants act as intermediary substances that mediate between the cement hydration process and the desired fast-setting outcome. Sodium bicarbonate, calcium chloride, and non-chloride accelerators facilitate faster cement hydration and strength development without proportionally increasing final compressive strength, enabling rapid utility trench filling while maintaining excavation feasibility.
3Productivity
If accelerants are used to achieve fast setting, then set time decreases, but future excavation becomes difficult
Solution Approach 1:
The patent carefully controls the dosage of accelerants (0.25-8% by weight) and cement content (3-25% by weight) to achieve fast setting while limiting compressive strength to below 1200 psi (preferably below 300 psi). This parameter control ensures the material sets quickly for rapid productivity but remains soft enough for easy future excavation by utility companies.
Solution Approach 2:
The invention creates local quality differentiation within the CLSM composition: the cementitious matrix with accelerants provides fast initial strength gain for quick setting, while the aggregate (60-90% by weight) and controlled water-cement ratio ensure the overall composition maintains low compressive strength. This local quality approach allows fast setting in the matrix while the bulk material remains excavatable.
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 composition sets quickly, reduces surface water, and maintains low compressive strength, allowing for rapid pavement repair and easy excavation, meeting modern construction demands.
Implementation Method 1
accelerating the set-times of Portland cement and/or aggregate mixtures, by using an accelerant, e.g., sodium bicarbonate
Data Source
AI summary
Fast-setting flowable fill compositions for filling ground trenches are described. The compositions set quickly but retain a low strength psi at 28 days. The compositions also reduce bleed water on the surface of the fast-setting flowable fill and therefor enable quicker application of surface repair material, e.g., pavement patches, to the trench. The compositions consist of aggregate, Portland cement, accelerant, water and sometimes air. The compositions may have a compressive strength of between 5 psi and 60 psi after 2 hours, a compressive strength of between 10 psi and 100 psi after 4 hours, a compressive strength of between 75 psi and 500 psi after 28 days, a penetration resistance of between 1.5 tsf and 75 tsf after 2 hours, a penetration resistance of between 4.5 tsf and 200 tsf after 4 hours, and a shrinkage of less than 2% as measured by ASTM C490. Also disclosed are methods of filling a trench with fast-setting flowable fill.