Storage and Handling Slag Cement
Slag cement, like portland cement, must be stored in bins or silos to provide protection from moisture and contamination. Since both slag cement and portland
cement are delivered in the same type of container truck, care should be taken to distinguish one material from the other in storage and handling. One quick method of distinguishing between slag cement
and portland cement is to compare their color. Slag cement is commonly lighter than portland cement. All handling equipment suitable for use with portland cement is also suitable for use with
Batching and mixing of concrete containing slag cement is similar to ordinary portland cement concrete. ACI 233 recommends that slag cement be batched following portland cement in the same weighing apparatus. The mixing time and the mixing equipment are the same.
Like all other concrete, slag cement concrete can be transported by a variety of methods and equipment, most commonly, revolving-drum mixers.
In some types of construction, concrete is placed in forms and then consolidated. Consolidation densifies fresh concrete within forms, and around embedded items and reinforcement; it also eliminates stone pockets, honeycombs, and entrapped air. Slag cement enhances the consolidation and pumping of concrete by improving its rheology. Although slag cement typically improves the placement characteristics of concrete, proper placing and finishing practices must be followed.
Finishing refers to leveling, smoothing,
consolidating and otherwise treating
surfaces of fresh, plastic concrete to
produce a desired surface or appearance.
The finishing operation should be
carefully planned. Skill, knowledge and
experience are needed to properly finish
concrete. The finisher must have the
proper tools and equipment and
adequate manpower. Proper timing of
the operations for the existing conditions
is critical. In warmer weather, the slower
setting characteristics of slag cement
concrete can be a benefit to the finisher
by allowing sufficient time to complete
each step in the finishing process. In
cooler weather, finishing operations may
need to be delayed due to the slower
setting characteristics. Set times can be
modified by the addition of chemical
Most concrete made with slag cement
will have less bleed water than concrete
made with portland cement alone.
Bleeding rates are also usually slower.
Virtually all slag cement used in the
United States is ground finer than Type I
or Type II cements. Coarser slag cements
could have equal or greater bleeding.
As with all concrete, proper curing practices
are essential to achieve the desired
properties of concrete. All curing practices
used with portland cement concrete
are generally compatible when slag
cement is used, such as wet curing
with fog sprays or burlap, or concrete
- ACI233R-95, Ground Granulated Blast-Furnace Slag As A Cementitious Constituent In Concrete, American Concrete Institute, Farmington Hills, Michigan, 1995.