Blog #7: Cement stabilized mud adobe

In a previous blog here, I went into detail concerning the problems with asphalt stabilized mud adobe homes. In this post, I will discuss strengths and issues with cement stabilized mud adobe homes.

Cement stabilized mud adobe inside garage.

First, what is the difference between the two? As you can read in the description from each of these adobes, they are both “stabilized.” What does this mean? When these adobes were made, two different “stabilizers” were added to the mud recipe with the intention of making them primarily more water resistant: Portland cement was added to what is known as “cement stabilized mud adobes” and asphalt emulsion was added to what is known as “asphalt stabilized mud adobes.”

What is the difference between asphalt stabilized mud adobes and cement stabilized mud adobes?The key difference between asphalt-stabilized mud adobes (ASMA) and cement-stabilized mud adobes (CSMA) lies in the stabilizing materials used to enhance the durability and water resistance of the adobe bricks.

1. Stabilizing Material:

  • Asphalt-Stabilized Mud Adobes (ASMA):
    • Stabilization is achieved by adding a small percentage of asphalt emulsion (a mixture of asphalt and water) to the mud mixture.
    • Asphalt acts as a binder that coats the soil particles, increasing water resistance and improving the adobe’s durability, particularly in environments with occasional moisture.
  • Cement-Stabilized Mud Adobes (CSMA):
    • Stabilization is achieved by adding Portland cement to the mud mixture.
    • Cement chemically binds with the soil, creating a harder and more durable adobe brick with enhanced resistance to water, weathering, and erosion.

2. Water Resistance:

  • ASMA:
    • Provides moderate water resistance, making it suitable for regions with light to moderate rainfall. The asphalt helps repel water, reducing erosion and preventing excessive moisture absorption.
  • CSMA:
    • Offers better water resistance compared to ASMA. The cement creates a denser, more impermeable brick, which can withstand higher moisture levels and is more resistant to erosion and degradation in wet conditions.

3. Durability and Strength:

  • ASMA:
    • Asphalt-stabilized adobes can have good durability, especially in arid or semi-arid regions. However, they are generally not as strong as cement-stabilized adobes.
  • CSMA:
    • Cement-stabilized adobes are stronger and more durable than their asphalt-stabilized counterparts, making them more suitable for load-bearing walls and structures exposed to harsher environmental conditions.

4. Environmental Impact:

  • ASMA:
    • Asphalt is a petroleum-based product, so its use has a higher environmental impact due to the fossil fuel content. However, the overall impact might be lower if only a small amount is used.
  • CSMA:
    • Cement production is energy-intensive and generates significant carbon dioxide emissions. While it provides strong stabilization, the environmental footprint is generally higher compared to using asphalt.

5. Application and Cost:

  • ASMA:
    • The application of asphalt emulsion can be less costly and easier to manage in some cases, particularly for smaller projects or where cement is less accessible.
  • CSMA:
    • Cement-stabilized adobes might be more expensive due to the cost of cement and the need for proper mixing to achieve uniform stabilization. However, the longer-term durability might offset the initial cost.

6. Aesthetic and Textural Differences:

  • ASMA:
    • Asphalt-stabilized adobes are darker or more varied appearance due to the asphalt content.
  • CSMA:
    • Cement-stabilized adobes tend to have a more uniform, lighter color and a smoother texture due to the cement content. Their drawback is they don’t look like traditional, sun-dried mud adobe which is usually dark in color; the cement content (usually around 8-10% and sometimes higher) is what causes their light color, as seen in the picture above.

In summary, asphalt-stabilized mud adobes are better suited for areas with mild moisture concerns and where environmental impact is a consideration, while cement-stabilized mud adobes offer greater strength and water resistance, making them more suitable for more demanding structural applications and wetter climates.

All soils are not created equal and this fact is especially pronounced when it comes to the manufacturing of adobe blocks. As Marcus Aurelius said, “Well begun is half done,” and this is no truer than when choosing the correct soil mixture for adobe manufacturing: an adobe which will survive for generations will need to begin its life with the optimum soil/sand/clay ratios properly calibrated.

My experience with CSMA is they seem to be a better block. What I mean by this is they are more resistant to being damaged by rain and moisture issues. This is not to suggest they do not need to be treated with a quality water repellent like the Silox Adobe and I have sprayed the Silox on CSMA before. But like all adobes exposed to the sun, wind, and rain, they too need to be treated with a speciality water repellent like the Silox if they have any hope of outlasting their owners.