Statistical Assessment on the Use of Crushed Oyster (crassostrea Iredalei) Shell as an Additive Material for Concrete

Chapter 1

THE PROBLEM AND ITS BACKGROUND

Introduction

Enormous amounts of oyster shell have been disposed of by farmers and consumers in the Philippines every year. According to Fisheries and Agriculture Organization of the United Nations, the Philippines have produced an estimated 36 million metric ton of oyster by the year 2010 [1]. With this amount of oyster produced, almost the same amount of oyster shell is wasted. Being surrounded by bodies of water, the country has abundant marine resources. Oyster farming is one of the most important production and activities for the country’s economy. Most of the oyster shells are discarded with no further use once the flesh is stripped off; except that some are used for reasons commonly as art decorative. As a result, piles of discarded shells are common in areas of oyster production with no further use. If the shell strength could be put to use instead of waste, then it would decrease the seafood waste impact on the environment, while also giving benefits for the construction industry [2]. Despite the effort of many organizations to lessen the amount of wasted oyster shell, oyster shell waste is still apparent in every place in the country. Oyster shells are composed of 97% calcium carbonate which is an ideal material for concrete blocks due to its hardness [3]. Due to the physical and chemical properties oyster shells, they can be an effective substitute and additive for aggregates. The crushed shells would be beneficial to stop the increasing waste problem and to help with the construction industry. When the shells get crushed they can be substituted or added for different aggregate types. In this study, we aim to utilize oyster shells in making concrete blocks and to evaluate the possibility of recycling this waste for use as a construction material. The testing consisted of five mix designs that contained crushed oyster shells and the mechanical characteristic of the concrete blocks with crushed oyster shell is to be tested in terms of its potential utilization as an additive material.

Background of the Study

        Throughout history, methods, techniques and procedures used for construction of buildings and infrastructures have varied through time. These variations have been proven to be effective because of the improvements that each method or technique has produced in order to achieve a much better output. In today’s era these methods have evolved into a more improved, more effective and more efficient than all the previous techniques that had been available. Though there were many changes in the methods used, there were still common things that each technique has shared such as the use of concrete or cement along with water and some additives like sand.

            Concrete has played a vital role in and even widely used during ancient times. During ancient times, “Egyptians used calcined gypsum as and the Greeks and Romans used lime made by heating limestone and added sand to make mortar, with coarser stones for concrete.”[4]. “The Romans found that cement could be made which set under water and this was used for the construction of harbors. This cement was made by adding crushed volcanic ash to lime and was later called "pozzolanic" cement, named after the village of Pozzuoli.”[5].

        Concrete is one of the most essential and the most commonly used construction material for various infrastructures and buildings. It also has an estimated 33 billion tons per year.  Concrete has also been used in different kinds of projects which ranges from the simplest forms such as pedestrian walkways up to the most durable infrastructures such as dams, high rises and bridges. Cement’s durability, strength and low cost have served as its backbone of structures in the infrastructure world. [6] Modern cements are made of limestones, silicon, calcium and often aluminum and iron.

        Cement is one of the ingredients in making concrete. As one of the ingredients, there are different types of cement available that can be used for making concrete. Those are Rapid Hardening Cement, Quick setting cement, Low Heat Cement, Sulfate resisting cement, Blast Furnace Slag Cement, High Alumina Cement, White Cement Colored cement, Pozzolanic Cement, Air Entraining Cement, Hydrographic cement [7]. Each type also has different uses and purpose depending on how it will be used. The type of cement used in almost all concrete is Portland cement [8]. Some types such as Blast Furnace Slag Cement and Pozzolanic Cement have their compositions mixed with Portland cement.  

        Concrete’s basic components such as water, cement and some aggregates or additive mixtures are still being used since the day it was made. While the basic components or ingredients have remained the same, various materials that can comprise with the use of cement and some aggregates or additives have been numerous. Some additives are constantly being evaluated for much better alternatives and to provide better quality for the cement or concrete. One example of a proposed additive in cement are seashells such as oyster shells, also known as “talaba” in the Philippines. Seashells such as oyster shells in the Philippines have been numerous. Using this numerous number of shells as an additive in cement may provide a cheaper alternative to increase the strength of a concrete or cement in which it could also provide a method to dispose the number of seashells.

        Considering the details mentioned, the researchers have opted to perform a statistical assessment on the use of crushed “talaba” shells (Crassostrea Iredalei) to test its effectiveness and usability.

Statement of the Problem

• Is there a small value of standard deviation for the sake of consistency in the making of the cubes?
• Does the compressive strength of the mortar cube correlate with the amount of crushed oyster (scientific name) shell added?
• What is the amount of crushed oyster shell should be added in order to gain optimal compressive strength?

Significance of the Study

          This study proposes a method of utilizing oyster shells as an additive in concrete.  It is about the effectiveness and efficiency of the shells specifically crushed as a medium in creating infrastructural concrete block. The shells being crushed into small grains will certainly produce different results than the other studies having the same material but different particle size. For efficiency, there is a high number and percentage of waste seashells in the Philippines, therefore efforts must be done not only for recycling but also finding ways producing products from these resources in attempt to reduce the large amount of waste, especially mineral waste.  The controlled variable will be the specified type of specie of the oyster shells that will be used as well as having a concrete block without any additive to also the test and observe the consistency of the production of the blocks. In terms of effectiveness; the compressive strength of each blocks made would tested. The data gathered will conclude whether the crushed oyster shells are effective as an additive material or not.