The stabilization of soil through the addition of fly ash has been shown to be an effective alternative for improving the strength and stiffness of soil through the resulting chemical reactions. The chemical reaction that occurs dissociates the lime (CaO) in the fly ash, and the establishment of cementitious and pozzolanic gels (consisting of calcium silicate hydrate (CSH) gel and calcium aluminate hydrate (CAH) gel) binds the soil particles and increases the strength and stiffness of the soil. Investigations into the mechanical properties of sands stabilized with fly ash (fly-ash-stabilized sands) were conducted through a series of unconfined compressive strength (UCS) and direct shear strength tests for various fly ash percentages, curing times, grain sizes, degrees of saturation during sample preparation, and content of fines. It was found that the mechanical properties—UCS and direct shear strength (DSS)—of fly-ash-stabilized sands increased with both increasing fly ash content in the specimen and curing time, but decreased with increasing grain size, degree of saturation during sample preparation, and content of fines. The results indicated that fly-ash-stabilized sands required more than a month to attain their optimum performance with regard to binding sand particles.

Nickel slag is one kind of nickel ore smelting waste after the combustion process. Production of nickel slag PT. Antam Pomalaa Kolaka Southeast Sulawesi province during the period 2011-2012 period approximately 1 million tons of slag / year, with a nickel content in ore processing of nickel is between 1.80% to 2.00%. Visually, the physical form of this nickel slag aggregate resembles. Research on the use of nickel slag as an aggregate in concrete mixture is carried out using a cylindrical specimen with a diameter of 15 cm and 30 cm high by 48 pieces were tested at 28 days with some variations in the mix. Variation 01, 100% natural aggregate, variation 02, nickel slag as coarse aggregate, variation 03, nickel slag as fine aggregate, and variation 04, nickel slag as coarse aggregate and fine aggregate. Aggregate gradation in the mixture is set and is designed so that it meets the specifications gradation mix for maximum aggregate size of 40 mm. The composition of the concrete mixture used is a mixture of concrete with the ratio of cement : fine aggegate : coarse aggregate is 1: 2: 3 in a weight ratio with cement water ratio (fas) is set at 0.5. The results showed that when compared with the use of natural agregate, terak nickel is used only as a coarse agregate, a fine agregate only and combined agregate coarse and fine agregates resulting slump values ??fell 39.47%, an increase of 55.26%, and an increase of 34.21%. As a coarse agregate, terak nickel increases the compressive strength, modulus of elasticity and splitting tensile strenght, respectively for 42.27%, 19.37% and 23.46%. As fine agregate, nickel terak resulting value of compressive strength, modulus of elasticity and tensile strength divided down respectively by 16.75%, 6.70% and 24.58%. As a combination of coarse and fine agregate, terak nickel increases the compressive strength, modulus of elasticity and splitting tensile strenght, respectively for 10.31%, 9.26% and 6.70%.

This study is a follow-up of nickel slag waste used for building construction materials. Paving blocks were made using a mixture of cement and aggregates in a ratio of 1: 3 and 1: 5 which used a mixture of nickel slag waste and natural sand with aggregate gradation in zone III of the rather fine sand category based on SNI 03-2834-2000. Sand substitution with nickel slag waste has used a variation of the composition of the mixture of 0% (without slag), 25%, 75%, and 100% (without sand). The behaviour would be obtained the compressive strength value of paving blocks and average water absorption. Paving blocks compressive strength were tested at the age of 28 days, while the average value of water absorption was performed by immersing the paving block specimens for 24 hours. The physical strength and absorption value of paving block water refer to SNI 03-0691-1996. The results showed that the use of nickel slag waste in making paving blocks could increase the compressive strength of paving blocks, while water absorption in all compositions and variations of the paving blocks mixture was decreased in line with the increase of nickel slag composition.

This study analyzed the effect of blood clamshell substitution (Anadara granosa) on the mechanical properties of concrete, namely compressive strength and flexural strength, using clamshell material originating from the Bungkutoko island region, Abeli District and Toronipa coastal area Soropia District, Konawe Regency, Southeast Sulawesi Province. In this study, the concrete was made using blood clamshell (Anadara granosa) waste as a substitute for coarse aggregates. As a control, normal concrete was made using natural materials, namely the Moramo split and Pohara sand. The results show that partial substitution of coarse aggregates using blood clamshell concentrations of 15%, 25%, and 50% reduced the compressive strength of concrete by 11.00%, 16.20%, and 30.62% when compared to the control, respectively. Meanwhile, the respective concrete bending strength also decreased by 7.33%, 13.83%, and 32.53%. The compressive strength testing of 28 days-concrete with the shellfish compositions of 15% and 25% showed the values of 25.35 MPa and 23.87 MPa, respectively, which can be categorized as a medium-quality concrete (structural concrete). Meanwhile, the 50% shell composition had a compressive strength of 19.895 MPa, which can be categorized as a low-quality concrete (non-structural concrete).

This paper is a continuous study that outlines Self Compacting Concrete (SCC) behavior on high strength concrete with nickel slag as fine aggregate. The percentage of nickel slag substitution as fine aggregate varies from 0% to 100% with an increase of 25%. This laboratory study aims to obtain the effect of seawater curing on the concrete compressive strength. The specimens immersed in seawater for 220 days will provide a SCC behavior assessment towards seawater immersion. The results obtained show that concrete with 25% nickel slag gives the most maximum effect. Compared to concrete without slag, SCC with 25% nickel slag has a higher compressive strength of 17%. Besides, the slump test also showed good condition. All specimens using nickel slag in seawater immersion show greater strength when compared to non-slag concrete. This means that concrete is very suitable at a curing age of 220 days when substituted with nickel slag. The mixture using nickel slag of 100% (SCC100 specimen) illustrates a reasonably stable strength from 28 days of immersion.