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Parepare City is located on the coast with significant fisheries and maritime potential. The processing and consumption of shellfish in this city produces a lot of shellfish waste, which is often not utilized and accumulates into an environmental problem. To improve the properties of concrete, several types of additives that have certain functions are added to the concrete mixture, namely increasing the workability, durability, and hardening time of concrete. This study aims to determine the compressive strength of concrete and the composition of coarse aggregate of shells with superplasticizer added materials that are optimally produced. Using an experimental method carried out at the Laboratory of Structure and Materials, Muhammadiyah University of Parepare. The results showed that substitution of coarse aggregate with 5% shellfish waste and 0.5% superplasticizer increased the compressive strength of concrete at the ages of 7, 14, and 28 days. The 10% substitution still meets the compressive strength requirements at 28 days, although slightly lower than normal concrete. Substitution of shells up to 5% increases the compressive strength of concrete, and the 10% content is optimal, reaching the maximum value without significant decline. It is recommended that the use of shells as a substitute for coarse aggregate does not exceed 10% for optimal results and meets the planned compressive strength of 25 MPa.

Concrete is an artificial stone made from a mixture of cement, sand, aggregate and water. For this reason, this construction material is considered very important to continue to be developed. One effort to develop is by improving the weak properties of the concrete itself. From this, researchers will use additional materials such as fiber palm fiber and sika visconcrate in the concrete mixture. Fiber fiber itself has durable properties and does not rot easily in open conditions or embedded in the ground, while sika visconcrate is a chemical that is used as an additive in the mixture to increase the workability, quality and strength of concrete with the desired properties. The method used in this research is quantitative experimentation. The aim of this research is to determine the characteristics of concrete using palm fiber and sika visconcrate with variations of 3%, 5% and 7% from normal concrete. The results of the research show that the average compressive strength of normal concrete is 25,572 MPa, 3% SI+SV variation concrete has an average of 27,365 MPa, 5% SI+SV variation concrete has an average of 26,704 MPa, and 7% SI+ SV variation concrete The average is 26,044 MPa. The split tensile strength test results of normal concrete averaged 6.074 MPa, 3% SI+SV variation concrete averaged 6.444 MPa, 5% SI+SV variation concrete averaged 7.852 MPa, and 7% variation concrete averaged amounting to 8,148 MPa.    

This study investigates the effect of roof tile waste used as a partial replacement for fine aggregate on the fresh and hardened properties of concrete, with the aim of promoting more sustainable and environmentally friendly construction materials. The research employed an experimental laboratory method with quantitative analysis. Roof tile waste was incorporated into concrete mixtures at substitution levels of 0%, 5%, 10%, 15%, and 20% by weight of fine aggregate. The workability of fresh concrete was evaluated using slump tests in accordance with SNI 1972:2011, while compressive strength tests were conducted on cylindrical specimens after 28 days of curing based on SNI 1974:2011 standards. The results indicate that increasing the proportion of roof tile waste reduced concrete workability, as shown by a decrease in slump values from 10 cm in the control mix to 8 cm at the 20% replacement level. Compressive strength also exhibited a declining trend, decreasing from 14.63 MPa to 11.90 MPa at the highest substitution, representing an approximate reduction of 18.7%. Nevertheless, concrete containing 5% roof tile waste achieved a compressive strength of 14.32 MPa, which is comparable to normal concrete. These findings suggest that roof tile waste can be utilized as a partial fine aggregate replacement at limited levels. A 5% substitution was identified as the optimal proportion to maintain acceptable workability and strength while supporting sustainable concrete development.

Self Compacting Concrete (SCC) is an innovative concrete that can compact itself (without vibrators) and flow under its own weight to saturate the shape without segregation. The SCC material is not much different from ordinary concrete, namely coarse aggregate, fine aggregate, cement, water, only SCC has additional ingredients such as superplasticizer. This research uses quantitative methods. The aim of this research is to determine the workability, compressive strength, flexural strength of SCC concrete with the addition of 2% fiberglass to each sample with added material in the form of sika visconcrete with variations of 0%, 1%, 1.5%, and 2%, % of the cement weight. Slump flow testing was carried out which was obtained from several variations of SV `0%, 1%, 1.5%, 2%, the slump flow values were obtained for 80 mm fiber concrete and 550 mm, 575 mm, 600 mm SCC concrete with the time taken to reach 500 mm of 4.25 seconds, 3.57 seconds and 2.11 for SCC concrete. The compressive strength value of the cylinder size (15 x 30) in samples BFS0, BFS1, BFS2BFS3 aged 28 days obtained a compressive strength of 30.29 Mpa, 34.44 Mpa, 31.23 Mpa, while the flexural strength test of the beam was 15 x 15 x 60 d samples BFS0, BFS1, BFS2BFS3 obtained results of 3.11 Mpa, 4.35 Mpa, 3.64 Mpa and 3.29 Mpa, excessive use of visconcrete in the concrete mixture can reduce the strength of the samples.