A Concrete company’s “MIXES” are the recipes it uses to produce the wide ranging variety of concrete its customers require. These mixes might be similar among competing Ready Mix companies or radically different depending upon past experience or specific customer needs. It’s all a matter of producing a concrete mix which will perform as intended and giving the customer the finished product that they need. Concrete is often viewed as a simple or basic element of construction, because it is composed of 4 simple basic ingredients; Cement, Fine Aggregate, Coarse Aggregate and Potable Water. After all how complicated can it be? Just mix them all together and you get concrete…..right? Actually it can be that simple, but overall it is a bit more complicated than that. The proportions of these 4 basic ingredients coupled with various Concrete Admixes, are what eventually evolve into the Concrete Companies “Mixes”. Salmon Bay currently has 1100 various mixes which we can and do produce. The variety of concrete produced needs to be extensive, in order to meet various building codes, engineering requirements, environmental issues, finished appearances and a multitude of other finish, function and performance factors. Construction professionals worldwide consider concrete as being one of constructions most versatile components. Right here in Seattle; whether you’re a construction professional or a first time DIY homeowner, Salmon Bay has the mixes that are versatile enough to meet your Ready Mix Concrete needs. For more information about concrete visit the Portland Cement Associations website:
Sand Slurry is a self-compacting form of Controlled Density Fill (CDF) primarily used for filling tanks and large voids in excavation. A small portion of cement may be used in order to help firm up the mix and dissipate the large volume of water typically in the mix. As the name implies, it is generally all sand and water, with the occasional addition of cement and/or Fly Ash to make it pumpable. The PSF (lbs/square foot) of non-cementitious sand slurry is usually equal to that of the surrounding native soil.
Controlled Density Fill (CDF)
Salmon Bays CDF, “Bay Flow”, is a more flowable version of Sand Slurry. It is designed to flow into tight locations and areas with smaller voids to be filled. Bay Flow is self-consolidating mix containing cement, which usually has a higher PSF than the surrounding native soils. Used mostly in utility work, during back filling applications, it generally comes right out of the truck and into the ground. CDF can be pumpable with the addition of higher proportions of cement and/or fly ash.
The next progressions in strength generating mixes, after CDF’s, are lean mixes. A lean mix is measured in PSI (lbs/square inch). A Lean mix is used in applications where a solid surface or sub-base is needed, never for walls or structural applications. Generally developing 2000 psi or less and placed in thicknesses of 2 inches or more. The mix can use up to 4 sacks of cement per cubic yard and contains both fine and coarse aggregates. Lean Mixes will pump if the cementitious value is high enough and there is Fly Ash in the mix to aid in pumpability. If lean mixes contained a higher content of cement they would become regular concrete.
Basic…everyday concrete used by homeowners and contractors alike. Very straight forward mixes that describe just what the mix is….”5 ½ sack Pea”…is 5 ½ sacks of cement per cubic yard of concrete with Pea gravel as the coarse aggregate. Sackage mixes range from 4 ½ sx to 6 ½ sx, all of which are intended to meet the Seattle IBC. These mixes are suitable for flatwork and meet the building code for specified strengths of 2000 psi to 4000 psi. Mixes with higher proportions of cement are pumpable if the proper equipment is used. Pump companies should always be consulted prior to a concrete placement to insure that the right equipment is available for the mix being used.
Design Mixes (CA)
A design mix is a variation or adaptation of one of the more conventional Standard Mixes typically used by contractors. They have been “Designed” for a particular application, be it strength, placement, finish or appearance. For structural requirements, Continuously Approved (CA) design mixes must be approved by the City of Seattle’s Dept. of Planning and Development. The ultimate strength of these mixes can range from 2500 psi to12000 psi. Any mix exceeding 4000 psi must have onsite field inspection and those exceeding 6000 psi must have a Batch Plant inspector, as well. These mixes have been aggressively designed to achieve a particular strength and finishability, through the use of less cement and lesser amounts of water (a low water/cement ratio) with the use of specialized add mixtures. For example; a 4 ½ sack standard mix, which meets the Seattle IBC, will have a 2000 psi rating, where as, a 4 ½ sack CA mix can typically achieve 4000 psi. Other applications for design mixes are: higher earlier strengths, placement in and around congested steel reinforcement, architectural concrete finishes and Flowable Thermal Backfill (FTB)
These mixes are cement rich, generally in the 6 ½ sx to 8 sx range with up to an 80%-20% blend of Building Sand and Pea Gravel. Ultimate compressive strengths of 2000 psi to 6000 psi are typical. The delivered slump averages about 2 inches, in order for the mix to virtually stand on its own against a one sided forming system or earthen wall having steel reinforcement. Shotcrete and Gunite are air-placed concrete mixes which incorporate the use of a grout pump that introduces compressed air at the discharge nozzle. Shotcrete is a structural mix suitable for soil stabilization all the way to finished in-place load bearing walls. These structural applications (one sided placement or slip form) must be executed by a City of Seattle certified contractor. Gunite, on the other hand, is considered to be less of a structural mix and is used in soil stabilization projects or more commonly for “in ground” concrete pools.
These mixes can be the most cement rich and most fluid of all the many concrete varieties. Masonry Block fill has the lowest strength, usually in the 2000 psi range and at the upper end are the Auger Cast grouts, which have cement content up to 10sx per cubic yard. Strength is critical in auger cast placements, since ultimately the finished product becomes a subterranean column supporting an above ground structure. All these mixes are pumpable and are generally exclusively sand mixes. The delivered Slump is a very high 6” to 10” so that the mix will flow; in the case of masonry fill, or is very fluid; in the case of auger cast piles to allow for the insertion of intricate rebar cages
This is a Salmon Bay specialty, which we have developed quite a reputation for over the years. Our mix is more cement rich than a standard mix, usually 5 ½ to 6 ½ sack, over rocked with pea gravel to create a dense aggregate surface and is air-entrained for freeze thaw protection. We suggest the use of some Lampblack to darken the cement paste and highlight the color of the aggregate as well as Fibermesh 150 for secondary reinforcement. Our mix can be pumped or tailgated right out of the truck. A properly prepared sub-grade and an experienced finisher to do the exposing, will assure a good looking finish……it doesn’t come out of the truck and look that good all by itself.
Annually Salmon Bay produces a lot of concrete, which is a color other than gray. Our integrally colored concrete mixes incorporate the use iron oxide pigments, which develop into a variety of popular earth tone colors. A contractor, well versed in the placement of colored concrete, can create beautiful architectural finishes. Colored concrete can be an enhancement to a structure or to the landscaping design, but it is expensive and can be temperamental. As a result, careful planning, consistency in procedures at the job site and proper execution at the time of placement are critical in achieving a successful project. It’s all the same color when it’s in the truck….just not everyone can make it turn out that way when it’s on the ground. For additional information visit this website:
This hybrid concrete is gaining in popularity, as we adapt to the “greening” of developments and the retrofitting of existing hardscapes. Pervious Concrete is a highly permeable surface, which reduces water runoff and allows surface water to penetrate into the substrate. Various aspects of the project need to be taken into account prior to the placement of the product. Consequently, consultation with experienced concrete personnel and a qualified Pervious contractor is suggested prior to beginning a project. “In-place” Pervious projects are generally 25% to 30% more expensive than those using standard mixes, prep and placement methods. These mixes have a cement content in the 5 ¼ to 6 sack range and contain no fine aggregates….only large coarse aggregate is in the mix. The thickness of the placement depends on the load rating required i.e., sidewalks don’t have to be as deep as driveways. The substrate must be over excavated to accommodate properly graded aggregates, which will provide adequate drainage. Pervious Concrete will only remain pervious, if properly maintained.