Concrete

Pumice, Rice husk, Manufactured sand, Slag sand, Powdered glass, Fly ash, Quarry dust, Processed Crushed rock fines, Mersey silt, Sugarcane bagasse ash, Groundnut shell, Cork, Tobacco waste.

Understand the role of aggregate in concrete,

-it should be strong enough (at least stronger than the concrete you want) – weakest phase material

– its chemistry should not be very reactive – durability and dimensional stability perspective.

– size and shape should accommodate for rheology and hardened state properties of concrete

– Should cater to early age properties of concrete by providing adequate resistance against shrinkage.

Practically, anything from furnace bottom ash to lightweight pumice can be used as aggregate – it depends on what the specifications for concrete are.

IS 10262: 2009 and IS: 10262: 2019 in concrete mix design:

This IS provides guidelines for proportioning concrete mixes as per requirements using the concrete materials and the supplementary materials. IS 10262: 2019 is the second revision of the first edition IS 10262: 2009 in concrete mix design in which the following major changes have been made(As per the description of the code):

• The standard was divided into five sections as General, Ordinary and standard grades of concrete, high strength grades of concrete, Self-compacting concrete and Mass concrete.
• A new section for Mix proportioning procedure for High strength concrete for M65 and above(up to target strength of M 100) was included.
• The formula for the target mean strength for mix proportioning for refined by including a new factor based on the grade of the concrete. It was done to ensure a min margin been the characteristic compressive strength and the target mean strength.
• A graph of W/C vs. 28 days strength of concrete introduced for different grades and types of cements for an alternative to initial water-cement ratio assumption.
• In the design of normal concrete mix proportion, the consideration of air content was reintroduced.

In simple terms, sugar acts as a retarder and delays the setting time of concrete.

This is the reason why transit mixer drivers are sometimes advised to add some soft drink to the concrete mix if the vehicle gets stuck up in the traffic for too long.

Technically speaking,

Sugars have been categorized as ‘cement destroyers’ and when sugar is added to Portland cement paste at the onset of mixing, hardening may be delayed indefinitely.

Concrete hardens due to formation of calcium silicate hydrate.

The retarding action of sugar is probably by the prevention of the formation of calcium silicate hydrate.

Sugar exceeding 0.2% by weight of concrete will slow down the reaction drastically.

Sugar increases the setting time of cement up to 1.33 hrs at dosage level of 0.06% by wt of cement. There will be no effect on workability, compaction by the use of sugar as admixture in concrete. Higher long-term compressive strength is achieved in concrete by the use of sugar as admixture.