Particle Size Effect of Oyster Shell on Mortar: Experimental Investigation and Modeling

Abstract

In order to solve the problem of lack of natural river sand, crushed waste oyster shells (WOS) were used to replace river sand. By replacing 20% river sand, WOS mortar with different particle sizes of WOS were made for the experiment. Through experimental observation, the initial slump and slump flow loss rate were studied. The effects of different particle sizes and curing times on the compressive strength, flexural strength, static elastic modulus, and dry shrinkage of WOS mortar were analyzed. The relationship formulas between the compressive strength, flexural strength, particle size, and curing age were proposed. The results showed that the setting time and slump flow decreased with a decrease in the particle size of WOS. It was also found that the mortar with fine crushed WOS had high compressive strength, flexural strength, and static elastic modulus at both early and long-term curing age. A formula was proposed to describe the development of the compressive strength with the particle size of WOS and curing time, and the relations among these mechanical properties were discussed. Furthermore, drying shrinkage increased when WOS was used and could not satisfy the standard requirement of 0.075%. In contrast, the addition of fine WOS and double-dose sulfonated naphthalene-formaldehyde superplasticizer (SNF SP) reduced the shrinkage rate of the mortar by 8.35% and provided better workability and mechanical properties for mortar.

Engineering Properties of PVA Fibre-Reinforced Geopolymer Mortar Containing Waste Oyster Shells

“…F0 exhibited a significantly high drying shrinkage, and its drying shrinkage at 28 d was 0.88%. The 28 d drying shrinkage of cement mortar containing 20% WOS aggregates was about 0.048–0.061% [ 1 ], whereas that of the geopolymer mortar was 0.88%. The geopolymer mortar in this study exhibited a much higher drying shrinkage than the cement mortar.…”

“…This accounts for the geopolymer mortar’s greater drying shrinkage than cement mortar. Second, WOS aggregates have a higher water absorption than river sand [ 1 ], which reduces the amount of capillary free water retained in matrix. This causes a higher loss of capillary free water and results in a higher drying shrinkage of the mortar containing WOS aggregates than that containing 100% river sand.…”

“…The ratio of activators to precursors was 0.6, and that of fine aggregates to precursors was 1.6. The replacement ratio of river sand with WOS aggregates was 20%, which was recommended by Liao et al [ 1 ] and Liu et al [ 3 ].…”

“…Oysters are a common aquatic product. In 2010, China’s oyster shell production reached 5 million tons [ 1 ]. The global quantity of waste oyster shells (WOS) is about 200,000 million tons per year [ 2 ].…”

“…Crushed WOS also have a lot of potential as an aggregate in cement mortar and concrete. [ 1 , 3 , 11 , 12 ]. WOS aggregates have the following benefits of sustainability relative to river sand.…”