Mud Brick Construction

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Text of Mud Brick Construction

Alternative Methods of Stabilisation for Unfired Mud Bricks

Doug HarperB.Eng Civil and Structural Engineering School of Civil Engineering & Geosciences, Newcastle University 2011

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Executive Summary

Mud brick construction dates back, in various forms, for several thousand years. Recently, Interlocking Compressed Soil Blocks (ICSB) have emerged as a viable, sustainable and affordable construction material, suitable for the provision of low cost housing in the developing world. However, questions have been raised as to their long term durability and susceptibility to water damage. Traditionally, unfired mud bricks have been stabilised with cement to overcome these short comings but the use of cement reduces the environmental differential between unfired bricks and fired ones. This report investigates the use of Ground Granulated Blast furnace Slag (GGBS) and Pulverised Fly Ash (PFA) as alternatives to cement for the stabilisation of ICSB. Sample bricks were constructed using varying concentrations of PC, PFA and GGBS and the samples compressive strength and Initial rate of Water Absorption (IRA) compared. Simultaneously, a sustainability study was undertaken to contrast the three materials in terms of ease of manufacture, financial cost and implications to health. The PC stabilised bricks displayed the highest compressive strength (4.3-6.0 kN/mm2) followed by the PFA bricks (0.75-0.98 kN/mm2) and then the GGBS samples (0.12-0.17 kN/mm2). Only two of the samples, both stabilised with PC, had compressive strengths acceptable under UK Building Regulations. All of the tested samples had an IRA of less than 0.13 kg/m2/min, significantly below accepted limits. The report concludes that whilst GGBS and PFA are alternative stabilisers for ICSB they do not perform as well as PC in the proportions tested. The sustainability study concludes that GGBS is more sustainable (though the limitations of any definition of sustainability are acknowledged) than PC and PFA. This is contrary to previously published information that would define both GGBS and PFA as more environmentally sound. The use of GGBS and PFA in ICSB ultimately depends on two factors: whether the observed engineering properties are sufficient for the requirement and whether the alternative stabilisers are available.

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Table of ContentsList of Figures: ......................................................................................................................... 6 List of Tables: ........................................................................................................................... 7 1.0 2.0 3.03.1

Introduction ................................................................................................................. 8 Aims and Objectives ............................................................................................... 10 Literature Review ................................................................................................... 11Background......................................................................................................................... 12 Mud and Earth Construction............................................................................................. 12 Interlocking Compressed Stabilised Blocks ............................................................... 16 3.1.1 3.1.2

3.2 3.3 3.4

A Review of Potential Stabilisers for Unfired Masonry Bricks ......................... 20 A Comparative Study of the Selected Stabilisers ................................................... 22 Testing Procedures for the Mechanical Properties of Masonry ...................... 24 Compressive Strength Testing of Masonry ................................................................. 24 Shrinkage Testing of ICSB .................................................................................................. 25 Absorption Testing of Masonry ....................................................................................... 26

3.4.1 3.4.2 3.4.3 3.5

Key Points from the Literature Review .................................................................... 26

4.0

Proposed Method Statement ............................................................................... 284.0.1 4.0.2 4.0.3 4.0.4 Research .................................................................................................................................... 28 Preliminary Experiments ................................................................................................... 28 Laboratory Experiments .................................................................................................... 29 Sustainability Study .............................................................................................................. 30

4.1

Timeline ............................................................................................................................... 31

5.05.1

Method Statement .................................................................................................. 33Constructing the Mud Bricks ........................................................................................ 33 Equipment Required ............................................................................................................ 33 Health and Safety ................................................................................................................... 34 Procedure ................................................................................................................................. 34 Equipment Required ............................................................................................................ 38 Health and Safety ................................................................................................................... 39 3 5.1.1 5.1.2 5.1.3

5.2

Shrinkage Testing ............................................................................................................. 38

5.2.1 5.2.2

5.3.3 5.3 5.3.1 5.3.2 5.3.3

Procedure ................................................................................................................................. 39 Equipment Required ............................................................................................................ 40 Health and Safety ................................................................................................................... 40 Procedure ................................................................................................................................. 40

Absorption Testing .......................................................................................................... 40

5.4

Compressive Strength Testing ........................................................................ 415.4.1 5.4.2 5.4.3 Equipment Required ............................................................................................................ 41 Health and Safety ................................................................................................................... 41 Procedure ................................................................................................................................. 42

6.1

Preliminary Experimental Results ............................................................................. 43

6.06.2

Results ......................................................................................................................... 43Main Laboratory Experimental Results.................................................................... 44 Shrinkage Testing .................................................................................................................. 44 Sample Appearance and Texture .................................................................................... 44 Absorption Testing ............................................................................................................... 44 6.2.1 6.2.2 6.2.3

6.2.4 7.07.1 7.2 7.3

Compressive Strength Testing .................................................................... 46 Sustainability Study................................................................................................ 49Ease of Manufacture ........................................................................................................ 50 Financial Cost ..................................................................................................................... 51 Health Implications.......................................................................................................... 53 GGBS (CEMEX, 2008) ........................................................................................................... 53 PC (US Department of Health and Human Services, 1995).................................. 53 PFA (Scotash, 2005) ............................................................................................................. 54

7.3.1 7.3.2 7.3.3 7.4

Quantitative Ecopoints Analysis ................................................................................. 54

8.08.1 8.2

Discussion ................................................................................................................ 56Preliminary Experiments .............................................................................................. 56 Sustainability Study ......................................................................................................... 57 Defining Sustainability ..................................................................................................