---
title: "Maturity; shrinkage and creep"
subject: "Concrete Technology and Masonry Structure"
chapter: 4
key: "semester_5/concrete_technology_and_masonry_structure:maturity-shrinkage-creep"
source: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/maturity-shrinkage-creep
site: BCT Engineering
---

# Maturity; shrinkage and creep

Concrete Technology and Masonry Structure · Chapter 4: Properties of hardened concrete

- Asked in: 2076 Ashwin, 6 marks
- Video: [Difference between Shrinkage and Creep](https://www.youtube.com/watch?v=xLUsS7XKgDk) — Civil Engineering
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/maturity-shrinkage-creep
- Whole chapter: https://www.bctengineer.com/md/semester_5/concrete_technology_and_masonry_structure/chapter-4

## Question

Explain maturity of concrete. Define shrinkage and creep of concrete.

## Short answer

Maturity M = Σ(T - T0)Δt (datum -10.5°C) indicates strength development; same maturity yields similar strength. Shrinkage: time-dependent volume reduction due to moisture loss and chemical reactions, typically 300–800 microstrain. Creep: gradual strain increase under sustained stress from gel water movement, with about 50% occurring in first 3 months.

## Answer

**Maturity of concrete** is the product of curing time and temperature above a datum temperature. It lets the strength of concrete cured at different temperatures be compared, since strength is a function of maturity (Saul's rule).

$$
M = \sum (T - T_0)\,\Delta t
$$

where $T$ = mean temperature of concrete during the interval $\Delta t$ (°C), $T_0$ = datum temperature (about $-10.5$ °C as per Saul; $-11$ °C is often used), and the unit of $M$ is °C-hours (or °C-days).

Concrete of the same mix that has the same maturity has about the same strength, whatever its temperature history.

**Example.** Concrete cured at 20 °C for 28 days has maturity $= (20+10)\times 28\times 24 = 20160$ °C-h. Concrete cured at 10 °C reaches the same maturity in $20160/((10+10)\times 24)= 42$ days. Concrete at 30 °C needs only $20160/((30+10)\times 24) = 21$ days.

#### Shrinkage
**Shrinkage** is the time-dependent reduction in volume of concrete, without any applied load, caused by loss of moisture and by chemical reaction (hydration and carbonation). Typical long-term values are 0.0003 to 0.0008 (300 to 800 microstrain). The main types are plastic, drying, autogenous and carbonation shrinkage.

#### Creep
**Creep** is the gradual increase in strain of concrete with time under a constant sustained stress, over and above the instantaneous elastic strain. It is caused mainly by seepage of gel water out of the C-S-H layers and by slip of gel particles. Creep continues for years, with about 50% occurring in the first 3 months and 75 to 80% in the first year.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Maturity of concrete is:
   A. the age of concrete in days from casting
   B. the sum of (temperature above datum) x time, used to compare strength of concrete cured at different temperatures
   C. the ratio of 28-day strength to 7-day strength
   D. the degree of hydration measured by UPV
   Answer: B. M = sum (T - T0) delta t; same mix with same maturity has about the same strength. (Key point: Maturity concept)

2. Concrete cured at 20 C for 28 days has maturity 20160 C-h (datum -10 C). Time for the same maturity at 10 C is:
   A. 56 days
   B. 14 days
   C. 28 days
   D. 42 days
   Answer: D. 20160/((10+10)x24) = 42 days; lower temperature needs longer time for the same maturity. (Key point: Maturity example)

3. Shrinkage of concrete is:
   A. a time-dependent reduction in volume without applied load, due to moisture loss and chemical reaction
   B. an increase in strain with time under constant sustained load
   C. an instantaneous strain that disappears on unloading
   D. a loss of strength under repeated loading
   Answer: A. Shrinkage occurs with no load; the other options describe creep, elastic strain and fatigue. (Key point: Definition of shrinkage)

4. Creep in concrete is:
   A. the reduction in volume with time without any load
   B. the failure under repeated cyclic load
   C. the gradual increase in strain with time under a constant sustained stress, beyond the elastic strain
   D. the instantaneous strain on loading
   Answer: C. Creep needs a sustained load and appears as strain growth over and above the instantaneous elastic strain. (Key point: Definition of creep)

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