Assessment of the Possibility of Using Fly Ash from Biomass Combustion for Concrete

Comparative Analysis of Woody Biomass Fly Ash and Class F Fly Ash as Supplementary Cementitious Materials in Mortar

Biomass fly ash is a sustainable, eco-friendly cement substitute with economic and performance benefits, being renewable compared to coal fly ash. This study examines using biomass fly ash (BFA) as a sustainable cement substitute, comparing it with Class F fly ash (CFA). With a water-binder ratio of 0.5 and replacement rates of 10%, 15%, 20%, 25%, and 30% (by mass), the research highlights BFA's promising applications. BFA and CFA were mixed into cement paste/mortar to analyze their reactivity and properties, with hydration products CH and C-S-H evaluated at 7, 28, and 91 days. Compressive strength, micro-pore structure, and drying shrinkage (assessed from 7 to 182 days) were tested. Results showed BFA had similar pozzolanic reactions to CFA at later stages. While compressive strength decreased with higher BFA replacement rates, early-stage performance matched CFA; growth was CFA-10 (18 MPa) and BFA-10 (17.6 MPa). BFA mortars exhibited slightly better deformation properties. BFA-30 cement had superior performance, with a lower drying shrinkage rate of 65.7% from 14 to 56 days compared to CFA-10's 73.4% and a more stable shrinkage growth rate decrease to 8.4% versus CFA-10's 6.4% after 56 days. This study concluded that BFA, usable without preprocessing, performed best at a 10-15% replacement rate.

Recycled Materials in Civil Engineering Application

In recent years, the construction sector has shown great interest in the use of various by-products and industrial waste, as well as the consumer products used [...].

Experimental Validation of the Cementation Mechanism of Wood Pellet Fly Ash Blended Binder in Weathered Granite Soil

In response to climate change, wood pellets have been increasingly utilized as a sustainable energy source. However, their growing utilization increases the production of wood pellet fly ash (WA) by-products, necessitating alternative recycling technologies due to a shortage of discharging landfills. Thus, this research seeks to utilize WA by developing a new sustainable construction material, called wood pellet fly ash blended binder (WABB), and to validate its stabilizing performance in natural soils, namely weathered granite soil (WS). WABB is made from 50% WA, 30% ground granulated blast-furnace slag (GGBS), and 20% cement by dry mass. WS was mixed with 5%, 15%, and 25% WABB and was tested for a series of unconfined compressive strength (qu), pH, and suction tests at 3, 7, 14, and 28 days. For the microstructural analyses, XRD, SEM, and EDS were employed. As the WABB dosage rate increased, the average qu increased by 1.88 to 11.77, which was higher than that of compacted WS without any binder. Newly cementitious minerals were also confirmed. These results suggest that the effects of the combined hydration mechanism of WABB are due to cement's role in facilitating early strength development, GGBS's latent hydraulic properties, and WA's capacity to stimulate the alkaline components of WABB and soil grains. Thus, this research validates a new sustainable binder, WABB, as a potential alternative to conventional soil stabilizers.

Analysis of Durability of Watertight Concretes Modified with the Addition of Fly Ash

The growing demand for watertight concrete structures is conducive to the development of research in this area, but their results are rarely published. In order to partially fill this gap, the authors of the publication present the results of research into the effect of fly ash addition on the watertightness of concrete. Prior to the tests, a recipe for a concrete mix with the addition of a sealing admixture modified with fly ash was developed. The following properties were analyzed: consistency of the concrete mix, air content in the concrete mix, compressive strength of concrete, depth of penetration of water under pressure, and frost resistance of concrete for F150 level. The work meets the expectations of the construction industry with respect to the production of concrete structures resistant not only to the penetration of water into concrete but also resistant to aggressive substances dissolved in water that accelerate the destruction of concrete and corrosion of reinforcement bars. Based on the test results, it was found that the addition of fly ash to the concrete mix enhances the positive impact of the applied sealing admixture, increasing the tightness of the concrete. It reduces the depth of penetration of water under pressure and therefore increases the frost resistance of concrete.

Modification of Concrete Composition Doped by Sewage Sludge Fly Ash and Its Effect on Compressive Strength

The sustainable development of construction materials is an essential aspect of current worldwide trends. Reusing post-production waste in the building industry has numerous positive effects on the environment. Since concrete is one of the materials that people manufacture and use the most, it will continue to be an integral element of the surrounding reality. In this study, the relationship between the individual components and parameters of concrete and its compressive strength properties was assessed. In the experimental works, concrete mixes with different contents of sand, gravel, Portland cement CEM II/B-S 42.5 N, water, superplasticizer, air-entraining admixture, and fly ash from the thermal conversion of municipal sewage sludge (SSFA) were designed. According to legal requirements in the European Union, SSFA waste from the sewage sludge incineration process in a fluidized bed furnace should not be stored in landfills but processed in various ways. Unfortunately, its generated amounts are too large, so new management technologies should be sought. During the experimental work, the compressive strength of concrete samples of various classes, namely, C8/10, C12/15, C16/20, C20/25, C25/30, C30/37, and C35/45, were measured. The higher-class concrete samples that were used, the greater the compressive strength obtained, ranging from 13.7 to 55.2 MPa. A correlation analysis was carried out between the mechanical strength of waste-modified concretes and the composition of concrete mixes (the amount of sand and gravel, cement, and FA), as well as the water-to-cement ratio and the sand point. No negative effect of the addition of SSFA on the strength of concrete samples was demonstrated, which translates into economic and environmental benefits.

Mechanical Properties and Microstructural Features of Biomass Fly Ash-Modified Self-Compacting Coal Gangue-Filled Backfill

To achieve sustainable utilization of a large amount of mine solid waste, this study investigated the performance of self-compacting coal gangue-filled backfill (SCFB) containing biomass fly ash (BFA) generated from biomass power plants as a supplementary cementitious material (SCM). The correlations between the physical structure and compressive strength of SCFB samples were obtained by ultrasonic pulse velocity (UPV). The failure process of the SCFB samples was monitored by the digital image correlation (DIC) technique, and the stress-strain relationship and failure pattern were also analyzed. The micro-morphological structure and hydration products of SCFB samples were evaluated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and backscattered electron imaging (SEM-BSE). The results show that the usage of 30~40% BFA in SCFB improves the physical structure and strength of the samples. The compressive strength and UPV value of SCFB samples with different water-to-cement (w/c) ratios showed a similar trend of increasing and then gradually decreasing as the proportion of ordinary Portland cement (OPC) replaced by BFA increased. BFA exhibits better reactivity and filling effect in SCFB samples with a high w/c ratio. The peak stress of SCFB samples gradually decreases, and resistance to deformation gradually weakens with the increase in w/c ratios, while the DIC results further verify the mechanical experimental results. Microstructural analysis revealed that reducing the w/c ratio and incorporating specific ratios of BFA can reduce the thickness of the interface transition zone (ITZ) and porosity. The results of the study will provide theoretical guidance for the modification, stability monitoring, and strengthening of SCFB.

Influence of Post-Consumer Waste Thermoplastic Elastomers Obtained from Used Car Floor Mats on Concrete Properties

In this paper, the influence of post-consumer thermoplastic elastomer (TPE) additive derived from used car floor mats on the physical and mechanical properties of concrete is presented. Waste elastomer (fractions 0-2 and 2-8 mm) was used as a substitute for sand or fine aggregate in the amount of 2.5, 5.0, 7.5, and 10.0% by weight of cement. For all series, the physical and mechanical properties of concrete (for example, compressive strength, flexural tensile strength, water absorption, density, and frost resistance), as well as its microstructure, were tested. It has been shown that post-consumer elastomer waste from used car floor mats in the amount of 2.5% of cement weight can replace sand and gravel aggregate in concrete without reducing their mechanical strength and without changing their microstructure. The compressive strength (after 28 days) of concretes in which the waste was introduced as a substitute for sand and aggregate was 57.0 and 57.2 MPa, respectively (the strength of the control sample was 57.0 MPa). The use of post-consumer waste in concrete allows for a reduction in the consumption of natural aggregate (the addition of 2.5% of waste material saves natural aggregate approximately 20 kg/m³), which reduces the cost of concrete production and also has a positive impact on the environment (i.e., it saves cost and space in landfills, where currently used car floor mat are deposited).

The Performance of Concrete Made with Secondary Products-Recycled Coarse Aggregates, Recycled Cement Mortar, and Fly Ash-Slag Mix

The properties of cement concrete using waste materials-namely, recycled cement mortar, fly ash-slag, and recycled concrete aggregate-are presented. A treatment process for waste materials is proposed. Two research experiments were conducted. In the first, concretes were made with fly ash-slag mix (FAS) and recycled cement mortar (RCM) as additions. The most favorable content of the concrete additive in the form of RCM and FAS was determined experimentally, and their influence on the physical and mechanical properties of concrete was established. For this purpose, 10 test series were carried out according to the experimental plan. In the second study, concretes containing FAS-RCM and recycled concrete aggregate (RCA) as a 30% replacement of natural aggregate (NA) were prepared. The compressive strength, frost resistance, water absorption, volume density, thermal conductivity, and microstructure were researched. The test results show that the addition of FAS-RCM and RCA can produce composites with better physical and mechanical properties compared with concrete made only of natural raw materials and cement. The detailed results show that FAS-RCM can be a valuable substitute for cement and RCA as a replacement for natural aggregates. Compared with traditional cement concretes, concretes made of FAS, RCM, and RCA are characterized by a higher compressive strength: 7% higher in the case of 30% replacement of NA by RCA with the additional use of the innovative FAS-RCM additive as 30% of the cement mass.

Experimental Study of Hardened Young's Modulus for 3D Printed Mortar

Few studies have focused on determining the Young’s modulus of 3D printed structures. This study presents the results of experimental investigations of Young’s modulus of a 3D printed mortar. Specimens were prepared in four different ways to investigate possible application of different methods for 3D printed structures. Study determines the influence of the number of layers on mechanical properties of printed samples. Results have shown a strong statistical correlation between the number of layers and value of Young’s modulus. The compressive strength and Young’s modulus reduction compared to standard cylindrical sample were up to 43.1% and 19.8%, respectively. Results of the study shed light on the differences between the current standard specimen used for determination of Young’s modulus and the specimen prepared by 3D printing. The community should discuss the problem of standardization of test methods in view of visible differences between different types of specimens.