Update March 2014
New production facility commissioned, Lytag ^® show off their true colours at the recent Concrete Show (NEC Feb 27/28th 2014). As sales manager Michelle Walker explained, Lytag has been used as a lightweight structural aggregate on many of London's iconic buildings including The Shard and the Post Office Tower.

Main Story Sept 2013
With Lytag^® commissioning a new production facility at Drax in Yorkshire (Sept 2013), for the manufacture of pulverised fuel ash based lightweight aggregate, Specialist Aggregates review the relative merits of the lightweight aggregate market supplied by Lightweight Expanded Clay and Lytag^® aggregates

Lightweight expanded clay and Lytag^® are superficially similar, both being expanded “fired” honeycombed pellets, however, for many applications the choice is a compromise between achieving a beneficial light weight advantage by using an expanded clay against the additional strength achieved by employing pulverised fuel ash based Lytag^®.

Lytag^® is approximately half as dense as normal limestone or gravel aggregate, however, Lightweight Expanded Clay Aggregates are generally half as dense as Lytag^® (i.e. four times lighter than “normal aggregate”). Broadly, use Lightweight Expanded Clay Aggregates where reduction in weight is the primary consideration, for example backfill to structures, for drainage especially green roofs and as fill for feature plant containers. Lytag^® is used where design strength needs to be achieved with reduction in weight compared to natural aggregates, for example in wet pour and precast concrete, or loose backfill to services where loads may be applied, it has also been successfully used for vehicle arrester beds.

r There is no absolute correlation between lightweight aggregate properties and concrete strength, however, as a loose material Lytag^® has a greater crushing strength than Lightweight Expanded Clay Aggregates (BSEN 13055). Direct correlation cannot be made between the crushing strength of lightweight and “normal aggregates” as differing test methods are used.

Both Lightweight Expanded Clay Aggregate and Lytag^® provide thermal insulation to a similar degree, exact data should be obtained from manufacturers if this aspect is critical for a given application.

When loose laid, in the short term Lytag^® has a lower water absorption compared to Lightweight Expanded Clay Aggregates. However, in the long term the water absorption of both products is similar at around 30%.

Lytag^® can claim green credentials as it is a secondary aggregate produced from the ash of coal fired power stations – although clearly the coal has to be mined and burnt in the first place! Lightweight Expanded clay aggregates are naturally produced from virgin clay aggregate. Whilst we have not seen absolute figures the energy required to manufacture both products is likely to be similar.

Both products are chemically inert, do not degrade and are not frost susceptible.

Neither Lytag^® or many of the available types of Lightweight Expanded clay Aggregate are pretty! Although Leca^®LWA produce a terracotta version of their product which is widely used as a decorative lightweight aggregate.

Absolute quantitative comparison has not been made in this précis of characteristics – for definitive data see manufacturer’s individual data sheets.

Specialist Aggregates supply both products. For further details please use the "Contact Us" facility or follow the link below.

Bridport Gravel, once the industry standard for fully rounded “pea gravel” against which all other gravels were compared, ceased supply around ten years ago. Since that time many have searched in vain to discover a suitable alternative.

Earlier this year Specialist Aggregates finally located exactly what was required, an environmentally sustainable deposit of durable and fully rounded pea gravel, but with a modern twist - the material comes in natural multi coloured hues of charcoal black.

Since visiting the deposit Specialist Aggregates have been working closely with the owners to develop products suitable for the UK market. From the first week in November we will have the following available:

Technical Aggregates
Fully rounded gravels in sizes of 1-4mm, 2-6mm and 4-8mm
Support media for specialist high volume filtration
Backfill to boreholes with minimal annular space.
Gravels for test tracks and skid pans.

Dried Aggregates
Fully rounded dried gravels in sizes of 1-4mm, 2-6mm, 4-8mm and 6-15mm
Resin based flooring
Terrazzo including swimming pool surrounds.
Decorative wall boards.
Extenders for self levelling cement applications
Shotcrete
These clean dried gravels are also ideal for promotions, photoshoots and staged events.

Decorative Aggregates
Sizes as described above plus fully rounded gravels graded as 6-15mm, and 20- 30mm
Decorative landscape applications
Pebble dashing
Floriculture

As an historical endorsement of the once esteemed gravels worked on the western end of Chesil Beach we have decided to call our new range of products “Bridport Black Gravel “ .

A link to the products is shown below.

Our Images show examples of Bridport black gravel being used in resin based flooring in a hotel foyer and office reception areas. The gravels can also be seen utilised as a striking pebble dash to a seaside bungalow.

Little did German chemist Johan Glauber realise the influence of the crystals he named Miracle Salt (Sol Mirablis). Not only would the material go on to become a major constituent of modern day soap powders, but it is also a vital constituent of glass manufacture and a “stepping stone” used in making a wide range of other industrial chemicals.

The chemical is known today as sodium sulfate (or sulphate for those of us old enough to remember real Bunsen burners and stained wooden bench tops in the chemistry lab).

Now, the miracle has become something of a curse when purchasing post WW2 properties built in former coal mining areas.

The problem has arisen as in late 1940's and 50's there was both was a chronic need for housing, and a shortage of imported wood to facilitate the suspended type floors that had been in vogue pre-war. The solution was to build up the under-floor with mining waste and to cap off with what was often a poorly specified and uncontrolled concrete.

The result thirty to forty years later has been that sulphate minerals both in the shale waste and un-burnt pieces of coal have dissolved in ground water and then re-precipitated as Glauber's miracle salt. Just like ice crystals in a frozen pipe these minerals punch well above their weight and have the capability of causing concrete floors to crack and heave, and in extreme situations can even cause external walls to shift on their foundations.

The only solution is to remove the old sub-floor and to replace with a non sulfate bearing hardcore: for example Leca® LWA insulation fill and top off with modern quality controlled concrete.

Our images show a property where leca® LWA has been used. The “before” images clearly show the offending red shale being excavated from the kitchen floor and later pieces of the shale and coal that have been collected and washed. Our "after" images show the ease with which 50ltr packs of Leca® LWA insulation fill can be installed.