Compressive Strength of Concrete and Mortar Containing Ashes as Partial Replacement for Cement

Compressive Strength of Concrete and Mortar Containing Ashes as Partial Replacement for Cement

Chapter One

Aim and objectives

This research work is aimed at determining the influence of three ashes i.e. RHA, POHA, and CHA on the fluidity and compressive strength of mortar and concrete.

The objectives of this research work are to:

Determine the physical and chemical properties of cement and ashes.
Determine the physical properties of aggregates.
To evaluate the fresh concrete properties containing the ashes partially replaced with cement at different
Determine the compressive strength of concrete and mortar containing these ashes separately.

CHAPTER TWO

LITERATURE REVIEW

Nowadays, for the concrete production, the majority of the commonly used cement is ordinary Portland cement (OPC). For these, the cost of cement is continuously rising and natural resources are reducing (such as clinker i.e. cement raw material). Cement acts as the main ingredient for the production of concrete. The demand of cement is increasing day by day for the mentioned reasons. During the cement production, clinker is burnt at about 1450⁰C (Neville, 1995) consequently huge amount of CO₂ is emitted to the atmosphere. Hence the temperature of the globe is increasing which is one of the reasons for climate change. About 7% of world’s CO₂ is produced from the manufacturing of cement. In consequence, global warming is increasing continuously (Mehta, 1999). To solve these, researches in cement and concrete technology have been concentrated on the use of waste material as a potential alternative to cement in the construction industry.

During recent decades, about thousands of tons of palm oil husk ash (POHA) are produced yearly by operation of 200 palm oil mills in Malaysia and most of these POHA are normally disposed for landfill without any commercial return (Awal, 1997). Over half of the world’s total palm oil is produced from the oil palm industry in Malaysia; the country has a plan to grow further with the world increase in vegetable oil demand. Though, environmental pollution is also increased for this palm oil sector, annually 2.6 million tonnes of solid waste is produced in the form of oil palm shells (Basri, 1999). The production of oil palm is increasing according to the demand; as a result the production of POHA is rising every year. Now, POHA has become an important environmental disposal issue. Malaysian government desires to focus for assigning more hectares of land for

disposal of these huge amounts of waste; and financial losses are also involved for transporting as well as handling purposes of these wastes. Similar problem has been shown for the production of slag – a by product from the still mills, rice husk ash – a waste from rice processing mills, and saw dust ash/ash from timber. However, dumping issues of these waste and environment sustainability can be ensured by proper utilisation or recycling of these materials. Recently, many researches have been performed in cement and concrete technology for the use of biogenic wastes – POHA and rice husk ash Awal and Hustin (1997); Basri et al (1999); sawdust ash Elinwa and Mahmod,( 2002) and bagasse ash (Chusilp, 2009)–as constituents in concrete. On the other hand, slag and fly ash have been used in cement and concrete as a supplement for many years, more than a century. All of these wastes contained a high amount of silicon dioxide in amorphous form and as a result they could be used as pozzolanic materials. Besides, strength and durability properties of concrete containing these ashes are improved significantly, as stated in different published literatures. Therefore, mentioned problems regarding cement production, waste material and environmental pollution can be controlled or minimized with proper consumption of these wastes during cement manufacturing and concrete production which will meet the concrete requirements. These wastes are abundantly available in Malaysia, thus, there is a great opportunity of producing concrete from Malaysia’s industrial by-products and biogenic wastes and today it is an important issue for the sustainable development that needs to be addressed.

Sustainability and Sustainable Concrete

Today, sustainability is a key issue for the global concrete industry. Achieving sustainability has become more and more important question all over the world during the last decade. It is well known that sustain means to support or to maintain a process going, and the objective of sustainability is that life on the universe can be sustained for the projected future. Environment, economy, and society are the components of sustainability. At the present time, the environment is probably the most important component, and an engineer or architect exercises sustainability to reduce negative impact on the environment. Thus, the word sustainable tends to be identical with environmentally sound or friendly and green Leslie and Jonathan. Large amounts of low cost building materials (Portland cement concrete) is required for the construction of infrastructure due to rapidly industrialising world and this trends will be continued. The unlimited use of natural resources and huge amounts of environmental pollution is a principal caution for the preservation of the life- sustaining environment on the globe. Why the problem of sustainable industrial development has recently considered enormously significant? A difficult question that we have to identify is how a sustainable development will be executed (Mehta, 1999). The various related concerns which lead us to the way of sustainable development that are mentioned below (Meyer, 2002):

Previous mistake could be cured by purifying the polluted water and
Reducing the global warming by neglecting the contamination of air, water and soil, as well as CO₂
Balancing between consumption and generation of natural resources (material orenergy).
Searching for equilibrium between economic development and preservation of the environment (upgrading social life and the living standard by avoiding the disturbance of environment as much aspossible).

However, for developing sustainability and sustainable concrete, engineers who are related to the concrete construction have to perform active responsibility in this area. They have professional duty to inform and teach clients, the public and fellow engineers about: the current building codes and laws, the long term benefits from using new environmentally- friendly technology and higher quality, durable designs. Engineers also take the following special responsibility to develop a world view in problem solving which considers the effects of infrastructure decisions on the earth and on all living things (Fredrik, 1999):

For the conservation and preservation of present resources, engineers should to be aware and
Environmentally friendly technology could be implemented by their direct participation in order to execute a more sustainable future; and,
They must apply a valuable leadership in this

CHAPTER THREE

MATERIALS AND METHODS

Materials

Tests were conducted to assess the properties of the constituent materials which include the cement, Palm oil fuel ash (POFA), Rice husk ash (RHA), Coconut hush ash (CHA), coarse aggregate and fine aggregate (sand) at the Department of Civil Engineering Concrete laboratory Ahmadu Bello University Zaria (A.B.U).

Cement

This includes the Plain Cement (OPC) and Cement Partially Replaced with POFA, RHA and CHA:

Consistency Test (%)

The test was carried out in accordance with BS 4550: Part 3: Section 3.5:1978 using Vicat apparatus with plunger. Cement paste of standard consistence has a specified resistance to penetration by standard plunger The water required for such a paste is determined by trial penetrations of pastes with different water contents. Content of water was expressed as percentage by mass of the cement. Table 3.1 show the result:

CHAPTER FOUR

ANALYSIS AND DISCUSSION OF RESULTS

The constituent materials used for the concrete and mortar mix as stated in chapter three are: cement, fine and coarse aggregates, rice husk ash, palm oil fuel ash, coconut husk ash and water. The properties test results of these materials and their effect on concrete and mortar are thus tabulated, compared and discussed below.

Properties of Constituent Materials

Properties of Cement and Cement/Ash Paste (RHA, POHA & CHA): Table 4.4 show the results for the physical properties of plain cement paste and cement paste containing ashes. The results highlight the consistency, setting time and soundness of the materials which indicates an increase in the consistency with increase in the percentage of the ashes i.e. RHA, POHA and CHA. This implies that the quantity of water required to keep the mix in a uniform paste has increased and this can be attributed to the increase in particle size and carbon content from the ashes. This is similar to Al-Khalaf and Yousif (1984).

CHAPTER FIVE

CONCLUSIONS AND RECOMMENDATIONS

The Partial replacement of Agro-waste ashes (RHA, POHA and CHA) with cement in concrete and mortar production has gained considerable importance because of the requirements of environmental safety and more durable construction in the future. The use of these ashes as partial replacement of cement in mortar and concrete has extensively been investigated.

Based on the experimental results, the following conclusions and recommendations can be drawn.p

Conclusions

Low cost concrete and mortar using RHA, POHA and CHA as partial replacement with cement in concrete and
The utilisation of RHA, POHA and CHA in concrete and mortar will solve the problem of its disposal thus reducing waste material from the
Concrete with POHA at 20% replacement after 28 days of standard curing is considered to be optimum for normal or moderate strength concrete. RHA and CHA ash at 15% – 25% replacement are considered low strength concrete. This is due to the fact that RHA and CHA with 15% -25% replacements have compressive strengths that are inferior in all stages as compared with control at 0% replacement. Thus, concrete with RHA and CHA ash with 15% – 25% replacement will have a negative effect on the compressive strength of the concrete.
Percentage replacement of POHA and CHA ashes in mortar up to 20-25% could be desirable for some application of

Recommendations

The Agro waste ashes (RHA, POHA and CHA) should be used in Civil Engineering construction works to reduce environmental pollution and also reduce the cost of concrete and mortar production.
It is recommended that the POHA should not exceed 20% of the weight of cement in concrete production for best
It is also recommended that the RHA, POHA CHA should be within the range of 20-25% replacement of the
It is recommended to explore the effect of chemical admixture and other additives such as super-plasticizer and silica fume in other to enhance its workability and strength.

REFERENCES

ACI, Committee, (1996). “Use of Fly Ash in Concrete”, ACI, 232.2R-96.
ACI, Committee, (2001). “Use of Raw or Processed Natural Pozzolanas in Concrete”, In ; Committee Report, pp. 1-10. ACI, Farmington Hills, Michigan. Pp1-19.
Ahmadi, M .A, Alidoust, O, Sadrinejad, I and Nayeri, M. (2007), “Development of Mechanical Properties of Self Compacting Concrete Contain Rice Husk Ash”. http://www.waset.org/publication/7882
Altwair, N. M. And Kabir, S. (2010) “ Green Concrete Structure by Replacing Cement With Pozzolanic Materials in Reduce Greenhouse Gas Emissions for Sustainable Environment”. 6
Apata. A.O. and Alhassan, A. Y, (2012), “Evaluating Locally Available Materials as Partial Replacement for Cement”, Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 3 (4): 725-728 © Scholarlink Research Institute Journals, (ISSN: 2141-7016) ,jeteas.scholarlinkresearch.org.

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