Workability Of Concrete Research Articles

The Effect of Rice Husk Ash as Cement Substitution on the Compressive Strength of Self-Compacting Concrete

Self-Compacting Concrete (SCC) is an innovative solution in today's world of concrete technology. Unlike traditional concrete, it does not require a vibrator for compaction, which makes concrete work easier. One of the key features of SCC is its high workability, which is achieved through the use of chemical admixtures and mineral additives. Rice husk ash is one such additive that can be used as a pozzolanic material for concrete mixtures, which is important as rice husk waste can cause environmental problems. The objective of this study was to investigate the effect of rice husk ash on SCC concrete. The study involved using Rice Husk Ash (RHA) as a partial replacement for cement in SCC concrete at varying percentages (0%, 5%, 10%, and 15% of cement weight). The results of the slump flow test showed that the highest value of 775 mm was achieved at 15% RHA, meeting the specifications of SCC concrete. In terms of compressive strength, the results showed that the SCC mixture without rice husk ash (0% RHA) had the highest average compressive strength, which was 30.56 MPa at 14 days and 31.66 MPa at 28 days of concrete. On the other hand, the average compressive strength of SCC concrete with rice husk ash mixture was highest at 5% RHA, with 25.04 MPa at 14 days and 28.81 MPa at 28 days. Overall, the study found that the use of rice husk ash in SCC concrete had a significant effect on its compressive strength, with the highest compressive strength being achieved at 5% RHA.

The Effectiveness Of Using Column Formwork In A Multi-Story Building Construction Project

Building the structural components is crucial for constructing a multi-story building. In the process of creating these components, which is commonly done through casting, a tool called formwork is required. Formwork is a tool used to mold the necessary concrete structures, ensuring that their shape and dimensions align with the concrete material's planning. Formwork tasks for concrete work significantly impact costs. Different formwork options, including traditional, semi-system, and full-system forms, are available. This research aims to assess cost-effectiveness through value engineering, specifically focusing on column formwork, by comparing their utilization in a multi-story construction project. The study begins by collecting primary data, namely working drawings, so that the volume of conventional formwork can be calculated. Then, budget planning calculations are made to analyze the cost comparison of each formwork alternative. The selection of the appropriate formwork affects the speed of execution and the costs incurredIn this construction project for the building, the conventional column formwork results in expenses amounting to IDR 587,749,263.04 and requires 28 days for completion, while semi-system column formwork achieves a 37% cost saving with the same duration of 28 days, and full-system column formwork becomes 64% more cost-effective with a construction period of 10 days.

The effect of chemical oxygen demand of domestic wastewater on workability, mechanical, and durability of self- compacting concrete

Due to worldwide water scarcity, especially in arid regions, and the substantial use of drinking water in concrete production, the consideration of gray water usage is growing. However, wastewater contamination adversely affects concrete's mechanical strength and durability, with Chemical Oxygen Demand(COD) as one of the indicator. In the present work, the effect of COD of different types of domestic wastewater on workability, mechanical, and durability properties of self-compacting concrete (SCC) with 400 kg/m3 and 440 kg/m3 of cement, and water-to-cement ratios of (w/c) 0.36 and 0.5 for 12 different SCC mixture designs were investigated. The results of the experiments indicated that increasing the COD of domestic wastewater negatively impacts the workability of fresh concrete. Additionally, as the COD of the wastewater increases, the compressive strength of SCC decreases at 7 and 28 days when using raw sewage, sewage sludge, and artificial wastewaters. However, by 90 days, the compressive strength showed no significant difference compared to SCC made with tap water. With increasing COD of wastewater, the 28-day tensile strengths of SCC decreased by 6–10 %. The COD of wastewater did not significantly affect the flexural strength. However, the fracture toughness, at a water-cement ratio (w/c) of 0.5, decreased with increasing COD, reaching a reduction of 36 % at a COD of 940 mg/L. As the COD concentration rises, water absorption increases. In SCC samples containing sludge water and raw sewage, capillary water absorption was at its maximum due to the presence of impurities, as well as organic and mineral materials.

Assessment of quality indicators in construction

Introduction. Ensuring proper quality of construction is one of the pressing challenges of our time. Consumers expect cheap products from developers in the form of commercial or residential real estate that meet all the required quality indicators. Most accidents in monolithic construction occur due to non-compliance with technological procedures at low temperatures. The purpose of the study is to develop a framework for assessing the quality of concrete work at subzero temperatures (during winter work) based on the results of studies of technological parameters of winter concreting, their impact on the quality and safety of erected monolithic structures of industrial and civil buildings (structures).Materials and methods. The study used the method of approximating distributions of random variables, expert estimates, the theory of multiple principles, and mathematical statistics. The experiments were carried out in the laboratories of the Don State Technical University, as well as in the conditions of actual concrete work on a construction site in winter. The work uses a correlation-regression analysis of the dependence of the organizational and technological causes of inconsistencies (factors) and quality indicators of concrete work production. Statistical information on structural damage and collapse of buildings during their operation was processed. To make organizational and technological decisions to improve the quality of concrete work, it is proposed to take the influence of defects on the load-bearing capacity of buildings as an indicator of the quality level.Results. Using practical and expert methods, the most significant reasons (factors) for the occurrence of inconsistencies in the level of quality of concrete work production have been established. Factors have been identified that have the greatest influence on the change in the load-bearing capacity and reliability of buildings and structures being erected when performing the main types of construction and installation work. The nomenclature of technological quality indicators during winter production of concrete work, their influence on quality substantiated, and methods for assessing the quality of winter concreting technology are developed. Quantitative indicators of the quality of construction of monolithic reinforced concrete structures were obtained.Discussion and conclusions. The practical value of the work lies in the development of a methodological tool for creating a regulatory framework for operational construction control of the production of monolithic and prefabricated monolithic construction and installation works under conditions of exposure to low temperatures, as well as for acceptance control of compliance of completed construction projects with quality requirements. Proposals are given for establishing regulatory tolerances, ways to improve the manufacturability of the equipment used, a new method for designing winter concreting technology, and a quality control method focused on ensuring structural safety have been developed. By developing the research, it is further possible to develop methods for calculating technology parameters taking into account technological variability, as well as establish new indicators to regulate the required level of quality and safety of buildings being built.

The Effect of Copper Tailings Sand on the Workability and Mechanical Properties of Concrete

The Effect of Copper Tailings Sand on the Workability and Mechanical Properties of Concrete

Extended discharge time of ready-mixed concrete: Myth or necessity?

A significant volume of pre-mixed concrete is frequently sent back to batching plants for disposal due to various factors such as excessive slump loss during transportation, overproduction, and experimentation with new batches. It is estimated that approximately 3 % of the total concrete production becomes waste. Rejecting numerous truckloads of concrete is typically based on strict adherence to the concrete discharge 90-minute time limit. This study investigates the effects of extending the discharge time on the properties of fresh and hardened ready-mixed concrete, as well as its durability. To emulate typical field construction conditions, we formulated representative concrete mixtures and sourced, batched, and poured them from a local ready-mix concrete supplier. To maintain the concrete's workability without altering the mix design, high-range water reducer (retarder or stabilizer), and air-entrainment admixtures were incorporated as needed. The fresh and hardened concrete properties were evaluated at batching and at time intervals of 60, 90, 120, and 150 minutes for three different concrete mixtures. Fresh concrete properties included air content, slump, and temperature, while hardened concrete properties encompassed compressive strength, freeze-thaw resistance, and surface resistivity. Remarkably, the discharge time had no significant impact on the fresh and hardened concrete properties even up to 150 minutes. This indicates that the strict discharge time limit is overly cautious. Embracing an extended discharge time offers numerous economic and sustainable advantages.

Studying the usability of recycled aggregate to produce new concrete

One of the most significant environmental issues worldwide is garbage, particularly waste from construction materials, which is generated in substantial numbers. However, in the building industry, the significant extraction of natural resources such as cement, natural sand, and natural gravel poses a critical environmental challenge, depleting these resources at an alarming rate. There are some solutions that developed countries are resorting to, namely the division of construction waste into groups, where it is reused under the name of recycling construction waste to produce new, environmentally friendly building materials. The aim of this research includes a laboratory process study as it includes the use of the following ratios: 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100%, under the process of replacing coarse plain aggregates including coarse recycled aggregates and studying the most important mechanical properties of concrete. This research was carried out using fresh concrete properties such as workability tests and hardened concrete properties such as compressive strength, splitting, and flexural tensile strength examined at the durations of 7, 14, and 28 days. The research includes the investigation of the three main properties of concrete. After conducting the tests, the results have shown that the main property of recycled concrete is lower strength than that of conventional concrete, but it can be said that it is within the limits that can be used for construction. The results also showed that compared to normal aggregates, development in the recycled aggregate percentage rates reduces the operational workability of concrete. The research proved that the maximum decrease in compressive, flexural, and tensile strength, density and the slump were 19.4, 18.3, 19.6, 19.5, and 25.0% respectively compared to the control concrete samples.

Axial compression behavior of carbon fiber reinforced polymer confined partially encased recycled concrete columns.

Partially encased concrete (PEC) has better mechanical properties as a structure where steel and concrete work together. Due to the increasing amount of construction waste, recycled aggregate concrete (RAC) is being considered by more people. However, although RAC has more points, the performance is inferior to natural aggregate concrete (NAC). To narrow or address this gap, lightweight, high-strength and corrosion-resistant CFRP can be used, also protecting the steel flange of the PEC structure. Therefore, carbon fiber reinforced polymer (CFRP) confined partially encased recycled coarse aggregate concrete columns were studied in this paper. With respect to different slenderness ratios, recycled coarse aggregate(RCA) replacement ratios, and number of CFRP layers, the performance of the proposed CFRP restrained columns are reported. The RCA replacement ratio is analyzed to be limited negative impact on the bearing capacity, generally within 6%. As for the slenderness ratio, the bearing capacity increased with it. However, wrapping CFRP significantly increased the bearing capacity. Considering the arch factor, a simple formula for calculating the ultimate strength of CFRP-confined partially encased RAC columns is developed based on EC4 and GB50017-2017. By comparison with the experimental values, the error is within 10%.

The influence of slag content on the mechanical properties of high-strength concrete

In light of the current situation where excessive amounts of excavated earth from subway tunnel construction are being stacked with low utilization and value, this study used residue as a mineral admixture to investigate the effects of different proportions of residue content (0%, 2.5%, 5.0%, 7.5%, and 10.0%) on the workability and mechanical properties of C50 concrete. The results indicate that: (1) The initial slump and slump loss of C50 concrete decrease gradually as the residue content increases. (2) The compressive strength of C50 concrete with varying residue contents is lower than the control group at early stages (3d, 7d), while it is higher than the control group at 28d. There exists an optimal content of residue for improving C50 concrete compressive strength, and it is found that the highest compressive strength at 28d is achieved when the residue content is 7.5% of the cement content. (3) The microscopic structure of C50 concrete with different residue contents at 28d shows that as the residue content increases, the microscopic structure of C50 concrete gradually becomes more compact and the porosity decreases.

Performance of steel fibre reinforced lightweight aggregate concrete in fresh and hardened state

Abstract There is a growing interest in the manufacture of lightweight aggregate concrete (LWC) due to its low density, which is below 2000 kg/m3. However, the trade-off for the lower density is a reduction in strength, leading to a drop in crack resistance. Therefore, steel fibre inclusion was implemented to augment the crack resistance of lightweight concrete (LWC). Thus, the present study aims to examine the impact of steel fibre on both the workability and mechanical properties of lightweight aggregate concrete (LWC) that incorporates lightweight expanded clay aggregate (LECA). Three varieties of concrete were fabricated, namely normal weight aggregate concrete (NC), lightweight concrete (LWC), and steel fibre lightweight concrete (SFWLC). The SFLWC incorporated hooked-end steel fibres as reinforcement, with fibre volume percentages of 1 % and 2 %. A strength assessment was undertaken to ascertain the concrete properties, with particular emphasis on compressive and tensile strength. The findings indicate that the incorporation of both LECA and steel fibre led to a notable reduction in the workability of concrete. Incorporating a 2 % steel fibre content into LWC yields a marginal enhancement in compressive strength. Steel fibre demonstrates enhanced efficacy when subjected to tension, with the most significant increase measured at around 152 %.

Quality assessment standards and production technology of artificial sand based on hydraulic concrete construction specifications

Natural sand and gravel resources are a local resource. Natural sand and gravel are non-renewable in a short time and are not suitable for long-distance transportation. After decades of mining, sand and gravel resources in some areas have been exhausted. The transportation distance of natural sand and gravel is getting farther and farther, and accordingly, the price of natural sand and gravel continues to rise. At the same time, continuous and disorderly mining has caused serious damage to the environment and resources. During the construction of large and medium-sized water conservancy and hydropower projects in China, due to the lack of surrounding natural aggregates, most projects use artificial aggregates. In the current national standards for water conservancy projects, the content of artificial sand and gravel powder is clearly defined. Based on the “Hydraulic Concrete Construction Specifications” (SL677-2014), this article summarizes the particle shape, gradation and surface structure of artificial sand, and also calculates the theoretical gradation of artificial sand. To find out the impact of stone powder content on the performance of artificial sand, different levels of stone powder content need to be selected for research and analysis to clarify the impact of artificial sand powder content on concrete properties. Research shows that for concrete made from artificial sand, increasing the aggregate content with a particle size less than 0.075 mm can significantly increase the compressive strength of the concrete. In artificial sand, the content of stone powder will affect the workability, polishability, durability, permeability and water release of concrete. In the artificial sand and gravel production process system, crushing and sand making equipment are the most important sand and gravel production equipment. The research results provide theoretical reference for the application of artificial sand in concrete and the update of artificial sand production technology and equipment.

Freeze-Thaw Cycle Durability and Mechanism Analysis of Zeolite Powder-Modified Recycled Concrete.

The inferior mechanical performance and freeze-thaw (FT) resistance of recycled concrete are mostly due to the significant water absorption and porosity of recycled coarse particles. In this study, different dosages of zeolite powder were used in recycled concrete. A series of macroscopic tests were used to evaluate the workability and FT durability of zeolite powder-modified recycled concrete (ZPRC). X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to reveal the micro-mechanisms of FT resistance in ZPRC. The results show that the increase in zeolite powder content leads to a decrease in the slump and water absorption of ZPRC. Additionally, ZPRC with 10% zeolite powder has superior mechanical characteristics and tolerance to FT conditions. The higher strength and FT resistance of the ZPRC can be attributed to the particle-filling effect, water storage function, and pozzolanic reaction of zeolite powder, which results in a denser microstructure. The particle-filling effect of zeolite powder promotes the reduction of surface pores in recycled coarse aggregates (RCAs). The water storage function of zeolite powder can provide water for the secondary hydration of cement particles while reducing the free water content in ZPRC. The pozzolanic reaction of zeolite powder can also promote the generation of hydrated calcium silicate and anorthite, thereby making the microstructure of ZPRC more compact. These results provide theoretical guidance for the engineering application of recycled concrete in cold regions.

Review on metakaolin impact on the workability and compressive strength of concrete

Review on metakaolin impact on the workability and compressive strength of concrete

Effect of Construction Delays and the Preventive Role of Concrete Works Optimization: Systematic Literature Review

Delays in construction are a widespread global problem, leading to potential cost overruns and legal disputes. Additionally, delays can result in a decline in construction quality and loss of public trust. The aim of this study is to examine the effects of project delays in various regions and the preventive role of optimizing concrete works. Literature review and bibliometric analysis are carried out to determine global research trends. Findings show that optimizing concrete works can provide benefits such as cost savings, time savings, improved quality and safety, and environmental benefits. Optimization of concrete material composition is one of the most examined topics in this field. Based on the findings, construction firms have the potential to attain cost efficiencies while concurrently mitigating carbon emissions.

Statistical Model for Compressive Strength of Metakaolin Concrete

In the present research work, investigations were carried out to improve the performance of concrete in terms of strength by incorporating metakaolin (MK) as mineral admixture in concrete. Parametric study was carried out by considering w/c ratio, various percentage of MK and age of concrete as parameters to understand the effect of each parameter. The study was conducted for different w/c ratios of 0.32, 0.35, 0.4 and 0.5. The MK proportion was varied from 0 to 15% with an increment of 5% and age of concrete from 3 to 90 days were considered and experiments performed accordingly. The effects of above said parameters on the various properties of concrete such as workability, compressive strength and pH of concrete were investigated, and the results of metakaolin concrete were compared with the conventional concrete. From the results, it was observed that MK concrete showed greater strength for higher water cement ratios (0.4 & 0.5). A Multiple non-linear regression analysis was used to develop a statistical model to predict the strength and found to have good correlation between the observed and predicted values. It was concluded that the concrete developed in this study have significant potential for use on real time projects.

Development of sustainable interlocking concrete paving blocks using bamboo leaf ash and metakaolin

Eco-friendly interlocking concrete pavement block was developed using the admixture of bamboo leaf ash and metakaolin. This was done to develop an eco-friendly interlocking paving block for sustainable pavement construction. Bamboo leaf ash and metakaolin were added as a supplementary cementitious material. The supplementary cementitious material (bamboo leaf ash and metakaolin) were admixed and added at 0, 5, 10, 15, 20, 25 and 30 % replacement of cement. The workability of the fresh concrete (slump) at the varied percentage additions, and the mechanical properties of the concrete at 7, 14, 28, and 56 days of curing were assessed, including their microstructural characteristics. The outcome of the research showed that increasing the percentage of (bamboo leaf ash + metakaolin) reduces the workability of the concrete. With a 20 % addition of this cementitious material, the developed fresh concrete became unworkable. In addition, replacing up to 10 % of the concrete in the pavement with bamboo leaf ash and metakaolin increased the mechanical strength of the concrete by 28.7 %. At 30 % a percentage increase of 3.6 % was recorded. However, the strength at 5 % was still adequate for pavement construction with a 13.62 % increase in mechanical strength. The compressive strength at 5 % and 10 % addition of the supplementary cementitious material at maturity met the criteria for constructing a semi-rigid pavement, using IRC standards. The microstructural assessment showed that the number of pores in the mature concrete samples decreased at 10 % addition of bamboo leaf ash and metakaolin. The research data provides construction workers, researchers, and highway engineers with vital information regarding the viability of these sustainable materials for pavement improvement.

Study of the Workability of Self-Compacting Concrete (SCC) Using Experimental Methods and Artificial Neural Networks (ANN)

Study of the Workability of Self-Compacting Concrete (SCC) Using Experimental Methods and Artificial Neural Networks (ANN)

A Comprehensive Review on the Use of Wastewater in the Manufacturing of Concrete: Fostering Sustainability through Recycling

The primary aim of this review article is to find the influence of wastewater and its characteristics on recycling as an alternative to potable water for concrete preparation. On the other hand, scarcity, and the demand for freshwater for drinking are also increasing day by day around the globe. About a billion tons of freshwater is consumed daily for concrete preparation for various operations such as mixing and curing, to name a few. The rapid development of certain industries such as textile, casting, stone cutting, and concrete production has caused the water supply to be severely affected. Recycling wastewater in concrete offers various potential benefits like resource conservation, environmental protection, cost savings, and enhanced sustainability. This article reviews the effect of various types of wastewater on various physical and chemical properties of wastewater, rheological characteristics, strength, durability, and microstructure properties of concrete. It also explores the potential effects of decomposing agents on enhancing concrete properties. Currently, limited research is available on the use of various types of wastewater in concrete. Hence, there is a need to develop various methods and procedures to ensure that the utilization of wastewater and treated wastewater is carried out in the production of concrete in a sustainable manner. Although wastewater can reduce the workability of fresh concrete, it can also increase its strength and long-term performance of concrete. The use of various types of wastewater, such as reclaimed water and tertiary-treated wastewater, was found to be superior compared to those using industrial- or secondary-treated wastewater. Researchers around the globe agree that wastewater can cause various detrimental effects on the mechanical and physical properties of concrete, but the reductions were not significant. To overcome limited scientific contributions, this article reviews all the available methods of using various types of wastewater to make concrete economically and environmentally friendly. This research also addresses possible challenges with respect to the demand for freshwater and the water crisis.

Influence of Steam Curing Temperature on the Characteristic of Self-Compacting Concrete Incorporating Palm Shell Ash

Self-Compacting Concrete (SCC) is proven as durable concrete and applied to constructions. In this paper, a study was conducted to analyze the influence of variations of steam curing temperature (SCT) and water/binder (w/b) ratio on the characteristics of SCC incorporating 10% Palm Shell Ash (PSA) as a partial substitution for cement mass. The SCT was arranged from 25 C to 80 C. The variation of w/b in the compositions of SCC was 0.325, 0.350, and 0.375. The results showed that using PSA, the variation of SCT and the w/b ratio influenced the workability of the fresh concrete. The PSA, SCT, and the w/b ratio affected the concrete compressive strength and mass density. The increased SCT caused a lighter density and greater compressive strength. However, the decreased compressive strength occurred due to an excessive SCT of 70 C and above. The SCT of 60 C, 10% PSA, and w/b ratio of 0.350 in the mixture produced the greatest compressive strength of 36.27 MPa at 28 days of age, while without SCT, the greatest compressive strength of 36.78 MPa was achieved at the age of 28 days containing 10% PSA and w/b ratio of 0.325. It indicated that the w/b ratio was more influential than the SCT on the increase of the SCC compressive strength.

Experimental Investigations on Mineral Admixtures and Steel Fibers in High Strength Concrete

In the process of manufacturing of concrete sand is the most commonly used fine aggregate. The main sources for the natural sand are river beds. These characteristic assets are getting depleted because of over abuse and defilement by chemicals and waste from nearby industries. The waste generated from the demolition of existing structures for various reasons causes great concern and ecological issues. In this project our main objective is to study the influence of partial replacement of F.A with recycled fine aggregate and to compare it with the compressive strength and workability of high strength M60 concrete. We are also trying to replace the various percentages of recycled fine aggregate to study the tendency of the Characteristic strength of concrete.