Higher Compressive Strength Values Research Articles

Compressive behavior of additively manufactured lightweight structures: Infill density optimization based on energy absorption diagrams

The use of 3D-printed components as load-bearing structures is widely studied, while their use as energy absorbers constitutes a gap in the additive manufacturing (AM) field. Most of the reported works address the compressive behavior of AM parts up to low strains (<15%), thus omitting many important properties. Therefore, this paper presents the compression characterization of Polylactic Acid (PLA) samples with different infill densities-IDs (10–100% range, with a step of 10%) fabricated by material extrusion (MEX) AM process. The physical (dimensional accuracy, printing time and sample mass) and mechanical (elastic, strength, strain and energy absorption) properties are determined and discussed in detail, along with the failure mechanisms that occur in the samples. Moreover, an ID optimization is performed based on the energy absorption diagrams (EAD), a unique approach in the AM field. The highest values of compressive strength (81 MPa) and modulus (1306.6 MPa) are found for 90%-ID, over 2.2% higher than those obtained for 100%-ID. On the other hand, based on three different approaches, EAD identified 30%-ID as optimal. The 30%-ID samples absorb the largest amount of energy (12 MJ/m3) at the lowest (ideal) peak stress value (23.57 MPa), which is 69.1% lower than that for 100%-ID. At low IDs (<30%), the samples exhibit a brittle behavior, changing to a ductile one with the increase of ID (≥40%). The MEX-printed PLA samples show a dimensional relative error below 0.15%, and the optimization process reduces the amount of filament material by 54.3% and the printing time by 42.7%.

Selective laser melting of partially amorphous regolith analog for ISRU lunar applications

As the idea of crewed outposts on the Moon gains momentum, In-Situ Resource Utilization (ISRU) technologies tend to become imperative to fulfill astronauts' needs. This article explores a way to use the lunar regolith as a source material for the additive manufacturing of complex objects, based on the selective laser melting (SLM) technique. A lunar regolith analog, Basalt of Pic d’Ysson (BPY), is used as a starting point for this study, to investigate the now demonstrated impact of amorphous analog content in the powder bed, substrate type, and post-SLM annealing treatments on the mechanical properties of 3D-printed objects. Improvements to the manufacturing and sample extraction stages are proposed to systematically reproduce the high compressive strength values obtained, thus contributing to the robustness and reliability of the process.

Importance of pumice amount in the design of self-compacting lightweight concrete

Although concrete has high compressive strength values, it has a heavy unit volume and low tensile strength. In this study, the normal-weight aggregate, which takes up the most space in concrete by volume and mass, was partially replaced with pumice aggregate, and macro steel fiber (30 mm) was also added to the mixtures. This experimental work aims to investigate the effect of pumice aggregate amount on the fresh and hardened properties, as well as the flexural performance of the self-compacting lightweight concrete (SCLC). The replacement proportions of pumice aggregate with crushed sand were arranged as 45%, 50%, and 55% of the entire aggregate by weight. Three mixtures, each with 1% macro steel fiber reinforcement and without fiber, were prepared for each mixture scenario. The mix design of these six mixtures was arranged to achieve the self-compacting ability and the workability tests recommended by EFNARC (slump-flow, T50, J-ring) were taken into account. To investigate the mechanical properties (compressive, splitting tensile, and flexural strengths) and flexural toughness of the samples, the specimens were cured in water at 23±2 °C for 28 days. As a result, the unit volume weights of the specimens produced from pumice-substituted mixtures decreased with the increase in the pumice dosage, while the compressive, splitting tensile, and flexural strengths decreased. However, it has been determined that all SCLC mixtures including pumice aggregate provided workability properties in general and had enough compressive strength to be used in the production of structural bearing elements, regardless of fiber content. As a result, the optimum pumice aggregate replacement percentage with crushed sand was found to be 45% and the best flexural performance values of the specimens having macro steel fiber were observed in the ones having 45% pumice aggregate substitution.

Pengaruh Penggunaan Zeolit dan Serat Agave Sisalana Terhadap Kuat Tekan dengan Metode Self Compacting Concrete (SCC)

Self Compacting Concrete (SCC) is concrete innovation which does not require vibrations during installation and compaction. SCC concrete can flow freely with its weight and is capable of filling a mold well, ensuring perfect compaction without vibration. In 1988, in order to eliminate or reduce the need for vibration to achieve density and thereby reduce the labor required for concrete placement, SCC was developed in Japan. In this research, the production of SCC was investigated by replacing the fine aggregate in the SCC mixture by 3%, 7% and 11% of zeolite material and by adding 0.005% of agave sisalana fiber of cement weight. The 15/30 cm concrete cylinders were used in 16 samples for compressive strength. It is shown that the values of flowability, filling capacity, and permeability decrease with increasing use of zeolite content based on the results of the research conducted. The results of the compressive strength test show that the variation of 7% zeolite + 0.005% sisalana fiber has the highest value of compressive strength at FAS 0.43, with an average of 38.46 MPa, and the highest value of compressive strength at FAS 0.45, with an average of 37.07 MPa.

Use of Various Industrial and Eggshell Wastes for the Sustainable Construction Sector

The alternative composites’ production alleviates the serious problem generated by global warming. Methods to reduce the amount of cement used in concrete production, for example, are being investigated to determine how to reduce carbon dioxide emissions in many applications. Egg shells and various industrial wastes, which are recommended to use in the construction sector at an appropriately high rate, also cause serious environmental damage. Bottom ash (BA) and marble powder (MP) wastes are used today in civil engineering applications. In addition, it is important to increase the use of eggshells due to their rich calcium carbonate content. In this work, BA and MP wastes were blended with eggshells to produce cement paste composites. Two different sets of composites were prepared during this study. The composites were prepared with cement (80%), BA (20%), and MP (20%) wastes by weight with 0.3%, 0.75%, 1.5%, and 2.5% eggshell waste. The fresh (flow table), physical (dry unit mass, apparent specific gravity, and porosity), mechanical (unconfined compressive strength and flexural strength), and durability (water absorption, seawater resistance) tests were conducted. According to the experimental results, the composites can be classified as lightweight construction materials. The test results showed that 0.75% eggshell by weight of cement in bottom ash and marble powder can be used as an optimum value for better performance. The bottom ash mixtures groups are higher water absorption and porosity values when referring to the marble powder mixture groups. The highest compressive strength value was found at 56.03 MPa in the MP mixture group and 52.79 MPa in the BA mixture groups with these optimum eggshell combinations at 56 days. The MP mixture group showed better resistance to seawater when referring to the bottom ash blended mixtures. Laboratory-produced composites are possible candidates for cost-effective and environmentally friendly building materials. The eggshells have a promising alternative binder for concrete in the near future and they are utilized together with industrial wastes such as BA and MP in sustainable concrete construction.

Effect of iron‐containing fillers on heat release kinetics and strength properties of polyester resin

AbstractThe influence of filling by iron‐containing fillers on the heat release kinetics and mechanical properties of industrial unsaturated polyester resin PN‐1 is investigated experimentally. The iron ore concentrate, electrostatic precipitator dust, high alumina cement grade HAC‐1, shavings made of cast iron, fine grade sand are used as fillers. To improve the strength characteristics of polyester resin composites the small amount (0.2–1.0 wt%) of organosilicon additives such as synthetic silicone rubber, tris(trimethylsiloxy) phenylsilane, octamethyl cyclotetrasiloxane are used. The heat release kinetics is studied for different ratios between accelerator (cobalt naphthenate) and initiator (cyclohexanone peroxide). The time to reach the maximum temperature of the heat release is significantly reduced when a large amount of iron ore concentrate is used as filler. The temperature of maximum heat release decreases and the time to reach it increases when adding electrostatic precipitator dust in small amount of 5 wt% to the high filled by iron ore concentrate (295 wt%) composite system. The optimum in strength indicators associated with the ratio of different fractions in systems consisting of two fillers of different properties and granulometric composition is found. The highest values of compressive strength in the cement–iron ore concentrate and sand–iron ore concentrate systems are observed. An increase in the strength characteristics of composites by 15%–20% with organosilicon additive introduction is observed. The addition of the silicone rubber increases the strength properties of samples the most among all additives considered.Highlights Effect of filling by iron‐containing fillers on the heat release kinetics and mechanical properties of polyester resin is found. The time to reach the maximum temperature of the heat release is significantly reduced when the resin is filled by a large amount of iron ore concentrate. The temperature of maximum heat release decreases when the electrostatic precipitator dust in small amount is added to the high filled by iron ore concentrate. An increase in the strength characteristics of composites by 15–20% with introduction of organosilicon additives is observed.

Pengaruh Air Laut terhadap Kuat Tekan, Permeabilitas, dan Mikrostruktur Beton Geopolimer dengan Flyash dan Tanah Putih sebagai Pengganti Semen

The increasing infrastructure development of an area is sometimes located in an aggressive environment, one of which is in coastal areas so that direct contact with sea air cannot be avoided. This research aims to determine the effect of sea water on geopolymer concrete using fly ash and white soil as cement substitutes with testing parameters for compressive strength, permeability and microstructure. The test objects used were cylindrical in shape measuring 150x300 mm and 100x200 mm. The ratio of fly ash and white soil used was 85%:15% and the activator used was NaOH 8M and Na2SiO3 with a ratio of 1:2,5. The mixture proportion using a ratio of 1 fly ash: 1,497 sand: 2 split: 0,451 alkali activator with a mutual plan is 35 MPa. Tests were carried out after the concrete had gone through a curing process for 56 days, then the concrete was conditioned without soaking and with soaking for 28 days. Tests were carried out at concrete ages of 56 and 87 days. The test results show that geopolymer concrete with the influence of sea water has a higher compressive strength value and a smaller permeability coefficient compared to concrete without the influence of sea water. Microstructural testing of geopolymer concrete under the influence of sea air produces a matrix-shaped structure morphology that is denser with fewer pores compared to concrete without the influence of sea air.

Spark plasma sintering of cenosphere-derived Cs/Sr-aluminosilicates for 137Cs and 90Sr immobilization in mineral-like ceramics

In this study, a promising method of spark plasma sintering (SPS) was investigated for the fabrication of ceramic matrices designed for the reliable immobilization of highly radioactive radionuclides 137Cs and 90Sr. The ceramic matrices were derived from a mixed composition of two aluminosilicate mineral-like phases – pollucite (Cs,Na)AlSi2O6 and gehlenite Sr2Al2SiO7. The originality of the developed approach lies in the utilization of hydrothermal synthesis for obtaining granulated precursor material. Hollow aluminosilicate microspheres (cenospheres) from coal fly ash served as the initial raw material, which were treated with alkaline solutions containing Cs+ and Sr2+ ions as simulants for the corresponding radionuclides. This method facilitated the achievement of high efficiency in cation removal from solutions exceeding 98 %. For a comprehensive examination of the composition and morphology of cenosphere-derived precursor particles, and the influence of sintering temperature on phase and structure formation of ceramic matrices under non-equilibrium conditions of spark plasma heating, various analytical techniques were employed. These included thermogravimetry/differential thermal analysis (TG/DTA), powdered X-ray diffraction analysis (PXRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), as well as the method of low-temperature nitrogen adsorption for determining the specific surface area. The obtained ceramic samples exhibited high values of specific density (2.688–2.915 g/cm³), compressive strength (666–808 MPa), and Vickers microhardness (1.8–2.5 GPa), attesting to their high quality and stability. The results of the hydrolytic stability assessment revealed that the leaching rates of Cs+ and Sr2+ ions from the ceramics are extremely low, within the range of 10−5–10−6 g/cm²·day. These values fully satisfy the requirements of GOST R 50926–96 and the international standard ISO 6961:1982 for solidified forms of high-level waste.

Exploring the Potential of Native Urease-Producing Bacteria of Hilly Terrain for Soil Strength Enhancement

Bio-cementation of weathered soils of hilly regions using native ureolytic bacteria is a practical approach to improve soil strength. This study aimed to isolate and characterize native urease-producing bacterial strains from different slope failure regions of Uttarakhand, India, through multi-step screening, and showcased their potential in soil improvement. A total of 80 bacterial strains were isolated from thirteen landslide-prone sites to screen for potent native urease-producing strains. Interestingly, nine native strains exhibited high calcium carbonate precipitation (158–187 mg/10 ml) and urease activity (657–3495 µM/mL) compared to Sporosarcina pasteurii (NCIM 2477), a potent bacterium commonly used for bio-cementation. These strains belonged to various genera, including Lysinibacillus sp., Sporosarcina sp., Pseudochrobactrum sp., and Cytobacillus sp. Cohesionless soil samples treated with the native strains exhibited high unconfined compressive strength values ranging from 0.1 MPa to 1 MPa, whereas those treated with S. pasteurii were 0.15 MPa. The urease-producing bacterial strains with CaCO3 precipitation activity influenced the soil strength and failure patterns. FESEM, XRD, and acid-washing tests revealed that native bacterial strains precipitated CaCO3 more than S. pasteurii strain. The study explores, for the first time, the potential of native ureolytic bacteria from different regions of Uttarakhand, India, for soil strength enhancement.

A comparative investigation of eco-friendly fly ash-based geopolymer mortar produced by using electrical and heat curing: Mechanical properties, energy consumption and cost

This study investigates the eco-friendly fly ash-based geopolymer mortar (GM) production using electrical curing (EC) and heat curing. Within the scope of the study, GM produced using the EC method was compared with GM produced using the heat curing (HC) method in terms of mechanical properties, energy consumption, and cost. The study consists of a preliminary experiment to determine the parameters to be used, mortar experiments using the limited parameters defined in preliminary experiments, and an energy consumption and cost analysis. In the preliminary experiments, different mix designs produced according to different MS modulus and Na2O concentrations were studied to decide an applicable range for temperatures of HC and an applicable range for voltages of EC. In the second stage, EC and HC were compared according to temperature changes in GMs, current changes in GMs, and compressive strength (CS). As a final stage, an energy consumption and cost analysis were performed to compare two curing methods according to the updated dollar-based unit prices for electricity per kWh for industrial uses in various countries in February 2024. Results showed that the MS modulus should be at least 1.2 and the Na2O concentration should be 10 % on average to obtain a workable mortar. The compressive strength of all mortars with any MS modulus increased up to 100 °C and then decreased HC applied samples. Stress values of 20, 25, 30, and 35 volts are applicable and the highest compressive strength values could be obtained with 25 volts, and 6 h of application is sufficient at 25 volts EC. MS module is a key parameter in current and temperature change. In EC application, 30 volts is the threshold value, and when an electrical voltage above 30 volts is applied, the mortar's internal temperature suddenly reaches the peak value and the desired compressive strength results cannot be achieved. According to the cost analysis, it is seen that the HC electricity cost is 6.78 times more than the EC cost. A comprehensive efficiency calculation is strongly recommended for future studies. It has also been concluded that geopolymers could gain strength at much lower voltage values, so they have the potential to consume less electrical energy in comparison to conventional concrete.

Mechanical and Thermal Properties of 3D-Printed Acrylonitrile Butadiene Styrene Reinforced with Rubberwood Fiber

An additive manufacturing (AM) has become very popular due to its simplicity in producing complicated products using just one process due to the layer-by-layer addition of material, which makes it possible for more complicated products to be created. The constraint of Fused Filament Fabrication (FFF) printed components with inadequate mechanical qualities has prevented AM from being widely adopted by numerous industries. The mechanical and thermal qualities of FFF printed components which is a pure polymer could be enhanced by reinforcing the wood fiber into the polymer. In this study, the twin-screw extruder was used to produce the wood plastic composites (WPCs) filaments, which were made with ABS (Acrylonitrile Butadiene Styrene) as the matrix material and 1-3wt% rubberwood fiber (RWF) for reinforcement. The effects of the extrusion parameter, such as the volume fraction of RWF and the temperature of the extrusion process, on the 3D-printed WPCs samples were investigated. The experimental results of 3D-printed WPC sample were found that the highest compressive strength value is 24.3 MPa, obtained from the rubberwood 1wt% at the extrusion temperature 218 °C whereas the pure ABS filaments obtaining from the commercial and extrusion process gave the values of 28.9 and 14.5 MPa, respectively. The highest value of tensile strength is 8.4 MPa with the rubberwood 2wt% and temperature 198 °C whereas the pure ABS filaments obtaining from the commercial and extrusion process gave the values of 10.9 and 7.4 MPa, respectively. The morphological analysis of the 3D-printed WPC sample was observed to exhibit an effect of printing process. The result showed that an increasing temperature of extrusion process increases both tensile and compressive strengths of the samples whereas an increasing amount of fiber increases the tensile strength but decreased the compressive strength. Analysis of variance demonstrated linear factor and 2-way interaction factor of the extrusion parameter influence on compression and tensile strength significantly. The rubberwood 2wt% and the temperature 218 °C was suggested to achieve the suitable condition for extrusion process for the 3D-printed WPC sample. In addition, the discussions were supported with the thermal properties achieved from Thermogravimetric analysis and Differential Scanning Calorimetry.

Evaluating Technical properties of fired clay Brick production with mosaic sludge: A comprehensive study on heavy metal leachability for sustainable environmental and economic benefits

Mosaic sludge, generated from mosaic industrial activities such as cutting, polishing, and grinding, is often disposed of in landfills or discharged into drainage systems without adequate treatment. This study aims to reuse mosaic sludge from the mosaic industry by incorporating it into fired clay bricks. This approach offers an alternative disposal method, improves brick quality, and minimizes heavy metal leachability, contributing to environmental and economic sustainability. X-Ray Fluorescence (XRF) was conducted to determine the heavy metal concentration from two types of mosaic sludge bodymill mosaic sludge (BS) and polishing mosaic sludge (PS). The result indicates that the highest element concentration in mosaic sludge (BS and PS) shows that barium is the highest with 3253 ppm and 3260 ppm. Meanwhile, the lowest element concentration obtained in BS and PS is cesium with 14 ppm and 17 ppm. SPLP and TCLP also conducted in this study and the result show that, even though the element such as ferum (Fe) and cadmium (Cd) was not detected in XRF but in SPLP and TCLP, it shows that these two elements exist in clay, BS and PS with low concentration. In order to evaluate the compressive strength conducted by incorporating with different proportions 0 %, 1 %, 5 %, 10 %, 20 % and 30 % of BS and PS into fired clay brick. The result shows that compressive strength BS brick was stronger than PS brick. The maximum sludge percentage used in BS brick is 5 % with value of compressive strength is 28.10 MPa. Meanwhile, PS brick had the higher value of compressive strength at 30 % sludge percentage with the value 23.46 MPa. Static Leachate Test (SLT) was performed to evaluate heavy metal leachability from bricks containing different proportions of BS and PS sludge. In the SLT results, Fe exhibits the highest concentration of heavy metals at various proportions of BS and PS: 2.11 mg/L and 2.27 mg/L at 1 %, 1.77 mg/L and 1.88 mg/L at 5 %, 2.34 mg/L and 3.29 mg/L at 20 %, and 2.79 mg/L and 3.64 mg/L at 30 % respectively, among other elements. On the other hand, elements including Cr, Ni, Cu, As, Cd, and Pb demonstrated lower concentrations ranging from 0.00 mg/L - 1.0 mg/L. The result for control brick, BS brick and PS brick shows the same pattern. However, overall results show that the concentration still under limit set by USEPA.

Studi Kuat Tekan Batulanau Berdasarkan Uji Lapangan dan Uji Laboratorium Pada Formasi Kampungbaru dan Pulaubalang Daerah Kutai Kartanegara Kalimantan Timur

Rock strength is the ability of a rock to maintain its strength until it breaks when a force is applied. Rock compressive strength is a very important parameter in the world of mining. The compressive strength of the rock determines the mining method that will be used. Several things that influence the compressive strength of rock include porosity, true specific gravity, and water content. With the same volume, if the porosity value is high, the true specific gravity value will be low because of the large number of pores in the rock. This allows the compressive strength value to be low because the rock will crumble more easily when pressure is applied. After testing, the highest compressive strength value was in the Pulaubalang Formation, location 2, with a value of 2.19 MPa. Meanwhile, the lowest compressive strength value was in the Kampungbaru Formation, location 1, with a value of 1.49 MPa. In accordance with the stratigraphic layers in the Kutai Basin, the Pulaubalang Formation is older than the Kampungbaru Formation.

Kekuatan Tekan Beton Berpori Additive Sika Fume Mix Self Compacting Concrete

This research aims to determine the effect of adding the additive Sika Fume on the compressive strength of hollow concrete. This research uses a type of quantitative research with experimental methods, namely by carrying out several tests on test objects in the laboratory. The results of this research show that the compressive strength of hollow concrete with the addition of sika fume with a variation of 0% and 2% of the weight of cement, the experimental results obtained for the compressive strength of hollow concrete for 28 days of concrete with a variation of 0% with an average of 16.83 Mpa. For a variation of 2% with an average of 17.42 Mpa. So it can be concluded that concrete with a variation of 2% with an average of 17.42 Mpa is the variation with the highest compressive strength value and reaches the design compressive strength. Meanwhile, the 0% variation with an average of 16.83 Mpa is the lowest compressive strength value and does not reach the design compressive strength.

Effect of Cold Compaction Pressure on Porous NiAl Articles Produced by Using Space Holder Urea via VCS

Porous NiAl samples were obtained by using 20, 40, 60 vol.% space holder urea particles. The urea particle size was in the range of 150-300 µm. Pressures of 50, 100, 200 and 300 MPa were applied by cold press to the mixtures formed by nickel, aluminum, preformed NiAl powders and urea particles. The dimensions, macrostructure, microstructure and compressive strength of the parts produced with different cold compaction pressures were analyzed after volume combustion synthesis (VCS). The aim of the study is to determine the cold compaction pressure which provides the closest dimensional changes after VCS, in samples having different urea amounts. These samples will be used for forming a multi-stack article in a further study. Since a high difference in dimensional change of different layers during VCS will lead to cracking and separation, similar dimensional change is required for different layers in a multi-stack sample design. The samples which were cold pressed with 300 MPa pressure sometimes contained cracks after they were taken out of the die after cold pressing or after VCS. Therefore, they could not be subjected to characterization. The closest dimensional change and higher compressive strength values after VCS were obtained in samples having different urea contents, when they were cold pressed at 200 MPa. The highest mean compressive strength (218.8±29.5 MPa) was attained in the sample which was prepared with 20% urea particles and which was cold compacted with 200 MPa.

Pengaruh Serbuk Kaca Sebagai Substitusi Parsial Semen terhadap Kuat Tekan Beton Alir

AbstractIn the current construction development, concrete is the main material used because of its advantages in strength and durability. One of the innovations in the use of concrete is flow concrete, which allows use without compactors and has optimal viscosity. The use of glass powder as a partial substitution of cement is an attractive alternative because of its potential in improving concrete properties. Glass powder has a fairly large silica (SiO2) content of 75%. Silica has a strong relationship with the compressive strength of concrete. Proper silica in concrete mix can increase the compressive strength of concrete. This study aims to determine the effect of glass powder with variations of 0%, 6%, 8%, 10%, 12% on the compressive strength of flow concrete with a proportion of superplasticizer 1.5%. Compressive strength testing is carried out when concrete reaches the age of 7, 21, 28 days using cylindrical specimens measuring 15 × 30 cm. From the test results, the highest compressive strength value was obtained at 28 days concrete age, namely in an 8% glass powder mixture of 25.61 Mpa and the lowest compressive strength value in a 12% glass powder mixture of 21.26 Mpa. Based on the results of this study, it can be concluded that glass powder as a partial substitution of cement can increase the compressive strength of flow concrete with an optimal glass powder mixture of 8%. Keywords— Flowing Concrete, Glass Powder, Compressive Strength

Early Strength of Concrete by using Ground Granulated Blast Furnace Slag and Local Ordinary Portland Cement Materials

It is well known that using Ground Granulated Blast Furnace Slag (GGBFS) to replace some of the cement in concrete will cause it to take longer to reach its ideal compressive strength. However, several precast concrete manufacturing processes require high initial compressive strength values to speed up production. The impact of partially substituting GGBFS for cement on the initial strength values of concrete is investigated in this work. The 300 concrete cylinder samples were used to accomplish the study's goals. Compressive and split tensile tests determined the concrete's initial compressive strength and split tensile strength outputs. Therefore, the ideal percentage of GGBFS can replace cement by 20–30% to achieve the desired early compressive strength of 16 MPa in 16 hours by setting the proper water-cement (w/c) ratio at about 0.25. Because a low w/c ratio leads to low workability, some additives, such as silica fume or superplasticizer, can be employed to further increase the workability and performance of concrete.

Kepah Shell Waste as A Coarse Aggregate Substitution Material on Concrete Mixture

This research uses kepah shell waste as a substitute for coarse aggregate. The purpose of this study is to determine the value of slump and compressive strength values in concrete variations. Variations of concrete consist of normal concrete, mixed shells of waste concrete with 5%, 10%, and 15% substitution of coarse aggregate. The concrete maintenance period was carried out for 7 days, 14 days, and 28 days. The results of the slump value research show that the lowest slump value is normal concrete, while the highest slump value is concrete with a mixture of 15% kepah shell waste. For the results of the compressive strength value, the highest compressive strength value is concrete with a mixture of 5% kepah shell waste. For the most economical cost with high quality of concrete compression strength is the concrete mixture with 5% of kepah shell waste. The greater the percentage of kepah shell waste, the cheaper the concrete price, but higher percentage of kepah shell waste will result a decrease in the quality of concrete.

Analysis of Environmentally Friendly Concrete (Green Concrete) Using Coal Fly Ash as a Substitute Material for Portland Cement in Road Pavement

The development of technology in the field of construction, especially in concrete technology, is now becoming more rapid, which requires concrete materials that can adapt to the times. As well as for energy savings from normal concrete materials from a mixture of fine, coarse, cement and water can now be added to other materials. In this era, the use of cement for concrete making materials is very identical, therefore to reduce the use of cement, it is necessary to mix other materials. The research method that researchers use is the experimental-laboratory method by making test objects in the form of concrete cylinders with a size of 15x30 cm. Analysis of concrete testing using Fly Ash mixtures in this study there are several variations of fly ash mixtures, namely fly ash 50%, 60%, and 70%. In testing several Fly Ash mixtures produced a compressive strength value of 50% Fly Ash percentage and 2% Accelerator of 161.630 kg/cm2, 60% Fly Ash and 2% Accelerator of 154.189 kg/cm2, 70% Fly Ash and 2% Accelerator of 92.670 kg/cm2. In the results of this study with several variations of fly ash mixtures, the highest compressive strength value was obtained at a percentage of Fly Ash 50% and Accelerator 2%, which amounted to 161.630 kg/cm2 with the first variation test specimen sample at the age of 28 days of concrete.

Impact of Recycled Polypropylene Fibers on the Density and Strength of Unreinforced Concrete

Polypropylene (PP) is widely used in the construction industry to produce a variety of materials. Accordingly, a huge amount of waste is produced during or after the construction activity. The PP fiber provides a good alternative solution to enhance concrete properties and more sustainable concrete produced in terms of isolation and weight reduction. In this study, 24 concrete cubic samples are cast by adding different PP fiber content to characterize this fiber effect on concrete density and unconfined compressive strength (UCS). The results demonstrate that using higher fiber content of 2%, 6%, and 10% leads to a mass reduction that equals to 59, 157, and 290 kg compared to normal concrete per one cubic meter. However, at higher PP fiber content, the unconfined compressive strength decreases compared to the controlled samples. The concrete mix with 2% PP fiber revealed a higher value of compressive strength with increment by (10-12)% at age (7-28) days compared to normal concrete. The outcomes imply that using PP fiber contributes to the protection of the environment by reducing the quantity of PP waste from construction materials.