5.3
체 분석 및 등급 곡선
체 분석은 골재 재료의 입자 크기 분포를 결정하는 데 사용되는 방법입니다. 이 프로세스에는 다음 단계가 포함됩니다.
- 건조된 골재 시료의 필요한 양을 칭량한다.
- 무게를 잰 골재는 구멍 크기가 가장 큰 것을 맨 위에 두고, 구멍 크기가 큰 순서대로 정사각형 구멍이 있는 체…
응집체의 체 분석은 조리개 크기의 내림차순으로 위에서 아래로 적층된 체 세트를 사용하여 수행됩니다.
체의 크기는 굵은 응집체와 미세한 응집체에 따라 다릅니다.
공기 건조된 골재 샘플의 무게를 측정하고 체를 통해 기계적으로 또는 지정된 시간 동안 수동으로 흔들어 체를 통과합니다.
이 과정에서 각 체는 메쉬 크기보다 거친 입자를 유지하면서 더 미세한 입자가 다음 체로 통과할 수 있도록 합니다.
각 체에 유지되는 분획의 무게가 기록되고 전체 질량의 백분율로 표시되며 표로 표시됩니다.
가장 미세한 체에서 시작하여 위쪽으로 이동하면서 각 체를 통과하는 누적 비율이 계산되고 가장 가까운 1%로 반올림됩니다.
또한, 반로그 그래프는 y축의 통과 백분율과 로그로 스케일링된 x축의 체 조리개를 나타내는 데 사용됩니다.
이 그래프에서는 각 체 크기에 해당하는 누적 통과 비율이 표시되어 크기에 따른 응집체 입자의 분포를 나타내는 등급 곡선을 얻습니다.
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Q1: How is sieve analysis performed on aggregate samples?
Sieve analysis begins with weighing an air-dried aggregate sample, then passing it through a stack of sieves arranged in descending order of aperture size from top to bottom. The sieves are shaken mechanically or manually for a specified time, allowing finer particles to pass through while coarser particles are retained. The weight of material retained on each sieve is recorded and expressed as a percentage of total mass.
Q2: What is the purpose of calculating cumulative percentage passing in sieve analysis?
Cumulative percentage passing is calculated from the finest sieve moving upward to establish the foundation for grading curve development. This calculation, rounded to the nearest one percent, represents the proportion of aggregate particles finer than each sieve size. These values are plotted on the y-axis of a semi-logarithmic graph to visualize particle size distribution.
Q3: Why is a semi-logarithmic graph used to represent grading curves?
A semi-logarithmic graph is used because sieve apertures are plotted on a logarithmically scaled x-axis while cumulative passing percentages are plotted linearly on the y-axis. This scaling approach effectively displays the wide range of aggregate particle sizes and produces a grading curve that clearly indicates the distribution of particles across different size ranges.
Q4: What information does a grading curve provide about aggregates?
A grading curve visually simplifies the distribution of particle sizes within an aggregate sample by plotting cumulative passing percentages against sieve apertures. This graphical representation is essential for ensuring that aggregates meet required grading specifications for construction projects and helps engineers assess whether the material is suitable for specific applications.
Q5: How do sieve sizes differ between coarse and fine aggregates?
Sieve sizes vary for coarse aggregates and fine aggregates to accommodate their different particle size ranges. Coarse aggregates require larger mesh openings, while fine aggregates use smaller mesh sizes. The specific sieve stack selected depends on the aggregate classification and the particle size distribution being analyzed.
Q6: What does the weight retained on each sieve represent in sieve analysis?
The weight retained on each sieve represents the mass of particles coarser than that sieve's mesh size. This weight is recorded after sieving and then expressed as a percentage of the total sample mass. These percentages are essential for calculating cumulative passing values and constructing the grading curve.
Q7: Why must aggregate samples be air-dried before sieve analysis?
Air-drying the aggregate sample ensures consistent and accurate results by removing surface moisture that could affect particle behavior during sieving. Moisture can cause particles to clump together or stick to sieves, leading to incorrect weight measurements and inaccurate particle size distribution data.