3.4　Materials

3.4.1　Concrete used for metallurgical equipment foundations shall meet the following requirements:

1　Concrete of C10 should be used for foundation beds，and C15 for foundation beds with waterproof concrete slabs.C15 may be used when the bedsare made of pumped concrete.

2　Concrete to be reinforced for equipment foundations shall be of strength no lower than C20.Concrete for massive equipment foundations and underground works should be of strength of C25-C35，no higher than C40.

3　C20 should be used for small auxiliary equipment foundations if plain concrete is recommended.

4　When a secondary grouting layer is as thick as 50mm or greater，fine aggregate concrete should be used，with strength one grade higher than the foundation concrete and no lower than C25.When the secondary grouting layer is thinner than 50mm，cement mortar of 1∶2 should be used.If necessary，cement-based grouting materials may be employed to substitute the fine aggregate concrete and cement mortar.The performance of cement-based grouting materials shall follow the current national standard Code for Application of Cement-Based Grouting Materials（GB/T 504418）.Fine aggregate concrete mixed with steel fibers may be applied to the secondary grouting layers subject to fairly strong impact.

5　The impermeability grade of waterproof concrete should be determined according to the ratio of the maximum ground water head to the waterproof concrete thickness as per Table 3.4.1，and should be no lower than P6.

6　For metallurgical equipment foundations made of ordinary reinforced concrete and plain concrete，the surface heating temperature shall be no higher than 150℃.For ordinary concrete with structure heating temperature of 60℃-150℃，aggregate featuring fair thermal stability and low expansion coefficient under temperature effects should be employed，which shall not contain any metallic minerals，mica，sulfates or sulfides.The strength of concrete and rebars under temperature effects shall be designed in accordance with the current national standard Code for Design of Chimneys（GB 50051）.Heat-resisting concrete shall be used in accordance with the current national standards.

7　The durability of concrete used for metallurgical equipment foundations shall follow the current national standard Code for Design of Concrete Structures（GB 50010），depending on the environment category and designed service life.

8　Concrete for metallurgical equipment foundations and underground works should be made of ordinary Portland cement.In case of mass concrete，medium-，low-heat Portland cement or low-heat slag Portland cement should be used.Cement for waterproof concrete should be used in accordance with the current national standard Code for Water Protection and Prevention of Underground Works（GB 50108）.Iffreeze-thaw actionsare considered，puzzolan cement and flyash Portland cement shall not be used.Concrete subject to erosive media shall follow the current national standard Code for Anti-Corrosion Design of Industrial Buildings（GB 50046）.

9　Concrete used for metallurgical equipment foundations and underground works which is to be mixed with admixtures shall follow the current national standard Technical Code for Application of Admixture in Concrete（GB 50119）.The typesand quantity of admixtures shall be determined according to the suitability tests.Chloride shall not be used as admixture for antifreeze and early strength purpose.

3.4.2　Rebars for metallurgical equipment foundations shall be selected as follows:

1　HPB235 should be used when the diameter of rebars is 8mm-10mm.

2　HRB335 and HRB400 should be used when the diameter of rebars is 12mm-40mm.HRB335 and HRB400 may be used when the diameter of rebars is greater than 40mm if good experience in similar projects is available.

3.4.3　Embedded parts subject to stresses should be of Q235B（or Q345B，if necessary）.HRB335 or HRB400 should be used for anchorage rebars.HPB235 may also be applicable to anchorage rebars for embedded parts.Welding rods should be selected in accordance with the relevant national standards.For welding of two different steel grades，the welding rods of the lower steel grade should be preferred.Use of cold rebars is strictly prohibited for anchorage of embedded parts.