Making Building Blocks with

the CINVA-Ram Block Press

 

This article was found at

 

http://www.cd3wd.com/CD3WD_40/VITA/CINVARAM/EN/CINVARAM.HTM

 

 

VITA

VOLUNTEERS

IN TECHNICAL

ASSISTANCE

VITA

1600 Wilson Boulevard, Suite 500

Arlington, Virginia 22209 USA

Tel: 703/276-1800 . Fax: 703/243-1865

Internet: pr-info@vita.org

 

This manual was compiled by VITA (Volunteers in Technical

Assistance) from material based on the experience of

several field workers who have used the CINVA-Ram Block

Press. It is hoped that the manual will make it easier

to use the machine. VITA would appreciate receiving any

criticisms or suggestions for improving the manual.

 

VITA, Inc.

 

First printing 1966

Revised January 1972

Minor revision May 1975

Reprinting February 1977

 

 

Making Building Blocks with

the CINVA-Ram Block Press

 

 

Table of Contents

 

I. INTRODUCTION

 

II. EQUIPMENT

 

III. TESTING SUITABILITY OF SOIL

 

IV. MAKING BLOCKS AND TILES

 

V. BUILDING

 

VI. REFERENCES

 

VII. OTHER MACHINES FOR MAKING BLOCKS

FROM STABILIZED EARTH

 

VIII. STRUCTURAL CHARACTERISTICS OF SOIL-CEMENT

BUILDING BLOCKS

 

I. INTRODUCTION

 

1. Purpose This manual combines the experience of four men who

used the CINVA-Ram Block Press and figured out answers, bit

by bit, to the inevitable problems of detail as they came up

day after day. That was the hard way to learn how to use

the press; this handbook is intended to make it easier.

 

2. The Press The CINVA-Ram Block Press is a simple, low-cost

portable machine for making building blocks and tiles from

common soil (see Fig. 1). The press, made entirely of steel,

 

mbb1x1.gif (600x600)

 

has a mold box in which a hand-operated piston compresses

a slightly moistened mixture of soil and cement or lime.

(An equipment list is on page 3.)

 

The press was developed as a tool for small individual

or mutual self-help programs. It was designed by Raul

Ramirez, an engineer, at the Inter-American Housing

Center (CINVA) of the Organization of American States

in Bogota, Colombia.

 

3. Advantages CINVA-Ram blocks and tiles have many

advantages over other building materials.

 

**They are easier to make than concrete blocks:

they can be removed immediately from the press

and stacked for curing without the use of a

pallet.

 

**The cost of building material is greatly reduced,

since most of the raw material comes from your

own land.

 

**Transportation costs are avoided since the machine

is portable and the blocks are made near the construction

site.

 

**Depending on the quality of materials used, CINVA-Ram

blocks can be superior to adobe and rammed

earth.

 

**The blocks are easily handled.

 

**The blocks need no baking, since the curing process

is completely natural .

 

**The press makes variations of the block adapted to

the various phases of construction.

 

4. Note to the Field Worker When teaching people how to use

the CINVA-Ram Block Press, make your instructions as simple

and clear as possible. Do not quote from this manual, but

master each phase of the operation so that you can teach it

in your own words. Encourage the workers to take satisfaction

from the completion of each step, every one of which is a

move toward the final goal.

 

5. Soil testing, block production and the use of the blocks are

all important, but they are less important than the will of

the families to help themselves in building a home. This may

well need to be awakened and supported by your words of

encouragement and inspiration.

 

6. Try to make at least one person in the group familiar with

the whole operation so that the local community will possess

the skill to carry on the work alone.

 

II. EQUIPMENT

 

7. CINVA-Ram Block Press

 

Weight: 140 lbs. (63 kilos)

 

Height and base width: 10" x 16" x 26" (24 x 37 x 64cm)

 

Application force of lever: 80 lbs. (36 kilos)

 

Bearing Strength (Fully cured blocks) 200-500 psi (14-35 kg/[cm.sup.2])

 

Size of block (3-1/2" x 5-1/2" x lays up 4" x 6" x 12"

11-1/2") (9cm x 14cm x 29cm) (10 x 15 x 30cm)

 

Size of tile (1-1/2" x 5-1/2" x lays up 1-1/2" x 6" x 12"

11-1/2" (5cm x 14cm x 29cm) (5 x 15 x 30cm)

 

Average number of blocks or tiles 300-500

can be made by two people per day:

 

Average number of blocks needed 2500

for a two-room house:

 

Average number of blocks per 150

100 lbs. of cement:

 

Inserts: Four different molds for producing

different kinds of blocks and tiles.

 

Cost in United States: $175 FOB Warehouse Tallmadge, Ohio

 

AVAILABLE FROM: Bellow's Valvair International

200 W. Exchange St.

Akron, Ohio 44309

216-762-0471

 

Metalibec Ltda.

Apartado Aereo 233-NAL 157

Bucaramanga, Colombia

South America

 

Materiel Industriel et Menager Japy

6 rue de Marignana

Paris [8.sup.e] FRANCE

 

Frazer Engineering Company

116 Tuam Street

Christchurch, NEW ZEALAND

 

8. Other Equipment Needed

 

1 Wide-mouth glass jar

 

1/4" to 3/8" (6mm to 10mm) mesh wire screen

 

Box, inside dimensions: 24" x 1-1/2" x 1-1/2"

(60cm x 4cm x 4cm)

 

Fine sieve

 

Suitable mixing boards - good sizes are 4' x 8'

and 8' x 8' (1.2M x 2.5M and 2.5M x 2.5M)

 

Bottomless measuring box

 

Bottomed measuring box

 

Shovel

 

Sprinkling can

 

Mounting board at least 9' long, 8" wide and 2" thick

(2.50M x 20cm x 5 cm)

 

4 Bolts at least 1/2" (1.5cm) diameter and 3" (8cm)

long

 

8 Washers

 

III. TESTING FOR THE SUITABILITY OF THE SOIL

 

9. Need for Testing Making blocks from stabilized earth is a

simple process, but it will not be successful unless the soil

is properly tested. It would be a serious mistake to treat

this step lightly. Scarce money and labor could be wasted

for an unsatisfactory result.

 

10. Soil is a variable and complex building material. Every sample

is different from every other sample. But building blocks can

be made successfully from a wide variety of soils.

 

11. Purpose of the Tests The tests described here will tell us:

 

(1) How much sand and how much clay is in the soil to

be used (Particle Determination Test and Compaction Test,

paragraphs 16 and 17).

 

(2) How much cement or lime should be added (Box Test,

paragraph 18).

 

12. Clay It is mainly the clay content which gives the mixture

cohesion.

 

13. Stabilizer One of the important functions of the

stabilizer is to reduce the change in the volume of the clay, which

swells as it takes up water and then shrinks as it dries.

Portland cement is the best stabilizer, but slaked lime can

also be used. In some areas, lime is readily available and

cheaper than cement. With lime, a higher percentage is needed

for stabilizing than with cement. Lime does not work well with

all soils, however; careful experimentation is therefore

necessary. Lime can often be used with excellent results in

combination with cement. This cuts down on the amount of

cement needed. But it is important to remember that lime

dries more slowly and therefore needs a longer curing period.

Tests have shown good results with 1/3 cement - 2/3 lime mixture.

 

14. Organic impurities Organic material is found in the

surface layer of most soils. Soil used for block making should be

reasonably free of organic matter, which hinders the setting

and hardening of the cement and results in weak blocks. Therefore,

the topsoil should not be used unless most organic

material is removed.

 

15. Mixture A wide range of soils is suitable for making blocks.

We want: (1) a good proportion of sand to form the body of

the block; and (2) a certain amount of cohesive or plastic

fine particles (clay) to bind the sand particles together.

Good blocks can be made with even a small amount of clay, but

there must always be some clay. If a small amount of stabilizer

is enough, save on cost reducing the amount used. Learn to

find sand by testing, because soils commonly considered clay

may contain a good percentage of sand.

 

Simplified Field Tests

 

16. Particle Determination Test This test analyzes the soil to

find the ratio of sand to clay and/or silt:

 

(1) Pass the soil through a 1/4" (6mm) screen

 

(2) Pour into a wide-mouth jar enough soil to fill the

jar half full.

 

(3) Fill the jar with water and cover it.

 

(4) Add 2 teaspoons of salt to help the clay/silt

particles settle faster.

 

(5) Shake the jar vigorously for 2 minutes.

 

(6) Set the jar on a level spot.

 

The soil should settle in about half an hour. The sand

will settle quickly to the bottom. The clay/silt particles

will settle last. Measure the layers to determine the ratio

of sand and clay/silt (see Fig. 2).

 

mbb2x6.gif (600x600)

 

 

Use soil that is at least one-third sand and between

5 and 30% Clay/silt. If the soil at hand is not suitable,

it can be made suitable by adding sand or clay. Record the

percentages of sand and clay/silt in the soil used. This

will help in deciding which soil makes the best blocks.

 

17. Compaction Test. This test indicates the packing quality of

the earth, which depends on the percentage of clay in the

sample.

 

(1) Take a handful of dry, screened earth and moisten it

until it is damp enough to form a ball when squeezed

in the hand, but not so damp that it will leave more

than a slight trace of water on the palm.

 

(2) Drop the ball from a height of about three feet

onto hard ground. If the ball breaks into a few smaller

pieces, the packing quality is good to fair. If it

disintegrates, the quality is poor.

 

18. Box Test The box test is a guide to the proper soil-cement

ratio. It measures the shrinkage of soil which contains no

stabilizer. The box should have these inside measurements:

24" x 1-1/2" x 1-1/2" (4cm x 4cm x 60 cm) (see Fig. 3).

 

mbb3x7.gif (486x486)

 

 

 

(1) Oil or grease the

inside surfaces of

the box thoroughly.

 

(2) Pack the box well

with moist soil

(previously passed

through a 1/4" -3/8"

(6mm-10mm)

mesh screen). The

soil should be

moistened to pack

well, but it should

not be muddy.

 

(3) Tamp, especially at the corners.

 

(4) Smooth off the surface with a stick.

 

(5) Place the box in the sun for three days or in

the shade for seven days. It should be protected

from rain.

 

19. Measure the contraction (shrinkage) by pushing the dried

sample to one end of the box.

 

Shrinkage Cement to Soil Ratio

 

Not over 1/2" (15mm) 1 part to 18 parts

 

Between 1/2" and 1" (15mm - 30mm) 1 part to 16 parts

 

Between 1" and 1-1/2" (30mm - 45mm) 1 part to 14 parts

 

Between 1-1/2" and 2" (45mm-60mm) 1 part to 12 parts

 

When lime is used instead of cement, use double the amount.

Do not use the soil if it has many cracks (not just three or

four); if it has arched up out of the box; or if it has shrunk

more than 2" (60mm).

 

IV. MAKING BLOCKS AND TILES

 

 

20. The proportion of cement and/or lime needed to stabilize the

mixture has been determined by the box test.

 

21. The number of blocks and tiles needed should be calculated

from the plans for walls and floors. Three blocks (laid

flat) give one square foot of wall (33/[m.sup.2]); two tiles give

one square-foot of flooring (22/[m.sup.2].

 

22. You may not be present during the block-making. Go through

each step with the group doing the work until you are satisfied

that the steps are clearly understood. Be generous

with encouragement. Organize the physical layout of the

 

mbb4x9.gif (600x600)

 

steps of the operation as efficiently as possible. The

movement of the operation should be a flow of work, with

the fewest possible number of footsteps, toward the final

stacking near the construction site in the following order:

 

(1) Digging and screening the soil

 

(2) Preparing the mixture

 

(3) Pressing the blocks

 

(4) Curing and stacking the blocks

 

23. Circumstances will not always permit a direct flow. Therefore,

some forethought is needed to set up the best operation for

your situation.

 

Digging and Screening

 

24. Digging At the selected excavation spot, strip the surface

soil of all vegetation. If the vegetation is carefully removed

and stored, it can be used later for planting around the completed

house or for replanting the soil supply pit.

 

25. The amount of topsoil which must be removed to avoid getting

organic matter into the mixture varies in different locations.

It may go to a surprising depth of several feet, or it may not

be necessary to remove any at all. Normally, six inches

to a foot (15cm-30cm) should be enough.

 

26. Generally the soil gets sandier as the hole gets deeper.

Sandy soil with a low proportion of clay makes the best blocks.

Sometimes a layer of clay subsoil will be followed by very

sandy soil, and combining the two in the screening or mixing

steps will produce a stronger block.

 

27. If, as the hole gets deeper, the pit produces soil which is

not good for block-making, there is no choice but to enlarge

the excavation area.

 

28. The person supervising the work will probably not be present

during the digging. Therefore he should give a simple

explanation of soil composition at the start of digging so

that any pronounced change in sand or clay content will be

noticed.

 

29. In Case of Rain In a period of alternating showers and sunshine,

provision should be made to cover the pit (for

example, with roofing sheets), so that work can continue

immediately after the showers. Where surface water can run

into the pit, put up a small retaining barrier of soil. The

pile of screened soil should, of course, be protected by a

covering which will shed most of the rain.

 

30. Screening The soil should be

screened through 1/4" or 3/8"

(6mm or 10mm) wire mesh (see

Fig. 5).

 

mbb5x10.gif (600x600)

 

 

 

 

The screen should be mounted at

a level where it can be shaken

by hand without back-bending; for

example, by suspending it from

two trees or posts (see Fig. 5).

The screening operation is one

where women and children can help

in block-making.

 

31. It is important to keep the CINVA-Ram operating steadily.

It should not be idle while soil is being dug and screened

 

32. Experience is needed to know how large a stockpile of

screened earth is needed for different sized buildings.

It can be estimated, since it will take up 1-1/2 to 1-2/3

times its volume in the compacted blocks.

 

33. Preparing the Mixture The importance of thoroughness in

both cement mixing and moisture mixing, two distinct steps

in preparing the mixture, cannot be emphasized too strongly.

 

34. Cement Mixing A suitable mixing board (good dimensions:

4' x 8' or 8' x 8' [1.2M x 2.5M or 2.5M x 2.5M]) is needed.

A flat concrete slab or an area of compacted and stabilized

earth serves equally well.

 

35. Measuring boxes whose sizes can be determined from the

tests in paragraphs 16-19 can be very effective in making

sure that the correct proportions of soil and cement are

mixed.

 

(1) Set a large bottomless measuring box on the

mixing board.

 

(2) Fill it with soil and level off the top.

 

(3) Lift the box, leaving a measured pile of soil

on the board. The soil should be spread out

over the mixing board as the box is lifted.

 

(4) Use a smaller bottomed measuring box for a measured

amount of cement. The cement should be emptied

evenly over the soil.

 

(5) After the proper number of boxes are emptied on

the mixing board, mix the cement and soil by

turning it over with a shovel until it changes

uniformly throughout to a different shade of color.

 

36. Do not use lumpy cement. Pass it through a fine screen (window

screen or finer); discard lumps which will not break up easily

with the fingers and pass through the screen.

 

37. Moisture Mixing

 

(1) Spread out the thoroughly

mixed soil-cement mixture

on the mixing board.

 

(2) Add water with a sprinkling

can without making puddles

(see Fig. 6).

 

mbb6x11.gif (486x486)

 

 

(3) Mix it thoroughly again, by

turning it over with a

shovel.

 

38. Keep the amount of water less than what seems to be enough.

More water can be mixed in, but much time can be lost in

getting rid of excess water.

 

39. With a little experimentation it will be possible to calculate

the amount of water for each mix. This will save the

time it takes to make small additions of water and repeat

the mixing process. It is important to remember that the

mixture will look as though it is not moist enough.

 

40. Testing for the Correct Amount

of Moisture. The correct amount of

moisture is quickly learned through

experience. To test it, squeeze a

handful of the mixture. (See Fig. 7.)

 

mbb7x12.gif (353x353)

 

If it is moist enough it will keep the

shape it is squeezed into. If dropped

onto a hard surface from shoulder

height, it should break into small

fragments. The mixture is too moist

if water is squeezed out of the top

of the machine box when a block is

pressed.

 

41. The mixture should be used within one hour after water

has been added.

 

42. Pressing the Blocks The first point that must be driven home

to all operators of the CINVA-Ram is that they should not put

too much strain on the machine when they press a block. Never

should two men press on the handle to bring it down in making

a block. Nor should anyone jump on the handle to force it

down with repeated thrusts of his body. This point cannot be

emphasized too strongly because such a strain will damage the

machine.

 

43. Mounting the Machine The CINVA-Ram Press (see Fig. 1) should

 

mbb1x1.gif (600x600)

 

 

be mounted on a board at least 9' long, 8" wide and 2" thick

(2.5M x 20cm x 5cm). A narrower board will let

the press tip sideways; a shorter board will lift up at the

ends, making it hard to get the right amount of pressure on

the block; a thinner board will split under pressure.

 

44. The bolts should be at least one-half inch in diameter and

three inches long (1.5cm x 8cm). It is good to

put washers under the heads of the bolts on the underside of

the board, especially on the end of the press with the lower

rollers, since this end receives the greatest pressure. The

washers help to keep the bolt head from pulling through the

board. If the heads do start to pull through, install larger

washers immediately; the great strain put on a loosely mounted

press can easily throw it out of adjustment and eventually

break it.

 

45. Pressing.

 

(1) Open the cover.

 

(2) Make sure the piston is all

the way down. If it is part

way up it will not be possible

to get the correct amount

of mixture into the box.

 

(3) Dump the proper amount of

soil-cement mixture into the

box (see Fig. 8). The supervisor

 

mbb8x13.gif (437x437)

 

should determine the

correct amount of mixture for

each block - a measuring box

can be used to make sure that

the same amount is used each

time. Uniformity in loading

is absolutely necessary for

producing uniform blocks.

 

(4) Fill the corners of the box to

the top so that the corners of

the finished block will be well

pressed.

 

(5) Press a bit in the corners with

your fingers.

 

(6) Replace the cover.

 

(7) Move the lever to a vertical

position, letting the lower

rollers fall into place

(see Fig. 9).

 

mbb9x13.gif (437x437)

 

 

(8) Disengage the lever latch.

 

(9) Move the lever to a horizontal

position on the side opposite

the lower rollers.(compression

cycle) (see Fig. 10). If the

 

mbb10x13.gif (437x437)

 

right amount of mixture is used,

one man of average weight should

be able to move the lever down

alone with only two or three

pushes. The lever must be

lowered completely; otherwise the block will be too

thick, wasting material and producing a block which

may be too thick to use.

 

(10) Move the lever to a vertical position, engage the

lever latch and return the lever to its rest position

on the lower rollers.

 

(11) Open the cover (see Fig. 11).

 

mbb11x14.gif (437x437)

 

 

(12) Depress the lever steadily to eject the block (see

Fig. 12). If the block is cracked or deformed, it

 

mbb12x14.gif (437x437)

 

should not be used. Read the instructions in paragraphs

52-61, Adjustments.

 

(13) If the blocks are lifted from the machine and carried

properly and carefully, and if the mixture is correct

and the machine is in good adjustment, the blocks

will not break easily.

 

(a) Press in on opposite ends of the block with

the fingers closed, the thumbs in close to

the fingers, and using part of the palms

(see Fig. 13).

 

mbb13x15.gif (437x437)

 

 

(b) To set the brick down, tip it into place

on its side.

 

46. Try to have at least two men operating the machine, because

it is very time-consuming to have one man moving from one side

of the machine to the other to press and eject. But it can be

done by one man if only one is available. Four persons make

an ideal team for pressing: one filling, one pressing, one

ejecting, and one removing. A team of four can easily produce

two blocks a minute if the mixture is prepared and

close by.

 

47. Sticking Some soils stick more than others. An occasional

cleaning of the corners of the press box with a metal scraper

may be necessary. The blocks should come out of the press

with sharp corners. Sticking can be overcome by slightly

moistening the points where it occurs with a bit of kerosene

on a rag.

 

48. Rotating Jobs On a job where there is enough labor to have

all the steps -- digging, screening, mixing, loading, pressing,

ejecting, and carrying -- going on at the same time, it is

fair and good for morale to rotate the jobs every hour or so.

 

Maintenance and Repairs

 

49. Lubrication All moving parts and wearing parts (rollers,

pins, pressure plate, guide plates, piston cylinder, bearings

and supports of axles) should be well lubricated every

four to eight hours with heavy oil or grease to insure smooth

operation and cut down on wear.

 

50. Pins The pins which secure the pivot shafts, compression

yoke and rollers should be replaced when broken by the

largest nails available, because they will last longer than

the average cotter pin. If C-ring replacements are not

available, broken C-rings can be replaced by wrapping a

piece of wire in the groove.

 

51. Clean Surfaces The inside of the box and the under surface

of the cover-must be kept clean.

 

52. Adjustments The CINVA-Ram press should not be tampered with

unnecessarily, but the following suggestions

may help if the press produces faulty blocks.

 

53. Breaks and Cracks Breaks and cracks are caused by loose or

incorrectly adjusted guideplates.

 

54. Side Breaks (See Fig. 14.)

 

mbb14x16.gif (353x353)

 

 

 

Move the lower adjusting bolts

(G and H) sideways toward the

high side of the break (see Fig. 1).

If more adjustment is needed, move

the upper adjusting bolts (E and F)

toward the low side of the break.

This can sometimes be done simply

by hammering the bolt sideways (with

a piece of wood, so that the threads

will not be damaged) rather than by

loosening and tightening the nuts.

After the bolts are hammered over,

tighten the nuts.

 

55. End Breaks (See Fig. 15.) Move

 

mbb15x16.gif (353x353)

 

the guide plate opposite the end

where the break occurs inward by

turning lower adjusting bolt G or

H, depending on the guide plate to

be moved (See Fig. 1). NOTE: Moving

one end of a guide plate in one direction forces the other

end of the same plate in the opposite direction. If this

loosens the piston much at either the top or the bottom of

the guide plate, the other end of the plate must be moved

inward. The free play should be corrected because it will

cause the piston to crack the blocks by compressing them

in one direction in the compression cycle (with the upper

saddle as the pivot point) and in another direction in the

ejection cycle (with the lower rollers as the pivot point).

Also, the guide plates must be tight enough against the

piston to keep it from jerking and jumping upward at the

end of the ejection cycle.

 

 

56. If end cracking is not stopped by tightening the plates

against the piston, it may be necessary to tilt the guide

plates and the piston, so that the pressure plate will be

higher at the end which is cracking. This is done by

moving the tops of both guide plates toward the cracked end.

 

57. Corner Breaks A corner break

is caused by a combination of

a side break and an end break

(see Fig. 16).

 

mbb16x17.gif (317x317)

 

 

(1) Fix the side crack by moving

the bolts sideways, as

in paragraph 54 (usually it

is only necessary to move the

bottom bolt on the end with the crack toward the

side where the crack occurs).

 

(2) Fix the end crack by moving the lower adjusting

bolt opposite the cracking end inward against

the piston, as in paragraph 55.

 

58. Tapering Tapering is caused by incorrectly adjusted guide plates.

 

59. Side Taper (See Fig. 17.)

 

mbb17x17.gif (317x317)

 

First move the guide plate

on the thicker side outward; then

move the other guide plate inward

(see Fig. 1). The guide plates

should be kept parallel to each

other. Move both the tops and

bottoms of both guide plates the

same distance.

 

60. End Taper (See Fig. 18) Move the

 

mbb18x18.gif (317x317)

 

tops of both guide plates toward

the thin end. Move the bottoms of

both guide plates toward the thick

end. (See Fig. 1) The tops should

be moved as far in one direction as

the bottoms are in the other.

 

61. Corner Taper (See Fig. 19) A

 

mbb19x18.gif (285x285)

 

corner taper (one corner thinner

than the rest) is caused by a

combination of a side taper and an

end taper. First, fix the side taper

by moving the guide plates as in paragraph

59. Second, fix the end taper

by moving the guide plates as in paragraph

60.

 

62. Curing and Stacking the Blocks The curing of the blocks is

another important step which must be taken with care. To become

careless at this point could ruin all the careful work that has

gone before.

 

63. The moisture in the blocks must

come out slowly and evenly.

 

64. The blocks should be laid on

flat, unwarped, clean planks

wide enough to support the full

width of the blocks (See Fig. 20)

 

mbb20x18.gif (393x393)

 

If such boards are not available,

the blocks should be placed on

smooth ground covered with paper

or leaves so that they will not

be in direct contact with the

earth

 

65. The blocks should not be pushed

into another position after

being placed. If it is necessary

to move the blocks at this

point when they are very weak,

they should be carefully lifted

and carefully placed again. If the blocks cannot be put inside

or under a shelter, cover them with heavy paper or plastic. (Paper

cement bags carefully opened and separated make excellent coverings).

If there is a shortage of storage space, the blocks can be

stacked five rows high after three or four hours of drying

-- if they are very carefully handled.

 

66. The next day, the first operation is to move the blocks to

make room for another day's production.

 

67. After the overnight drying, the blocks should still be protected

from the weather because they must still cure slowly

for four or five more days. Soaking will harm the blocks

at this stage. Sunshine will make them cure too quickly,

reducing their strength. In very hot climates blocks should

be kept moist during this period. In any climate they should

be prevented from curing too fast. For the first four days

they should be sprinkled lightly with water twice a day. A

plastic cover is useful to maintain moisture in the pile. If

lime is used, double the curing time. The blocks can be restacked

ten rows high on edge for the next curing period of 10

days. The blocks must not be stacked solidly; there should be

a space of about an inch between blocks to let them cure properly.

A good stacking arrangement is three blocks side by

side with an inch space between them crossed with three blocks

above -- alternating the direction of each layer (See Fig. 21).

 

mbb21x19.gif (353x353)

mbb21x19.gif (353x353)

 

 

68. In carrying out the curing process, try to be moving the blocks

closer to the construction site.

 

69. Never underestimate the importance of careful curing.

 

70. Variations of Blocks, Floor Tiles The CINVA-Ram box, when

used without any inserts, produces a solid block 11-1/2" x

5-1/2" x 3-1/2" (9cm x 14cm x 29cm). Inserts for the box,

which are included with the CINVA-Ram will change the size or

shape of the blocks.

 

71. Frog A wooden "frog" (see Fig. 22)

 

mbb22x20.gif (353x353)

 

is used in the box to produce a block

with a partially hollow core. The

advantage of this block is that it

uses only four-fifths the mixture

used in a regular block -- reducing

both cost and labor. These blocks

are also ideal for designing patterns

in walls using blocks laid on

edge. The "frog" must be kept clean.

 

72. Some soils will stick to the wooden

mold. A quick wipe with a kerosene-dampened

rag will overcome this.

 

73. Blocks can be made with hollow cores

running the whole length of the

block, but this takes a little more

time. The proper molds for these

blocks have to be made (see Fig. 23);

 

mbb23x20.gif (317x317)

 

they do not come with the press.

These blocks can be used where metal

reinforcing rods are to be run through

the laid blocks.

 

74. With a little experience, operators

will become proficient in making

these blocks.

 

75. Floor Tiles Tiles produced with the

CINVA-Ram Block Press make inexpensive,

attractive and durable flooring.

The tile insert is a wooden

block with a metal face (see Fig.24).

 

mbb24x20.gif (317x317)

 

The wearing surface on the tile is

made with a cement mixture.

 

(1) Screen the sand for this mixture as finely as possible:

the finer the sand, the smoother the tile face will be.

 

(2) Mix two parts sand with one part cement. Mineral coloring

can be added to produce different colored tiles.

 

(3) Mix water with the sand cement mix, as in paragraphs 37-39.

 

(4) Place the tile-making insert in the box.

 

(5) Spread the cement mixture over the insert to a depth

of one-quarter to three-eights of an inch (6mm - 10mm).

 

(6) Add the soil-cement mixture to this without completely

filling the box. The two mixtures should be equally

wet.

 

(7) The tile is then pressed and ejected in the same way as

the blocks. (See paragraphs 45 and 46.

 

76. A pallet is helpful in carrying the newly pressed tiles. The

tiles, which are thinner than the blocks, are more easily damaged

in handling. Cured or partly cured blocks can be used as pallets.

The tiles are turned over when removed from the machine and cured

face up. They can be carried on the insert to the curing spot

if pallets are not used, and then inverted when placed down; but

this operation is a little awkward and slows the tile making.

 

77. It is extremely important that the tiles rest on a flat surface

for the first day of curing. A bowed surface will make the

tile sag to the bow and the tile will either cure in a warped

shape or crack.

 

78. A different method of facing is to place a dry mixture of cement,

sand and coloring into the box and then add a soil-cement mixture

which is slightly wetter than usual. This saves the time it

takes to make a wet mixture. It also spreads out easier on the

insert.

 

79. The tile facing may stick to the insert. Rust on the metal face

can cause this. If nothing else stops the sticking, put a

sheet of plastic or a piece of heavy paper (one ply of paper

cement bag will do) cut or torn to the size of the insert into

box before filling. The plastic or paper can be peeled off the

face of the pressed tile. One paper will last for about twenty

tiles.

 

80. Curing and Stacking Tiles are cured in the same way as the

blocks, but they are stacked only two high, with the faces together.

 

81. Other inserts provided with the CINVA-Ram Block Press can be used

to make I-shaped blocks, blocks for utility conduction, and lintel

blocks (for placing door supports).

 

82. Testing the Blocks The strength of the cured blocks should be

tested. Most countries have a university or building products

laboratory which can test the blocks.

 

V. BUILDING

 

83. Mortar The mortar joints between CINVA-Ram blocks and tiles

should be 1/2" (1cm) thick. Since the blocks are 11-1/2" x

5-1/2" x 3-1/2" (9cm x 14cm x 29cm) the building unit is 12"

x 6" x 4" (10cm x 15cm x 30cm). In flooring, the 11-1/2" x

5-1/2" (14cm x 29cm) tiles plus the half inch (1cm) mortar

joints, make a unit of 12" x 6" (15cm x 30cm).

 

84. The foundation for the blocks must be firm. Use a cement-sand

mortar for the first two layers to allow waterproofing.

 

85. The mortar recommended for the rest of the building is one part

cement, two parts lime and nine parts of the same soil used to

make the blocks. Lime is used because it forms a more plastic

mortar; since it sets more slowly than cement, it is less

likely to crack. The mortar should be a moist mixture which

does not flow as freely as cement-sand mortar.

 

86. Surface Coating Let the mortar dry for about a week. Then,

using a narrow brush, paint all the joints with a thin cement

wash which can be brushed into any fine cracks. Stir the cement

wash frequently. Where large cracks develop they should be

gouged out to hold a packing of soil-cement mortar. Wet the

crack. Press the mortar in and smooth it off.

 

87. The blocks alone have an attractive finish but they can also be

coated in the following way: after a day, paint all the exterior

walls with a cement wash of about rich milk consistency. Work

in the shade, keeping the cement wash well stirred. Three

coats are recommended. The coats should be thin to keep from

building up a crust of cement. Allow a day between each coat.

 

88. A lime wash can be applied to make the building waterproof.

This usually needs to be done again every year.

 

89. A silicone base wash (clear in appearance) is an excellent

water repellent for very rainy areas. In experiments this

solution has waterproofed blocks which were not coated with

a cement wash. In areas of freezing weather, experimentation

should precede the use of CINVA-Ram blocks.

 

VI. REFERENCES

 

90. Using Low Cost CINVA-Ram Earth Blocks for Construction in

Cold Climates, by Chris Ahrens, U.S. Office of Economic

Opportunity, Arlington, Virginia, December 1970.

 

CINVA-Ram Handbook, by John R. Hansen, volunteer in American

Friends Service Committee Summer Project, July 1963, Patzicia,

Guatemala.

 

Earthen Home Construction: A Field and Library Compilation

with an Annotated Bibliography, by Lyle A. Wolfskill,

Wayne A. Dunla and Bob M. Gallaway, Texas Transportation

Institute, A. & M. College of Texas, Bulletin No. 18, March

1962.

 

Earth for Homes, Ideas and Methods Exchange No. 22, U.S.

Housing and Home Finance Agency, 3rd printing, revised

September 1963.

 

VII. OTHER MACHINES FOR MAKING BLOCKS FROM STABILIZED EARTH

 

91. Landcrete, manufactured by Messrs. Landsborough Findlay

(South Africa) Lts., Johannesburg, and Trans-Atlas Ltd.,

15 Duke St., Dublin 2, Ireland. A well-designed hand-operated

toggle press, sturdily constructed and simple to operate.

 

92. Winget, manufactured by Messrs. Winget Ltd., Rochester, England.

A hydraulic press powered by a gasoline engine. The quality

of the blocks produced is helped by high operating pressures,

but the production rate is the same as that of a hand-operated

machine.

 

93. Ellson Blockmaster, manufactured by Ellson Equipments (Pty).

Ltd., Johannesburg, South Africa. The machine uses a toggle

switch lever system giving a constant length stroke which

standardizes the thickness of the blocks.

 

If you need more information on the material in this manual or on other

technical matters, VITA (Volunteers in Technical Assistance) can send

it to you. If you have specific questions, VITA can put you in contact

with an expert who can answer them. VITA is an international

association of scientists, engineers, technicians and businessmen who

volunteer their spare time to consult on questions from persons in

developing areas. Simply send your request to:

 

VITA

1815 North Lynn Street, Suite 200

Arlington, Virginia 22209 USA

 

VIII. STRUCTURAL CHARACTERISTICS OF SOIL-CEMENT BUILDING BLOCKS

 

(Reference: U.S. National Bureau of Standards - Building Materials and

Structures Report BMS 78).

 

Note: The pressurized blocks tested by The National Bureau of Standards were

made using a laboratory machine press which produced a block of similar quality

to the CINVA-RAM block. Mix: Soil, 50% sand, 50% silt and clay; cement 8%.

 

General - A high-grade block is superior in many respects to a common burned

brick and other usual masonry materials. Even the lowest density CINVA-Ram

press block has structural qualities more than sufficient for one and two-storey

houses and other small structures.

 

Compressive Strength - Blocks withstood pressures up to 800 pounds per square

inch. When you consider that the load at the foundation line of a one-storey

house is only about 30 pounds per square inch, there is a factor of safety of

over 20. Adobe blocks seldom withstand more that 100 pounds per square inch.

 

Transverse Loading (wind load) - A wall made of pressurized blocks withstood a

transverse load of 112 pounds per square foot. This will withstand winds of

top hurricane strength.

 

Weather Resistance - The pressurized block wall only leaked through poor mortar

joints. The unprotected block surface showed very little erosion under severe

surface treatment for low density blocks.

 

Impact and Concentrated Loading - The preformance of a pressurized block wall

under those loadings was superior to many types of masonry walls.

 

Resistance to Racking - This is the eccentric force on a wall caused by

settling of part of a foundation - also the type of force most often encountered

in a wall during an earthquake. The test wall of pressurized

blocks withstood twice the force applied to a conventional frame wall and

over one-third more than the force applied to a cement-block wall.

 

Fire Resistance - The pressurized soil-cement block is fireproof.

 

Insulating Quality - The rate of heat passage through a pressurized block

wall is about the same as for a solid concrete wall of the same thickness.

 

CRBP Blocks compared with Adobe and Rammed Earth - A pressurized block of soil-cement

such as is produced by the CINVA-RAM Block Press is a comparatively

new building product. However, adobe and rammed earth have been used for

centuries in building constructions throughout the world. There are many

buildings in the U.S. constructed of adobe and rammed earth over 100 years

old and still in good condition. The CINVA-Ram press block is far superior

in all respects to either adobe or rammed earth as brought out in the Bureau

of Standards tests as well as all other comparative tests of records.

 

 

ABOUT VITA

 

Volunteers in Technical Assistance (VITA) is a private, nonprofit,

international development organization. It makes available

to individuals and groups in developing countries a

variety of information and technical resources aimed at fostering

self-sufficiency--needs assessment and program development

support; by-mail and on-site consulting services; information

systems training.

 

VITA promotes the use of appropriate small-scale technologies,

especially in the area of renewable energy. VITA's extensive

documentation center and worldwide roster of volunteer technical

experts enable it to respond to thousands of technical

inquiries each year. It also publishes a quarterly newsletter

and a variety of technical manuals and bulletins.

 

VITA's documentation center is the storehouse for over 40,000

documents related almost exclusively to small- and medium-scale

technologies in subjects from agriculture to wind power. This

wealth of information has been gathered for almost 25 years as

VITA has worked to answer inquiries for technical information

from people in the developing world. Many of the documents contained

in the Center were developed by VITA's network of technical

experts in response to specific inquiries; much of the

information is not available elsewhere. For this reason, VITA

wishes to make this information available to the public.

 

For more information, contact VITA, P.O. Box 12438, Arlington,

Virginia 22209, USA.

 

"Ode to a CINVA-Ram Block-making Machine"

 

I'll sing you the song of a CINVA:

A simple portable thing.

Earth pressing -- no messing!

A fabulous blessing

When it comes to house construction.

 

Shovel earth into the mold box,

Then cover and give a big heave.

In compacting it's acting,

The pressure reacting:

Eject, and the brick is achieved.

 

I'll sing of a brand-new CINVA:

It calls us to start the day.

At dawning we're yawning

But the bricks, they are spawning,

And that has the biggest say!

 

So wherever you are in the wilds

Frustrated by lack of success,

A CINVA is soothing,

So useful it's proving,

Your project is bound to impress!

 

John Miles

International Voluntary Service

(British Branch of Service Civil

Internationale)

Suihari, Dinajpur, EAST PAKISTAN