GB/T 20491-2017Steel slag powder used for cement and concrete (English PDF)

Foreword

This Standard is drafted in accordance with the rules given in GB/T 1.1-2009. This Standard replaces GB/T 20491-2006 "Steel slag powder used for cement and concrete". As compared with GB/T 20491-2006, in addition to editorial modifications, the main technical changes are as follows: - DELETE "products of steel slag powder combined with ground granulated blast furnace slag powder and fly ash" in the "Scope"; - DELETE the definitions of "comparison sample, test sample, comparison mortar, test mortar, activity index, fluidity ratio" in the "Terms and definitions"; - In the definition of steel slag powder, CHANGE "When grinding, it is allowed to add appropriate amount of gypsum in accordance with GB/T 5483 and cement grinding process admixture conforming to JC/T 667" to "When grinding, it is allowed to add cement grinding aid in accordance with GB/T 26748"; - For the specific surface of steel slag powder, "The primary and secondary specific surfaces are not less than 400 m2/kg" is changed to "The primary and secondary specific surfaces shall >=350 m2/kg" (SEE Table 1); - The density of steel slag powder is changed from "not less than

2.8 g/cm3" to ">=

3.2 g/cm3"; - The free calcium oxide content of steel slag powder is changed from "not more than 3.0%" to "<=4.0%"; - DELETE the definition and index of the basicity factor of steel slag powder; - ADD chloride ion content index of steel slag powder. The value is <=0.06%; - The fluidity ratio is changed from "not less than 90" to ">=95"; - In the soundness of steel slag powder, autoclave method is changed from "When the content of MgO in steel slag is more than 13%, it shall be qualified" to "6 h autoclave expansion rate <=0.50% (If the content of MgO in steel slag powder is not more than 5%, autoclave soundness may not be inspected)"; - The reference method for the determination of free calcium oxide content is changed from "YB/T 140 'Methods of chemical analysis of steel slag'" to "YB/T 4328 'Determination Method for Free Calcium Oxide Content in Steel Slag'"; Steel slag powder used for cement and concrete

1 Scope

China's national standard for ground steel slag used as a supplementary cementitious material in cement and concrete. It specifies the terms and definitions, the classification, the technical requirements, the test methods, the inspection rules, and the packaging, marking, transport and storage, and it applies to steel slag powder used in cement and in concrete. Steel slag is the slag from the steelmaking vessel, not from the blast furnace, and the distinction is the whole point of this standard. Blast furnace slag, quenched to a glass, is reliably hydraulic. Steel slag is cooled slowly, is crystalline, and is only weakly cementitious - and it carries a specific hazard that blast furnace slag does not: free lime and free magnesia. Both hydrate slowly and expand as they do, and expansion in hardened concrete is destructive. Steel slag used without control has caused failures that appeared months or years after placement, and that is why the soundness requirement is the central clause of the document rather than one of several. The standard therefore sets the soundness test and its limit, the free calcium oxide content, and the ageing or treatment implied by them, alongside the properties that determine whether the material is worth using at all: the specific surface area, since steel slag is hard to grind and its reactivity depends almost entirely on fineness; the activity index at defined ages, which states its contribution to strength relative to a control; the water demand ratio; the moisture, the sulfur trioxide content and the metallic iron content. Classification by activity grade lets the material be specified for the use it actually suits. Issued on 7 September 2017 and in force since 1 June 2018, it replaces GB/T 20491-2006.

This Standard specifies the terms and definitions, technical requirements, test methods, inspection rules, packing, marking, transport, and storage of steel slag powder used for cement and concrete. This Standard is applicable to steel slag powder used for cement and concrete.

2 Normative references

The following documents are indispensable for the application of this document. For the dated references, only the versions with the dates indicated are applicable to this document. For the undated references, the latest version (including all the amendments) are applicable to this document.

GB/T 176 Methods for chemical analysis of cement

GB/T 208 Test method for determining cement density

GB/T 750 Autoclave method for soundness of Portland cement

GB/T 1346 Test methods for water requirement of normal consistency, setting time and soundness of the Portland cement

GB/T 2419 Test method for fluidity of cement mortar

GB/T 8074 Testing method for specific surface of cement - Blaine method

GB 8076 Concrete admixtures

GB/T 9774 Sacks for packing cement

GB/T 12573 Sampling method for cement

GB/T 17671 Method of testing cements - Determination of strength

GB/T 51003-2014 Technical code for application of mineral admixture YB/T 022 Steel slag used for cement YB/T 804 Terminology for iron and steel slag and treatment and utilization It shall be carried out according to GB/T 8074.

5.2 Density It shall be carried out according to GB/T 208.

5.3 Water content It shall be carried out according to Appendix C of GB/T 51003-2014.