Cement Choice for Thin RCC Members – which cement should be avoided? For the construction of thin reinforced concrete (RCC) sections where early formwork removal and adequate early strength are desired, which type of cement is generally avoided in standard practice?

Introduction / Context:
Different cement types exhibit distinct heat evolution and strength development profiles. Choosing the appropriate type for a given member thickness and construction schedule is crucial. Thin RCC elements typically require adequate early strength and normal heat evolution to support early handling and formwork removal without undue delay.

Given Data / Assumptions:

• Members are thin RCC sections (slabs, shells, precast thin elements).
• Normal ambient conditions and curing are assumed.
• No aggressive sulphate environment is specified.

Concept / Approach:
Low heat cement is engineered to produce less heat of hydration and slower early strength development. This is very useful for mass concrete to reduce thermal cracking. However, in thin sections, thermal gradients are small and early strength gain is often desired for schedule reasons. Therefore, low heat cement is generally avoided for thin RCC where slow early strength could be a disadvantage.

Step-by-Step Solution:
Match cement type to requirement: thin sections need normal or higher early strength.Low heat cement → slower early strength → not ideal for thin members.Hence, among the listed options, “Low heat cement” should be avoided.

Verification / Alternative check:
Textbook guidance distinguishes use cases: low heat for mass foundations/dams; rapid-hardening or ordinary Portland for thin sections and early striking. Slag cement may also have slower early strength, but its selection depends on performance specifications; the canonical “avoid” in exam contexts is low heat cement for thin RCC.

Why Other Options Are Wrong:

• OPC: widely used and suitable with proper curing.
• Rapid-hardening: specifically improves early strength.
• Blast furnace slag cement: may gain strength slower but is not categorically “to be avoided” for all thin RCC; performance depends on blend and curing.
• Sulphate resisting cement: selected for sulphate exposure, not directly linked to section thickness.

Common Pitfalls:
Overlooking curing; even with suitable cement, poor curing can negate early strength gains and increase cracking risk.

Final Answer:
Low heat cement