Effect of metakaolin on the properties of conventional and self compacting concrete

Assessment of fresh and hardened properties of concrete using supplementary cementitious materials

In recent years, a growing focus has been on creating eco-friendly concrete alternatives, garnering increased attention and support. Using natural fibers in the construction industry will minimize the exploitation of natural raw materials and promote sustainability in the construction industry. This work aims to investigate the influence of palmyra fruit mesocarp fiber (PFMF), Polyolefin fiber (PF), and glass fiber (GF) on the production of self-compacting concrete (SCC). The fiber content was used in three ratios, 1, 1.5, and 2%, as an alternative to fine aggregate. This research was conducted in two phases. In the first phase, a preliminary investigation was carried out to find the maximum adding percentage of fiber content in the successful production of SCC. The mechanical characteristics (compressive, split tensile, and flexural strength) and durability (water absorption, Acid attack, and ultrasonic pulse velocity) were evaluated. The second phase incorporates the fresh characteristics (T500 and slump flow). Adding 1.5%(PFMF/PF/GF) with 10% SF in SCC significantly enhanced the mechanical and durability properties. The compressive, splitting tensile strength, and flexural strength at 28 days increase to 4.30 MPa, 120 MPa, and 4.3 MPa compared to SCC. Scanning electronic microscopic (SEM) and X-ray diffraction (XRD) analysis was performed to evaluate the microstructure of concrete samples. Overall, the incorporation of up to 1.5% as a replacement of fine aggregate in manufacturing fiber-blended SCC mixtures can be recommended.

SCC (Self compacting concrete) can fill formwork and encloses reinforcing bars under gravity and maintains homogeneity without vibration. SCC shortens the period of construction, guarantees compaction in confined zones, moreover terminates noise due to vibration. The wide spread application of SCC is restricted because of the high cost for the production of SCC with high cement content and chemical admixtures. In order to make the production of SCC economical, and to reduce the high cement content the Ordinary Portland Cement in SCC can be blended with pozzolanic materials like rice husk ash and supplementary cementitious materials like fly ash. In this paper the fresh state properties and mechanical properties such as compressive strength, split tensile strength and flexural strength of SCC with ternary blends of rice husk ash (RHA) and fly ash (FA) were studied. For this purpose, different mixes were prepared by replacing Ordinary Portland Cement (OPC) with 5%, 10%, 15% and 20% of rice husk ash (RHA) and the percentage of addition of fly ash (FA) is fixed as 15% for all these mixes. It was observed that the specimen incorporating 10% of rice husk ash (RHA) and 15% of fly ash (FA) as ternary blend exhibits better mechanical properties such as: Compressive, split tensile and flexural strengths at 28 days of age as compared to traditional mix of SCC without RHA (Rice Husk Ash) and FA (Fly Ash). This research demonstrates that the ideal percentage for a mixture of rice husk ash (RHA) and fly ash as ternary blend is 10% and 15% respectively.

Concrete is the most widely used construction material because of its mouldability into any required structural form and shape due to its fluid behavior at early ages. Thorough compaction, using vibration, is normally essential for achieving workability, the required strength and durability of concrete. Inadequate compaction of concrete results in large number of voids, affecting strength and long-term durability of structures. Self-compacting concrete (SCC) provides a solution to these problems. As the name signifies, it is able to compact itself without any additional vibration or compactive effort. However, widespread applications of self-compacted concrete have been restricted due to lack of standard mix design procedure and testing methods. Self-compacted concrete is used as a special concrete in place of standard concrete due to lack of mix design procedures. It is gaining wide acceptability because no vibration is needed and noise pollution is eliminated thereby. The construction process is safer and more productive. This paper presents the performance of self-compacted concrete by using ordinary Portland cement, metakaolin (MK) as a mineral admixture and Glenium B233 as a superplasticizer. Metakaolin is produced by heating kaolin, one of the most abundant natural clay minerals, to temperatures of 700–850 °C. The performance of metakaolin in self-compacting concrete is not well documented, particularly over a wide range of grades. In particular, the effects of metakaolin as a high surface area mineral addition on the workability as well as mechanical properties of self-compacting concrete need to be fully recognized. Therefore, the present study is an effort to characterize the fresh and hardened properties of self-compacting concrete containing metakaolin. Glenium B233 is an admixture of a new generation based on modified poly carboxylic ether. It is free from chloride and is compatible with all types of cements. This experimental study demonstrates that metakaolin can be successfully used as an admixture in the preparation of self-compacting concrete (SCC). In order to prepare suitable mix proportions for different grades of metakaolin based self-compacting concrete, investigations were undertaken replacing cement with 0, 10, 15, 20, 25 and 30 % of metakaolin and with different percentages of superplasticizer (Glenium B233). As per the European guidelines for self-compacting concrete, slump flow test, V-funnel test and L-box test have been carried out on fresh properties of metakaolin based self-compacting concrete. The compressive strength, split tensile strength and flexural strength of the specimens have been analyzed for 7 and 28-days curing. In addition, finally mix proportions have been recommended for low, medium and high strength grades of metakaolin based self-compacting concrete. The fresh concrete test results revealed that by substituting different percentages of metakaolin in self-compacting concrete, satisfactory workability and rheological properties could be achieved, even though no viscosity-modifying agent was needed. In general, it seems that metakaolin can be considered as suitable replacement regarding to the economic efficiency, fresh and hardened properties of metakaolin based self-compacting concrete. The test results for acceptance characteristics of self-compacting concrete such as slump flow test, V-funnel test and L-Box test were satisfactory as per EFNARC for developed mix proportions of M60, M40 and M20 grade self-compacting concrete mixes. Further, compressive strength, tensile strength and flexural strength at the ages of 7 and 28 days were also determined and 10–15 % replacement of metakaolin can be regarded as a suitable replacement and mix proportions have been recommended for low (M20), medium (M40) and high (M60) strength grades of metakaolin based self-compacting concrete from this study.

The environmental impact of concrete production, mainly due to cement manufacturing, has prompted the search for sustainable alternatives, such as agricultural byproducts. Rice husk ash (RHA) and coffee husk ash (CHA) show promise as supplementary cementitious materials that can enhance concrete’s strength and durability. However, RHA’s fine particles reduce workability, and CHA’s lower silica content limits its pozzolanic reactivity. While both have individual benefits, their combined effects on concrete properties remain underexplored. This study investigates the influence of RHA and CHA as partial cement replacements on the fresh and hardened properties of concrete. A C‐25 mix was designed using the ACI 211.1 method, with RHA and CHA proportions ranging from 0% to 25% and 0% to 15%, respectively, in 5% increments. Workability was assessed using slump tests, and mechanical properties—including compressive, split tensile, and flexural strengths—as well as durability (measured through water absorption, strength, and weight loss under 5% sulfuric acid exposure) were evaluated. The results show that both RHA and CHA significantly affect workability, strength, and durability. RHA reduced workability more than CHA due to its finer particles and higher water absorption. The optimal mix of 10% RHA and 5% CHA improved compressive strength by 5.04% and 7.87% at 28 and 56 days, respectively, and enhanced flextural and split tensile strengths by 11.45% and 7.41%, respectively. Durability tests showed that the combination of 15% RHA and 5% CHA (R15C5) significantly reduced water absorption and improved sulfuric acid resistance, indicating a denser microstructure and greater environmental resilience. SEM analysis shows that adding RHA and CHA enhances concrete’s microstructure. The R10C5 mix (10% RHA and 5% CHA) strikes a good balance of strength and refinement. While R15C5 (15% RHA and 5% CHA) improves durability, it shows similar strength and durability to R10C5 due to dilution and higher water demand, as confirmed by statistical analysis. These findings demonstrate that the synergistic use of RHA and CHA can optimize concrete performance, providing a sustainable alternative for enhancing both strength and durability. However, excessive use of RHA or CHA beyond the optimal proportions can compromise performance due to interference with hydration and workability.

Mechanical response and microstructural evolution of fibre-reinforced one-part geopolymer and portland cement concretes

Influence of metakaolin and Recron 3s fiber on mechanical properties of fly ash replaced concrete

The growing demand for low-carbon construction materials has intensified research on supplementary cementitious materials (SCMs) as partial replacements for ordinary Portland Cement (OPC). While several agricultural ashes such as rice husk ash and sugarcane bagasse ash have been extensively studied, limited investigations have comprehensively examined the microstructural behavior and durability performance of sunflower husk ash (SHA) in self-compacting concrete (SCC). Addressing this research gap, the present study evaluates the performance of SCC incorporating SHA as an environmentally sustainable SHA demonstrates potential as a supplementary cementitious material that may contribute to cement reduction at replacement levels of 0%, 5%, 10%, 15%, 20%, and 25%. Fresh properties were assessed using slump flow, T₅₀ time, and V-funnel tests. Mechanical performance was evaluated through compressive, split tensile, and flexural strength tests at 7 and 28days. Durability performance was determined using water absorption and rapid chloride penetration tests (RCPT). Microstructural characterization was conducted using SEM, EDAX, FTIR, and XRD analyses to investigate phase development and hydration mechanisms. The results indicate that 20% SHA replacement yields the highest performance among the tested mixes balance of workability, strength, and durability, achieving a 28-day compressive strength of 53.0MPa, split tensile strength of 4.7MPa, and flexural strength of 6.5MPa, along with reduced water absorption and chloride ion permeability. Beyond 20% replacement, performance declined due to dilution of cementitious phases. The findings establish SHA as a viable supplementary cementitious material for high-performance SCC, offering a sustainable pathway for reducing OPC consumption, particularly in regions with abundant sunflower waste.

Now a day’s research is more concern on the successful utilization of different mineral admixture so as to cut down the environmental pollution caused by cement industries throughout cement production. Self-Compacting Concrete (SCC) is a new generation concrete has been developed without compromising the strength characteristics with minimum time and labour cost. So to make more economic and environmental friendly concrete, two mineral admixtures (waste products of the industries) i.e. Silpozz and Lime Stone Powder (LSP) were used during this experimental work. The aim of this study is to evaluate the fresh and hardened properties of the conventional concrete (CC) and Self Compacting Concrete (SCC) containing mineral admixtures. Cement is partially replaced with Silpozz and LSP as 0%, 10% and 20% for both CC and SCC. Total ten numbers of concrete mixes have prepared for M30 grade of concrete. Fresh concrete properties of CC have evaluated by slump test and for SCC, slump flow, T500, V-funnel and J-ring test were conducted. Hardened concrete properties were evaluated after 7 and 28 days for compressive, split tensile and flexural strength test. The desired amount of superplasticizer (SP) is used in SCC to make the concrete workable. The test results indicate that the 20% replacement of Silpozz influences the mechanical properties of concrete as compared to LSP replacement.

India, as the world's second-largest consumer of concrete, faces an urgent need for sustainable construction practices to address the environmental challenges of cement production and its eventual scarcity. This research investigates the effect of fly ash (FA) as a partial replacement for cement in self-compacting concrete (SCC) across various grades (M30, M50, M70), focusing on both fresh and hardened properties. The study explores the impact of fly ash content (ranging from 0% to 50%) on workability, compressive strength, split tensile strength, and flexural strength. Fresh properties were evaluated through slump flow, V-funnel, L-box, and J-ring tests, demonstrating that fly ash enhances flowability, passing ability, and filling ability up to 30% replacement. However, higher FA content negatively impacted the fresh properties, particularly in lower-grade mixes. In terms of hardened properties, compressive, split tensile, and flexural strengths improved up to 20-30% fly ash, attributed to its pozzolanic reaction and better particle packing. Beyond these levels, strength reduced due to increased paste viscosity and cement dilution. Overall, the research emphasizes the need for optimal fly ash content to maximize strength, workability, and durability in SCC applications

The replacement of natural resources in the manufacture of cement and sand is the present issue in the present construction scenario. Copper slag and Ground Granulated Blast furnace Slag (GGBS) are industrial by-product materials produced from the process of manufacturing copper and iron. Use of Copper slag and GGBS does not only reduce the cost of construction but also helps to reduce the impact on environment by consuming the material generally considered as waste product. Hence in the current study an attempt has been made to minimize the cost of cement and sand with concrete mix grade M25 by studying the mechanical behavior of this concrete mix by partial replacing with advanced mineral admixtures such as Copper slag and GGBS in concrete mix. In this study, partial replacement of Cement with GGBS and Sand with Copper Slag considered. Experimental study is conducted to evaluate the workability and strength characteristics of hardened concrete, properties of concrete have been assessed by partially replacing cement with GGBS, and sand with Copper Slag. The cement has been replaced by GGBS accordingly in the range of 0% (without GGBS), 5%, 10%, 15%, and 20% by weight of cement for M25 mix. The sand has been replaced by Copper slag accordingly in the range of 0% (without Copper slag), 10%, 20%, 30%, and 40% by weight of cement for M25 mix. Concrete mixtures were produced, tested and compared in terms of compressive, flexural and split tensile strength with the conventional concrete. Keywords - Copper slag, GGBS, Workability, Compressive strength, Split tensile strength, Flexural strength.

Today significant research study is ongoing into the use of waste materials like, fly ash, GGBS, waste glass powder etc. as Portland cement replacements. A ceramic waste powder is used as a binder with partial replacement of cement which takes some part of reaction at the time of hydration, and also it acts as a filler material. This study is focused on the waste ceramic powder used as a replacement to the concrete ingredient i.e. cement and the strength properties like compressive, split tensile and flexural strengths were measured and the size effect of ceramic waste powder on strength of concrete. To check the strength effect of replacement of cement by ceramic waste powder, the cement ingredient in concrete is replaced at 10%, 20%, 30%, 40% and 50%. This paper focuses on the size effect of ceramic waste powder, having a size less than 90 micron and another size ranges from 90 microns to 150 microns. For this study, concrete mixtures were prepared, for low-grade M20 and medium grade M40. Strength studies like compressive, split tensile and flexural strengths were conducted and comparisons have to be made with the conventional concrete.

This study investigates the impact of Recron 3S fiber addition on the mechanical properties of M20 grade concrete, aiming to enhance its strength, durability, and crack resistance. Recron 3S, a synthetic micro-fiber, was incorporated into concrete mixes at varying percentages (0%, 0.25%, 0.50%, 0.75%, and 1% by weight of cement), and the resulting properties were compared with conventional concrete. Fresh and hardened properties, including workability, compressive strength, split tensile strength, and flexural strength, were evaluated through laboratory testing on casted cubes and cylinders at 7, 14, and 28 days of curing. The results demonstrate that the inclusion of Recron 3S fibers significantly improves the tensile and flexural strength of concrete, effectively reducing crack formation and enhancing impact resistance. Notably, the split tensile and flexural strength showed considerable improvements with the addition of fibers. However, an increase in fiber content slightly reduced the workability of the concrete mix, necessitating potential adjustments in water content or admixture dosage. The study concludes that incorporating Recron 3S fibers is an effective method to enhance the mechanical performance of concrete, making it suitable for applications demanding enhanced durability and crack resistance, such as pavements, bridges, and industrial floors. This research contributes to the development of high-performance fiber-reinforced concrete, offering a cost-effective solution for improving the properties of conventional concrete and promoting sustainable and durable construction practices, supporting the growing trend of utilizing fibers for composite fortification due to their high strength and thermal resistance. Keywords:Recron 3S fibers, fiber-reinforced concrete, compressive strength, tensile strength, flexural strength, durability, crack resistance, workability, M20 concrete, sustainable construction.

Strength and durability of fiber reinforced concrete with partial replacement of cement by Ground Granulated Blast Furnace Slag

Self compacting concrete (SCC) is special type of concrete which is highly flowable and non-segregated and by its own mass, spreads into the formwork without any external vibrators, even in the presence of thick reinforcement. But SSC is also brittle nature like conventional concrete, which results in abrupt failure without giving any deformation (warning), which is undesirable for any structural member. Thus, self-compacting concrete (SCC) needs some of tensile reinforcement to enhance tensile strength and prevent the unsuitable abrupt failure. But fiber increased tensile strength of concrete more effectively than compressive strength. Hence, it is essential to add pozzolanic materials into fiber reinforced concrete to achieve high strength, durable and ductile concrete. This study is conducted to assess the performance of SCC with substitutions of marble waste (MW) and coconut fiber (CFs) into SCC. MW utilized as cementitious (pozzolanic) materials in percentage of 5.0 to 30% in increment of 5.0% by weight of binder and concrete is reinforced with CFs in proportion of 0.5 to 3.0% in increment of 0.5% by weight of binder. Rheological characteristics were measured through its filling and passing ability by using Slump flow, Slump T50, L-Box, and V-funnel tests while mechanical characteristics were measured through compressive strength, split tensile strength, flexure strength and bond strength (pull out) tests. Experimental investigation show that MW and CFs decrease the passing ability and filling ability of SCC. Additionally, Experimental investigation show that MW up to 20% and CFs addition 2.0% by weight of binder tend to increase the mechanical performance of SCC. Furthermore, statistical analysis (RSM) was used to optimize the combined dose of MW and CFs into SCC to obtain high strength self-compacting concrete.