Concrete Production Research Articles

RECYCLING OF ASPHALT PAVEMENT AGGREGATES AND WASTE PLASTIC BOTTLES IN ADDITION TO HOT-MIX ASPHALT PRODUCTION: ADEQUATE RECYCLING RATE

This study focused on the recycling of asphalt pavement aggregates and waste plastic bottles (WPB) in addition to hot-mix asphalt (HMA) production. To achieve this objective, non-probable sampling methods were used to gather samples from the study locations. Crushed stone aggregate (CSA), bitumen, mineral filler, reclaimed asphalt pavement aggregate (RAPA), and WPB were the ingredients employed based on the requirements in the standard specification for asphalt concrete production. Initially, the Marshall Stability Test was then carried out using CSA with 6% and bitumen levels of 4.0, 4.5, 5.0, 5.5, and 6% by weight of the total mix to ascertain what the bitumen content should be with RAPA with replacement rates of 10, 20, and 30% and that of WPB with 2, 6, 8, 10, 12, and 14%. In the Marshall Stability Test, which consisted of three trials of 195 samples and 60 mix designs, 45 were for the control mix and 150 for the replacement proportion. In the Marshall Stability Test, the ideal value for CSA was 5.1%; for RAPA, 5.1%; and for WPB, 7.7, 5.5, 5.4, 5.0, 5.5, and 5.4% optimum bituminous content (OBC). 20% RAPA and 10% WPB by weight of OBC in the stability-modified asphalt mix satisfies Ethiopian Road Authority (ERA) and American Society for Testing and Material (ASTM) specifications for all qualities tested. Finally, for improved asphalt mix performance, a combined 70% CSA, 20% RAPA, and 10% WPB should be used in asphalt mixes at 5.0% OBC. These experimental Marshal Stability Test findings satisfy the necessary specifications of ERA and ASTM for all tests used in HMA production. Thus, this proportion is strongly advised.

Elucidating the reaction of seashell powder within fly ash cement: A focus on hydration products

The use of shellfish waste as a raw material in cement and concrete production is recognized as a feasible approach. Similar to limestone, seashell powder (SP), which is primarily made up of calcium carbonate, has been identified as a promising supplementary cementitious material (SCM). However, the current understanding of SP's chemical interactions within aluminum-rich cement systems remains limited, often resulting in its classification as simply an inert filler. Therefore, this research seeks to clarify the contribution of SP to fly ash (FA) cement by investigating the hydration products. The investigation reveals that SP facilitated hydration albeit to a lesser extent compared to limestone. In cements incorporating SP, the AFm phases, characterized by carboaluminate formations, became predominant, and the calcium carbonate content diminished over time, indicating reactive engagement of SP. The addition of 5 % SP enhanced the polymerization of the C-(A)-S-H structure in FA cement. Moreover, the substitution of cement with SP elevated the effective water to cement ratio, leading to a reduction in the Ca/Si ratio of C-(A)-S-H, while the Al/Si ratio remained virtually unchanged. Analysis identified the presence of monocarboaluminate (Ca/Al/C atomic ratio of 4: 1.97: 4.39) and hemicarboaluminate (Ca/Al/C atomic ratio of 4: 2.25: 2.40) in FA cements with 5 % and 10 % SP additions, respectively. Nonetheless, incorporating SP negatively impacted the compressive strength of FA cement, underscoring the importance of using SP in moderation. Specifically, the 28-day compressive strengths of FA cements with 5 % and 10 % SP additions measured at 42.9 MPa and 40.2 MPa, respectively. Moreover, SP-FA cement offers significant environmental advantages. This research innovatively elucidates the reaction mechanism of SP within fly ash cement, offering vital insights into SP's impact on the hydration process and advancing the recycling of shellfish waste.

Analisis Beban Kerja Pada Produksi Beton Pracetak Untuk Menentukan Jumlah Kebutuhan Pekerja

Manufacturing company PT. Varia Usaha Beton provides concrete products. On the concrete production line in Gresik, the company makes various types of concrete, one of which is precast concrete. In manufacturing activities, there are problems when carrying out production where there are orders whose production has not been fully realized. Aspects of workload can influence production demand which cannot be realized in its entirety because workers expend too much energy resulting in workers not being optimal and the limited number of workers resulting in demand not being met. To address this problem, researchers conducted a workload analysis on precast concrete production activities for each product and determined the number of workers needed according to production demand. The method used is using working time measurements and the Full Time Equivalent method to analyze workload and determine the number of workers according to the FTE value index. The results obtained after data processing and data calculations were carried out for operators working to produce precast concrete, 13 of which were overloaded and 2 of which were normal. After calculating the need for workers, the workers needed to meet the demand for precast concrete production requires 52 workers from the initial 24 workers. Keywords: Full-Time Equivalent, Workload, Worker Needs

Multi-criteria decision making tool for sustainable concrete production using waste polyethylene terephthalate bottle cap aggregates

The widespread use of concrete has raised concerns about the consumption of its raw materials. To address this issue, researchers are actively exploring alternative waste materials to reduce the environmental impact of the construction industry. With this objective current study aims to investigate potential use of waste polyethylene terephthalate (PET) bottle cap aggregates on the characteristics of concrete, both in its fresh and hardened states. Three variations of modified waste PET aggregates (PETA): full (F), half (H), and quarter (Q), with the aim of evaluating their suitability as replacements for conventional coarse aggregates (CCA) was examined. The research assesses the effects of different PETA proportions (3%, 5%, and 8%) on concrete workability, compressive strength, splitting tensile strength, and flexural strength. The findings reveal that PETA-F and PETA-H adversely affect workability, primarily due to their larger surface area and difficulty in achieving homogeneous blending with other ingredients. In contrast, PETA-Q exhibits superior workability. The use of PETA-Q results in reduced compressive strength due to its smaller size and limited load-bearing capacity. Notably, PETA-H demonstrates improved compressive strength after 28 days. Interestingly, PETA-Q shows enhancements in splitting tensile and flexural strength, making it the top-performing alternative for fresh and hardened concrete properties. Overall, this research indicates that PETA-Q is most suitable for sustainable concrete production. Furthermore, the application of a multi-criteria decision-making tool validates our findings and determines that a 5% replacement of CCA with PETA is optimal, as higher replacements result in strength reduction. The utilization of PETA not only minimizes CCA consumption but also contributes to the development of eco-friendly, sustainable concrete. This study underscores the potential of environmentally conscious concrete and encourages the adoption of sustainable solutions for plastic waste management.

Opening and out‐of‐plane shear fracture performance of steel and natural sisal hybrid fiber reinforced concrete

AbstractThe key objective in developing sustainable concrete is enhancing performance by mitigating adverse environmental effects simultaneously. Using short and discrete steel fibers to reinforce the concrete matrices is a widely accepted approach to improve the ductility of concrete. Although the utilization of traditional steel fibers enhances the strength of the concrete, it simultaneously leads to an increase in its weight. Also, the production of steel fibers is an energy‐intensive and carbon‐emitting process. To attain sustainability, it is imperative to reduce the use of steel fibers by including a suitable alternative through the hybridization of fiber reinforcements. The concrete developed in this study was composed of a ternary blended binder containing Ordinary Portland Cement, Ground Granulated Blast furnace Slag and Microsilica. Fibers were hybridized by partially replacing 25%, 50%, and 75% of steel fibers with natural sisal fibers. Mixes reinforced with 100% steel fibers and 100% sisal fibers were also assessed for better understanding. Basic properties such as workability, compressive strength, and splitting tensile strength were assessed. Fracture performance of the prepared mixes under pure and mixed, opening, and tearing modes of loading was also assessed by conducting disc bending tests. It can be observed from the results that, steel fibers can be replaced with sisal fibers up to 25% of the total fiber volume without greatly compromising the workability, strength and fracture performance of concrete. Hence, hybridizing steel fibers with sisal fibers can be considered a viable option to reduce the overall weight of the structural components, which can further help reduce the environmental impacts and overall cost of concrete production.

Carbonation of Recycled Concrete Aggregates for New Concrete and Concrete Fines to Make Cement-Free Hollow Blocks

Mineral carbonation provides a way to increase the recycling of concrete waste in added-value products, and contributes to the principles of the circular economy. At present, most concrete waste is still downcycled. The high water absorption of recycled concrete aggregates, among other factors, impedes their recycling in the concrete industry. The quality of coarse recycled concrete aggregates (RCA) can, however, be enhanced by carbonation. Even when starting with high-grade RCA obtained from a selective demolition process, the carbonation process can decrease the water absorption of the RCA to as low as 3.0%. Concrete with a 50% replacement rate of carbonated RCA can be produced without a significant compressive strength reduction. The research further shows that carbonation can be performed at atmospheric pressure and low CO2 concentrations (e.g., 10%). The recycled concrete fines (RCF, 0–4 mm) in combination with 25% stainless steel slag were used to make zero-cement hollow blocks (39 × 19 × 9 cm) by carbonation curing without using any hydraulic binder. The hollow blocks have a compressive strength of 15.4 MPa at the lab scale. Both technologies were demonstrated on a pilot scale. In both processes, CO2 is immobilized in the resulting construction product. The developed production processes use less primary raw materials and cause less greenhouse-gas emissions than the production of traditional concrete products.

Key durability characteristics of GGBS-cement kiln dust based concretes

With the advent of global warming, the concrete industry has the potential to drive the future of construction through sustainable cement technologies. These technologies rely on activation of industrial waste materials, such as Cement Kiln Dust (CKD) and Ground Granulated Blast Furnace Slag (GGBS) while Portland cement (PC) content is maintained at a minimum, resulting in concrete products of reduced embodied carbon footprint. This work reports on the durability of mixes made from PC, GGBS and CKD at incremental contents of 40-75% and 0-35% for GGBS and CKSD, respectively, in an attempt to identify durable formulations while maintaining blends at low embodied CO2 emissions in the Sultanate of Oman. Dimensional changes, sulfate and chloride resistance, as well as surface resistivity were determined and compared to those of a PC-based concrete formulation. The results suggest that, when GGBS and CKD were incorporated within the mix at an optimum content of 55% and 20% respectively, the concretes appeared to have exhibited promising durability characteristics which could lead towards the material’s implementation within a greater context.

Development of low carbon concrete and prospective of geopolymer concrete using lightweight coarse aggregate and cement replacement materials

The use of Ground Granulated Blast-furnace Slag (GGBS) as an alternative cement replacement material in combination with conventional coarse aggregate have been successful in the production of near green concrete. Undoubtedly, GGBS has exhibited good cementitious attributes, however, there are concerns with slow strength development and workability owing to its non-pozzolanic activities as well as some degree of porosity notwithstanding the sustainability potential. Therefore, this study presents a lytag based geopolymer lightweight concrete with high strength development, improved mechanical properties and reduced embodied carbon. To further improve and enhance the potential production of green concrete, complete replacement of conventional coarse aggregate with a recycled lightweight aggregate from industrial waste was carried out. The geopolymer precursors consisted of sodium hydroxide, sodium silicate, GGBS and silica fume to optimize the performance of the concrete at 60–80% cement replacement for a target design mix of 20, 30, 40, and 50 MPa. The performance of lytag based geopolymer concrete was compared with that of non-geopolymer lytag based concrete (control samples). The results show a 42% increase in compressive strength for the geopolymer lightweight concrete and a 22% increase in ultimate compressive strain which is an indication of improved moment of resistance in structural design. The results also show a 46–61% reduction in embodied carbon for the use of non-geopolymer lytag based concrete and 69–77% reduction for lytag based geopolymer concrete. The geopolymer concrete between 7 and 63 days of loading increases by 0.55% in creep strain compared with increases of 2.81% for non-geopolymer lytag based concrete and reduction to 27.96% for the normal weight concrete. Modulus of Elasticity reduces with age of loading for the geopolymer concrete during creep at 0.39% compared to reduction of 1.93% for non-geopolymer lytag based concrete and increase of 12% for the normal weight concrete.

EVALUATION OF LOCUST BEAN POD ASH AS MINERAL FILLER IN HOT MIX ASPHALT

An increase in the consumption of agricultural products generates large quantities of waste daily. The husks of the locust bean seeds when removed from the plant are littered in the environment which negatively affects the environment. In this research, locust bean pod ash (LBPA) was used as a mineral filler in hot mix asphalt. Physical and chemical tests were done on the aggregate, bitumen and LBPA, showing adequacy for use in asphalt concrete production. All tests were conducted in accordance with relevant standards. LBPA was admixed with granite dust from 0–50% (at intervals of 10%) with varying bitumen content from 4–7% (at 0.5% intervals). For this experiment, the Marshall mix design method was used. The Marshall stability of samples containing LBPA improved by 19%, from 8.16kN to 9.67kN. Similarly, Marshall flow decreased by 19% from 3.4 mm to 2.75 mm. The density-void analysis of the asphalt samples also revealed an improvement. The microstructural examination revealed an enhanced structural arrangement due to the flocculation of the LBPA particles. Overall, the hot mix asphalt samples meet the Federal Ministry of Works and Housing specifications for flexible pavement-wearing courses. It was determined by the study that adding 40% LBPA with 60% granite dust at 5% bitumen content would improve the performance of hot mix asphalt.

Strength and Durability Characterization of Structural Concrete Made of Recycled Plastic.

This study investigates the feasibility of utilizing recycled plastic waste as a partial substitute for sand in concrete production. Reprocessing used plastic items or materials involves collecting, cleaning, shredding, and melting, resulting in reprocessed plastic particles. Incorporating these recycled plastic particles into concrete addresses environmental concerns related to plastic disposal and the growing scarcity and increasing cost of natural sand. To evaluate the sand replacement capacity of recycled plastic, four types of mixtures were created with varying levels of recycled plastic replacement (5%, 10%, 15%, and 20%). All mixtures maintained a water-to-binding ratio of 0.55 and were tested at 7, 28, and 56 days. The testing regimen encompassed determining the slump value, density, compressive strength, tensile strength, and resistance to freezing and thawing. The findings revealed that replacing sand in the concrete mix with recycled plastic enhanced workability, which was attributed to the hydrophobic nature of the plastic particles. However, both compressive and tensile strength exhibited a declining trend. Additionally, after undergoing multiple freezing and thawing cycles, the concrete mix exhibited poor durability properties and brittleness. These issues may arise due to factors such as incompatibility, non-uniformity, reduced cohesion, and the lower density of plastic particles.

Alkali-silica reaction of ferronickel slag fine aggregate in Portland cement and alkali-activated slag mortars: Pessimum effect investigation

Ferronickel slag (FNS) with dense and hard nature exhibits great potential to be utilized as recycled aggregate in concrete production. This study investigated the alkali-silica reaction (ASR) and the pessimum proportion of FNS fine aggregate in Portland cement (PC) and alkali-activated ground granulated bast furnace slag (AAS) mortars as a substitute for river sand. Over a 120-day period, the accelerated mortar bar test revealed that the addition of FNS fine aggregate in both cases resulted in harmless ASR expansion. In PC mortars, the ASR expansion consistently decreased from 0.569 % to 0.114 % as the FNS content increased. In comparison, AAS mortars with higher pore solution alkalinity had the pessimum proportion of 30 % FNS. The ASR expansion values initially increased from 0.472 % to 0.554 % with an increase in FNS content from 0 % to 30 %, but then decreased to 0.146 % as the FNS content was further raised to 100 %. The amorphous ASR gel was identified as a hydrated alkali silicate gel and present within the existing veins in the river sand grain. The ASR reaction of FNS fine aggregate exhibited a self-mitigating effect on the deleterious expansion through its pessimum behavior. Additionally, the addition of FNS fine aggregate yielded a beneficial outcome by reducing the cumulative pore volume in the mortars, and thus enhanced the compressive strengths.

Utilisation of Waste Shea Nutshell Fine-Grained Particles to Enhanced Strength and Durability Behaviour of Concrete

Shea nutshells possess properties that stabilise soil enough to resist water penetration. It is a waste material and incorporating it as an additive material in concrete will be a means by which it can be recycled. With this projection, the study incorporated shea nutshell particles (SSP) as fine aggregates in concrete. The aim was to determine their influence on strength and durability properties. Fine aggregates were partially replaced with 0%, 10%, 20%, 30%, and 40% SSP based on the weight of the aggregate, and labelled as A0, S10, S20, S30 and S40 respectively. Concrete cubes of size 150 mm and cylinders of diameter 150 mm and height of 300 mm were prepared and cured for 7, 14, 28, and 90 days. The concrete was tested for density, compressive strength, split tensile strength, water absorption, and sulphate attack. The inclusion of the SSP did not improve the compressive and split tensile strengths. However, water absorption and sulphate attack decreased with further addition. Though, strength properties did not appreciate, values at 10%, 20% and 30% additions in 28 and 90 days satisfied the 28 days minimum requirement of 25 N/mm2. Hence, the study recommends the use of SSP in concrete production up to 30%.

Performance of coal gangue concrete with fly ash and ground-granulated blast slag: Rheology, mechanical properties and microstructure

This paper aims to examine the effect of coal gangue aggregate (CGA), fly ash (FA), and ground-granulated blast slag (GGBS) on the rheological, mechanical and microstructure properties of concrete. The rheological properties, compressive strength, splitting tensile strength, flexural strength, and uniaxial tensile behaviour of coal gangue concrete (CGC) were determined, and the microstructure of the concrete mixtures were investigated by use of XRD and SEM analyses. The results revealed the action mechanism of CGA and mineral admixtures on the microstructure and macroscopic properties of CGC. FA first increased and then decreased the yield stress and plastic viscosity, while GGBS considerably increased the yield stress and plastic viscosity. Furthermore, a constitutive model was established for CGC containing FA and GGBS under compression. The proposed stress–strain model for CGC is accurate and can be used for nonlinear analysis of structures made of this type of concrete. Moreover, the addition of FA and GGBS consumes calcium hydroxide, but increases products such as hydrated calcium silicate aluminate. These findings elucidate the understanding and optimisation of CGA use in concrete production, while contributing to lowering carbon emissions.

ENHANCING CONCRETE STRENGTH WITH RECYCLED CERAMIC TILES AND DENTAL ADMIXTURES

This study explores for the first time the utilization of combined use of ceramic tile aggregate and dental cast stones in the concrete production process. Ceramic tiles, sourced from manufacturing industries as well as construction and demolition sites—sources contributing to environmental pollution—were employed, along with waste dental cast stones obtained from hospitals in Metro Manila. The integration of crushed tiles as a replacement for coarse aggregate in concrete not only addresses environmental concerns but also holds promising economic benefits. Consequently, the incorporation of these ceramic wastes into concrete production emerges as a viable strategy for environmental preservation while simultaneously enhancing the concrete's properties particularly compressive strength. In the experimentation phase, crushed ceramic tile serves as 100% substitute for coarse aggregate while the dental cast stones serve as additive at varying percentages (1%, 3%, and 6%). The concrete mixtures, adhering to M20 grade standards, were meticulously prepared and subjected to casting, followed by thorough testing for Compressive Strength after curing period of 28 days. The obtained results reveal that excellent compressive strength is achieved with the replacement of ceramic tile aggregate in conjunction with natural coarse aggregate and pulverized dental cast stones as natural additive. In Addition, the obtained result of adding 1% waste additive material yields an average increase of 0.64% higher than the standard mix (controlled). The mixture with 3% waste additive material yields an average increase of 13.06% and while adding 6% waste additive material yields an average increase of 30.07% in comparison to conventional concrete with both respective curing period of 7, 14, 28 days. This insightful exploration underscores the potential of sustainable practices in concrete production for environmental benefits.

Mechanical Properties of a Sustainable Low-Carbon Geopolymer Concrete Using a Pumice-Derived Sodium Silicate Solution.

A geopolymer is an inorganic amorphous cementitious material, emerging as an alternative sustainable binder for greener concrete production over Ordinary Portland Cement (OPC). Geopolymer concrete production promotes waste reuse since the applicable precursor materials include agricultural and industrial waste that requires disposal, helping to reduce waste in landfills and ensuring sustainable environmental protection. This study investigates the development of an environmentally friendly sodium silicate alternative (SSA) derived from pumice powder (PP) in place of a commercial Na2SiO3 solution at a 10 M concentration. Six concrete batches were produced at alkaline/precursor (A/P) ratios of 0.1, 0.2, 0.3, 0.4, and 0.5. The geopolymer mix AF4, with an A/P ratio of 0.4, became the optimum geopolymer concrete design; however, it recorded lower compressive, tensile splitting, and flexural strengths, respectively, against the control OPC concrete. The geopolymer formulations, however, obtained 28-day-hardened concrete densities comparable to the control concrete. The 28-day compressive strength of the OPC concrete was 29.4 MPa, higher than the 18.8 MPa recorded for AF4. However, the 56-day strength of AF4 improved to 22.4 MPa, an around 19% increase compared to the 30.8 MPa achieved by the control mix on day 56, having experienced only a 5% strength increase. The low mechanical performances of the geopolymer formulation could be attributed to extra water added to the original geopolymer design to improve the workability of the geopolymer mix. Therefore, the SSA alkaline solution using PP showed some potential for developing geopolymer concrete for low-strength construction applications.

An Experimental Study of Concrete Mixed with Coconut Shell as Partial Replacement of Course Aggregate

The high cost of conventional construction materials affects the economy of structure. The possibility of utilizing recycled coconut shell aggregates in concrete as coarse aggregate is examined in the present study. An optimum percentage replacement of coarse aggregate with coconut shell aggregate is determined from the study. Coconut shell is a lightweight material thus producing lightweight concrete. The replacement of coarse aggregate of coconut shell by 10%, 20% and 30%. The Design mix used is M20 grade and testing of specimens are conducted after 7 and 28 days of curing. The flexural and compressive strength of concrete are tests. The main objective is to encourage the use of these waste products as construction materials in low-cost housing Aggregate is a major ingredient for making concrete, occupying almost 70-80% part of concrete. Conventionally crushed rocks are used as coarse aggregate and river sand as fine aggregate. Both are naturally available materials. Due to the speedy growth of construction works, conventional aggregate sources are exhaust very fast leading to a significant increase in the cost of construction. For sustainable development, these materials should be used wisely and alternative materials need to be searched to replace regular aggregate. A large number of studies have been done to search for alternative materials for the production of concrete. At the same time due to fast industrialization, production of waste material is increasing day by day. Its disposal has become a real problem. It can be concluded that the ideal amount of coconut shell replacement for coarse aggregate for M20 Concrete is 10% -20%. Key Words: Concrete Mix, Coconut shell, Low cost housing, Flexural strength, Compressive strength, Design mix, Replacement of Course Aggregate.

Response Surface Optimization of Rice and Guinea Corn Husk Ash Blended Concrete

Concrete, a fundamental construction material, consists of aggregates, water, cement, and additives. Unfortunately, the large-scale production of cement is a major contributor to carbon dioxide (CO2) emissions, primarily from the manufacturing process and the consumption of fossil fuels. This not only incurs environmental costs associated with global warming but also depletes vital limestone deposits. To mitigate these issues, this study aims to explore the optimal utilization of Guinea Corn Husk Ash (GCHA) and Rice Husk Ash (RHA) in concrete. This research investigated the chemical properties of GCHA and RHA, and their impact on the compressive and split-tensile strengths of concrete when integrated in various proportions. The study reveals that both GCHA and RHA meet the minimum oxide content requirement of 70% set by ASTM C618, with silicon dioxide (SiO2) as the predominant oxide. Increasing the content of RHA and GCHA from 5% to 10% improves the concrete's compressive and split-tensile strengths after curing for 56 days. Optimization results indicate that the ideal mix consists of 10% GCHA, 8.5% RHA, and 82.5% cement, yielding a compressive and split tensile strength of 31.34 N/mm² and 3.07 N/mm² respectively. This study thus offers a promising solution for sustainable concrete production by reducing the environmental footprint of cement while enhancing material properties and promoting an eco-friendlier approach to construction. Keywords: Concrete, Guinea Corn Husk Ash, Rice Husk Ash, Compressive Strength, Split-Tensile Strength

Effect of steel slag powder and stone powder by-product from manufactured sand on the mechanical properties and microstructure of cementitious materials

Incorporating steel slag (SS) and stone powder (SP) as supplementary cementitious materials (SCMs) in cement and concrete products is an effective approach to promoting environmental protection. Recently, the effect of using steel slag alone is not satisfactory and the performance of blended cementitious materials is expected to improve after compounding with other admixtures. In this study, steel slag powder (SSP) and SP by-products from manufactured sand were employed with a total dose of less than 30% as a replacement for cement. The results revealed that the blended cementitious materials exhibited excellent mechanical strength and pore structure with the synergistic effect of SSP and SP. Compared to SSP or SP doping alone, the activity index of the composite 25% SSP and 5% SP was higher. SSP offers a considerable retardation effect on cement, while SP has little effect. Conversely, the effect of steel slag on mortar fluidity is neglected and SP decreases the fluidity. When 5% SSP is combined with 5% SP, the initial and final setting times of cement are increased by 39% and 25%, respectively. The reduction in mortar fluidity amounted to an insignificant reduction of only 0.7%, and the strength of the mortar at 28 d and 180 d was only lost by 7% and 5%, respectively. The coaction of 15% SSP and 15% SP was observed to promote the wollastonite generation, enhance the crystallization degree of xonotlite phases, decrease the microcrack widths, and optimize the pore structure of the blended cementitious materials.

Results of experimental research of the process of forming reinforced concrete products by the centrifugation method

The method of conducting an experimental study of the process of forming reinforced concrete products is disclosed. The key factors influencing the quality indicators of the product being formed are defined and considered. On the basis of the conducted active, factorial experiment, a regression equation was compiled, graphical dependences of the influence of these factors on the process were obtained, rational parameters of the centrifugation process were determined, which are decisive in the manufacture of reinforced concrete products by the centrifugation method. Based on the results of laboratory experiment data processing, recommendations were developed for optimizing the operating parameters of industrial equipment for forming reinforced concrete products by the centrifugation method. Problem. When forming reinforced concrete products by the centrifugation method, some problems may arise, uneven distribution of the mixture in the mold body and of reinforcement, formation of voids or cracks, insufficient compaction of the mixture. If the parameters of the centrifugation process are not properly controlled, the quality of the products may vary, which may lead to deviations from specifications and standards. Problems with the deformation of the molds after forming the product can lead to damage to the product or difficulties in its removal. Goal. Based on the results of the conducted factorial experiment, recommendations are developed regarding the rational parameters of the process of forming columns of reinforced concrete supports for power transmission lines by the centrifugation method in the conditions of an operating technological line. Methodology. The basis of the research is the method of conducting a planned factorial experiment with further statistical processing of the obtained results using a computer program. Results. Based on the processing of the obtained results of the conducted factorial experiment, the following recommendations are suggested regarding the rational parameters of the process of forming reinforced concrete pillars for power lines by the centrifugation method in the conditions of an operating technological line.

Statistical assessment of the factors influencing fly ash reactivity

Siliceous fly ash is a pozzolanic supplementary cementitious material often used in cement and concrete production. The influence of the chemical, mineralogical and physical properties of 75 siliceous fly ashes on their reactivity was examined in this study. The reactivity was analyzed by relative mortar compressive strength and a rapid screening test (a version of the R³ test). A statistical data analysis was carried out to evaluate the factors influencing the reactivity of the ash. The screening test was found to be able to predict the reactivity within short periods of time, while the relative strength is not a good measure for reactivity. It was also found that the TiO2 and chloride content of the fly ash can serve as an indicator for its reactivity.