The strength of zinc phosphate cement is linearly related to its()
A.pH
B.powder-to-liquid ratio
C.fluoride content
D.glass content
The strength of zinc phosphate cement is linearly related to its()
A.pH
B.powder-to-liquid ratio
C.fluoride content
D.glass content
A.spatulation time
B.liquid-powder ratio
C.temperature ofthe mixing slab
D.number and size ofpowder increments
A.Clay
B.Lime
C.Gypsum
D.Water
A.Clay
B.Lime
C.Gypsum
D.Water
A.water glass
B.cement
C.gypsum
D.lime
A、clay bricks
B、Portland products
C、cement concrete
D、gypsum products
Plain concrete is formed from a hardened mixture of cement, water, fine aggregate, coarse aggregate (crushed stone or gravel), air, and often other admixtures. The plastic mix is placed and consolidated in the formwork, then cured to facilitate the acceleration of the chemical hydration reaction of the cement/water mix, resulting in hardened concrete. The finished product has high compressive strength, and low resistance to tension, such that its tensile strength is approximately one tenth of its compressive strength. Consequently, tensile and shear reinforcement in the tensile regions of sections has to be provided to compensate for the weak tension regions in the reinforced concrete element.
听力原文: One of the important materials used in the construction of buildings and roads is cement. It is a powder made mainly from limestone and clay. Even though the ancient Egyptians and Romans used a kind of cement, it was not until 1824 that an English bricklayer developed cement strong enough for modern roads and buildings.
While the bricklayer was experimenting in his kitchen, he found that a mixture of limestone and clay that had been heated formed a substance. This substance became hard and stone-like as it cooled. When it was grounded into a fine powder, it could be stored.
When the powder was mixed with water, it made an excellent quality of cement that quickly hardened in sunlight or even under water, it made an excellent quality of cement that is used today.
(30)
A.An Egyptian.
B.A Roman.
C.A British.
D.A man named Blake.
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