我们为沥青混合料设计者提供了这条方便的经验法则。

　　We provide this convenient rule of thumb for asphalt mixture designers.

　　1 每变化0.3%的沥青用量，混合料空隙率大约变化1%在混合料配合比设计过程中，经常是一组试件非常接近于目标空隙率，但实际上并没有达到目标值。如果试件的VMA（矿料间隙率）低于小值，那么仅仅增加或减少沥青用量以达到目标空隙率是不够的，必须通过对每档集料的相对比例进行调整。如果VMA满足要求（少0.5%左右），则可以简单地通过增加或减少沥青用量调整空隙率，以达到目标值，问题是需要调整多少呢？

　　For every 0.3% change in asphalt dosage, the void ratio of the mixture changes by approximately 1%. In the process of designing the mix proportion of the mixture, it is often a group of specimens that are very close to the target void ratio, but in reality, they have not reached the target value. If the VMA (mineral aggregate void fraction) of the test piece is lower than the minimum value, simply increasing or decreasing the asphalt content to achieve the target void fraction is not enough, and it is necessary to adjust the relative proportion of each grade of aggregate. If VMA meets the minimum requirement (at least 0.5%), the void ratio can be easily adjusted by increasing or decreasing the amount of asphalt used to achieve the target value. The question is how much adjustment is needed?

　　尽管沥青用量（Pb）和理论相对密度（Gmm）之间的关系是完全线性的，但沥青用量和空隙率之间的关系并不是完全线性。随着沥青用量的增加，混合料空隙率逐渐降低原因有两个：1）沥青填充了试件中原先被空气占据的体积空间；

　　Although the relationship between asphalt content (Pb) and theoretical maximum relative density (Gmm) is completely linear, the relationship between asphalt content and porosity is not completely linear. There are two reasons why the void fraction of the mixture gradually decreases with the increase of asphalt dosage: 1) the asphalt fills the volume space originally occupied by air in the specimen;

　　2）沥青充当润滑剂，使混合料压实过程骨料颗粒更加紧密地嵌挤在一起。对于设计者来说，在混合料设计时，这种关系是相当线性的，随着混合料越来越密实，这种关系趋于平缓。

　　2) Asphalt acts as a lubricant, allowing the aggregate particles to be more tightly packed together during the compaction process of the mixture. For designers, this relationship is quite linear in the design of mixtures, and as the mixture becomes denser, this relationship tends to flatten out.

　　对于大多数密级配沥青混合料，每变化0.3%的沥青用量，混合料空隙率变化1%。沥青用量增加0.3%，混合料空隙率减小1%，沥青用量减少0.3%，混合料空隙率增加1%。例如，实验室设计目标空隙率为4%，而我们采用5%的沥青用量，次试验时混合料空隙率为5.3%，但混合料间具有足够的矿料间隙率，因此我们可能不需要改变混合料的骨架结构，根据我们的经验法则，第二次试验时我们选择5.4%的沥青用量，预计混合料的空隙率大约降低1.3%，满足4.0%的目标空隙率。

　　For most graded asphalt mixtures, for every 0.3% change in asphalt content, the void fraction of the mixture changes by 1%. An increase of 0.3% in asphalt content leads to a decrease of 1% in the void fraction of the mixture, while a decrease of 0.3% in asphalt content leads to an increase of 1% in the void fraction of the mixture. For example, in the laboratory design, the target void ratio is 4%, while we use 5% asphalt content. In the first experiment, the void ratio of the mixture was 5.3%, but there is sufficient mineral void ratio between the mixtures. Therefore, we may not need to change the skeleton structure of the mixture. According to our empirical rules, we chose 5.4% asphalt content in the second experiment, and it is expected that the void ratio of the mixture will decrease by about 1.3%, meeting the target void ratio of 4.0%.

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