Sustainable Cement Utilization
[Enugu, Enugu State Nigeria]

SOURCES POZZLANAS IN NIGERIA
 POZZOLANAS FROM AGRICULTURAL SOURCES
- RICE HUSK ASH
- CORN STALK ASH

 POZZOLANAS FROM CLAY SOURCES
- CALCINED OR BURNT CLAYS
- POTTERY CLAY MATERIAL, SHALES

 POZZOLANAS FROM PULVERIZED FUEL ASH
- FLY ASH

Nigeria is West Africa’s largest producer of rice, producing an average of 3.5 million tons of paddy rice annually in the past 5-years. Also, corn production in Nigeria is now in excess of 5.0 million tons per year. Rice and corn cultivation is wide spread in the country, extending from the northern to the southern zones. The figure below shows the crop zones in Nigeria for the production of Pozzolanic ash materials. With appropriate local/home-grown technology spread all over in small village set-ups, Nigeria is in position to produce over 340,000 tons of pozzolanic materials per annum from rice husk and corn waste materials but this potential source of pozzolanas cement remain undeveloped

Source: NSE NATIONAL ENGINEERING CONFERENCE, BAUCHI ‘08
FIG. 12 Crop Zones In Nigeria for Production Of Pozzolanic Ash

2.6.5 POZZOLANAS FROM CLAY SOURCE

Also readily available in Nigeria are pozzolanic material of clay origin. Calcined or burnt clays were the earliest pozzolanas used, in the form of crushed reject clay bricks, tiles, or pottery which were mixed with lime to produce cement for mortars. This process is still used in many countries today and is known as Surkhi in India, Homra in Egypt and Semen Merah in Indonesia.

These also readily available in Nigeria are pozzolanic material of clay origin. Calcined or burnt clays were the earliest pozzolanas used, in the form of crushed reject clay bricks, tiles, or pottery which were mixed with lime to produce cement for mortars. This process is still used in many countries today and is known as Surkhi in India, Homra in Egypt and Semen Merah in Indonesia. These clay materials are readily available in Nigeria, but their potentials as source of pozzolanas cement remain unexploited.

POZZOLANAS FROM PULVERISED FUEL ASH lvi On a lower scale, pulverized fuel ash (PFA), often referred to as fly ash, is also available in Nigeria. The Udi hill coal mines and the Oji River coal powered electricity generating station as well residues from steel mills activities could be a regular source of PFA in Nigeria.

FIG. 12 Coarse Aggregate

Lack of political will from Government to practically implement research findings. Governments and Organized Private Sectors should have confidence in results of research findings in Nigeria and adequately support their practical applications. Real life sizes are hardly sponsored (constructed) in order to subject specimens to tests for real life studies. There are no enabling acts or law to make it compelling on government lvii agencies to fund practical implementation of research findings that might be of practical benefits to the nation.

In pursuance of policies of sustainable development, all tiers of Government should deliberately direct efforts at promoting rural and semi urban industrialization for the processing of these wastes to ‘wealth’ through cooperative societies. Today, in all rural communities, agricultural products like Rice Husk Ash and corn stalks, palm kernel and coconut shells and fibres, etc are regarded as mere wastes. There is no local technology developed for their conversion to Ash, clean aggregates and reinforcements.

FIG.13 Bamboo and Palm Fibres as Alternatives to Steel Reinforcement
Lack of political will from Government to practically implement research findings. Governments and Organized Private Sectors should have confidence in results of research findings in Nigeria and ad Since the sources of some of these substitutes being proposed are agro based, measures should be taken to discourage rural – urban migration and encourage people to take on to farming and cultivation of the plants and crops whose wastes form the sources for the substitutes.

Inadequate access to long term credit facilities from government and financial institutions by individuals and rural groups tends to work against the development of entrepreneurship that could set up the cottage type industry that would develop and employ the use of these substitutes in construction equitably support their practical applications. Real life sizes are hardly sponsored (constructed) in order to subject specimen. There is need for code of practice on these substitute materials to encourage the users as much works have been done on replacement of constituents of normal concrete with locally sourced alternatives for use in construction of low-cost housing.

There is need to encourage researchers who are getting tired of working and development substitutes to import structural engineering materials without the practical application of findings. Although many attempts have been made both by government and private sector to alleviate the problem of housing shortages by providing affordable housing scheme to all categories of the population but such efforts have not been too successful. The utilization of readily available indigenous biological materials such as Rice Husk Ash, Corn Stalks, oil palm fibres, bamboo, etc. has a great practical value and potential in the construction and housing sectors. Therefore, there is the need by government to exploit/encourage the use of these materials in the construction of houses. Specimens to tests for real life studies. There are no enabling acts or law to make it compelling on government agencies to fund practical implementation of research findings that might be of practical benefits to the nation.

In pursuance of policies of sustainable development, all tiers of Government should deliberately direct efforts at promoting rural and semi urban industrialization for the processing of these wastes to ‘wealth’ through cooperative societies. Today, in all rural communities, agricultural products like Rice Husk Ash and corn stalks, palm kernel and coconut shells and fibres, etc are regarded as mere wastes. There is no local technology developed for their conversion to Ash, clean aggregates and reinforcements Government strategy for housing in Nigeria should be to provide a variety of housing types for the people with a special emphasis on affordable housing for low-income, moderate-income and special (handicapped) people. Government, re-strategizing to provide people with more choices in housing types throughout the country should be an important part of vision 2020 strategy. Achieving this will depend greatly on material sourcing and availability.
In order to achieve the vision 2020 on Housing For All, the emphasis in Nigeria should be on the development of technology for processing and use of locally available alternatives to major constituent materials in concrete (reinforced/unreinforced) and blocks (Load bearing and non-load bearing) such as pozzolanas for cements, bamboo, oil palm fibres, coconut fibres for steel reinforcement, periwinkle shells for granite/gravels, laterite for fine sand to mention but a few.

2.7 Use of Cement-Sand Admixture in Laterite Brick Production for Low Cost Housing

Laterite was modified with 45% sand content by dry weight and stabilized with up to 9% cement content respectively and used in the production of 330 mm × 150 mm × 150 mm bricks through the application of a pressure of 3 N/mm2 with a brick moulding machine. Results showed that laterite used in this study cannot be stabilized for brick production within the economic cement content of 5% specified for use in Nigeria. However, bricks made with laterite admixed with 45% sand and 5% cement attained a compressive strength of 1.80 N/mm2 which is greater than the specified minimum strength value of 1.65 N/mm2. Cost comparison of available walling materials in Makurdi metropolis showed that the use of bricks made from 45% sand and 5% cement resulted in a saving of 30 - 47% when compared with the use of sandcrete blocks while the use of fired clay bricks resulted in a savings of 19% per square meter of wall. The study therefore recommends the use of laterite bricks in Makurdi and other locations because it is more economical and environmental friendly than fired clay bricks (Ehinola2008). In many countries, the need for locally manufactured building materials can hardly be overemphasized because there is an imbalance between the demands for housing and expensive conventional building materials coupled with the depletion of traditional building materials. To address this situation, attention has been focused on low-cost alternative building materials.

In Makurdi, the capital of Benue State of Nigeria and its surrounding towns, the most common walling materials are the conventional sandcrete blocks and fired clay bricks. The cost of sandcrete blocks coupled with the low strength properties of commercially available blocks necessitated the search for an alternative that was fired clay bricks. These are smaller than sandcrete blocks and therefore require more bonding mortar. The production of fired clay bricks is labour intensive and the process of firing is usually carried out using given species of trees (prosopis Africana and melicia excelsa) which could lead to their extinction and deforestation.
Firing of bricks requires great quantities of firewood and energy loss in the  form of heat is about 40-50%. In addition to the environmental problem, clay bricks can only be produced in locations where suitable clay soil deposits exist.

In Makurdi and other locations within Benue State, abundant lateritic soil deposits exist which can be harnessed for brick production. This potential is not being maximized. Compared to sandcrete blocks, it is economic to use laterite for brick production because very little cement is required and the cost of transportation is eliminated as production takes place on site. Compared to fired clay bricks, the production of laterite bricks does not involve the firing process. To cure the laterite bricks, they are by covered with tarpaulin and waterproof devices thereby making the process to be more environmental friendly. Laterite bricks are fire resistant and bulletproof.