Deleterious materials Flashcards
What are deleterious materials?
Materials that can cause failures in buildings or are hazardous to health.
Asbestos and lead are hazardous but not deleterious.
What is asbestos?
Asbestos is a naturally occurring fibrous material that has been used on building due to its durability, resistance to fire, affordability, thermal and electrical conductivity
What are the three types of asbestos?
Amosite (brown) - accounts for 3% of asbestos used commercially
Crocidolite (blue) - accounts for 6% of asbestos used commercially
Chrysolite (white) - accounts for 90% of asbestos used commercially but is the least harmful.
Where might you find asbestos?
Ceiling voids – sprayed asbestos lagging or coating to structural members for fire protection.
Pipework – sprayed asbestos or lagging tied round pipework for insulation and fire protection.
Ceiling boards or boards applied to doors for fireproofing – Asbestos Insulating Boards (Asbestolux)
Roof Coverings – asbestos cement roofing
Water tanks may be made from asbestos cement
Floor tiles
Fire doors – may contain Asbestos Insulating Board for fire proofing.
What are the two types of asbestos survey?
Management: Required during normal occupation and use of the building to ensure continued management of the ACM’s in situ.
Refurbishment and demolition: Fully intrusive survey undertaken when the building is to be upgraded, refurbished or demolished.
What regulations cover the removal of lead paint?
The COSHH Regulations 2005 and Control of Lead at work 2002
What measures should you take when removing lead paint?
Wear disposable overalls and disposable mask with P3 filter
Use wet abrasive sandpaper
Personal decontamination: Wash hands and forearms before eating and drinking
What is calcium chloride concrete?
An additive commonly used in in-situ concrete as an accelerator prior to 1977. Reduced passivity of concrete in damp conditions and increases the risk of corrosion of steel reinforcement.
What is calcium silicate brickwork and what issues are associated with it?
Buff coloured bricks use on outside face of building.
A common fault in older buildings was to use calcium silicate bricks as a facing material with clay bricks as backing. Because of the propensity of the clay bricks to expand upon drying and the calcium silicate bricks to shrink, stresses inevitably built up, which caused fracturing.
How do issues with calcium silicate brickwork display themselves?
Shrinkage causes diagonal cracking with relatively constant widths rather than tapering.
Need to install additional movement joints.
What is high alumina cement and what issues are associated with it?
Mainly used in manufacture of precast beams and lintels between 1954 and 1974 as it developed strength rapidly and was therefore fast to manufacture. Prone to crystalline re-arrangement which reduces its strength often when high temperatures and/or high humidity is involved. Need chemical testing to confirm ID.
What are wood wool slabs and what issues are associated with them?
Often used as decking on a flat roof. May be acceptable so long as kept dry. Use as a permanent shutter may result in grout loss (honeycombing) or voidage of concrete near to or surrounding the reinforcement or reinforcement laid without spacers. This may result in reduced fire performance, reinforcement corrosion or in extreme cases loss of structural strength.
How can issues with wood wool slabs be resolved?
Can be repaired with application of sprayed concrete.
What is mundic concrete?
Concrete manufactured from quarry shale. There are 2 main mechanisms of deterioration, both based around the oxidisation of sulphide minerals in the aggregate. The deterioration process is complicated, but results in the decomposition of the concrete and its expansion.
Map cracking causes.
Common in west country
