Photo Album 

Contact Info
 

Copyright © 2002  Ventura Cast Stone.
PO Box 552, Somis, CA 93066   (805) 386-8185 Fax: (805) 386-3002

About Ventura Cast Stone
 

Cast stone

We at Ventura cast stone are pleased to introduce this lightweight cast stone or lightweight precast concrete if you will, into our line of precast concrete and cast stone. Because lightweight cast stone is made from fiberglass strand mixed with real limestone which gives it that stone look, it is suitable for fireplace mantle treatments.

Lightweight precast concrete
 Lightweight precast concrete is usually called GFRC or glass fiber reinforced concrete, and is manufactured by Ventura cast stone and installed in the Los Angeles, Ventura and Santa Barbara Counties. Precast concrete usually weights 100 lbs per cubic foot.  Gfrc usually weights 10 lbs per lin foot.  Precast concrete is a lower end product and does not simulate limestone as does cast stone. Precast concrete resembles finished concrete and the surface looks like your garage floor. Cast stone resembles limestone or sandstone. Lightweight GFRC precast concrete is not a new product but has been used for years, but not in architectural uses.

Our Cast Stone range of products are into two product types:

Dry Cast

The "Dry Cast" method is a two part process, a face material to give you the similar finish to natural stone. Mechanically compacted to the rear of this is the backing mix to give the units strength in the terms of handling ability

Dry cast units are immediately demoulded after casting and are hand finished to a very high standard.

Wet Cast

Wet Cast as the name suggests produces structural products like heads and sills but is also used for slabs, beams and other similar products, that are for high exposure or structural situations where greater loads are required on the finished unit. The Wet Cast also has the added advantage of specialist finishes with the use of special sand aggregates, a massive spectrum of colors can be achieved.

Introduction to Cast Stone (wet cast and dry cast)

Cast Stone is known by a variety of other names including art stone, reconstructed stone, reconstituted stone, artificial stone and manufactured stone. BS 1217 defines cast stone as any material manufactured with aggregate and cementicious binder and intended to resemble in appearance, and be used in a similar way to, natural stone. Cast stone is either homogenous through out or consists of a facing material and backing concrete.

The method of production is split into two categories.

Choice of manufacturing method

The majority of cast stone manufactures use the semi-dry method of production. And is the more commonly widely used method of manufacture. Early consultation with us is advisable to ascertain the correct method of production for your project.

Sizes: Components produced using the semidry method are limited in size with face dimensions of Ashlar units normally no greater than 1200x600mm. This is mainly because of the fact a semi dry mix is used, which require rapid and rigorous compaction with hand held pneumatic tampers. The semidry method of production is best suited to traditionally sized ashlars quoins, sills, copings, door and window surrounds, etc.

Structural requirements: Components requiring reinforcement which is more complex than a few straight bars or a layer of fabric reinforcement, must be produced using the wet cast method of production. This is because it is difficult to achieve thorough compaction of semidry mixes around congested reinforcement.

Appearance: Cast stone can replicate a variety of stone colors and finishes. The semidry method of production is used to simulate limestones and sandstones. Where a component has a particularly intricate pattern or profile including slender projections, precast concrete may have to be used in preference to the 'semidry' method. Good color matching between components can be achieved by both methods, although textural differences become apparent at close range.

Economics: Rapid production rates with frequent reuse of moulds are possible with cast stone produced using semidry mixes. Where as with the Wet Cast process a higher number of moulds is required to achieve the same casting program, but careful thought a planning stages of the contract can minimize the number of moulds. In Fact an additional 2-3 weeks extra lead-time for standard or semi standard products can sometimes be all that is needed to achieve the same casting program.

Comparison between the semidry and wet methods

The production of cast stone using semidry mixes differs from that of wet method in several ways.

Casting

Semi Dry ~ De-molding takes place immediately after compaction. This allows a rapid casting cycle with e.g. up to 100 or more basic components (sills, copings, etc.) a day from a single mould.

Wet Cast ~ Where as to manufacture the equivalent in wet cast it would not only take longer but you would require 1 mould per cast per day i.e. to produce 100 units a day you would need 100 moulds.

Semi Dry ~Compaction is carried out by pneumatic tampers rather than by vibration.

Wet Cast ~ Compaction is carried out by vibration.

Mixes

Semi Dry ~ *Separate facing and backing mixes are often used for components like ashlars, sills, heads and jambs, where the backing mix is concealed from view. Separate facing and backing mixes are used primarily to economize on the facing mix. BS1 217 requires a separate facing mix to be not less than 20 mm thick at any point, with semidry cement sand facing mixes and concrete backing mixes each mix is placed and compacted in immediate succession to ensure that they are effectively monolithic.

Wet Cast ~ Wet Cast units are manufactured from a through colored homogenous mix.

Semi Dry ~ Water repellent admixtures are invariably used in facing mixes to reduce permeability. Giving a water absorption of Grade B. All constituents are accurately weigh batched with the moisture content monitored regularly. Mix batches are necessarily small to prevent any premature drying of the mix. Thorough mixing and compaction are critical to ensure that the cast stone achieves the required density (typically between 1850-2100kg/m2), compressive strength and permeability.

Wet Cast ~ superplasticisers and accelerators are used to ensure good flow of the mix during vibration and compaction to achieve a smooth, compact and blow hole free finish (where ever possible finish smooth after dressing) also to give good early strength. Typical cube tests at 7-10 Days are that of the equivalent of that of a semi dry unit at 28 Days

Products are split into three categories.

Standard - Cast stone items that are manufactured in accordance with our Technical specification sheets. These items could be stock items or units, which are ready to cast at the first available production slot, with no moulds to produce. Products like standard head, cills or pier caps and copings. The cost of establishing the moulds is not same, thus for small production runs costs can be kept to the minimum. Also not forgetting lead times can be much shorter by not having to detail, obtain approval and then construct moulds.

Semi Standard - Cast stone items, which are similar to details within our Technical specification sheets. But say vary in length or require slight mould adaptation or modification.

Purpose Made - Cast Stone items which are manufactured in accordance with the contract documents. These units are made from new purpose made moulds. These would probably be specialized units, which are not contained in our brochure. We have our own in house design department, who will assist you in the process of your design advising you in Careful thought must be given in the planning process for purpose made products. The following points should be bore in mind before hand.

Remember adequate time must be allowed for all of the above to be in accordance with B.S.1217

Colors and Finishes

Natural stone colors are achieved either by reliance on the color of crushed rock and sands and aggregates or by the addition of pigments. White cement gray cement and a combination are often used. The use of pigments can give the cast stone greater scope in the selection of suitably graded aggregates, which permit good compaction and achieve a strong, dense mix. Iron oxides based pigments are normally used in small quantities (e.g. 0.2%-1% yellow iron oxide by weight of cement for yellow sandstone's and up to 5% red iron oxide for red sandstone). High proportions of pigment powder (above say 6 - 8% by weight of cement) are used sometimes to achieve unusual colors like blues and browns but generally these should be avoided.

A variety of traditional ashlar finishes can be replicated with cast stone, including plain, boasted, tooled, rockfaced, vermiculated. The other ashlar finishes are normally produced from latex:sand mould liners.

Here is where specialist aggregates can be used to achieve some wonderful and varied finishes and colors.

Structural Use

Dependant on the situation all cast stone both Wet and Dry Cast can be used. But there are limitations in the Dry Cast process as opposed to Wet Cast: -

Home