Pick up the correct statement(s) about concrete mixing practices:

Detailed Explanation: All Three Concrete Mixing Practices Are Correct

Why D (All options correct) is correct: Each statement reflects an established good practice for machine mixing of concrete.

Verification of Each Statement

Statement	Verdict	Technical Reason
A. No cement loss from charged drum	Correct	Cement is the most expensive and critical ingredient; any loss changes the w/c ratio and reduces strength. The drum should be properly charged and sealed during mixing
B. Mix for at least 1 minute	Correct	IS 1791 specifies minimum 2 minutes for batch mixers (some sources cite 1.5 min); 1 minute is the practical minimum to achieve homogeneity. Under-mixing leaves unmixed pockets of dry cement
C. 10% water first in drum	Correct	Adding a portion of water to the empty drum before dry materials prevents cement from sticking to drum blades and ensures aggregates are wetted progressively during mixing

Correct Machine Mixing Procedure

Step	Action
1	Start drum rotating
2	Add ~10% of water to wet the drum
3	Add coarse aggregate with remaining water
4	Add cement and fine aggregate
5	Mix for minimum 1.5–2 minutes (IS 1791)
6	Discharge completely; check drum for residue

• All three statements are correct — no cement loss, 1+ minute mixing, and 10% water first.
• IS 1791 specifies minimum mixing time for batch mixers: 2 minutes after all ingredients are in the drum.
• Over-mixing (>3 minutes) can cause aggregate breakdown and heat generation — also undesirable.