Structural Guide

Structural loads, structural analysis and structural design are simply explained with the worked example for easiness of understanding. Element designs with notes and discussions have added to get comprehensive knowledge. Also, construction materials, shoring system design, water retaining structures, crack width calculations, etc. have discussed in addition to other aspects. 

Testing of Fly Ash

Cement is one of the most widely used construction material today. It can’t even imagine construction without cement even different alternative materials have been introduced.

Having provided a higher content of cement in concrete leads may consequence such as the high heat of hydration, high cost of construction, the formation of ettringite with the increase of heat at the core of the concrete, etc. As a result of this, fly as was introduce as a substitute for concrete.

Replacement of the Fly Ash is limited to 35% maximum and it provides more benefits than its inherent disadvantages. Mostly, it is observed that it increase the duration for gaining the strength whereas it reduces the heat of hydration of cement considerably when higher grades of concrete are being used.

As a material to be added to the concrete or to be mixed with cement, it is required to check the quality of the fly ash. Frequent testing shall be done based on the requirement of the codes or as per the project specifications to make sure the consistency of the material.

Test and Limiting Values: Physical Properties

Test / Units Specification given in BS EN 450-1:2012
Fineness / % Category N: shall not exceed 40% and it shall not vary by more than ±10 percent points from the declared values.Category S: shall not exceed 12%
Particle Density / kg/m3 Shall not deviate by more than 200 kg/mfrom the value declared by the producer.
Soundness /mm Shall not be greater than 10mm
Activity Index / %28 days90 days
Not less than 75Not less than 85

Test and Limiting Values: Chemical Properties

Test / Units Specification given in BS EN 450-1:2012
Loss on Ignition / % by mass Shall not be greater than 5.0
Silica (SiO2) / % by mass Sum of the content shall not be less than 70
Aluminum Oxide (Al2O3) / % by mass Sum of the content shall not be less than 70
Iron Oxide (Fe2O3)/ % by mass Sum of the content shall not be less than 70
Total Calcium Oxide (CaO *)/ % by mass
Chloride content (Cl) / % by mass Shall not be greater than 0.10
Total Alkali equivalent as Na2O / % by mass Shall not exceed 5.0
Sulphate (SO3) / % by mass Shall not be greater than 3.0

Note: If the total content of calcium oxide does not exceed 10% by mass, the requirement for reactive calcium oxide shall be deemed to be satisfied.

 

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