Seashells and Oyster Shells: Biobased Fine Aggregates in Concrete Mixtures

The construction industry is the largest global consumer of materials, among which sand plays a fundamental role; now the second most used natural resource behind water, sand is the primary component in concrete. However, natural sand production is a slow process and sand is now consumed at a faster pace than it’s replenished. One way to reduce consumption of sand is to use alternative materials in the concrete industry. This paper reports the exploratory study on the suitability of aquaculture byproducts as fine aggregates in concrete mixtures. Seashell grit, seashell flour and oyster flour were used as sand replacements in concrete mixtures (10%, 30% and 50% substitution rates). All the mixtures were characterized in fresh and hardened states (workability, air content, compressive strength and water absorption). Based on compressive strength, measured at 7 and 28 days, seashell grit provided the most promising results: the compressive strength was found to be larger than for conventional concrete. Moreover, the compressive strength of the cubes was larger, when larger percentages of seashell grit were used, with the highest value obtained for 50% substitution. However, for oyster flour and seashell flour, only 10% sand substitution provided results comparable with the control mixture. For the three aggregates, workability of concrete decreases with fineness modulus decrease. For mixtures in which shell and oyster flour were used with 30% and 50% substitution percentages, it was necessary to increase the quantity of mixing water to allow a minimal workability. In conclusion, considering the promising results of the seashell grit, it is suggested to study further the characteristic of the material, also considering its environmental and physical properties, including acoustic and thermal performances. Higher substitution percentages should also be investigated. This research adds to the relevant literature in matter of biobased concrete, aiming at finding new biobased sustainable alternatives in the concrete industry.

The use of ceramics as an internal curing agent in high performance concrete with variable temperature curing to improve mechanical characteristics

Concrete curing is one of the most significant factors in the development of compressive strength, and a high temperature difference during curing may reduce strength. The microcracks created in the concrete as a result of the constant temperature change cause this exudation. Internal curing has become popular for decreasing the risk of early-age cracking in high-performance concrete by limiting autogenous shrinkage (HPC). This study looks at the effectiveness of internal wet curing offered by a new kind of aggregate called “recycled waste porous ceramic fine aggregates”. The evolution of measured mechanical characteristics is examined on three distinct HPCs, both with and without internal curing materials. Ceramic fine aggregates were used to replace two different quantities of regular weight fine aggregate. Ceramic fine aggregates were shown to be quite beneficial for internal cure. It has been discovered that incorporating 20% ceramic fine aggregates into HPC improves the properties of the material, resulting in low internal stress and a large improvement in compressive strength. It should be emphasized that, unlike some traditional lightweight aggregates, no loss in compressive strength has been seen for the various quantities of ceramic fine aggregates introduced at either early or later ages.

Effect Of Attapulgite as Internal Curing in High-Performance Concrete with Variable Temperature Curing to Enhance Mechanical Properties

One of the most important elements in the development of compressive strength is concrete curing, and a large temperature differential during curing may decrease strength. This exudation is caused by microcracks in the concrete caused by the continuous temperature fluctuation. By minimizing autogenous shrinkage, internal curing has become popular for reducing the danger of early-age cracking in high-performance concrete (HPC). The efficacy of internal wet curing provided by fine Attapulgite aggregate is investigated in this research. On three different HPCs, both with and without internal curing materials, the development of observed mechanical properties is investigated. Two different amounts of normal weight fine aggregate were replaced with attapulgite fine aggregates. Internal cure has been found to benefit from attapulgite fine aggregates. It has been found that adding 20% Attapulgite fine aggregates to HPC enhances the material’s characteristics, resulting in low internal stress and a significant increase in compressive strength. It should be noted that, unlike certain conventional lightweight aggregates, the different amounts of Attapulgite fine aggregates added at various ages have shown no decrease in compressive strength.

Experimental Study on Strength of Pervious Concrete by Using Fine Aggregate

Pervious concrete is a special type of concrete, which consists of cement, coarse aggregates, water and if required and other cementations materials. As there are no fine aggregates used in the concrete matrix, the void content is more which allows the water to flow through its bodyThe main aim of this project was to improve the compressive strength characteristics of pervious concrete. But it can be noted that with increase in compressive strength the void ratio decreases. Hence, the improvement of strength should not affect the porosity property because it is the property which serves its purpose. In this investigation work the compressive strength of pervious concrete is increased by a maximum of 18.26% for 28 days when 8% fine aggregates were added to standard pervious concrete Keywords: W/C ratio, pervious Concrete, sugarcane bagasse’s ash, rice husk ash compressive strength, fine aggregates

Analisis Karakteristik Serbuk Sabut Kelapa (Cocopeat) Sebagai Agregat Halus pada Campuran Beton

The advantages of coconut coir powder (cocopeat) are resistant to microorganisms, weathering and resistant to mechanical spelling, namely friction and blows. Based on these advantages, cocopeat can be used as a blend of fine aggregates in the manufacture of concrete. The sieve test was conducted on the cocopeat to determine the initial feasibility analysis of cocopeat as a blend of fine aggregates in the concrete manufacturing. The results of the cocopeat sieve test are that cocopeat is included in Region II which is classified as a fine module of slightly coarse grains with a fine module of fine aggregate grains of 2.37. This shows that cocopeat has a fairly good value in normal concrete mixtures but is not suitable for high resistance concrete mixtures that exceed 25 MPa. This was followed by a subsidence test that gave subsidence values for mixtures of concrete with a cocopeat composition of 25%, 50% and 75%, is 7.5 cm; 5.3 cm; and 2.2 cm. While a good subsidence ratio is used in the range of 6-18 cm. In addition, the concrete with a 25% blend of cocopeat has a stronger physical form and there are no fungus growing on the surface of the concrete. Meanwhile, concrete with a mixture of 50% and 75% cocopeat looks more fragile and forms molds on the surface of the concrete. Thus the concrete with a mixture of 25% cocopeat has better results.

A STUDY ON DIFFERENT PROPERTIES OF CEMENT MORTAR BY PARTIAL REPLACEMENT OF FINE AGGREGATE WITH BOTTOM ASH

This paper consists of the results of an experimental research on the effect of bottom ash as partial replacement of natural sand on the properties of cement mortar. The experimental works were carried out by replacement of fine aggregate with varying percentages of bottom ash i.e. 15%, 20%, 25% and 30%. As the microstructure of mortar matrix changes with varying water cement ratio, the w/c was kept constant i.e. 0.45.Mortar cubes of 70.6mm×70.6mm×70.6mm were casted and vibrated on an electrically operated vibrator. Then various tests including compressive strength, water permeable porosity (apparent porosity), percentage of water absorption, sorptivity were performed on mortar cubes replaced with bottom ash. The results were compared with the results of control mix and all the tests were performed at 3, 7, 28, 56 and 90 days. Based on the results, it is concluded that fine aggregates can be replaced up to 20% with bottom ash in cement mortar.

Evaluating the Possibility of Replacing Natural Fine Aggregates in Concrete with Recycled Aggregates

This paper presents an investigation on the possibility of replacing natural fine aggregates with recycled aggregates in concrete. The studied recycled aggregates were acquired from crushed waste concrete from demolishing works. The rate of replacement of natural fine aggregates was 10%, 20%, and 30% by weight. Compressive and flexural tensile strength of concrete incorporating recycled aggregates was investigated at 28 days of curing. The results show that the compressive and flexural strength of concrete is strongly affected by the percentage of recycled aggregates. It has been found that the strength decreases linearly with increasing recycled aggregate content. So, in order to apply recycled waste to concrete as fine aggregates, it is necessary to perform supplement research with appropriate additives to compensate for the loss of compressive and flexural strength.