Optimal Replacement of Granite Modified with Ife Iron and Steel Slag on Strength Properties of Concrete

Steel is produced from iron ore and purification of metal scrap, leading to manufacture of hundreds of tonnes of steel slag each year. This study investigated the optimum replacement of granite with Ife Iron and Steel Nigeria Limited (ISN) slag that produce maximum Compressive Strength (CS), Split Tensile Strength (STS) and Flexural Strength (FS) of concrete using Response Surface Methodology (RSM) from Design Expert Version 7.0. The outcome of the study showed that the optimum replacement of granite with ISN was 28.85% ISN at 0.47 W/C.

Effect of sodium hydroxide concentration on the compressive strength of geopolymer mortar using fly ash PLTU Tanjungjati B Jepara

Geopolymer concrete is concrete that uses environmentally friendly materials, using fly ash from waste materials from the coal industry as a substitute for cement. To produce geopolymer concrete, an alkaline activator is required, with a mixture of Sodium Hydroxide and Sodium Silicate. This research is an experimental study to determine the effect of variations in the concentration of sodium hydroxide (NaOH) 8 Mol, 10 Mol, 12 Mol, and 14 Mol on the compressive strength of geopolymer concrete. Mortar Geopolymer uses a mixture of 1: 3 for the ratio of fly ash and sand, 2.5: 0.45 for the ratio of sodium silicate and sodium hydroxide as an alkaline solution. The specimens used a cube mold having dimension 5 cm x 5 cm x 5 cm, then tested at 7 days and 28 days. The test resulted that concentration of NaOH 12 Mol obtained the maximum compressive strength of geopolymer concrete, that is 38.54 MPa. At concentrations of 12 Mol NaOH and exceeding 12M, the compressive strength of geopolymer concrete decreased.

Effects of Initial Surface Evaporation on the Performance of Fly Ash-Based Geopolymer Paste at Elevated Temperatures

Geopolymer concrete is a valuable and alternative type of concrete that is free of traditional cement. Generally, geopolymer concretes require a source material, which is rich in silicon and aluminum. Furthermore, fly ash-based geopolymer concretes have been proven to have superior fire resistance, primarily due to their ceramic properties, and are inherently environmentally-friendly given their zero-cement content. This paper presents the effects on initial evaporation on the performance of fly ash-based geopolymer pastes after exposure to elevated temperatures of 400 °C and 800 °C. The fly ash (FA) samples used in the present study included: Gladstone and Gladstone/Callide. The results for sealed samples placed in the oven during curing were much more consistent than the samples that were not kept covered. In addition, Gladstone fly ash-based geopolymer samples that were sealed recorded an initial maximum compressive strength reading of ca. 75 MPa, while sealed Gladstone/Callide fly ash-based geopolymer samples, of the same mix design, only recorded an initial maximum compressive strength reading of ca. 50 MPa (both subjected to oven curing at 60 °C for 24 h). However, Gladstone/Callide fly ash-based geopolymer samples exhibited a significant strength gain, ca. 90 MPa, even after being subjected to 400 °C.

Comparative Evaluation of Potential Impacts of Agricultural and Industrial Waste Pozzolanic Binders on Strengths of Concrete

Concrete is one of the most widely used construction material in the world which uses aggregates and cement as a binder. Use of cement concrete and mining/ transportation of raw materials makes the construction industry the biggest emitter of CO2 by contributing up to 7-10% of global emissions. The waste materials from different industries and agriculture contribute to 90% of waste disposal/ recycling effort in the world. This research has focused to use a selection of waste materials as supplementary cementitious materials (SCM) to minimize the emission of CO2 and recycling/ absorption of waste from other industries to construction industry to make it more sustainable. The contemporary research has established use of pulverized fly ash (PFA), silica fume (SF), metakaolin (MK) and granulated ground blast furnace slag (GGBS) as suitable SCMs. This study has focused on using two established industrial waste SF and MK and two agricultural wastes, rice husk ash (RHA) and palm ash (PA), to determine and compare their potential use as pozzolanic SCMs and to expand the family of alternative pozzolanic binders in addition to PFA and GGBS. The w/c (w/b) ratio was 0.4 with an intended design mix strength classification of C50/60. The chemical composition of all the materials was determined through x-ray spectrometry/ diffraction test to ascertain the chemistry. All four materials satisfied the ASTM constituent criteria for pozzolans. In comparison to the control mix (100% cement content), all these materials improved the compressive strength from 2.5% to 30% and enhanced tensile strength from up to 17%, indeed all the SCM mixes had a higher compressive strength than the control. RHA exhibited the best performance in agricultural waste with 10% optimum quantity to give maximum compressive strength of 83 MPa and PA exhibited the optimum performance with 2.5% content and gave maximum compressive strength of 78 MPa. The addition of MK progressively increased the compressive strength with 20% content mix giving a strength of 84 MPa. The SF performed the best at optimum quantity of 2.5% and exhibited the highest compressive strength of 90 MPa. The results suggest that these SCM based concrete are recommended for formulation of high-strength concrete applications, i.e., 60+ MPa. Furthermore, all the SCMs had at least one mix which satisfied the C60/75 classification without reducing the w/b ratio below 0.4; this has significant positive ramifications for the development of sustainable high-performance concrete. The absorption of waste materials from industrial and agricultural fields can substantially reduce waste disposal and more pertinently facilitate in reducing the CO2 emission associated with the construction industry

A Study of the Residual Strength of Reactive Powder-Based Geopolymer Concrete under Elevated Temperatures

This paper reports on studies relating to the unstressed residual compressive strengths of geopolymer pastes that are heated up to 800 °C, behavior of reactive powder concrete before and after exposure to elevated temperatures and thermal behavior of novel reactive powder geopolymer-based concretes. For this purpose, 10 geopolymer pastes and three reactive powder concrete mixtures were tested for residual strengths. Gladstone fly ash was used as the primary binder for both geopolymer pastes and reactive powder geopolymer concretes. In addition, four novel reactive powder geopolymer concrete mixes were prepared with zero cement utilization. While reactive powder concretes achieved the highest seven-day compressive strengths of approximately 140 MPa, very poor thermal behavior was observed, with explosive spalling occurring at a temperature of ca. 360 °C. The reactive powder geopolymer concretes, on the other hand, displayed relatively high thermal properties with no thermal cracking at 400 °C, or visible signs of spalling and very mild cracking in one case at 800 °C. In terms of the strength of reactive powder geopolymer concrete, a maximum compressive strength of approximately 76 MPa and residual strengths of approximately 61 MPa and 51 MPa at 400 °C and 800 °C, respectively, were observed.

Effect of Various Calcite Precipitating Bacteria on Compressive Strength of Concrete: A Comparative Study

The presence of micro pores in concrete makes the concrete weak and less durable, in this study an ecofriendly attempt has been made to minimize these micro pores by calcite precipitating bacteria i.e. Escherichia Coli, bacillus subtilisand pseudomonas aeruginosa which produce calcium carbonate when they blend with calcium lactate in presence of water and air thus filling up the micro pores, thus comparing their effects on compressive strength of concrete.Various proportions of E. coli, B.subtilisand P. aeruginosa bacterial media were impregnated in concrete viz. 10%,20% and 30% replacing the proportion of mixing water, small proportion of fine aggregate was also replaced by calcium lactate and silica gel. It was observed that concrete with 10% replacement of P. aeruginosa culture media with mixing water showed maximum compressive strength with 79.6% increase in the compressive strength of concrete where as concrete with B.subtilisbacterial media showed 61.1% increase in the compressive strength of concrete and concrete with E.coli bacterial media showed 23.5% increase in the compressive strength of the concrete, keeping 10-6 cells/ml the cell concentration for all bacterial concretes.

Analysis Of The Effect Of Bending Strength On Scaffolding System With Direct Analysis Method

Steel scaffolding is a very important component in formwork work to support further work. The purpose of this analysis is to review the maximum compressive strength that occurs in 3-story scaffolding before buckling occurs using the direct analysis method (DAM). The design of steel structures, which are generally slender, requires stability analysis. The result is influenced by imperfections (non-linear geometry) and inelastic conditions (non-linear material). In this final project, we use second-order inelastic analysis based on direct analysis method. The 3-level scaffolding model was analyzed using beam elements in the SAP2000 program with 6 variations of notional loads applied to the weak axis direction of the scaffolding pipe.The lowest compressive strength on 3-story scaffolding before buckling occurs is 18.24 kN with horizontal notional loads to the right on the first level scaffolding, left on the second level scaffolding and to the right on the 3rd level scaffolding. The results of the analysis show that the maximum compressive strength obtained results in a large displacement drastically in the iteration step. By using the analysis on the DAM method, the results obtained are more effective.

Kelayakan Abu Terbang PLTU Buntoi Sebagai Campuran Beton Geopolimer

The main basic ingredients needed for the manufacture of this geopolymer material are materials that contain a lot of silica and aluminia elements. The 1st stage test was carried out to determine the geopolymer paste with the maximum compressive strength at the ratio of NaOH to Na2SiO3 of 1; 1.5; 2; 2.5. The second stage of testing was carried out using a geopolymer paste with the highest compressive strength, namely the ratio of NaOH to Na2SiO3 of 2.5 with a compressive strength of 22.56 MPa. Based on the results of the compressive strength test, the maximum compressive strength at the age of 28 days is 7.64 MPa. The results of the compressive strength of concrete are much lower than the compressive strength of the paste, it shows that the paste does not bind too much with the aggregate. This is evidenced by the results of the compressive strength of conventional concrete which is much higher than that of geopolymer concrete using the same aggregate. With the results of the maximum compressive strength at the age of 28 days is 29.51 MPa.

An Experimental Study of Plastic Waste as Fine Aggregate Substitute for Environmentally Friendly Concrete

Decomposing plastics, including plastic bottles, is a very difficult process because it takes 50-100 years. Every year, the use of plastic bottles is increasing, but only few people are willing to treat plastic bottle waste. In this study, plastic bottle waste is used as a substitute of fine aggregate and shaped in such a way to have a sand-like gradation. The variations of graded plastic bottle waste are 0%, 5%, 10%, and 12%. The test objects for each variation consist of three specimens. Data are analyzed by using regression and classical assumption test with SPSS program. The results of the data analysis show that there is a simultaneous effect on the compressive strength with variations in plastic waste substitution. The compressive strength decreases with the increase in the percentage of plastic added. Maximum compressive strength is at the variations of 0% and 5% with19.192 MPa and 16.414 MPa, respectively.

Strength of Concrete with Recycled Manganese Slag

This paper studies the effect of replacing coarse aggregates with manganese slag on the mechanical properties of concrete. Air-cooled granulated manganese slag was used. The control sample was designed to achieve concrete strength of 30 MPa at 28 days. Tests were conducted on five different compositions of concrete having manganese slag to coarse aggregates ratios of 0, 0.2, 0.3, 0.4, and 1. The specimens were tested at 7, 14, and 28 days for their compressive and flexural strength. Test results revealed that all manganese slag concrete specimens had improved compressive and flexural strength. The maximum compressive strength achieved was 43.54 MPa, increased by 16% of the control specimen and the maximum flexural strength achieved was 4.50 MPa, increased by 22% of the control specimen. Both results were obtained in concrete with 0.4 manganese slag to coarse aggregate ratio. Besides, the study also showed that it might be possible to substitute all coarse aggregates in concrete with manganese slag without any loss in strength. However, it was observed that the concrete workability decreased when manganese slag was added. Nonetheless, this could be corrected using superplasticizer.