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

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Objectives:

- The study aims to observe and test the usability of waste oyster shells in the Philippines incorporated into a concrete mix as an additive to reduce the amount of shell waste.

Specific Objectives:

- To obtain a small value of standard deviation and mean among the blocks with the same amount of additives.

- To ascertain whether concrete blocks from different percentages of shells will produce data and results that will show a behavior or pattern of their compressive strengths.

- To test the initial hypothesis if the amount of additive in the cubes will be accepted.

Scope and Limitations

In the study to find the effects of added oyster shells in a standard cement mix, multiple factors are to be considered affecting the experimentation that results in the variation of data acquired.

In the experiment, a standard cement mix, which is 2 parts cement and 3 parts sand, for the base mixture and then different percentage of crushed oyster shells were added. The fact that the crushed a shells is a dry ingredient and is subject to absorb water, thus adding more water to the mixture as the percentage of oyster shells increases is required. Another factor to be considered in this experiment is the formation of the mortar cubes.

Since improvised molds are used, the firmness of the cement is not constant for each mixture, making some mortar cube with the same mixture differ with their strength. The amount of time given the mortar cubes to dry is another variable that may affect the strength of each cube. Though each mortar cube is constructed at the same time, the effect on each will be the same on each mortar cube. Thus, effects on data variation are negligible.

Definition of Terms

- Additive - agent or factor that, when combined with other agents and factors, adds to their cumulative effect or strength usually by a known degree or extent [9].

- Aggregate - in building and construction, is a material used for mixing with cement, bitumen, lime, gypsum, or other adhesive to form concrete or mortar. The aggregate gives volume, stability, resistance to wear or erosion, and other desired physical properties to the finished product. Commonly used aggregates include sand, crushed or broken stone, gravel (pebbles), broken blast-furnace slag, boiler ashes (clinkers), burned shale, and burned clay[10].

- Calcium carbonate - or CaCO3, comprises more than 4% of the earth’s crust and is found throughout the world. It’s most common natural forms are chalk, limestone, and marble, produced by the sedimentation of the shells of small fossilized snails, shellfish, and coral over millions of years [11].

- Compressive strength - is the maximum compressive stress that, under a gradually applied load, a given solid material can sustain without fracture. Compressive strength is calculated by dividing the maximum load by the original cross-sectional area of a specimen in a compression test [12].

- Flexibility- refers to the ability of a material to undergo bending without cracks or other failures being built [12].

- Soil structure - describes the way the sand, silt and clay particles are clumped together. Organic matter (decaying plants and animals) and soil organisms like earthworms and bacteria influence soil structure. Clays, organic matter and materials excreted by soil organisms bind the soil particles together to form aggregates [13].

- Soil texture - refers to the size of the particles that make up the soil and depends on the proportion of sand, silt and clay-sized particles and organic matter in the soil [13].

Chapter 2

REVIEW OF RELATED LITERATURE AND STUDIES

The review of the literature for this study focuses on procedures used to strengthen the quality of cement. The review focuses on a number of different things and ways to identify and use Talaba shells as an additive to intensify the product produced. This chapter includes foreign and local studies featuring the use of Talaba shells in ceramic, concrete and cement industry. It also includes some background information about Crassostrea iredalei (Talaba).

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Figure 2.1 - Crassostrea iredalei (Talaba)

Crassostrea Iredalei : Composition and Industrial Uses

Based on recent studies, about ninety seven and a half percent (97.5%) of the chemical composition of Talaba shell is Calcium Carbonate (CaCO3) or limestone [1]. Calcium carbonate or limestone is widely used in cement brick and ceramic tiles making for its high compressive strength and boiling point. Limestones are also used in the production of old style brick ovens. [2]. The huge amount of Calcium Carbonate in oyster shell is the main reason why it is suitable as an additive component in making Concrete mortar cubes. Aside from Calcium Carbonate, Talaba shell also contains a small amount of Aluminum, Iron, Manganese, Strontium, Magnesium and Sodium [1].

On a physical analysis done, calcium carbonate is found to have a dry brightness of 92.1, moisture at 105°C of 0.084%, oil absorption of 18.9g oil per 100g of oil, specific surface area of 0.423m2/g, weight/solid per gallon of 23.1lbs, specific gravity of 2.71, pH of 9.8, hexagonal particle shape, and density of 1.1 g/cm .Its general uses includes synthetic/cultured marble, ceramic floor tiles, stucco, caulking compound, building products, polishing compound, grouting and thin set mortars, abrasive in powdered cleansers, sealants, adhesives, putty, and glues, paints (water-based), animal feeds, insecticides, plastics, PVC pipes, carpet underlays and paper [3].

Aside from ceramic and cement industry, researchers in Florida and China have successfully developed a new oral Calcium supplement out of Talaba shell [4]. Moreover, powdered Talaba shells are now used as fertilizer and animal feeds. Studies shown that finely crushed oyster shells raises pH in acidic soils. It also has other nutrients and micronutrients, which keeps the natural balance of the soil [14].

Ceramic Tile Industry

Tiles are similar to concrete. They differ in uses, in shapes, and in finishing. While a concrete may be in the form of a block, a tile is in the form of a sheet. Both are made from the same process and materials but the tile may go through glazing which can give it a smooth