Slag cement is a material that is used in a wide variety of commercial and architectural concrete construction applications. This information sheet is intended to provide guidance to specifiers in the absence of slag cement specifications, or for the addition of slag cement to an existing specification.

Slag cement should be used as a pound for pound replacement for a portion of the portland cement in a concrete mixture. Depending on the desired properties or application, various replacement levels can be used. Table 1 lists suggested replacement levels for a variety of common applications.

As with all concrete mixtures, trial batches should be performed to verify concrete properties. Listed replacement rate ranges provide a starting point for trial concrete mixture design. These ranges typically accommodate optimization of replacement rates to achieve desired concrete performance in different environments and temperatures. Results may vary due to a variety of circumstances, including temperature and mixture components, among other things. You should consult your local slag cement representative for assistance in how to achieve maximum benefits using slag cement in your concrete project. Nothing contained herein shall be considered or construed as a warranty or guarantee, either expressed or implied, including any warranty of fitness for a particular purpose.

For General Use 

Cementitious Materials

1. Portland cement shall conform to the requirements in ASTM C1501  or ASTM C11572.

2. Slag cement shall conform to the requirements in ASTM C9893.

3. Blended cement shall conform to the requirements in ASTM C5954.

4. Pozzolans shall conform to the requirements in ASTM C6185.

5. Silica fume shall conform to the requirements in ASTM C12406.

6. The water-cementitious materials ratio (w/cm) shall be calculated by dividing the weight of water by the weight of portland cement, plus slag cement plus pozzolans.

Exposure to Sulfates

1. For moderate exposure, where ASTM C150, Type II cement is required, a Type I with 25 to 50% slag cement (by mass of cementitious material) can be used.

2. For severe exposure, where ASTM C150, Type V cement is required, a Type I or a Type II cement with 50 to 65% slag cement (by mass of cementitious material) can be used.

3. For very severe exposure, an ASTM C150 Type V cement with a minimum of 50% slag cement (by mass of cementitious material) can be used.

4. The sulfate resistance of the concrete shall be confirmed by testing in accordance to ASTM C10127.

Mass Concrete

1. For mass concrete placements, the percentage of portland cement to be replaced shall be 50 to 80% (by mass of cementitious material).

2. Thermal properties of the concrete shall be verified prior to construction to ensure conformity to project requirements.

Alkali-Silica and Alkali-Aggregate Reactivity

1. Mitigation of ASR shall refer to ASTM C1778 for guidance; on reducing the risk of alkali-aggregate reaction in concrete.

2. When using reactive aggregate, slag cement shall be used at replacement levels between 25 and 70% (by mass of cementitious material).

3. If the specific slag/portland cement mixture is shown to mitigate ASR in accordance with ASTM C1778, low alkali cement is not necessary.

Exposure to Deicing Salts

1. Concrete exposed to deicing salts shall have a w/cm ratio of 0.45.

2. Concrete shall have an adequate air-void system as defined in ACI 201.2R9.

3. Proper finishing and curing practices, in accordance with ACI 30210 and ACI 30811 shall be followed.

4. Slag cement replacement can be 25 to 50% (by mass of cementitious material).

Freeze - Thaw Durability

1. Concrete shall have a w/cm of 0.45.

2. Concrete shall have an adequate air-void system as defined in ACI 201.

3. Slag cement replacement can be 25 to 80% (by mass of cementitious material).

References

1. ASTM C150/C150M-19, “Standard Specification for Portland Cement,” ASTM International, West Conshohocken, PA, 2019.

2. ASTM C1157/C1157M-17, “Standard Performance Specification for Hydraulic Cement,” ASTM International, West Conshohocken, PA, 2019.

3. ASTM C989/C989M-18a, “Standard Specification for Ground Granulated Blast-Furnace Slag for Use in Concrete and Mortars,” ASTM International, West Conshohocken, PA, 2019.

4. ASTM C595/C595M-19, “Standard Specification for Blended Hydraulic Cements,” ASTM International, West Conshohocken, PA, 20019.

5. ASTM C618-19, “Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Concrete,” ASTM International, West Conshohocken, PA, 20019.

6.  ASTM C1240-15, “Standard Specification for Use of Silica Fume for Use as a Mineral Admixture in Hydraulic-Cement Concrete, Mortar, and Grout,” ASTM International, West Conshohocken, PA, 20019.

7. ASTM C1012/c1012M-18b, “Standard Test Method for Length Change of Hydraulic-Cement Mortars Exposed to a Sulfate Solution,” ASTM International, West Conshohocken, PA, 2019.

8. ASTM C1260-14, “Standard Test Method for Potential Alkali Reactivity of Aggregates (Mortar-Bar Method),” ASTM International, West Conshohocken, PA, 2019.

9. ASTM C1778- 19, “Standard Guide for Reducing the Risk of Deleterious Alkali-Aggregate reaction in Concrete,” ASTM International, West Conshohocken, PA, 2019.

10, ACI 201.2R-16, “Guide to Durable Concrete,” American Concrete Institute, Farmington Hills, MI, 2016.

11. ACI 302.1R-15, “Guide to Concrete Floor and Slab Construction,” American Concrete Institute, Farmington Hills, MI, 2015.

12. ACI 308.1-11, “Standard Specification for Curing Concrete,” American Concrete Institute, Farmington Hills, MI, 2011.

Case Study:

The Rowan

Designed by Handel Architects, the Rowan utilizes exposed structural cast-in-place concrete as a key architectural design element. Located in the old industrial wing of San Francisco, CA, the Rowan consists of 71,500 sq. ft. of mixed-living and residential space.

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