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THOMAS ARMSTRONG

(CONCRETE BLOCKS)

LTD

We are Part of the Thomas Armstrong Group

Storage and Laying of Concrete Blocks

Our concrete blocks are manufactured to the highest standards using quality raw materials. In order to maintain this quality, it is important that blocks are handled and stored correctly which will not only preserve product quality and appearance but will also be highly beneficial when it comes to laying of blocks and the application of finishes.

The guidelines in this section will, if adhered to, preserve product quality, maintain safety on site and result in better block laying and surfaces for accepting finishes.

  • General Good Practice for Site Storage of Blocks

    • We can deliver on a variety of vehicles from 6-wheeler rigid wagons to articulated crane and flat vehicles. Always be sure to check that the site can accommodate safely the vehicle type requested.
    • Minimise repeated handling and lessen the potential for damage to product by storing in positions as near to the point of use as possible.
    • The ‘cubed’ packs may vary in size and quantity depending on where they are manufactured and may or may not be delivered on wooden pallets.
    • Some of our factories can supply voided packs for handling with forks without the need for a wooden pallet.
    • Always check load and pack details with your sales office to ensure that the site is equipped with the correct offloading and handling equipment.
    • Unfinished blockwork and unused blocks must be protected from exposure to the weather especially when building work is paused for any period.
    • Prolonged exposure to the weather can cause deterioration of any block type and avoiding exposure is crucial to maintaining quality of product.
  • Safety and Manual Handling

    • Packs should be stored on firm, level ground no more than 2 packs high and protected from exposure to severe weather to preserve their quality.
    • Packs are banded and care must be taken when removing these bands as individual blocks may fall out. Never un-band packs above shoulder height.
    • For blocks above 20kg in weight, manual handling precautions must be taken on site. For further guidance on safe manual handling, see HSE Construction Information Sheet 37 (CIS 37).
    • Load units out to above knee height.
    • When cutting, drilling or chasing blocks, ensure that suitable eye protection is worn and if using mechanical cutting, suitable dust suppression and extraction measures should be provided on site.
  • Efflorescence

    Efflorescence on concrete blocks takes the form of a white crystalline deposit on the block surface and is caused by natural water-soluble salts migrating through the block and drying out on the surface. There are three things that must be in place in order to cause efflorescence:

    • Soluble salts present in the blocks or the mortar
    • Moisture entering the masonry blockwork
    • Salts reaching the surface and drying out
    • The absence of any one of these 3 criteria will prevent efflorescence happening.

    Efflorescence can be minimized by keeping blocks as dry as possible during the build and avoid excessive wetting. Moisture ingress into the wall / cavity must be minimized by well designed and installed details such as flashings, copings, cills, the use of weepholes and so on. Excessive lime must not be used in mortar mixes and mortar joints should be tooled smooth to minimize moisture ingress into the mortar and adjacent blockwork.

     

    This is a completely natural and harmless effect than can occasionally occur when concrete blocks are left exposed whose effects diminish over time as the soluble salts are washed away. Efflorescence is more common in the winter months. Dry surface deposits can be removed using a stiff brush (without wetting as this would re-dissolve the salts) and then any residues washed away with clean water preferably under pressure. This may have to be repeated several times allowing the blockwork to fully dry each time. The effect of efflorescence will diminish over time as the soluble salts in the blocks and the mortar are used up.

     

    Prevention of moisture ingress into the blockwork will minimise efflorescence occurring.

  • Block Laying

    General Good Practice for block laying

    • Blocks should not be laid if the temperature is at or below 3°C and falling unless it is at 1°C and rising.
    • Remove all dirt and debris from the block surfaces.
    • Blocks should always be laid on a full bed of mortar and the vertical perpend joints filled.
    • There is no need to wet the blocks before applying mortar. The consistency of the mortar mix should be adjusted to suit the suction of the block. For example, a slightly thinner mortar mix would suit Airtec blocks whose suction is higher than that of an Ultralite, Insulite or Dense Concrete block.
    • When building cavity walls, both leaves should be brought up together. However, if constructing using Airtec and thin-joint masonry the inner leaf can be built ahead of the outer leaf for external cavity walls (please see the Thin Joint Construction section).

    Block Bonding

    Blocks should be laid to achieve a good bond normally not less than one quarter of the length of the block. Other patterns may require the inclusion of bed joint reinforcement.

    Protection of Finished Blockwork

    Blockwork which remains unfinished and exposed must be protected from the weather with weatherproof sheeting which must be properly tied down. Care must be taken to cover all of the newly laid blockwork particularly if there is any possibility of extreme hot or cold weather.

     

    If blocks remain wet in frosty or freezing conditions, there is the possibility of damage through repeated freeze-thaw cycling. Unused blocks stored for prolonged periods must also be protected.

    Facing Blocks

    We strive to ensure that our facing blocks are consistent in colour and texture from the factory that they are produced in. However, due to the use of natural locally sourced aggregates, we cannot guarantee exact matches between blocks produced at different times and appearance of the block will vary between manufacturing locations.

     

    If using our ‘Fairtex’ or Rockfaced blocks whose finished appearance is critical, select blocks from more than one pack at a time during block laying to reduce the risk of banding or patchiness on the finished wall which may result on slight variability of shading from packs made on different days.

    Chasing

    Vertical chasing should be restricted to ⅓ the depth of the block thickness and for horizontal chasing, ⅙ the depth of the block. Chasing is not permitted in acoustic separating party walls and always avoid ‘back to back’ chases in any type of wall.

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