Hollow Stabilized Mud Blocksa

Journal of Civil Engineering Technology and Research
Volume 2, Number 1 (2014), pp.225-232
© Delton Books
http://www.deltonbooks.com
Hollow Stabilized Mud Blocks
Anupama B R, Rashmi S, Nethravathi S, Jagadish K S
Abstract:
The Stabilized Mud Block is the modern descendent of the molded earth block.
Stabilized Mud block technology offers an alternative kind of building
construction which is more accessible and of high quality. In the present study,
hollow stabilized mud blocks of dimension 23X19X10cm with varying number
of holes and diameters (3.9cm and 5.9cm) were casted using mardini machine by
adding cement as stabilizer (8% and 12%). Hollow stabilized mud block reduces
the dead load on the structure. Provision can be made for reinforcement, if
required. It can be used for aesthetic purpose and also for earthquake resistant
design. The properties of hollow stabilized mud blocks for compressive strength
and water absorption characteristics are tested. The strength of hollow stabilized
mud blocks are compared with solid stabilized mud blocks and the results
indicate that the strength of the block increases with increase in cement content.
The compressive strength attained by hollow stabilized mud blocks with one hole
was comparable with solid blocks. Moisture content of the stabilized mud blocks
decreases with increase in cement content. Moisture content of hollow stabilized
mud blocks with one hole was less than the solid stabilized mud blocks.
Keyword: Stabilizer, Compression strength, Water absorption.
Introduction
Earth has been the most widely known and abundantly available material for human society
to use it in construction. From the days of Egyptian and Mesopotamian earth is main part of
any construction in its different forms. Mud has been extensively used for building
construction in India and elsewhere since time immemorial. Mud wall construction is
common even now in the rural parts of India.
Some of the main advantages of earth are: availability in large quantities, low price, easy to
use and good fire resistance etc. It has some disadvantages, like its durability, which can be
affected by the action of the natural agents like rain, wind and others, but being a cost
effective and energy efficient material, it is very reliable for low rise buildings in general and
low cost buildings in particular. Researchers have found ways to enhance earth’s durability
and quality as a construction material for low-cost buildings. Stabilization is one such
technique used to overcome the drawbacks of pure mud construction [1].
The technology of stabilized soil for wall construction has been known in India for more than
60 years. The Stabilized Mud Block is the modern descendent of the molded earth block. A
mixture of soil, sand, stabilizer, and water is compacted using a machine to produce SMBs,
also called compressed earth blocks (CEB) or soil-cement blocks _when only cement is used
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Anupama B R, Rashmi S, Nethravathi S U & Jagadish K S
as a binder. Cement and lime are the most commonly used stabilizers in SMBs.Stabilized
Mud block technology offers an alternative kind of building construction which is more
accessible and of high quality. The experience of last three decades shows that properly
stabilized mud competes favorably with bricks or concrete blocks.
Hollow stabilized mud blocks, the subject of this paper, aims in producing hollow stabilized
mud block with various number of holes and diameter using mardini machine. This study is
focused on compressive strength and water absorption characteristic of the blocks and also
the effect of varying number holes and diameter.
Current Criteria for Selection of Suitable Soils
The varied composition and properties of a soil in its natural state introduces difficulties
during the selection of the material for stabilization. Not all soils found in their natural state
will necessarily be suitable for CSEB production.
Basic suitability requirements are varied with a broad set of requirements proposed in CSEB
literature [2]. For a soil to be suitable for stabilization, its particle size distribution, plasticity
and compressibility should be desirable. Existing suitability criteria require that the soil to be:
·
Well graded with a continuous or dense gradation. It should be neither gap neither
graded nor uniformly graded. The size of the maximum soil particle should be less
than 6 mm in diameter.
·
The clay fraction should be of low plasticity index, thus able to exhibit low rather
than high cohesion. The plasticity index of a soil can be altered by modifying its
particle size. The plasticity index can be lowered by adding sand, and raised by
adding clay. Adequate plasticity facilitates shaping the soil, thus contributing to
moulding and handling.
·
Compacted at its optimum moisture content for the maximum dry density to be
attained. At the maximum dry density, the porosity of the soil is at its minimum.
This increases both its shearing strength and compressive strength on loading.
·
Free of soluble salts and organic matter. These impurities can have harmful effects
on OPC both during hydration and even after hardening.
Thus, the size of the maximum size fraction (6 mm) and its distribution, and the clay content
(and type) emerge as the major factors to consider in soil suitability selection. The chemical
composition of a soil and its potential influence on the durability of the cement paste that
bonds blocks is likely to gain prominence as a new factor in the near future. Criteria limiting
the presence of soluble salts and sulphates in soil samples are likely to become critical in light
of recent scientific findings regarding their long term harmful effects. It is further noted that
certain special soil types such as lateritic soils may not conform to these guidelines. Chemical
tests for their composition are recommended [2].
Earlier Studies And Scope Of The Study
A number of studies have been carried out to understand the behavior of stabilized mud
blocks. Most of the investigations pertain to the compressive strength and other properties of
the blocks. There are no dedicated studies hollow stabilized mud blocks. The results of some
of the earlier studies are highlighted below.
Hollow Stabilized Mud Blocks
227
Venkatarama Reddy and K.S Jagadish [3] studied the influence of soil composition on the
strength and durability of soil-cement blocks. Soil grading as well as clay mineral type was
varied in assessing the characteristics of soil-cement blocks. They have concluded that:
1.Wet strength of soil-cement blocks using soils containing expansive clay minerals is very
sensitive to the amount of clay fraction in the mix. Strength decreases with increase in clay
content. 2. Blocks with sandy soils possess good dimensional stability and better performance
when subjected to cyclic wetting and drying. 3. Soils containing predominantly nonexpansive
clay minerals with a sand content of 70±5% and clay content 15% could be utilized for soilcement blocks. Walker and Stace [4] studied the properties of soil-cement blocks using a
range of composite soils. They have observed drastic reduction in block strength as the clay
content of block was increased. They conclude that for cement contents of 5 and 10%, soils
with clay fractions of 15 and 30% were most suitable from the durability point of view. B. V.
Venkatarama Reddy and Walker [5] have examined the strength and durability characteristics
of soil cement blocks. They recommended that the soil-sand mix used for soil cement block
should contain 10-12% of clay. B. V. Venkatarama Reddy and Ajay Gupta [6] explain that
the Stabilized mud blocks (SMBs) are manufactured by compacting a wetted mixture of soil,
sand, and stabilizer in a machine into a high-density block. Cement soil mortar is commonly
used for SMB masonry. This paper presents the results of an experimental investigation in
characterizing the properties of SMB masonry using cement-soil mortars. The compressive
strength, stress-strain relationships, and elastic properties of SMB masonry using three types
of SMBs and cement-soil mortars are discussed. The influence of a cement-soil mortar’s
composition and strength on masonry characteristics is examined. The results of masonry
using cement-soil mortars are compared with those using conventional mortars cement
mortar and cement-lime mortar. S. Krishnaiah and P. Suryanarayana Reddy [7] investigated
that a locally available inorganic soil has been used for stabilized soil blocks for masonry.
The grain size distribution curve falls in the range of typical grain size curves of suitable soil
samples for stabilization. In this study it has been observed that for a given percentage of
cement, there is a range of clay content in which the blocks satisfy the strength requirement.
Above and below this range the strength will be less.
Based on the above studies stabilized mud blocks were made using soil, sand, and cement.
Earlier studies say that with increase in percentage of cement the strength of the blocks also
increases. In the present study also we are adopting the same to increase the strength of
hollow stabilized mud blocks of varying number of holes and diameter. The present study
will focus on the production of hollow stabilized mud blocks and its behavior. The effect of
number of holes and diameter on the physical properties of hollow stabilized mud blocks is
studied. Comparative studies to examine the behavior of hollow stabilized mud blocks with
solid stabilized mud blocks is also done and develop good quality hollow stabilized mud
blocks suitable for wall construction.
Experimental Programme
The present work focuses on manufacturing of hollow stabilized mud block with various
numbers of holes and diameter with cement as stabilizer using mardini machine.
Materials used
Soil
A locally available red soil was used. This natural soil has 20% clay, 50% sand and 30% silt.
The liquid limit of soil is 37.5% and specific gravity is 2.55.
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Anupama B R, Rashmi S, Nethravathi S U & Jagadish K S
Quarry Dust
The clay content is varied by diluting it with quarry dust. The quarry dust has 86% sand, 14%
silt and 0% clay.
Cement
Ordinary Portland cement of 53 grade was used for the manufacture of blocks.
Iron pipes and wooden plates
Fig-1shows the iron pipes and Fig-2 shows the wooden plate which were used to produce
hollow stabilized mud blocks. The iron pipes were of 5.9cm and 3.9 cm diameter with height
of 7cm.
Fig -1: Iron Pipes
Fig -2: Wooden Plate
Procedure for manufacture of hollow stabilized mud blocks
The hollow stabilized mud blocks of size 230x190x100mm were manufactured using mardini
machine. Soil and quarry dust were mixed in proportion 1:1(by weight) such that the
resulting mix contains 10% clay, 22% silt and 68% sand size fractions. The optimum
moisture content of soil is 10%.
The hollow stabilized mud blocks with one hole of 5.9cm and 3.9cm diameter, two holes
blocks of 5.9cm diameter and solid stabilized mud blocks with cement as stabilizer at 8% and
12% by weight of mix are manufactured. The weight of the blocks for one hole of 5.9 cm
diameter is 8.56 kg, one hole of 3.9cm diameter is 8.78 kg, two holes of 5.9 cm are 8.17 kg
and a solid block is 9 kg.
The Procedure adopted for making of blocks is summarized as follows.
1) Mardini machine set up is done initially then the mould is greased. Wooden plate and iron
pipes are placed inside the mould. Plate and pipes are also greased for easy removal of pipes
from the blocks.2) The natural red soil and quarry dust are sieved through a 5mm sieve. 3)
Required quantity of soil, quarry dust and cement are mixed in dry condition first and then
mixed with about 10% of water by weight of the mix. Mixing operation was carried out
properly to get a uniform mix. 4) Required weight of wetted mixture of soil, quarry dust and
cement is taken in a scoop and poured into the mould and then compacted. The machine has a
fixed stroke length such that blocks of constant thickness are produced. Weigh batching is
adopted to control the block density. 5) The blocks are removed from the machine and then
Hollow Stabilized Mud Blocks
229
the pipes are removed from the blocks as shown in Fig-3 and are stacked as show in Fig4and then cured by spraying water for 28 days.
The same procedure is adopted for making solid block here iron pipes was not used.
Fig -3: Removing of Iron Pipe from the block
Fig -4: Stacking of the blocks
Testing Procedure
The following tests were carried on hollow stabilized mud blocks and solid stabilized mud
blocks.
Wet Compressive Strength
The compressive strength of soil-cement block is obtained by testing it in a compression
testing machine. The frogs on the bed surface of the blocks are filled with rich cement mortar.
Blocks are soaked in water for 48 hours before testing. Saturated block is mounted in the
compression testing machine such there is a thin steel plates on both faces of the block
between thick rigid platens. The ultimate crushing load is noted down to calculate the wet
compressive strength of the blocks.
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Anupama B R, Rashmi S, Nethravathi S U & Jagadish K S
Moisture Content
The object of this test is to determine the water content of a soil sample in the laboratory by
oven-drying method as specified by, IS: 2720 (Part 2) - 1969
Results And Discussions
The wet compressive strength of the blocks is as shown in table 1. The compressive strength
increases with increase in the percentage of cement. Chart-1 shows the variation of strength
in solid blocks and hollow stabilized mud blocks. The strength of one hole blocks are
comparable with the solid blocks. The moisture content of the blocks is as show in table 2.
The moisture content of the blocks decreases with the increase in the percentage of cement.
Table 1 Wet Compressive Strength of the blocks
Sl. No.
Specimen Number Cement
Wet Compressive
Covariance
of
Content
Strength Average
Average (%)
Blocks
(%)
(MPa)
1
2
3
Wet Compressive Strength (MPa)
4
1Hole
HSMB
(3.9cm)
6
8
9.91
3.48
6
12
13.46
3.56
1Hole
HSMB
(5.9cm)
6
8
9.31
6.92
6
12
11.06
15.40
2 Holes
HSMB
(5.9cm)
6
8
7.016
2.78
6
12
8.213
12.04
SMB
6
8
8.76
7.86
6
12
10.06
7.46
16
14
1 Hole HSMB
(3.9cm)
12
10
1 Hole HSMB
(5.9cm)
8
6
4
2 Holes HSMB
(5.9cm)
2
SMB
0
8%
12% Cement Content
Chart-1 Wet Compressive strength
Hollow Stabilized Mud Blocks
231
Table 2 Moisture Content of the blocks
Sl.
No.
Specimen
Number of
Blocks
Cement
Content
(%)
Moisture Content
Average
(%)
1
1Hole
HSMB
(3.9cm)
6
8
8.1
6
12
8.0
1Hole
HSMB
(5.9cm)
6
8
8.36
6
12
7.45
2 Holes
HSMB
(5.9cm)
6
8
14.4
6
12
12.13
SMB
6
8
14.01
6
12
13.78
2
3
4
HSMB-Hollow stabilized mud blocks, SMB- Stabilized mud blocks.
Conclusions
The strength of the blocks increases with the increase in percentage of stabilizers. With the
increase in diameter and number of holes the strength of blocks decreases. The blocks with
one hole of varying diameter are comparable with solids blocks. It is economical by using the
hollow blocks. The moisture content of the blocks decreases with the increase in the
percentage of cement.
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Walker P and Stace, T., (1997) Properties of some cement stabilized compressed earth blocks
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Venkatarama Reddy, B. V., and Walker, P. (2005). “Stabilised mud blocks: Problems,
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232
Anupama B R, Rashmi S, Nethravathi S U & Jagadish K S
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