low-quality aggregates

In some areas, excellent aggregates have been exploited and utilized, only low-quality aggregates left. Considering from construction economy, utilizing low-quality has been an inexorable trend .
優(yōu)良的骨料在某些地區(qū)已經(jīng)開發(fā)利用，賸下的是低品質(zhì)骨料，從建築經(jīng)濟(jì)上考慮，利用低品質(zhì)骨料已成必然趨勢。