Stressline Cast stone keystone lintel

Cast Stone: Why vapour curing is the only way

Andrew ALL, Cast Stone Leave a Comment

Is vapour-cured semi-dry cast stone the look that so many builders are going for? The answer is yes, and there are a number of reasons why but before we explain, we will look at the different products on the market.

Wet cast, semi-dry or GRC?

The myth surrounding cast stone is that semi-dry is an inferior product to wet cast or Glass fibre Reinforced Concrete (GRC or GFRC). Nothing could be further from the truth. Semi-dry is often the most cost-effective solution.

Vapour-cured cast stone can offer customers a cost-effective but robust solution.

Wet-cast and GRC tend to be at least double the price of semi-dry because of the product content, more expensive moulds and the requirement for a secondary finishing process like acid etching or sand-blasting.

The lead time of wet cast and GRC products also tends to be longer because one mould can turn out only one product per day; in comparison semi-dry moulds can turn out 30 or 40 products a day.

Wet cast products tend to be around about 15% heavier than semi-dry because of the density of the product as well.

So how do we address this myth about semi-dry cast stone? With a process called vapour curing.

A unique vapour curing process

Vapour curing in general, is the process of controlling the environment in which the cast stone is cured using temperature maintained moisture. Not only does this speed up the curing time, but it also creates a consistently high-quality finished product.

Our cast stone is machine compacted, meaning that operator fatigue is much less an issue.

At Stressline, we take vapour curing to a new level, enhancing the finished product even further.

Not only do we use moisture to cure the cast stone, but we introduce a small amount of exhaust gases as well. This hardens the product even further, and we are able to produce the very best semi-dry product available on the market.

In our experience vapour curing is the only way to go with cast stone, and the cost of not doing it can be huge. For example; If casts are not vapour cured and are left out in a hot and windy day (for example) this can lead to case hardening where, as the chemical process of the cement heats up the cast sucks the moisture content into the core whilst the heat and wind dries the surface too fast not allowing the chemical reaction to take place on the outer reaches of the cast. This will then provide a cast that will crumble under general movement and handling or the surfaces will start to delaminate over a period of time.

The myth is further expelled here at Stressline by using finer sands to give a closed and smoother texture and to sharpen arises, and we also mechanically compact the mixture, instead of by hand where operator fatigue can have an impact on the compacting quality.

All of our cast stone products are uniquely vapour cured, and all comply with British standard BS 1217:2008 Cast Stone Specification and for this reason, our vapour cured cast stone is the only way.

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