Indigenous Material

Clay Aggregates

One of the major factors limiting the development of paved roads in Guyana is the exorbitant cost of stone aggregate and binding materials (such as bitumen). Aggregates are typically mined in the interior of the country, and must be transported at great cost to the coast. Binding materials used on the wear layer of the road surface, such as bitumen, is imported at prohibitive cost, as the country does not yet have a local petrochemical industry.

During the periodic rainy seasons in Guyana, the agricultural access roads and the roads in rural villages are transformed into muddy morasses, which impacts not only the comfort of the villagers, but significantly impedes the transportation to Georgetown and other urban centers.

Fired clay aggregates have been used in Guyana since the early 1800’s, particularly by the sugar industry, as a road surfacing material. The process used has changed little since then, and represents a costly solution to the coastal lack of quarried material. The bulk of the costs incurred in firing clay (known as burnt-brick) are primarily due to the need to utilize expensive walaba and other woods as fuel. In addition, the process is conducted in open pits, resulting in significant losses of heat to the environment and as well in an un-equal application of heat to the clay material, resulting in consequential heterogeneity in the strength of the fired material.

A final consideration is that the size of the clay particles is generally not controlled and there is a lack of effort in manipulating the composition of the fired clay so as to include materials which may act as binders.

Puzzolanas are materials containing constituents which combine with lime at ordinary temperature in the presence of water to form stable insoluble compounds possessing cementing properties. These materials may be natural or artificial. Natural puzzolanas are of volcanic origin e.g. volcanic glass, volcanic ash, etc., but artificial puzzonlana may be prepared by heat treating clays, shales, etc.

Work has been conducted by the U.S. Army Engineer Corp where they have used alkali-activated alumino-silicate binders for the construction of military roads. In such work, potassium or sodium hydroxide (rather than lime) is mixed with a fine-grained non crystalline alumino-solicate (such as from fired clay). The resulting reactions are capable of producing a hardened binder which is an excellent road wear surface, similar to cement. Other forms of excellent alumino-silicate materials include rice husk ash, which is in plentiful supply on the coast of Guyana.

The development of effective, cost-competitive puzzolanas using materials available on the coast of Guyana would certainly have a significant effect on the commerce of agriculture and the quality of life of citizens residing in the rural areas of the coast.

It also has significant uses in the housing construction industry as a low-cost, durable and aesthetic alternative for for home building.

Both the production of clay aggregates and puzzolanic materials as binders would also impact heavily on low-cost housing construction. Therefore, the IAST has a major, multi-year project focused on the firing of coastal clays for the production of aggregate materials and for combination with lime, fired rice husk, and other binder materials to produce wear-resistant concrete-like binders.

Please view slide show to see the construction of the kiln built by the IAST and the production process in preparing clay aggregates.

Compressed Clay Blocks

For centuries, clay and the composites of clay have been a building material of incomparable usefulness and attractiveness. And still today clay has proven itself with excellent properties. From both environmental and economic perspectives, clay is still a valuable, healthy and efficient construction material.

Traditionally, bricks were hand pressed, either sun or kiln dried. Sun-dried earth bricks were produced from the natural sun and air drying process.

IAST developed high compression blocks using coastal clay, these compressed blocks were found to be equal in strength to the concrete blocks currently used in the construction industry at approximately 1/6 of the cost.

Tests and laboratory analyses were done to determine the most appropriate soil for making the compressed clay blocks.

Clay from a predetermined extraction pit was air dried and crushed to smaller particles. The soil was then sieved to remove debris and produce uniformity.

Batches of soil were weighed and the correct proportions of stabilizers, sand and water were added and mixed. Blended into a homogeneous mixture, it was placed into the mechanized block making machine where it was compressed, extruded and placed on the ground to be air dried.

The extruded blocks were stockpiled and covered and cured under a shed for at few weeks and then uncovered and dried for a number of days. The compressed earth blocks were then ready to be used.

The blocks are suitable for the construction of domestic dwellings, since it was tested for compressive strength and compared evenly with cement blocks.

IAST subsequently constructed at 20ft x 20ft Eco-house on the south western of its compound using the compressed earth blocks to build the external and internal walls.

The Environmentally friendly house also has a thatched roof constructed with trouli leaves and windows, doors and furniture made of bamboo materials. The house is power by a solar system.

The Completed Eco-friendly House made of Compressed Clay Blocks

Painted walls of the Eco-House with its Bamboo Furnishings

Waste Plastic Composite Building Materials

The Institute of Applied Science and Technology has invested in an extrusion and injection line that produces roof shingles from virgin or recycled plastic resins and waste agricultural fibers.

Plastic composite materials are used in prefabricated, portable, and modular buildings. They can also be used for interior and exterior construction projects such as:

Exterior cladding and wall panels
Roofs and Ceilings
Decks and floor tiles
Windows and Doors
Crown mouldings and baseboards
Bath and shower enclosures and sinks

IAST produces plastic composite materials by thoroughly mixing natural, pulverized agricultural fibers with a thermoplastic resin (waste water bottles, HDPE, etc.) and additives (dyes, chemicals for UV and fire protection).

The mixture is extruded with a parallel twin screw extruder to form a homogenous melt strand that is converted to pellets.

The pelletized material is heated until it is sufficiently fluid to allow for pressure injection into the shingle mold where it solidifies quickly.

IAST estimates a cost of G$280 to manufacture a 16″ (40cm) x 10″ (25cm) plastic composite roofing shingle.

Since 2014, significant effort has expended to engage the private sector in securing an investor to take this project to a commercial scale.

Rubberized Asphalt Cement

The institute has modified and developed technology to reclaim rubber from used tires, and furthermore, to process the recovered rubber particles into rubberized asphalt cement by reacting it with bitumen at high temperatures. The process avoids the use of liquid nitrogen, which is used in other countries, and most of the critical pieces of equipment were manufactured here in Guyana at the institute.

The rubberized asphalt cement was exhaustively tested as a high-friction coating for steel bridges, on the Demerara Harbour Bridge over a period of five years. Bridge engineers reported no failure of the material and superior performance over the imported coating material. The material is also well suited for the repair of highway cracks and for patching cracks and holes due to its high adhesiveness and wide ranges of extensibility, a role for which bitumen alone is ill-suited. In 2014, technical staffs were trained to operate the small mobile asphalt plant and asphalt pump that the institute acquired in 2013 in order to mechanize the operation, increasing production throughput and efficiency. The Institute is waiting on the Demerara Harbour Bridge for approval to commence coating of the entire harbor bridge.

INSTITUTE OF APPLIED SCIENCE AND TECHNOLOGY
UNIVERSITY OF GUYANA CAMPUS,
TURKEYEN, GREATER GEORGETOWN,
GUYANA
TELEPHONE: (592) 222-4212-5, (592)-222-4218, (592)-222-5864
FAX: (592) 222-4229

For further information kindly contact:

Mr. DEONARINE JAGDEO
Director (ag.)

RAYANN HINCKSON
Confidential Secretary
r.hinckson@iast.gov.gy