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GYPSUM ADOBE CONSTRUCTION TECHNOLOGY
February 14, 1997
Southern California Institute of Architecture 

BILGE IŞIK, Ph.D...,
Assoc. Professor
Istanbul Technical University
Istanbul - TURKIYE

OUTLINE

• Purpose
• The Soil
• Proportionning of Gypsum + Lime Adobe (ALKER)
• Properties of ALKER
• Workability
• Curing
• Construction
• Labor

Purpose 

Earthen construction is vulnerable to moisture and can be easily damaged by earthquake. However, indoor quality in earthen construction is very healthy. It provides protection against hot and cold weather conditions, in view of its high thermal capacity and insulating values. Because of these advantages, earthen construction technology is subject to research in both in the industrialized and unindustrialized countries.

In this research, gypsum and lime are mixed to the soil to promote the properties of the material. The gypsum stabilized soil sets in a short time, which makes the production time shorter and the curing unnecessary. It also makes the production period independent from the rainy days. The material is porous, thereby increases the insulting value.

The mechanized construction technology for the gypsum stabilized earthen construction aims to improve the local construction material for mass-housing. It will also contribute to preserve the natural sources and save funds for the country.

The Soil 

To obtain required strength and durability
 

Traditional Earthen Construction	ALKER construction
preprocessing	preprocessing is not necessary
grinding	____________
sieving	____________
setting the soil aside	____________
30% clay	10% clay

Proportion of ALKER(Gypsum + Lime Adobe)

 

Ingredient	% by Weight	Practical Measures
Soil	100	2 full wheel barrow
Gypsum	10	4 shovel full
Lime	2	1 shovel full
Water	18-20	1 bucket full

General Properties

• improves the water absorption property
• improves the mechanical properties
• improvers the heat insulation
• low shrinkage
• clean surface
• short setting
• short construction time

Physical Properties

 

Unit weight	1.6-1.7 kg/lt
Shrinkage	1.0-1.5%
Compressive strength	2.0-4.0 N/mm2
Shear strength	0.9-1.3 N/mm2
Water absorbtion	very low
Long term water exposure (except direct rainfall)	no erosion
Heat transfer value l	0.4-0.5 kcal/mhC
Specific calorific	1.0 kJ/kgK

Workability

 

Water Content	Workability
18-29%	rammed earth
20-22%	adobe blocks
24% and more	segregation

Curing 

To obtain required strength and durability
 

Traditional earth  construction	ALKER construction
15-21 days strengthing	20 min. strengthing
curing area	no curing area
water sprinkling	no water sprinkling
rain protection	no rain protection

Construction

• The gypsum stabilization enables a shorter construction time
• The external walls are 45cm tick, this provides thermal property
• The load bearing internal walls are 30cm
• Wall oppennings are 25%
• Foundations and tie beams are reinforced concrete

Labor 

ALKER  technique decreases a number of processes

• 4 laborers can erect 2.5-4.5 m3 of walls/day
• 100 m2 house has approximately 45 m3 walls, therefor, 4 laborers can complete a hose in 10 days

Production Method of Gypsum Adobe (ALKER) 

Material :

Earth:___________100 kg__________100%
without humus
clay (appr. %10) + silt + sand + grvel (7 cm)
Water:____________20 kg__________20%
Gypsum:___________10 kg__________10%
Lime:______________2 kg___________2%

 

Mixing : mechanical mixer (or shovel)

 

Process :
 

mixer + earth + 2 kg water	2 minutes mechanical mixing
barrow + water 18 kg + lime 2 kg + gypsum 10 kg	2 minutes hand mixing
pour the barrow full of mixture into the mixer (water 18 kg + lime 2 kg + gypsum 10 kg)	3 minutes mixing
pour the mixture to the wheel borrow; ramm it into the wall form	in no longer than 15 minutes

Please inform Bilge ISIK about the results with your full address and a short CV.
Your interest is appreciated.