In order to study the mechanical properties of rubber concrete (RC) with different rubber particle sizes after dry–wet cycles in a sulfate environment, apparent morphology analysis, mass loss analysis, relative dynamic elastic modulus analysis, compressive strength loss analysis, internal microscopic characteristics and deterioration degree analysis of ordinary concrete (NC) and rubber concrete after dry–wet cycles were compared and analyzed. The results show that with the increase in the number of dry–wet cycles, the surface caves of rubber concrete increase, the internal microcracks develop and penetrate, and the macroscopic strength increases first and then decreases significantly. The high elasticity of rubber effectively improves the expansion force caused by sulfate attack and the dry–wet cycle. The deterioration degree of RC in each dry–wet cycle stage is obviously better than that of NC. When the rubber particle size is 0.85 mm, the performance of the sample is the best. After 120 days of dry–wet cycle, the compressive strength is reduced by 37.4%, and the compressive strength of concrete with a rubber particle size of 0.85 mm is reduced by 11.2%. After cyclic loading, the deterioration degree of concrete is 5.1% lower than that of ordinary concrete.

/pdf/mechanical-properties-and-microstructure-of-rubber-concrete-3mdb1ces.pdf

Mechanical Properties and Microstructure of Rubber Concrete under Coupling Action of Sulfate Attack and Dry–Wet Cycle

Concrete extravagantly used as an anthropogenic building material, unabated in urban development. Globally the cement sector emits about 8% of CO2 (Carbon Dioxide), generated at a ratio of 1MT of CO2 per1MT of cement clinker sintering. Environmental concerns for its degradation through cement. To restrict cement production, natural clay materials and industrial refuges are in to substitute cement part or whole.  The present-day hunt is the usage of Metakaolin (MK), a copiously accessible clay in India, as a substituent for cement. The physical, chemical, and mechanical properties of the metakaolin concrete investigated using XRF spectrometer, Scanning Electron Microscopy and universal testing machine following laboratory procedures. The efficiency of MK-concrete at different percentage mixes (0-30%) of ordinary Portland cement replacement at water-cement ratio 0.48 for all the mixes observed. The results suggested that concrete strength reduced significantly during the initial hydration period, particularly at high MK content. The application of up to 15% MK beyond 28 days curing triggers initial setting, time, rises in concrete strength, and increases durability and is also not affected by alkali-silica gel reaction, chloride and sulphate attack. Depending on the age of curing and the MK-concrete durability increases. This work shall reduce the carbon burden of present atmosphere if 15% blended MK cement concrete used.

The Non-Carbon Kaolinite; Part Substituent of Cement in Concrete

Abstract: The literature study shows that some industrial waste material such as fly ash, GGBS, silica fume, metakaoline, etc. are good way to exchange cement in concrete and make it durable, strong, economic and environment friendly and also gives strength as per conventional concrete. These materials are often used as supplementary cementitious material because the replacement of cement in various percentages and make it high performance concrete which may be utilized in high rise building, flyovers, bridges, etc In this literature review study metakaoline looks to be promising supplementary cementitious material for high performance concrete. The substitution proportion of metakaoline is to be used was 0%, 10%, 20%, 30%, 40% by the weight of the cement. The cubes were made to check the compressive strength at 7, 28 and 56 days of curing. The results shows the many difference between the replacing mix upto last percent has effect on strength as compared with mix without metakaolin. Keywords: Metakaoline, concrete mix, compressive strength, ANSYS 

/pdf/a-comparative-study-on-hardened-properties-of-concrete-by-1cgokzdf.pdf

A Comparative Study on Hardened Properties of Concrete by Partial Replacement of Cement with Metakaolin by Experimental and ANSYS Approach

This experimental study investigates the influence of metakaolin as a mineral admixture on the compressive strength and flexural strength of standard concrete (M-25). Metakaolin, a highly reactive pozzolanic material, was introduced as a partial replacement for cement by weight. Metakaolin is a valuable addition to many concrete mixes. It can improve the strength, durability, and resistance of concrete, making it a more versatile and sustainable material. Here are some of the key properties of metakaolin:
• High pozzolanic activity: Metakaolin is a highly reactive pozzolan, which means that it reacts with calcium hydroxide to form a gel that binds the concrete particles together. This gel helps to improve the strength, durability, and resistance of concrete.
• Fine particle size: The particle size of metakaolin is smaller than the particle size of cement, which means that it can fill the voids in the concrete matrix and improve the density of the concrete.
• High surface area: The high surface area of metakaolin also contributes to its pozzolanic activity. The larger surface area provides more sites for the reaction between metakaolin and calcium hydroxide to take place.
• Low water content: Metakaolin has a low water content, which means that it does not contribute to the water-to-cement ratio of the concrete. This helps to improve the strength and durability of the concrete.
• Chemical resistance: Metakaolin is resistant to a variety of chemicals, including acids, alkalis, and salts. This makes it a good choice for use in concrete that will be exposed to harsh environments.
• Heat resistance: Metakaolin is also resistant to high temperatures. This makes it a good choice for use in refractory materials and other high-temperature applications.
The research aimed to assess the impact of metakaolin on the mechanical properties of concrete, with a focus on its ability to enhance compressive The research aimed to assess the impact of metakaolin on the mechanical properties of concrete, with a focus on its ability to enhance compressive strength and flexural strength. The study involved the preparation of M-25 grade of concrete mixes with PPC 33 grade cement, locally available sand and aggregate with varying metakaolin proportions, ranging 10%, 20% and 30% by weight of cement. Specimens were cast and cured under controlled laboratory conditions. Compressive strength tests were conducted on cubical specimens, and test after 7 and 28 days and flexural strength tests were conducted on beam specimens, and test after 28 days respectively. Results revealed that the inclusion of 10% and 20% of metakaolin led to improves the 28 days compressive strength and flexural strength by 3.33% and 5.34% as compared to normal concrete respectively. The increase in strength is attributed to the pozzolanic reaction between metakaolin and calcium hydroxide, resulting in improved microstructure and reduced pore size within the concrete matrix.

pdf/experimental-study-of-compressive-strength-and-flexural-1ba0trswih.pdf

Experimental Study of Compressive Strength and Flexural Strength of Standard Concrete by using Metakaolin as Mineral Admixture

Abstract Hot climates are typically marked by high temperatures, low rainfall, elevated salinity, and high humidity. These conditions accelerate the degradation of concrete, impacting its durability. In the Middle East, where a hot and humid climate prevails, several nuclear facilities, including those in hospitals, research centers, industries, and more recently, a nuclear power plant, are situated. In this updated review, the factors influencing the radiation shielding performance of concrete in arid climates are analyzed. The effects of high temperatures and chemical attacks, particularly sulfate attack, on shielding concrete are examined. The role of aggregate type and size, crucial for radiation attenuation, is also explored. Furthermore, commonly used additives and admixtures that enhance the attenuation coefficient of concrete are thoroughly reviewed. Methods for evaluating the radiation shielding properties of concrete, as reported in the literature, are discussed. Finally, case studies showcasing the application of radiation shielding concrete in extreme environmental conditions are highlighted. One major gap in existing research is the lack of comprehensive study on the effect of chemical attack on the shielding properties of concrete. As Middle Eastern countries, such as the UAE and Saudi Arabia, express interest in deploying nuclear energy, our goal is to present the first comprehensive article gathering all relevant information on the potential effects of the region's unique environmental conditions on the attenuation efficiency of concrete elements in such facilities. 

Factors Influencing the Radiation Shielding Capacity of Concrete Exposed to Aggressive Arid Environment: A Comprehensive Review

The problem of assessing the variation in natural frequency of a prestressed and un-prestressed beam has been of considerable interest to Structural Engineers. The objective of the present work is to find the effect of pre-stressing on Natural frequency of a Concrete beam and thereby establishing a relationship between the natural frequency of 1st mode of vibration and other modes. Conventional methods were used to calculate the natural frequency of 1 to 5 modes of vibration for un-prestressed beams while STAAD.Pro was used for assessing the same for prestressed beams. A 20 m span beam with different live loads and cross-sections were considered for the study. From the results, it was observed that as the cross-section of the beam increases, the natural frequency decreases. Comparing the natural frequency of 1st mode of vibration for beams with and without prestressing, it can be observed that within the scope of this work, the natural frequency of the un-prestressed beam with live load 15 kN/m is more than that for the prestressed beam. For the other two load-carrying capacities, it is vice-versa. It was also observed that the % difference of Natural frequency of a particular mode of vibration w.r.t mode 1 natural frequency is almost constant. In other words, the effect of live load and cross-section is negligible on the % difference of Mode i to Mode 1 natural frequency. Based on this characteristic, a mathematical model has been developed.

https://robots.iopscience.iop.org/article/10.1088/1757-899X/1025/1/012008/pdf

Mathematical Model for Natural Frequency of Prestressed Concrete beam using STAAD.Pro.

Sustainable development of the cement and concrete industry requires the utilization of industrial and agricultural waste components. At present, for a variety of reasons, the concrete construction industry is not sustainable. In general, high strength concrete made with ordinary cement is not durable and does not have good resistance to acids except for some weak acids if the exposure is occasional. Metakaolin is a supplementary cementitious material used as an admixture to produce high strength and high-performance concrete. The objective of this study is to arrive at Optimal quality of metakaolin that can partially replace the cement for M20, M30, M40, M50, M60, M70, M80 grades of concrete to get better strength and durability. The mix proportions of OPC concrete are obtained for M20, M30, M40, M50, M60, M70, M80 as per IS 10262 2009 [1]. Mix proportions with partial replacements of cement by 0%, 10%, 15%, 20%, 25%, 30% of Metakaolin with concrete were determined. Concrete specimens for compressive strength (150 mm x 150 mm x 150 mm cubes) are cast and Durability studies are conducted for all grades with partial replacement of cement by Metakaolin for 1% and 0.5% concentrations of HCl and H2SO4. From the results, it was concluded that the compressive strength of concrete is maximum at 15% replacement of cement by Metakaolin. The compressive strength of concrete showed better result at 15% replacement of Metakaolin for 0.5% and 1% HCl and H2SO4 at the age of 28days of strength. The effect of HCl on strength of the Metakaolin concrete is lower than the effect of H2SO4.

https://iopscience.iop.org/article/10.1088/1757-899X/1025/1/012004/pdf

Compressive strength and durability of Metakaolin blended concrete exposed to acid and sulphate attack

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Mathematical Model for Natural Frequency of Prestressed Concrete beam using STAAD.Pro.

Compressive strength and durability of Metakaolin blended concrete exposed to acid and sulphate attack