Lightweight Concrete Wythe Using CSA Cement and Expanded Slate
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Solution Overview
Problem
The precast concrete industry faces challenges in reducing the thickness and weight of insulated precast concrete panels, aiming for a 1.5-inch wythe thickness and 25 lb/ft² weight to decrease production, transportation, and installation time and cost, while maintaining adequate strength and durability.
Innovation Solution
A lightweight concrete composition is developed using Type III Portland cement, metakaolin, calcium sulfoaluminate cement, lightweight aggregates, and non-metallic fibers, with specific ratios of these components to achieve a flexural strength of at least 600 psi at 12 hours and a compressive strength of 7,000 psi at 28 days, while reducing density to 95-110 lb/ft³.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If conventional concrete mixes are used in precast panels, then the panels achieve adequate strength, but the weight and thickness cannot be reduced below 2 inches and 62 lb/ft²
Solution Approach 1:
The patent changes the chemical and physical parameters of the concrete mix by incorporating calcium sulfoaluminate cement (CSA) instead of conventional Portland cement, using lightweight aggregates (expanded glass, expanded slate), and adding specific admixtures (high-range water reducer, hydration controller). These parameter changes enable the concrete to achieve high early strength (600 psi flexural at 12 hours) at reduced thickness (1.5 inches) and lower weight (25 lb/ft²).
Solution Approach 2:
The patent uses composite materials by combining multiple cementitious materials (Type III Portland cement, metakaolin, calcium sulfoaluminate cement) with lightweight aggregates (expanded glass, expanded slate) and reinforcing fibers. This composite approach creates a concrete mix that achieves both high strength and low weight, resolving the contradiction between strength and weight reduction.
2Productivity
If conventional concrete mixes are used in precast panels, then the panels achieve adequate strength, but the production, transportation and installation time and cost increase
Solution Approach 1:
The patent applies preliminary action by designing a concrete mix that achieves high strength (600 psi flexural) at 12 hours, allowing the precast panels to be produced and handled much faster than conventional concrete. This early strength development enables accelerated production cycles and faster installation, directly improving productivity and reducing time loss.
Solution Approach 2:
The use of calcium sulfoaluminate cement and hydration controlling admixtures changes the time-related parameters of concrete setting and hardening. This enables the concrete to reach handling strength in 12 hours rather than the typical 28 days, dramatically reducing production and installation time.
3Length of stationary object
If wythe thickness is reduced to 1.5 inches, then weight decreases to 25 lb/ft², but achieving adequate strength becomes difficult
Solution Approach 1:
The patent changes the material parameters by using a specialized concrete mix with calcium sulfoaluminate cement, lightweight aggregates, and high-range water-reducing admixtures. This enables the 1.5-inch thick wythe to achieve 7,000 psi compressive strength at 28 days, proving that reduced thickness does not compromise strength when appropriate materials and proportions are used.
Solution Approach 2:
The composite concrete mix containing multiple cementitious materials (Type III Portland cement, metakaolin, CSA cement), lightweight aggregates, and non-metallic fibers creates a high-strength thin wythe. The synergistic combination of these materials allows the 1.5-inch thickness to achieve adequate compressive strength.
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 effectively decreases the weight and thickness of concrete wythes while maintaining high strength and durability, enabling faster and cheaper production, transportation, and installation, with the concrete wythes achieving the desired mechanical properties.
Implementation Method 1
type III Portland cement (lb/yd3) 200-900, calcium sulfoaluminate cement (CSAC) (lb/yd3) 40-840, water (lb/yd3) 300-350
Implementation Method 2
3/8'' lightweight expanded slate aggregate (lb/yd3) 70-550, lightweight fine expanded slate aggregate (lb/yd3) 300-550, expanded glass fine aggregate 35-90 0.02 to 0.04'' (0.5-1 mm) (lb/yd3), expanded glass fine aggregate 35-90 0.04 to 0.08'' (1-2 mm) (lb/yd3)
Data Source
AI summary
A lightweight concrete composition includes the concrete components, per yd3 of concrete: Type III Portland cement (lb/yd3) 200-900; metakaolin (lb/yd3) 100-520; calcium sulfoaluminate cement (CSA) (lb/yd3) 40-840; 3/8″ lightweight expanded slate aggregate (lb/yd3) 70-550; lightweight fine expanded slate aggregate (lb/yd3) 300-550; expanded glass fine aggregate (0.5-1 mm) 35-90 (lb/yd3); expanded glass fine aggregate (1-2 mm) 35-90 (lb/yd3); water (lb/yd3) 300-350; CSA cement set retarder 0.015 to 0.06 oz per lb of CSA cement; high-range water-reducing admixture 120-1000 (fl. oz/yd3); hydration controlling admixture 0-80 (fl. oz/yd3); reinforcing non-metallic lightweight fibers <1.5″ in length 0-8 (lb/yd3); wherein the concrete has a flexural strength of at least 600 psi at 12 hours, a density of 95 to 110 lb/ft3, and a compressive strength at 28 days of at least 7,000 psi. A lightweight concrete wythe and method of making a lightweight concrete wythe are also disclosed.