# Pavement Design Questions and Answers – Soil-Cement Stabilization – 1

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This set of Pavement Design Multiple Choice Questions & Answers (MCQs) focuses on “Soil-Cement Stabilization – 1”.

1. Which of the below is not an additive used to improve the properties of soil cement?
a) Magnesium sulphate
b) Calcium chloride
c) Sodium hydroxide
d) Sodium carbonate

Explanation: Sulphates are the soluble salts present in the mix and their maximum limit is 4%. Calcium chloride, sodium hydroxide and sodium carbonate are the three additives used to improve the properties when stabilizing clayey or organic soil using soil cement.

2. Cement stabilization cannot be used in which of the below soil types?
a) Granular
b) Silty
c) Lean clay
d) Organic

Explanation: The method of cement stabilization can be used in most of the soil types like granular, silty and lean clays. Cement cannot be employed in organic soils because the process causes a delay in setting and a reduction in strength.

3. Soil cement cannot be used as a surface course.
a) True
b) False

Explanation: Soil cement can be used as a base or sub-base course. It cannot be used as the surface course as it has poor resistance to abrasion and impact. These properties are the important properties required for a surface course.

4. Which of the below soil type and the amount of cement required pairs has been matched correctly?
a) Gravel – 15 to 20%
b) Sand – 7 to 12%
c) Silt – 12 to 15%
d) Clay – 12 to 20%

Explanation: It is important to know the appropriate amount of cement required to be added to the particular soil type. For gravel type, the amount of cement to be added varies from 5 to 10%.

5. Which of the below type of soil cement contains less amount of cement?
a) Soil cement base
b) Cement treated base
c) Cement modified base
d) Acrylic copolymer

Explanation: CMS or cement modified base contains less amount of cement compared to ordinary soil cement. Soil cement base contains a higher amount of cement compared to CMS.

6. By what mechanism does the cement stabilization take place in granular soils?
a) Formation of matrix
b) Reduction in plasticity
c) Vibro compaction
d) Hydration of cement

Explanation: The hydration process of cement leads to the development of the bond between hydrated cement and soil particles in case of granular soils. The reduction in plasticity and the formation of matrix around clay lumps helps in stabilizing fine-grained soils.

7. It is necessary to maintain the water-cement ratio in the cement stabilization.
a) True
b) False

Explanation: There is no such thing as a water-cement ratio while conducting a cement stabilization. The water is added to the mix until an adequate amount of compaction is achieved.

8. Which formula gives the amount of cement required for soil stabilization if other parameters are given?
a) $$(\frac{AHr_d}{100})\times(\frac{p}{100+p})$$
b) $$(\frac{AHr_d}{100})\times(\frac{p}{100-p})$$
c) $$(\frac{AHr_d}{100-p})\times(\frac{p}{100+p})$$
d) $$(\frac{AHr_d}{100})\times(\frac{p}{100})$$

Explanation:$$(\frac{AHr_d}{100})\times(\frac{p}{100+p})$$ is the right amount of cement required for soil stabilization. The explanations for the terms used in the equation are:
A – surface area of the soil layer (m2),
H – thickness (cm),
rd – dry density (tonnes/m3) and
p – percentage of cement required

9. The percentage of soil particles passing 4.75 mm sieve must be ______ to be used in soil-cement.
a) <50%
b) >50%
c) <40%
d) >40%

Explanation: The recommended amount of particles passing 4.75 mm sieve must be more than 50%, so as to be used for the soil stabilization using soil-cement. The amount of particles passing 0.075 mm sieve must be less than 50% and the liquid limit must be less than 40%.

10. What is the British method of the mix design of the soil-cement mix based on?
a) Stability
b) Durability
c) Compressive strength at 28 days
d) Compressive strength at 7 days

Explanation: There are two methods that are commonly used to design the soil-cement mix. They are the British method and the PCA method. The British method is based on the compressive strength of samples cured for seven days and the PCA method is based on the durability of the mix.

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