No Man's Land Machine and Foundry: Research Notes aka Book learning

My notes are in purple.

B. Thermal Shock (1)
This is measure of the refractory property when the refractory is exposed to alternate heating and cooling. It is an important property for a refractory material.Most high-temperature processes experience heating and cooling. Both refractory grains and the bonding system expand while being heated and contract during cooling. Having similar grains in the structure, the thermal shock resistance depends on the matrix bonding the grains. Thus, refractories having structures with built-in micro cracks of defects show better thermal shock resistance than with rigid systems. In some refractories, the bonding system, by nature, possesses micro structural defects or cracks that provide better thermal shock resistance.

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BENEFITS OF CEMENT-LIME MORTAR (2)

Autogenous Healing - When hairline cracks develop in the mortar, hydrated lime reacts with carbon dioxide in the atmosp
here. This reaction produces limestone which helps to seal the crack and fill voids in the mortar. This explains the increased moisture resistance
noted after six months of curing in two studies.
Extent of Bond - The extent of bond is the percent of brick to which the mortar adheres. The low air content and the fineness and stickiness of hydrated lime particles increase the extent of bond of mortar to brick. These factors allow cement-lime mortars to penetrate deeply into the brick and seal the brick/mortar interface.

Hydrated lime improves the strength of the mortar by several mechanisms:

Carbonation - Hydrated lime reacts with carbon dioxide in the atmosphere to form limestone.
Cementitious Reactions - Pozzolonic reactions can occur between hydrated lime and silica compounds in the mortar mix.
pH - Hydrated lime helps to maintain high pH levels in the mortar . This makes siliceous materials more soluble and reactive.

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Pozzolan (3)

Pozzolans are a broad class of siliceous or siliceous and aluminous materials which, in themselves, possess little or no cementitious value but which will, in finely divided form and in the presence of water, react chemically with calcium hydroxide at ordinary temperature to form compounds possessing cementitious properties.^[1] The quantification of the capacity of a pozzolan to react with calcium hydroxide and water is given by measuring its pozzolanic activity.^[2] Pozzolana are naturally occurring pozzolans of volcanic origin.

Reaction. The pozzolanic reaction is the chemical reaction that occurs in portland cement upon the addition of pozzolans. ... The pozzolanic reaction converts a silica-rich precursor with no cementing properties, to a calcium silicate, with good cementing properties. --------------------------

(5) Calcium Silicate Insulation

Over 1100 °C calcium silicates begin to sinter, therefore the
calcium silicates are limited to 1100 °C.

I need to take the oxy propane torch to a sample and see if I can break it down. Need to know if the additional components will take it past 1100C. 200C more would make bronze casting easier. OK looked up the melting point of Calcium Silicate. 2,130 °C (3,870 °F; 2,400 K) NICE

we do advise heat curing, before the first use as a front
layer, as this will be beneficial and will ensure an even
longer working life for your insulation.

-------------------------- Silica flour aka silica fume is a pozzlan. Are all the pozzolan bond based on water like the Portland cement bond ? ANSWER NO see above

(4) Pozzolan a material that, when used in conjunction with portland cement, contributes to the properties of the hardened concrete through hydraulic or pozzolanic activity, or both.

Clays → contain high amounts of silica & alumina but have a crystallic structure! (Do not possess pozzolanic activity) – However, by heat treatment, such as calcining ~700-900°C crystallic structure is destroyed & a quasi-amorphous structure is obtained.

Burned clay → possess pozzolanic property

Limestone breaks down at 825C but the temperature which calcified lime breaks down is over 4000C. (check this) Things are looking good.
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Thermal shock (1)
I was planning on making rings to test the refractories for resistance to thermal shock but this table has me wondering if this test only makes sense for dense refractories. The 2nd entry "High thermal conductivity" is especially troubling.