Precast Concrete Block Composite Section Spalling Reduction
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Solution Overview
Problem
Concrete blocks with composite sections often experience spalling, particularly in the slender head area, which affects their usability and is criticized by customers.
Innovation Solution
A concrete block design featuring a composite section comprising a cuboid lower body, a trapezoidal middle body, and a slanting truncated pyramid head body, optimized for concrete flow during filling and compacting to reduce spalling by minimizing air pockets and less dense areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If composite sections taper towards the upper side (conventional design), then the head area becomes slender to reduce material usage, but spalling occurs in the head area due to poor concrete flow and compaction
Solution Approach 1:
The composite section is divided into three distinct bodies (lower body A, middle body B, head body C) with different geometric characteristics. Each body serves a specific function: the lower body provides stability, the middle body transitions the shape, and the head body optimizes concrete flow. This segmentation allows the head body to have sufficient width for proper compaction while maintaining overall material efficiency.
Solution Approach 2:
Different parts of the composite section have different geometric properties optimized for their specific functions. The lower body has constant depth (TA) for stability, the middle body transitions with depth (TB) for shape change, and the head body has varying depth (TC) to optimize concrete flow and compaction. This local optimization prevents spalling in the head area while maintaining material efficiency overall.
2Loss of substance
If the head body is made slender to reduce material, then material usage decreases, but air pockets and less dense areas form due to poor concrete flow
Solution Approach 1:
The geometric parameters of the head body (depth TC, width B6) are specifically optimized to maintain adequate cross-sectional area for proper concrete flow and compaction. The slanting truncated pyramid shape with controlled dimensions ensures that concrete can flow smoothly and compact uniformly, preventing air pockets and density variations while still reducing material usage compared to a fully prismatic design.
3Productivity
If the composite section has a horizontal cross section that decreases with height, then concrete flow is optimized, but the head area becomes more slender which may cause spalling
Solution Approach 1:
The head body is designed with a specific slanting truncated pyramid geometry that optimizes concrete flow locally while maintaining sufficient width. The depth TC and width B6 are carefully controlled to ensure that the decreasing cross-section promotes concrete flow without becoming too slender, thus preventing spalling while maintaining productivity benefits.
Data Source
Figure 1~2
Figure 3~4
AI summary
The concrete block (1) has side surfaces (4) and a laminate section (3) arranged at one of the side surfaces. The laminate section has a lower body (A), a center body (B) and a head body (C), where the lower body is designed as cuboid and the center body is designed as a trapezoid column. Depth of the lower body corresponds to depth of the center body. The head body is designed as frustum of pyramid and leads to the side surfaces.