OVERVIEW OF MIXING/CASTING/FINISHING TECHNIQUES

 

Freestone Millworks, LLC™ (FSMW) ceramic aggregates can be added to the base concrete/ mortar mix or simply spread or coated onto the surface of the cast cement or molded products. The choice of techniques depends on the goals and limitations of the contractor and customer.  In order of increasing complexity, cost and performance the various techniques are as follows,

I. DECORATIVE SURFACE LAYERS/TOP COATINGS WITH DRY FSMW CERAMIC AGGREGATE

A. Spread dry decorative ceramic aggregate onto cast surfaces and work into top paste layer until flat/covered, followed by broom brushing/power washing after partial cure

B. Repeat A. with partial grind/burnish after cure to yield a smoother but textured surface

C. Repeat A. or B. but add a surface troweled/sprayed layer of cement paste to fill voids

D. Repeat A. or C., followed by fully grinding of surface to a smooth, polished finish 

II. SURFACE LAYERS/TOP COATINGS USING MORTAR WITH FSMW CERAMIC AGGREGATES

(Use same basic techniques as detailed under I., but apply ceramic aggregates as a premixed paste onto either cured or uncured cement mortar/concrete base layers)  

III. INTEGRAL, PRE-MIXED MORTAR/CONCRETE WITH FSMW CERAMIC AGGREGATES 

(Cement mixes using FSMW ceramic aggregates are cast/molded and after varied cure are finished, as desired, by brushing/washing/grinding/polishing, etc. as detailed above)

 

CEMENT MIX FORMULATION AND CASTING CONSIDERATIONS

Each of these techniques require the use of proper techniques and achievement of a proper cement formulation. Not all prepackaged or premixed cement formulations will work with all these techniques.  Specifically, the addition of the FSMW ceramic reinforcing aggregates to any cement mix requires that sufficient cement binder and proper water:cement ratios are used to insure a dense, hard, well-bonded matrix.  To this end the addition of the ceramic aggregates may necessitate the use of formulations with reduced levels of fine and/or coarse aggregate. For each increment of FSMW ceramic aggregates added to the mix a similar amount of sand or rock must typically be reduced in the base mix.  Conversely, a cement batch processor with adequate knowledge and skills may be able to increase the Portland cement and water levels to maintain the proper ratios of the main components when using an off-the-shelf bag cement mix.   

The user of any FSMW ceramic aggregate product is responsible for pre-testing any proposed mixes or processing techniques.  While spreading a thin layer (<1 lb/sq.ft.) of dry aggregate on top of a cast concrete slab is relatively simple and straight-forward, the use of FSMW ceramic reinforcing aggregates in mortar coatings or as an integral component of a pre-mixed batch requires care. In no case should any FSMW product be used in a structural or load-bearing application.  

As a general guide the following formulation has been used effectively:

 

 ◊1 part: water

 ◊3 parts: Type I Portland cement (or other similar common hydraulic cement binders) 

 ◊1 to 3 parts: manufactured & natural sands/fillers/fine aggregate (minimum coarse aggregate) 

 ◊3 to 5 parts: FSMW ceramic aggregate (use at 35-50% of total mix for best results)

NOTES:

1. Lower water:cement (w:c) ratios are more desirable for strength, but if additional water is needed to increase processing ability, the w:c levels are best kept below 0.35-0.40.

2. Cement paste levels (water and cement) should be at least 33% by weight of total mix. 

3. FSMW ceramic aggregates should be used in a premixed mortar/concrete or in coated   surface layers at a minimum level of 30% to help provide optimal aesthetics and strength

4. Optional components may include pigments, polymer additives, processing aids,  glass/polymer/basalt fibers, pozzolans and other admixtures often used in cast concrete  products to improve visual appearance, durability and the casting/molding processes.

In particular while thin, low basis weight (<1 lb./sq.ft.) surface coated aggregates can be applied to most standard concrete mixes with minimal issues, it is not highly likely that an off-the-shelf bag mix can be mixed with high levels of FSMW ceramic aggregates without problems.  The mix will have too little binder and require too much water addition to achieve a workable mix.  The resultant cement matrix will be porous and weak.  Therefore, when using FSMW ceramic aggregates in a cement mortar or concrete mix the batch will typically need to be made from scratch.   

PRE- AND POST-CURE PROCESSING

The basic techniques used to produced conventional exposed aggregate surfaces are also used with the FSMW ceramic aggregates. The user should be familiar with and experienced in using these techniques for optimal results.  The same tools and materials used with conventional exposed aggregates can potentially be used with FSMW ceramic decorative aggregates.  (Note: Pretest of all additives, formulas, techniques is required before attempting a full-scale project).

 

At the other end of the spectrum, techniques such as wet diamond grinding can be used with FSMW ceramic aggregates on flat surfaces to effectively produce smooth, mirror finishes that replicate polished granite.  Upon initial cure, mixes or surface layers using FSMW ceramic aggregates resemble typical cast concrete.  However, with a minimal amount of added effort the products can be profiled, ground, honed and polished to replicate the appearance of many common stone materials (granite, marble, slate, sandstone, soapstone, travertine, etc.).   

 

Most significantly, the use of this unique blend of the FSMW ceramic aggregates along with other fillers and additives provides a material that is easily finished (ground and polished) compared to conventional materials (cast concrete, filled acrylic polymers, stone, glass, ceramics, metals, etc.). These attributes allow FSMW materials to be used in a variety of designs and applications to create visually stunning products that are extremely durable but also easy to manufacture, finish and maintain, thus offering the user the opportunity for significant value over other material choices.