The prevailing practices of geopolymer concrete (GC) preparation use a high concentration of alkali activators, which is uneconomical. It is imperative to develop GC of low-concentration activators with enhanced durability for field implementation. Mechanochemical activation of geopolymer increases the reactivity of its raw materials by converting the crystalline phase to an amorphous phase. It has been illustrated in the present study that mechanochemical activation aids in achieving GC of desired properties at low concentrations of alkali activators. The mechanochemical activation of ground granulated blast furnace slag (GGBS) with sodium metasilicate was carried out to prepare GC of low (2 M) and high (12 M) alkali concentrations. The Portland slag cement-based concrete (PC) was cast to compare the durability performance of GC. The durability of the three concrete mixes was examined in terms of water absorption, the volume of permeable voids (VPV), water and chloride permeability, homogeneity, and acid resistance. The microstructural characterization of concrete samples exposed to acid were carried out by X-ray diffraction, field emission scanning electron microscope, and energy dispersive X-ray spectrometer. The results indicated that GC with a low concentration of activator exhibited lesser water absorption, VPV, and permeability, whereas it offered higher resistance to acids and chloride ion penetrability. Low-concentration GC had a dense and compact structure due to the coexistence of geopolymeric and hydration products, leading to better performance than high-concentration GC and PC. The evaluation of cost and carbon emission of PC, and GC mixes suggests GC as a sustainable alternative to traditional concrete. Although PC is economically viable, the study suggest use of GC with low alkali concentration due to its environmental benefits with a minor increase in cost.

Abstract: This research is conducted to study the performance of concrete mix containing Class-C Fly ash and P250 super plasticizer. The concrete mix are also proportioned to have various proportion of cement replacements by fly ash ranging from 10% to 30% by weight and super plasticizer PC250 from 0.5% to 1.5% by weight of cement. The performance of concrete is evaluated with respect to workability and compressive strength by Destructive and Non destructive test (rebound number). At 28 day. Concrete mix containing fly ash and super plasticizer shows consistently higher compressive strength compared to concrete with only fly ash and without fly ash. It has been observed that by addition of fly ash the initial compressive strength is lower because of unhydrated cement, since the addition of fly ash lowers the rate of hydration of cement. According to the analysis of results show that class- C fly ash could be substituted for cement replacement, as the concrete with fly ash 30% and super plasticizer shows 34.19% more strength as compared to non fly ash concrete. Similarly increase in workability also observed upto 240mm slump value.

Fly ash, bottom ash and granulated blast furnace slag (GBFS) are industrial wastes materials. These are using as concrete admixture by geopolymer techniques. Utilization of the above raw materials minimize the transportation, disposal, environment cost and consumption of cement. Ordinary Portland cement produce large amount of CO2 in atmosphere which is not eco-friendly material. This article especially focused on the utilization of raw materials as eco-friendly and check the effect of various chemical environments and exposure time on the compressive strength of products formed by geopolymer technique. The Compressive strength (C.S) changes with chemical environments and exposure durations.

The use of hybrid composites now a days has been very attractive due to their light weight, low cost along with high strength to weight ratio. Lot of research is going on to develop the newer composites with improved mechanical, tribological and thermal properties. From the last two decades, Aluminium alloys have gained lot of attention owing to their practical usage and the ease of processing. Aluminium matrix composites are most versatile materials which has applications in advanced structure, aviation, marine and defence application due to their excellent properties. It is a known fact that stir casting is one of the economical method of fabrication of the metal matrix composite, moreover it is also easy to fabricate the composites by stir casting rather than other processes of fabrication. But, the quality of metal matrix composites being cast through stir casting route are highly dependent on the process parameters and achieving the homogenous distribution of reinforcement is a big challenge. In the present investigation, AA2024/SiC/Gr/flyash hybrid composites were fabricated with the stir casting technique (having reinforcement weight composition of SiC 10%, Graphite 5%, and fly ash 5%). The morphological characteristics of the developed Metal matrix composite (MMC) have been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM). The uniform distribution of the reinforcement particles clearly depicts the development of homogeneous composite.

This study presents an experimental investigation on self-compacting concrete (SCC) with cement (Portland pozzolanic cement) replacement of a Silica Fume (5%, 10%, 15% and 20%) Metakaolin (5%, 10%, 15% and 20%) and addition of chemical admixtures like Poly carboxylate ether super plasticizer (SP). Self-Compacting concrete is a concrete that exhibit the high flow ability and avoid the segregation and bleeding. There are several methods for testing its properties in the fresh state: the most frequently used are Slump−flow test, V−funnel L−box and U-box. The slump, V-funnel and L-Box test are carried out on the fresh SCC and in harden concrete compressive strength and split tensile strength values are determined. Attempts have been made to study the properties of such SCCs and to investigate the suitability of Silica Fume(SF) and Metakaolin(MK) to be used as partial replacement materials for cement in SCC.

Geopolymer products are formed by mixing of raw materials in the presence of activator solution of sodium hydroxide. The raw materials such as fly ash & bottom ash are by-products of power plants and granulated blast furnace slag (GBFS) is a by product of steel production units. Environment friendly disposal of these by products are a challenging problem because of the cost involved. This paper deals with the development of eco-friendly geopolymer products by using these industrial by- products. For effective use of these products it is important to know how the composition, concentration of activator solution and exposure to adverse environment affects the compressive strength of the product. In order to develop mathematical models to predict the effects of proportion of different raw materials, exposure time in various atmospheres (such as air, acetic acid, magnesium sulphate, sodium sulphate and sodium chloride) and concentration of activator solution on compressive strength of geopolymers, the statistical technique of Central Composite Design is chosen. The maximum compressive strengths predicted by the models for the cases, when samples are exposed to 1%, 2%, 3% NaCl solution are 12.79Mpa, 10.91 MPa and 11.38 MPa respectively, at the end of 140 days. Compared to that, the predicted compressive strength of the sample exposed to airis 14.33 MPa at the end of 140 days. The other important observation is that, in both the cases, the compressive strengths are increasing with the length of exposure time. This assumes importance as NaCl solution is highly corrosive. The peak values in both the cases are yet to reach. These are the most significant results that are obtained in this study. (c) 2021 Elsevier Ltd. All rights reserved. Second International Conference on Aspects of Materials Science and Engineering (ICAMSE 2021).

Due to various architectural requirements the structures are subjected to large shear stresses and hence the study of shear performance of structural materials is essential. Push-off test is a simple test which can be performed to determine the in-plane shear strength (IPSS) of materials effectively. Geopolymer concrete is a recent construction material which is a suitable alternative cement concretes especially in precast construction due to the non-requirement of cement, the manufacture of which is energy intensive and involves the liberation of CO2 which is a known pollutant and leads to global warming. Concrete has good performance under compressive loads and fails generally due to crack propagation, bridging of these cracks can improve the load carrying capacity of the concrete, addition of fibre is one such method available where the fibres act as crack arrestors. The present experimental investigation has made an effort to understand the influence of fibres over shear strength of Geo Polymer Concrete (GPC) adopting push-off specimen. From the experimental studies it was observed that shear strength and resistance against cracking increased with increase in fibre volume and the effectiveness of GPC reinforced by fibres were higher than that of NSC specimen.

The corrosion of steel reinforcement in concrete due to environmental factors has been studied through numerous approaches and the reduction of corrosion has been managed by various methods; however, among the protection techniques, the use of corrosion inhibitors has gained encouragement. In this chapter, nitrites and nitrates of sodium and calcium and sodium molybdates and sodium tungstates (oxyanions of group VI) were studied and have gained sufficient scientific coverage. However, their exact role of inhibition was studied by simple polarization technique. In this chapter, we compare the inhibitive efficiency of nitrites and nitrates of sodium and calcium and also that of molybdates and tungstates. The results, however, indicate that among nitrites and nitrates, the calcium salts are more efficient and molybdates and tungstates are comparable in their inhibitive efficacy.

High Performance Concrete can be seen of as a natural progression from Cement Concrete, where the elements are balanced and chosen to effectively contribute to the many features of Cement Concrete in both the fresh and hardened phases. One of High Performance Concrete's characteristics that offers important structural advantages is higher strength. Concrete, steel reinforcement, and formwork make up the three main expenses for a structural member. This study compares these important elements when higher-grade concrete is used in the design, with the goal of demonstrating that high strength concrete offers the most cost-effective solution for designing load-bearing members and for carrying a vertical load to the building foundation through columns. The water-cementitious material ratio, total cementitious material, cement-admixture ratio, and amount of super plasticizer dosage are the mix design elements that have the greatest impact on concrete strength. To create a higher-grade concrete mix, these variables need to be examined.

The mechanical properties and durability parameters such as wet-dry cycles, water sorptivity, efflorescence and acid resistance of geopolymer concrete synthesized from fly ash of three different origins were evaluated. Scanning electron microscopy with energy dispersive X-ray spectroscopy and X-ray diffraction tests were conducted to examine the microstructure and mineralogical changes. It has been observed that the performance of geopolymer concrete containing fly ash with more glass content was better. The concrete samples were exposed to atmosphere for 180 days under a wide range of temperature (11 degrees to 39 degrees C) and relative humidity (42 to 82%). But the efflorescence was very low and the compressive strength deterioration was <10% from reference sample kept under controlled condition. This indicates good durability characteristic of fly ash based geopolymer concrete.

Purpose This paper aims to identify an inhibitor to protect rebar corrosion in concrete. Design/methodology/approach The authors use the simple method of polarization and calculate the change in open-circuit potential and corrosion current density. Findings Sodium molybdate is an efficient inhibitor compared with sodium tungstate for rebar corrosion in concrete. Research limitations/implications This paper has limitation of 0.0001 M concentration of inhibitors for 400 days of exposure in 3.5 per cent sodium chloride solution. Originality/value The research focused on the concentration of both inhibitors in the range from 0.1 to 0.0001 M, which resulted in greater structural protection from corrosion in adverse conditions, such as coastal areas.

The particle size of fly ash has influenced the physical and mechanical properties of geopolymers. Fly ash completely was ground to different pre-decided sizes, sieve sizes 180 μm, 90 μm and 45 μm (80 mesh, 170 mesh, 325 mesh) for formulation of geopolymer paste, and two activators were used: 8(M) NaOH and 1:1 mixture of NaOH and Na2SiO3. The heat evolution increased with increasing fineness of fly ash. The increase in ambient temperature enhanced the extent of geopolymerization. The maximum heat flow was obtained with the finest fly ash particle of size 45-μm (325 mesh). The microstructures of the various geopolymers revealed the compactness of the structure which had the finest 45-μm (325 mesh) particle size and silicate-activated geopolymers. Apparent porosity was found to decrease with increasing fineness and addition of sodium silicate. Mercury intrusion porosimetry (MIP) revealed the total porosity; median pore size and average pore diameter were found to decrease with increasing fineness. However, mesopores were seen to be more in 45-μm (325 mesh) fly ash geopolymers compared to 180-μm (80 mesh) fly ash geopolymers. Compressive strengths of geopolymer formed by 45-μm (325 mesh) particle size had greater compressive strength in comparison with the coarser one. Inclusion of sodium silicate in the activator solution was helped in enhancing the compressive strength.

The work aimed to classify a raw brown colour fly ash (RFA) into coarse grey fly ash (GFA) and fine brown fly ash (BFA) using a laboratory air classifier and to study the properties of grey fly ash-based blended cement. Portland cement (OPC) was partially replaced with 10-30% GFA by mass at 5% intervals to make blended cement. The physical and mechanical properties were determined as per Bureau of Indian Standards (BIS). The incorporation of GFA in cement mixes decreases the specific gravity, fineness, consistency, volume expansion and drying shrinkage while increases the setting time and flow-ability. The compressive strength of blended cement was observed lower than that of OPC at all ages, but the rate of strength development increases with the age. The replacement level up to 20% meets the BIS strength requirement of 33 MPa at 28 d for fly ash-based blended cement. The hydration studies were done using Isothermal Conduction Calorimetry (ICC) at 27 degrees C. The total heat of hydration was observed to decrease with the increasing GFA content. The microstructural characterisation of hardened cement pastes after 60 d using XRD, FTIR and SEM-EDS revealed the variations in mineralogical, structural and morphological properties.

The present study work was carried out to determine the effect of marble powder and fly ash on the strength properties of concrete grade M25 by partial replacement of cement with marble powder and fly ash. Marble powder and fly ash both are byproducts or waste of marble industries and coal thermal plant respectively. So to reuse of these by-products and to fulfill the objectives of the dissertation the cement is replaced by marble powder and fly ash in the percentage of 0%, 4%, 8%, 12%, 16%and 20% in present study work. The three strength properties of concrete are determined in experimental work namely compressive strength, split tensile strength and flexural strength at the curing age of 7days and 28 days respectively. After the experimental work, it was found that the 12% replacement of cement by marble powder and fly ash enhance the compressive, split and flexural strength properties of concrete as compared to the ordinary M25 grade concrete. The test result also shows the possibility about the reuse of byproduct or waste in construction line especially in concrete manufacturing to enhance the strength properties of concrete as well as to control the different kind of pollution which is originated by these type waste or byproduct.

This paper deals with experimental study on behavior of concrete M30 after adding a constant percentage 0.5% of steel fiber by the weight of concrete and replacement of cement by the weight of fly ash in the percentages of 0,3.5,7,10.5,14 and 17.5 % respectively . In the present study the Compressive strength, Split tensile strength, Flexural strength of steel fiber and fly ash based M30 concrete have been checked and the obtained results are compared with the control mix. Concrete related test were performed for the curing age of 7days and 28 days. Test results shows that at 0.5% replacement of steel fiber and 10.5 % replacement of cement by the weight of fly ash enhance the strength characteristics of M30 concrete as compare to the control mix for both the curing age of 7days and 28 days respectively.

Marble powder and fly ash both are the byproducts of marble cutting industries and coal based thermal power plants respectively. To fulfill the objective of dissertation work many kinds of researchers have studied. After that, it has found that there is feasibility in replacing the concrete ingredients with marble powder and fly ash. In the present dissertation work, we are replacing cement with marble powder and fly ash in the percentages of 0%, 4%, 8%, 12%, 16%and 20% respectively. By this replacement of cement with byproducts, we want to find out the effects of marble powder and fly ash on the strength properties of concrete mix M25. In this dissertation work, three strength characteristics are compared with ordinary M25 grade concrete namely compressive strength, split tensile strength and flexural strength.

Concrete is the primary material for construction and infrastructure activities worldwide. Conventional concrete using ordinary portland cement (OPC) has created a burden on the natural resources, environment and is also an energy-intensive process. The commonly used fine aggregate in concrete and mortar is river sand. The steep demand of river sand for infrastructure development is faced with problems of availability, its quality and rising cost.To overcome the present crisis, an investigation is made by replacing the OPC and river sand with fly ash (FA) and bottom ash (BA) which are by-products of coal combustion for synthesis of geopolymer concrete (GC). The specimens used in the studies are polymerized at ambient temperature with alkali activators of different concentrations. The water curing after casting was found not necessary for GC which is otherwise an essential part for conventional concrete. Workability and bleeding of fresh GC are studied. Compressive strength and split-tensile strength of hardened GC are also studied. Considering the fresh and hardened properties of GC, the FA and BA content is optimised at 35% and 10% of mix proportion.

This paper describes the applications and feasibility of steel fiber and fly ash in the concrete industry. This paper also helps in to identify the desired percentage of steel fiber and fly ash in the concrete mix. Many literature reviews have been studied deeply to carry out the proposed dissertation work in a scheduled manner and to achieve the project related goal. To find out the effect of steel fiber and fly ash on the strength concrete the compressive, tensile and flexural test will be conducted with the concrete mix. The final result will be compared with the control mix to find out the effect of steel fiber and fly ash on the strength properties of concrete M30.