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Construction inspection

Inspection should be carried out at all steps in the construction process to ensure quality. Completed structures should be inspected regularly to identify any deterioration, so that any necessary remedial action can be taken. Safety must be considered at all stages of investigation.

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jonnyhough

FRP reinforcement – design

The structural use of FRP reinforcement as opposed to steel reinforcement, is not covered in Eurocode 2.

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jonnyhough

cement retarding admixtures

Admixture standards

The British Standard for Admixtures BS 5075 has been replaced by six parts of BS EN 934 Admixtures for concrete, mortar and grout.

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jonnyhough

COSHH Regulations

The Control of Substances Hazardous to Health (COSHH) Regulations, issued by the Health and Safety Executive, cover many of the materials used in concrete and in construction (including cement, admixtures etc.).

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jonnyhough

Effect of clay in fine aggregate

Grading, shape and impurities a fine aggregate are key properties which need to be controlled for use in concrete. Clay contamination in sand is a natural impurity but excessive clay can affect water demand, strength and consistence.&nbsp

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jonnyhough

Can you use lime instead of cement in concrete?

Lime concrete, often referred to as ‘Limecrete’, is a combination of natural hydraulic lime, aggregate and water. Limecrete is slow setting and does not gain strength in the same way as traditional Portland cement-based concrete.

It can be used for non-structural elements such as a domestic floor. However, a damp proof membrane will affect the breathability of the material and without a membrane there is a high risk of damp penetration. Limecrete is often used in conservation or historic building projects where moisture is not an issue.

Hydraulic lime must not be mixed with cement or cement combinations as this would negate the breathability of Limecrete, but hydraulic lime can be used in hydraulically bound mixtures (HBM) and soil stabilisation below heavy duty paving. Externally exposed reinforced concrete should be avoided and it should not be used with structural reinforcement as lime increases carbonation.

Limecrete is usually batched in small quantities using bags of lime with an on-site mixer. If a large quantity (several cubic metres or more) of limecrete is required, then this would need to be arranged with a ready-mixed/volumetric supplier as a bespoke product.

If considering the carbon footprint then it is important to note that the manufacture of lime releases CO2 as does cement. However when mixed with water the CO2 is reabsorbed over time as a recarbonation reaction.

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jonnyhough

K-Value concept for cement additions

K-value comes from EN 206 and defines it as a factor which considers the activity of a type II addition, but the values used are not practical considering the need to use cement additions for durability and environmental aspects.

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jonnyhough

Volume stability (shrinkage) of aggregate

The principal effect of aggregate in concrete is to restrain the contraction of the cement paste, thereby helping to reduce the likelihood of cracking. In general, aggregates with a higher modulus of elasticity (greater stiffness), cubic shape and rough particle surface textures are likely to offer more restraint to concrete shrinkage.

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jonnyhough

Fineness Modulus of Fine Aggregate

Fineness Modulus (FM) is an empirical calculation used to support the optimisation of a concrete mix. It is used to determine ‘degree of uniformity of the grading’. This can create a relationship between grading and consistence and/or the amount of cement or water to fill the voids. An example would be that sand with a high FM will have lower voids between the particles.

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jonnyhough

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