STRUCTURAL INVESTIGATION ON CONFINEDMASONRY OF SOIL-CEMENT BRICKS TO
INCORPORATE INTO EL SALVADOR
HOUSING CODE
Mónica Patricia Gutiérrez Martínez ∗MEE08169

Supervisor: Tetsuro GOTO ∗∗ABSTRACT
Because of its natural formation, El Salvador is a country that has a lot of earthquakes and volcanoes.
Therefore, we can find soil that comes from volcanic ashes all round the country. This kind of soil has
been used for many years in El Salvador only for filling and compaction in construction, but now it isused as an alternative material to create brick. Soil-cement bricks, which are made of cement and soilthat comes from the ash of volcanoes, are eco-friendly alternative. To obtain the properties of soilcement masonry, tests in the material were performed. In addition, to know the structural performanceof the masonry walls, test in confined an unconfined masonry specimens were done. The specimens
were subjected to compression and shear test, from where strength and shear crack load were obtained
and recorded.
Keyword: Confined masonry, Soil-cement bricks and El Salvador housing code.

1. INTRODUCTION
In the year 2001, El Salvador experienced several earthquakes that created many damages around thecountry. A series of seismic events accompanied with several earthquakes and several aftershocks
started on January 13, 2001, causing serious damages on people, infrastructure, productive activities
and the environment. The first earthquake occurred on Saturday January 13 at 11:33 a.m. with amagnitude Mw = 7.6. Exactly a month later, on Tuesday February 13 at 8:22 am a second earthquakeof magnitude Mw = 6.6 was felt.
Red brick is a product widely used in confined masonry, due to it easy preparation andfabrication. Production of red bricks requires a large quantity of combustible materials; burning ofthese materials produces a big amount of smoke that pollutes the air. Use of wood for burning thebricks accelerates deforestation finding as a result the loss of aquifers and land erosion. Because thisprocess of burning is harmful to the environment, research is made to create and alternative brickinstead of red brick, such as soil-cement. The soil-cement brick was not invented in El Salvador, but
recently it has been used as an eco-friendly alternative for construction.
The main objective of this study is to be able to acquire more information on the behavior of
the soil-cement masonry, so that the study can be used as a guide for future design in house; byknowing how the behavior of these confined masonry, and how its fail will help us to learn more about
the interaction during earthquakes. Another specific objective that hopefully will be accomplished isthat this data can later be incorporated into and considered in an improvement of the Housing Code ofEl Salvador.
∗Universidad Centroamericana José Simeón Cañas of El Salvador
National Institute for Land and Infrastructure Management, Ministry of Land, Infrastructure, Transport andTourism, Japan.
∗∗12. INFORMATION OF ASHES IN EL SALVADORThe caldera of Ilopango is located at a latitude of 13° 40’N and a longitude of 89° 03’ W. The earliest
eruption of the volcano of Ilopango occurred in 430 A.C. This volcano nowadays look like a caldera
that contain a lake, covering an area of 72 km2 and has a depth of 230 m. The eruption covered a bigarea in El Salvador, and pyroclastic flows from the eruption are mainly deposited over present
metropolitan area. It is assumed that this volcano has made 4 explosive eruptions in the past 57,000years. The volume of the last eruption is considered to be of 20-30 km3, close to the border of thecaldera of Ilopango in which a 60 m thickness layer of ash can be found. Due to the peculiar color of
the ash the soil is called “Tierra Blanca” which means White Soil. This name was given by Hart, W.
and Steen-McIntyre in 1983.
2.1 What Are Soil Cement Bricks?
Adobe is a natural sundry brick made of clay, sand and water and in some countries it contains organic
or fibrous materials. Red bricks are made of clay, and clay needs burning or application to heat to
make it stable. The soil cement brick is different from adobe and red brick in that the soil used in thisbricks is not clay but soil that comes from ash which is considered as silt. They are not burn they arewind dried.

BrickAsh
Figure 1.Content of Soil-cement bricks

An investigation was performed as a part of the TAISHIN project to establish combination ofcement sand and silt which fulfills all the requirements of bricks for confined masonry in El Salvador.
As result they obtained that the combination could 50% ash and 50% sand or 25% ash 75% sand and a
proportion of 1 cement and 10 of soil.

3. EL SALVADOR STANDARDS FOR CONFINED MASONRY
Confined masonry in El Salvador can be explained as a wall
made of masonry of solid brick, which are traditionally confinedby reinforced concrete columns and beams. For the construction
process the reinforcement bars are put in place first, and later thewall is created by locating the bricks joining with mortar, asReinforcement
shown in figure 2, leaving for last the concrete casting to createbars
the confined wall.
In the 1997 Technical Standard for Design andWall of solid bricks
Construction of Masonry Structures of El Salvador, bricks madeof cooked clay or also called red bricks and concrete blocks are
the only materials considered for making confined masonry. But
in the 2004 Technical Standard for Design and Construction ofMasonry Structures of El Salvador which is not legally approved
yet but is in revision stage, soil cement bricks are considered asFigure 2. Typical confinedmaterial for confined masonry. There is no distinction between
masonry in El Salvador
both in the characteristics and in the construction process ofconfined masonry, by use of red brick and soil cement bricks.
BeamColumn

24. METHODOLOGY OF THE MASONRY STRUCTURAL TESTING OF
SOIL CEMENT HANDMADE BRICKS
4.1 Procedure of Elaborating Bricks
The combination of soil use for this study is 50 % sand and 50 % ash, with a relation of 1cement for 10 of soil. The mixture was done by mixing the soil, cement, ash, and water. The bricks
were elaborated by hand. The mixture is put in the mold and compacted by using the hand. The uppersurface of the brick must be smoothening with the hand or wooden ruler. The molds must be taken
immediately after the smoothening process. After 24 hours the bricks can be turn over so that thebottom part can get dry. On day 3, the bricks are ready to be pile up together.
4.2 Material Testing
The materials use for elaboration of the specimens such as mortar, concrete and steel bars ware tested
to make sure the behavior, properties and quality.
4.2.1 Mortar and Concrete
To obtain the compression strength in mortar and concrete, cylinders were made as the JapaneseIndustrial Standard JIS A 1108. The compressive strength is obtained by equation (1).

σ c = P π (d 2)2(1)where σc is compression strength in mortar, P is maximum load and d is the diameter of the specimen.
The mortar use for joining each brick has a relation of 1:3 (1 cement by 3 of sand). The bed join
between bricks was fixed to 1 cm. The concrete use for the elaboration of the confined element wasmade by using 955 kg sand , 244 cement and 923 kg coarse.
Concrete cylinders were subjected to the splitting cylinder test following the JapaneseIndustrial Standard JIS A 1113. The tensile strength can be calculated by using the below equation.

σ t = 2 P πdl(2)where σt is the tensile strength, P is maximum load, d is the diameter of specimen and l is the length ofthe specimen. The elastic modulus of concrete is defined as the slope of the stress-strain curve fromlaboratory test. The modulus of elasticity is obtained from the elastic deformation region of the stressstrain curve as in equation (3).

E =σ ε(3)where E is the modulus of elasticity, σ is the stress (Load/Area) and ε is the strain or unitary
deformation.
4.2.2 Steel Bars
The steel bars used to make the reinforcement in the specimen are D4 (diameter: 4 mm) and D6(diameter: 6mm). The tensile test was performed by the Japanese Industrial Standard JIS Z 2241.
4.2.3. Cylinders of Soil-Cement
There is no specific standard that covers soil-cement, therefore in this study cylinder of soil-cement
were done and tested. The test performed to the soil-cement cylinders are compression strength incylinder using equation (1), tensile strength will be calculated with equation (2) and modulus ofelasticity is obtained by using equation (3)310 cm

5 cm

10 cm

20 cm

5 cm

4. 3 The Dimensions and Construction ofSpecimens
Two types of bricks were elaborated as shownin figure 3. The first brick is a full size andsecond is half brick.

9.5 cmFigure 3. Dimension of bricks

4.3.1 Absorption
The absorption is calculated with the equation(4). Where Ww is wet weight of the brick andWd is dry weight of the brickAbsorption = (Ww − Wd ) Wd × 100(4)4.3.2 Compression in Bricks
The compression strength is calculated byusing equation (5), where f’u is compression
strength in bricks unit, P is the maximum loadand A is the area (obtained as: width x length)a)Unconfined masonry b)Confined masonry(URM)with plane concrete (CP)f 'u = P A(5)

4.3.3 Compression on Piles
The compression test of piles is done to know thecompression strength of the masonry. The piles are madeof 3 layer of bricks. Where f’m is compression strength inmasonry calculated with equation (6).

f 'm = P Ac) Confined masonry with reinforcebars(6)4.3.4 Diagonal Tension on Prisms
For the diagonal tension test, the prisms made had several
configuration, each test shows a different
characteristics of the masonry. The
procedure and the calculation for the test
are according to the ASTM E 519. For
obtaining the shear stress, the equations
below are uses.

S s = 0.707 P An

An = ((W + h ) 2)tn(7)(8)

where Ss is the shear stress on net area, P
is the applied load, An is the net area of thespecimen, W is width of the specimen, h isd) Confined masonry with reinforce bars and withheight of specimen, t is total thickness ofintermediate beam (CRM)
specimen and n is the percent of the grossFigure 4. Type of prisms
area of the unit that is solid, expressed asdecimal; since is a solid bricks this number is 1. The diagonal tests were performed by using a“Portable Structural Testing Equipment” (PSTE).

4

5. TEST RESULTS ANALYSIS
5.1 Result of concrete and mortar

Table 2.Modulus of Elasticityof concrete

Table 1. Compression strength in cylinders of mortar andModulus ofNo of2specimen Elasticity, N/mm
10.017051
20.017691
30.017191
Average
0.017311

MortarConcrete
No of specimen
123123Section area, cm219.7 19.8 19.7 78.54 78.54 78.54
Maximum load, KN
40.4492996
99.2 90.3
Compression strength, kN/mm2 20.49 24.76 14.71 12.23 12.63 11.5
Average, kN/mm2
2012.12

Table 3. Splitting test on concrete cylinders
N o of specimen
Height, cmDiameter, cm
Maximum load, kN
Tensile strength, N/mm 2Averag e, N/mm21201037.70
1.202201033.30
1.06
1.10

3201032.80
1.04

Concrete compression strength has an average of
12.12 kN/mm2. The average value of tensile
strength is 1.10 N/mm2. As it was expected, thetensile strength of concrete is around 10% of thecompression strength.

5.2 Reinforce bars.
Table 4. Results of the tensile test reinforce bars
Yield
Yield Yield
Maximum
Diameter
Maximum
Deformation
force
strengthmm
load KN strength
mm/mm
KN N/mm2N/mm2
4.98
416.9
2096
6.97
583.5
D43.9
5.04
421.9
2146
7.26
607.7
5.08425.3
1876
7.32
612.8
D6
6.3
8.18
262.4
1766
16.05
514.9

Type

5.3 Soil - Cement Cylinders
The soil cement is not cover in
the JIS or in any other standard,
the tests were carried out in orderto get more knowledge of thebehavior and to set a parameterfor future references, see
Table 5. Results of the compression Table 6. Modulus of Elasticity oftable 5, 6, and 7.
test in cylinders of soilcementsoil-cement cylinders
Modulusof
N o of specimen
123Table 7. Splitting test on soil-cement
No of2
Section area, cmMaximum load,kN
Compression
strength, N/mm2Average, N/mm278.54 78.54 78.54

specimen

24.79 25.19 23.66
3.16

3.21
3.13

123Average

3.01

Elasticity,
N/(mm2 x106 )0.001633
0.002887
0.002626
0.002382

5.4 Bricks and Masonry of Soil Cement

N o of specimen
119.8
Height, cm
10Diameter, cm
Maximum load, kN 10.40
Tensile strength,
20.33
N/mm
Average, N/mm2219.8
106.30

32010
5.85

0.20
0.24

0.19

Table 8. Compression in half size bricks
Identification brick
1Length, cm10Width, cm
9.5
Thickn ess, cm5.1Area, cm295
Maximum load, kN
41
2Compression Strength, N/mm 4.316
2Average, N/mm

29.7
9.5
59 2.15
4 0.31
4 .374

3410
9.7
9.4
9.3
5.1
5.1
91.18 90.21
38.52 39.57
4.098 4.386
4.24

Table 9. Compression piles in half size bricks
Identification pile
1Area, cm 2
185.25
Maximum load, kN
6 4.402Compression Strength, N/mm
3.25
Average, N/mm22188.16
69.59
3.48
3 .27

3
189.15
61.85
3.10

559.8
9.4
5.1
92.1236.994.015

The capacity of the soil-cement
bricks to absorb water is 21.4%.
This value is from the average ofthe absorption test made in half andfull size bricks. The relation
between the compression strength
ofthemasonry
andthecompression strength of the brick is 0.7, it canbe express as f m '= 0.7 f 'u . Piles with fullsize bricks where also done to know thedifference between full and half-size strengthin pile the compression strength obtained was
2.99 N/mm2.

The shear crack load was read when the first visible crack appears on the specimen, this value
is an approximation. The first cracks that appear on the specimens were shear crack and as the tests
continue other types of cracks also appear, such as bond and crush of concrete. The crush of concrete
appeared at the last stages of the tests due to the holders use for support the measurements instrument.
Table 9. Resume of the diagonal test in all type of prisms
Identification URM-1 URM-2
Sh ear crack
41
41.45
load, KN
Maximum shear
8.02
8 .57
strength, kg/cm2
Maximum sh ear
0.8020.857stren gth, N/mm 2
Average,N/mm 2

URM-3

URM-4

URM-5

CP-1

CP-2

CP-3

CR10 CRM10

54.7

50

50.1

33

6 2.2

54.4

75

86.4

9.44

8.96

9.78

5.64

10.45

9.11

12.65

16.03

0.944

0.896

0 .978

0.564

1.045

0.911
1.265

1.603

0.895

0.840

CONCLUSIONS
1. The bricks made for the study had a compression strength of 4.2 N/mm2, El Salvador requires thatthe compression strength for red bricks must be 4 N/mm2 (for a 1 or 2 story houses). El Salvador
2bricks of soil-cement had a compression strength of 7.797 N/mm . Although the strength isdifferent, it can be taken that the compression strength of bricks that have dosage of 50% sand 50% ash and a relation of 1:10 can be found in the interval of 4-8.N/mm2.
2. The difference can lie in many aspects like the scale factor. The different in the type, together withthe possibility that temperature and humidity can change the water content in the mixture.
3. As for the shear strength of unconfined masonry, the average value is 0.68 N/mm2 in El Salvador
and the average is 0.89 N/mm2 in this study. If we consider that both values of shear strength havestandard deviation, the difference between them becomes approximately of 1 N/mm2. We canconclude that the interval for shear strength can be from 0.6 to 0.9 N/mm2.
4. For this study, 4 different types of diagonal test were performed. A lot of new information has
been gathered to impact and set background for making changes in the El Salvador Housing Code.
In the case of the prisms, URM and CP show that degradation and collapse occurred after reaching
maximum load. CR and CRM prisms give a clear view of why confinement is necessary and how
the strength incremented by giving more confinement to the masonry.
5. It is necessary to reflect and incorporate in the Housing Code, specific parameters for calculating
the compression strength so that can be used for the design of confined masonry of soil cement
bricks.
It is highly recommended that furthermore experiments are needed to be done to analyze the scale
factor in soil cement bricks, and more diagonal tension tests are required to be able to give generalized
values of shear strength and shear crack.

ACKNOWLEDGMENT
To Mr. Mamoru Nemoto my warmest gratitude for your help during laboratory works. I will like torecognize all the help I receive from Patricia Hasbun and Adolfo Ramos for sending me the data.

REFERENCE
Ministerio de Obras Públicas, San Salvador, El Salvador.
Patricia Méndez de Hasbun and Manuel Gutierrez and Others, 2007, Project TAISHIN.
Patricia Méndez de Hasbun and Manuel Alfredo López Menjivar, March 2007, Project TAISHIN.
Reinaldo Rolo and Julian J. Bommer, 2004, Geological Society of America Special Paper 375.

6