Reconstructed Stone

Fortress Stone is a homogenous mix of natural aggregates sourced from various areas of the United Kingdom and Ireland. The mix design, developed over many years incorporates an integral waterproofer, thereby producing a high quality cast stone product.

The compressive strength is a minimum of 25N/mm2 when tested to BS1881 Pt 116 1983 and BS 1217 1986.

The drying shrinkage of Fortress Stone when tested in accordance with BS 6073 PT1 shall be 0.06%.

The thermal conductivity is typically 1.2w/mk.

Mean coefficient of water absorption due to capillary action shall not exceed 3kg/cm.

Density is typically within range 2000 – 2150 kg/m3.

At the early stages of design cost savings can be achieved on the overall cast stone package through careful attention to each component. Components can be designed to ensure that each unit optimises mouldage recovery and can be handled easily on site. Consult out Technical Department to discuss how savings can be achieved.

Cast stone units can be cut as per quarried stone, when units are to be butted together. However great care must be taken with units which contain either handling or reinforcement steel. A bench type masonry saw is recommended for cutting cast stone. Once cut the units should be washed with clean water to remove any dust before incorporating into works.

Cast stone repairs can be undertaken is small areas of damage. Repair work utilises the base aggregate of the original stone and will therefore take time to weather to the same colour. As many of the repair techniques vary for each stone type. Fortress Stones Technical Department should be consulted for advice prior to the commencement of repairs.

Due to the fine textured finish and pale colours of most forms of cast stone the removal of mortar or other forms of staining can be difficult. It is for this reason that great care and protective measures must be taken to avoid intital contamination.

Some stains may be removed with the use of a mild brick cleaner. As with all cleaning treatments cleaning should initially be undertaken in a non prominent area to ascertain possible differences which may occur in stone shading/texture.

In the event of severe staining the stone may be cleaned with a mild solution of Hydrochloric acid and water.

For further information on cleaning contact our Technical Department on 02893 350202.

Specification for cast stone

All materials, workmanship and tests where required shall comply with Fortress Stones Technical Specification which in any cases exceeds BS1217 1986 and DIN 18500.

The contractor shall ensure that safety health and welfare measures required under or by virtue of the provision of any enactment or regulation or the working rules of any industry are complied with.

Cement shall conform to one of the following:
Ordinary Portland Cement – BS12
Portland Blastfurnance Cement – BS146

High Alumina Cement shall not be used in the manufacture of any Cast Stone product. The total NA2 0 (acid soluble) content from the cement shall not exceed 0.75%. Prior to the commencement of work if required the contractor shall submit to the SO test certificates from an independent and accredited testing laboratory giving the results of tests on samples relating to the cement to be used in manufacture.

Water shall be clean and free from harmful matter either organic or inorganic and shall comply with BS 5328. If so required by the SO it shall be tested in accordance with BS 3148.

All aggregates shall conform to BS 882 (except grading and silt content requirements for fine aggregates.)

Steel Bar Reinforcing: High – yield steel deformed bars shall comply with BS 4449. Cold twisted steel bars shall comply with BS 4461. The contractor shall provide if required pieces 500mm long selected by the SO forwarded by the contractor to a materials testing station for testing.

Calcium Chloride as a admixtures containing Calciurm Chloride must not be used.

Pigments either organic or inorganic must not be used without the written approval of the SO. If pigments are to be used these shall comply with the BS 1014.

The use of accerlerating, retarding water reducing and hydrophobic admixtures/ additions shall be permitted and shall conform with BS 5075 Part 1.

All cast stone shall comply with the following tests unless written instructions from the SO are obtained to the contrary.

The average crushing strength of 3 cubes tested to BS 1881 Part 116 should not be less than 25N/mm2.

The samples are tested in accordance with appendix 1 with an immersion time of 10 minutes, the mean coefficiesnt of water absorption due to capillary action of the three samples shall not exceed 3g cm-2 min –1/2 with no individual value exceeding 4g cm-2min-1/2.

The average drying shrinkage of three specimens of cast stone sampled in accordance with BS 1217 1986 and tested in accordance with BS6073 shall be no greater than 0.06%.

All cast stone shall comply with the following tolerances unless written instructions from the SO are obtained tot he contrary.

The actual dimensions of individual regular units should conform to the declared work dimensions subject to the tolerances given below.

Length	Length tolerance mm	Width Tolerance mm	Thickness Tolerance mm
Up to 1000	+ - 3	+ - 3	+ - 3
Over 1000 up to 2500	+ - 4	+ - 4	+ - 4
Over 2500 up to 4000	+ - 5	+ - 5	+ - 5
Over 4000	+ - 6	+ - 6	+ - 6

Maximum permitted variation form plane –1.3% of the maximum dimension of the item or 3mm whichever the greater.

The length divided by the side dimension of the largest square that can be drawn wholly inside the smallest cross section shall be no greater than the values given below:

Up to 1m	20mm
1 to 2m	16mm
Over 2m	12.5mm

The colour and texture of the exposed face of cast stone should be agreed between the suppliers and the SO.

All cast stone products are to be Fortress Stone supplied and manufactured by Fortress Stone, 8 Sloefield Park, Carrickfergus, County Antrim or other equal and approved manufacturer. The written permission of the SO must be obtained prior to the appointment of a supplier.

All cast stone shall be carefully loaded and packed for transportation exercising customary and reasonable precaution against damage whilst in transit.

All cast stone shall be received and unloaded at the project site by competent operatives with the necessary care in handling to avoid damage.

All cast stone shall be stored on firm level hard ground standing in a separately identified area of the site. Pallets must not be stacked. It shall be protected from weather by suitably lapped weatherproof materials. Cast stone must not be placed prior to building on anything other than its delivery pallet.

The first course of cast stone should be set out without mortar to check the layout using small fillets of timbers to ensure correct mortar spacing. Once the setting has been checked and approved the first course may be laid.

A damp proof course shall be placed horizontally between cast stone and all other materials.

Stainless steel or plastics shims shall be used when necessary to support stones prior to the mortar setting. All ties and other fixings shall be installed tot he SO instructions.

Suitable weep-holes to the SO’s approval shall be placed at regular intervals immediately above any continuous support angles or concrete ledges on which stone is being built.

All joints will be raked back during building to allow for pointing later. Before pointing, suitable masking tape should be fixed to either side of the joint to project the stones from mortar stains.

All cast stone shall be protected from rain during building and at the end of each day, the top of all stonework should be protected and the cavity covered.

All cast stone once incorporated in the building must be adequately protected against scaffold splash, mortar drops, damage etc, as these can be difficult to remove.

All cast stone which shows sign of dampness must not be incorporated in the building if the air temperature is below 4 degrees celsius.
Appendix One

The test specimens shall be dried to constant mass Md in a ventilated oven. Constant mass is reached when two measurements 24 hours apart give a difference of less than 1% of the mass of the dry specimen.

Place a tray to contain one unit on a level surface. Place the specimen, with its face side down, supported clear of the base of the tank to a depth of 5mm in water. Activate the timing device. In the case of units with irregular surfaces every point on the surface should be at least 5mm into the water.

The water level is kept constant throughout the test by adding fresh water when necessary.

After ten minutes in water, remove the specimens, wipe off the surface water and weigh the unit (Mw).

C, the coefficient of water absorption due to capillary action of the units is calculated as follows:

C = (100xM)
_______

A x t ½

Where
M = Mx – Md
Mw = mass of the specimen after soaking (in grams)
Md = mass of dried specimen (in grams)
A = area of face immersed in water (in cm)
t = time of soaking (in minutes)