A Comparative Study on the Mechanical Properties of Pulverized Crassostrea gigas (Oyster) and Perna viridis (Mussel) Shells as Cement Block Aggregates

Abstract

INTRODUCTION

Pollution caused by massive waste seashells had been one of the greatest problems in the Philippines (Galiotto, 2013). These shell wastes that are disposed from households, seashores, markets, and farms are dangerous to the environment if not carefully managed. Thus, recycling these seashells is helpful to decrease the waste materials in the environment. This research study aimed to incorporate oyster and mussel shells as aggregates in cement block production which minimized the waste pollution caused by the seashells. Moreover, it was also done to improve the cement blocks' mechanical properties since cement blocks made within the country are generally weak.

METHODS

Oyster and mussel shells were gathered and pulverized after being cleaned. The pulverized seashells were added to the formulation. Different setups of blocks for compressive strength and water absorption test were prepared. The cement hollow blocks were cured for 7 and 14 days and were tested for their mechanical properties after curing. in addition, three trials were done on each setup to get more accurate results. The test results were subjected to two way-ANOVA statistical test to determine if there are significant differences between the data.

RESULTS

Results showed that the cement blocks with oyster shells yielded the highest compressive strength with an average of 2.26 MPa for 7-day cured setup and 3. 74 MPa for 14-day. Also, the cement blocks with mussel shells have the lowest absorption rate of (+)11.4% and (+) 15.6% for the 7 and 14-day curing period. Also, it was revealed that the curing period affects the blocks as it was directly proportional to the compressive strength and water absorption rate. After subjecting to two-way ANOVA, the results yielded P-values of 0.17 and 0.67 for the compressive strength and water absorption test respectively. Seeing that the P-values are greater than the significance level, it was then declared that there is no significant difference between the data values.

DISCUSSIONS

The results revealed that all the cement blocks except for common blocks have passed the standard compressive strength and only the cement blocks incorporated with mussel shells for water absorption. The results were affected by the curing period as the longer curing time strengthens the cement blocks but lessen its capability to resist water. This means that incorporating the waste seashells as aggregates can strengthen the blocks and lessen the pollution in the environment.