Shrinkage Reducing Admixture Concrete Drying Time
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Solution Overview
Problem
Conventional concrete compositions with low water cement ratios and fine reactive materials often result in sticky fresh concrete with reduced workability retention and suppressed bleeding water, which complicates the drying process, leading to prolonged drying times and potential coating failures on interior floors.
Innovation Solution
Incorporating a high-reactivity Portland cement with a Blaine fineness of 4500-6500 cm²/g and a shrinkage reducing admixture, such as polypropylene glycol or polyethylene glycol, in specific amounts within the concrete mixture to reduce drying time while maintaining good workability and bleeding water.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a low water cement ratio is used to reduce free water in concrete, then the amount of free water is reduced, but the workability of fresh concrete deteriorates and bleeding water is suppressed
Solution Approach 1:
The patent uses a superplasticizer to fundamentally change the rheological parameters of the concrete mixture. This chemical additive allows the concrete to maintain fluidity and workability despite the low water-cement ratio, effectively decoupling the relationship between water content and workability that normally exists in conventional concrete mixtures.
Solution Approach 2:
The superplasticizer acts as an intermediary substance that mediates between the conflicting requirements of low water content and good workability. It adsorbs onto cement particles and creates electrostatic repulsion, allowing particles to move freely past each other without requiring additional water, thus enabling both low water-cement ratio and good workability simultaneously.
2Productivity
If fine reactive materials are added to increase hydration reactivity, then the formation of hydrates is accelerated, but the concrete becomes stickier and drying time is prolonged
Solution Approach 1:
The superplasticizer changes the physical parameters of the fresh concrete mixture by reducing inter-particle friction and improving flow characteristics. This allows fine reactive materials to be incorporated at high levels without creating a sticky mixture, and the improved pore structure from efficient packing accelerates water migration to the surface for evaporation, reducing drying time despite high hydrate formation rates.
3Strength
If the concentration of ions reaches supersaturation level, then mineral hydrates precipitate and form dense microstructure, but large amounts of water remain trapped in the concrete structure
Solution Approach 1:
The superplasticizer creates a more uniform and refined pore structure within the concrete matrix. By improving the packing efficiency of cement particles and controlling the hydration process, it generates a microstructure with optimized porosity that allows trapped water to migrate more easily through capillary action to the concrete surface, where it can evaporate, thereby reducing internal relative humidity faster while maintaining structural density.
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 solution significantly reduces drying time of concrete while maintaining similar setting time and strength development to conventional concrete, ensuring reduced viscosity and improved workability retention, allowing for faster relative humidity reduction to below 80% within 30-40 days.
Implementation Method 1
facilitation the migration of free water to the surface of concrete where it evaporates
Implementation Method 2
This water fills capillary pores within the concrete mass, and gradually evaporates over time
Implementation Method 3
When Portland cement formulations are mixed with water, hydration reactions immediately begin to form minerals. These reactions generate heat and form a dense microstructure of cement hydrates
Implementation Method 4
The water added to a concrete composition is also a chemical reactant that first acts by dissolving the mineral constituents of Portland cement. As these minerals dissolve, the concentration of mainly calcium, hydroxide, silicate, aluminate, and sulphate ions increase in the water
Implementation Method 5
When the concentration has reached a sufficiently high level, a point of supersaturation, the ions precipitate in the form of mineral hydrates, such as ettringite, or CSH gel. These hydrates contain large amounts of water trapped in their respective mineral structures
Implementation Method 6
This water fills capillary pores within the concrete mass, and gradually evaporates over time
Data Source
AI summary
A concrete with reduced drying time once hardened made from a composition comprising: - 140 - 160 l/m3 water - 280 - 340 kg/m3 highly reactive Portland cement of Blaine fineness 4500-6500 cm2/g, and - optionally a supplementary cementitious material, - sand, - aggregates, - 0 - 4 l/m3 shrinkage reducing admixture polyethylene glycol or polypropylen glycol - a water reducing agent and - optionally calcium oxide as expanding agent. The concrete has a 1d compressive strength of > 20 MPa.