我們?yōu)闉r青混合料設(shè)計者提供了這條方便的經(jīng)驗法則。

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

　　1 每變化0.3%的瀝青用量，混合料空隙率大約變化1%在混合料配合比設(shè)計過程中，經(jīng)常是一組試件非常接近于目標(biāo)空隙率，但實際上并沒有達(dá)到目標(biāo)值。如果試件的VMA（礦料間隙率）低于小值，那么僅僅增加或減少瀝青用量以達(dá)到目標(biāo)空隙率是不夠的，必須通過對每檔集料的相對比例進(jìn)行調(diào)整。如果VMA滿足要求（少0.5%左右），則可以簡單地通過增加或減少瀝青用量調(diào)整空隙率，以達(dá)到目標(biāo)值，問題是需要調(diào)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?

　　盡管瀝青用量（Pb）和理論相對密度（Gmm）之間的關(guān)系是完全線性的，但瀝青用量和空隙率之間的關(guān)系并不是完全線性。隨著瀝青用量的增加，混合料空隙率逐漸降低原因有兩個：1）瀝青填充了試件中原先被空氣占據(jù)的體積空間；

　　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）瀝青充當(dāng)潤滑劑，使混合料壓實過程骨料顆粒更加緊密地嵌擠在一起。對于設(shè)計者來說，在混合料設(shè)計時，這種關(guān)系是相當(dāng)線性的，隨著混合料越來越密實，這種關(guān)系趨于平緩。

　　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.

　　對于大多數(shù)密級配瀝青混合料，每變化0.3%的瀝青用量，混合料空隙率變化1%。瀝青用量增加0.3%，混合料空隙率減小1%，瀝青用量減少0.3%，混合料空隙率增加1%。例如，實驗室設(shè)計目標(biāo)空隙率為4%，而我們采用5%的瀝青用量，次試驗時混合料空隙率為5.3%，但混合料間具有足夠的礦料間隙率，因此我們可能不需要改變混合料的骨架結(jié)構(gòu)，根據(jù)我們的經(jīng)驗法則，第二次試驗時我們選擇5.4%的瀝青用量，預(yù)計混合料的空隙率大約降低1.3%，滿足4.0%的目標(biāo)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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