This is a question which debated many a times amongst engineers, owner and contractors.if you ask me my answer or opinion it's as follows:
If u are not concerned about cost and don't trust quality control/assurance of your site team or your contractor then you should definitely go with Rmc from reputed vendor since Rmc is plant made product with better control over quality and proportioning of materials. But in my experience which many site engineers will agree that Rmc procurement many a times becomes headache, small orders are kept on last priority by Rmc suppliers due to which delays are common and loss in terms of time money and idle Manpower is Common. Also after batching at plant Rmc transit mixer reaches site many a times after very long duration due to which workability required on site is not met and additional water is added which reduces strength and durability drastically, also one practical problem while concreting columns and similar elements with Rmc lot of time is required due to which intermittently even more water has to be added to get required slump as a result quality of concrete and resulting structure is quite low in reality. I suggest always take concrete cubes at end to ensure strength and quality.
On other hand if quality of fine and course aggregate procured at site is controlled strictly by engineer in charge and with good mix design and using flyash, super plasticizers, modern efficient batching, mixing equipment much better concrete can be made at site which is much cheaper then rmc. Efficiency of work can be improved with no delay, no last minute dependency on Rmc vendor, Following things to be strictly supervised to achieve quality:
1)Water required per batch should not deviate from design.right amount of plasticizer dose shall be added in every batch. water/cementious ratio is most important aspect of achieving strength and durability
2) Quality check of material at time of procurement by engineer.
3) Strick checking on batching. Concrete to be mixed properly
If u are not concerned about cost and don't trust quality control/assurance of your site team or your contractor then you should definitely go with Rmc from reputed vendor since Rmc is plant made product with better control over quality and proportioning of materials. But in my experience which many site engineers will agree that Rmc procurement many a times becomes headache, small orders are kept on last priority by Rmc suppliers due to which delays are common and loss in terms of time money and idle Manpower is Common. Also after batching at plant Rmc transit mixer reaches site many a times after very long duration due to which workability required on site is not met and additional water is added which reduces strength and durability drastically, also one practical problem while concreting columns and similar elements with Rmc lot of time is required due to which intermittently even more water has to be added to get required slump as a result quality of concrete and resulting structure is quite low in reality. I suggest always take concrete cubes at end to ensure strength and quality.
On other hand if quality of fine and course aggregate procured at site is controlled strictly by engineer in charge and with good mix design and using flyash, super plasticizers, modern efficient batching, mixing equipment much better concrete can be made at site which is much cheaper then rmc. Efficiency of work can be improved with no delay, no last minute dependency on Rmc vendor, Following things to be strictly supervised to achieve quality:
1)Water required per batch should not deviate from design.right amount of plasticizer dose shall be added in every batch. water/cementious ratio is most important aspect of achieving strength and durability
2) Quality check of material at time of procurement by engineer.
3) Strick checking on batching. Concrete to be mixed properly
