Pob zeb yog cov khoom siv hauv tsev uas muaj ntau tshaj plaws uas siv niaj hnub no uas muaj cov cement, dej, aggregate, chemical additives, thiab mineral additives vim nws cov yam ntxwv xws li pheej yig, siab-siab tsis kam, siv tau ntev, thiab yooj yim rau cov duab. . Qhov zoo ntawm cov khoom no, w ...
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