Ndi Asphalt Solid kapena Liquid

Phula lilipo m'magawo awiri oyambirira: imakhalabe yolimba pa kutentha kozungulira ndikusintha kukhala madzi ikatenthedwa.

Mukumanga, Ogwira ntchito amatenthetsa phula pamadzi ake ndikuyiyika pamalo ogwirira ntchito. Pozizira, zimakhazikika kukhala zokutira zoteteza, kuonjezera kuteteza madzi, nthawi zambiri amagwiritsidwa ntchito pomanga misewu ndi ntchito zofolera.