Influence of Chemical Admixtures on Fresh and Hardened Properties of Prolonged Mixed Concrete (original) (raw)
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EFFECT OF CHEMICAL ADMIXTURES ON PROPERTIES OF CONCRETE: A METHODOLOGICAL REVIEW
International Journal of Research and Analytical Reviews (IJRAR), 2018
As we know that concrete is a mix of cement, sand, aggregate, water and additional materials such as Admixtures and Mineral additives. In these years, government and industries emphasize on high initial strength and high quality concrete in less times. Because of these reasons researchers have been focused to bring some variations in concrete components to achieve a good quality and high strength concrete. Nowadays using of chemical Admixture become more and more because everyone and every industry want to have a good quality and high strength concrete. We have different additive that we can get these factors so soon such as Mineral additives and Chemical Admixtures and in this review paper we cover Chemical Admixtures such as Plasticizer, Super Plasticizer, Retarding, Accelerating, Air Entraining and each of them has their own properties and different chemical influences on the properties of concrete like compressive strength, tensile strength, workability, water content etc.
Civil engineering design, 2020
We studied the effects of superplasticizer (SP) (PCE1 and PCE2), air-entraining admixtures (AEA), and supplementary cementitious material (silica fume and fly ash) on the mechanical and durability properties of concrete samples. Eight concrete mix designs were prepared. The first six concrete mix design contained similar aggregates, PCE2 SP, AEA, 350 kg/m 3 cement, and water to cement ratio equal to 0.38, and one of the mentioned mix design was selected as control samples with water to cement ratio equal to 0.57, without PCE2 SP and AEA. We used a different quantity of PCE2 SP and AEA and replaced the fly ash or silica fume as part of cement in two of the mentioned mix designs. The last two concrete mix designs studied the effect of PCE1 SP and AEA on freezing and thawing of concrete mix design. Adding PCE2 SP in concrete mix design increased compressive strength at age 11, 42, and 90 days sharply and reduced the depth of water penetration at the age of 28 and 90 days compared to the control sample. Using simultaneous PCE2 and AEA in concrete mix design did not improve compressive strength significantly and increased slightly depth of water penetration compared to only using PCE2. However, increasing the quantity of AEA to 5% improved both compressive strength and reduced depth of water penetration. In the second group of concrete mix design, adding both PCE1 and AEA increased the number of resistible freezing and thawing cycles of concrete. Side chain length and molecular weight of PCE1 and PCE2 SPs had no important effect on the compressive strength and performance properties of concrete. K E Y W O R D S durability, fly ash, air-entrained admixture, freezing and thawing, silica fume 1 | INTRODUCTION Concrete is one of the most commonly used building materials in the world. However, the long-term performance of the concrete and the influence of environmental parameters on its properties are not fully known. Concrete deteriorations and corrosion of steel reinforcement were generated, for example, by carbonation reaction, chloride ion penetration, freezing and thawing cycles, sulfate attacks, and alkaliaggregate reactions. Choosing and using inappropriate materials, the absence of quality control execution or poor performance of the quality control process and improper curing may shorten the service life and impose high costs. Therefore, some guidelines and standards were approved for concrete durability in constructions, especially in conditions that are vulnerable to environmental attacks such as chloride penetration, carbonation as well as freezing and thawing cycles. Economic impacts resulted from durability problems motivated scientists in the last three decades to do comprehensive researches on this issue, which provided an appropriate basis to increase the durability of concrete structures. 1 Concrete properties such as strength, durability, shrinkage, and permeability are directly influenced by the number, size and distribution of pores in cement paste, aggregate characteristics and interface
Influence of chemical admixtures on density and slump loss of concrete
International Journal of Modern Engineering Research (IJMER)
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Effect of Admixtures on Strength and Permeability of Concrete
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The effects of water-cement ratio and chemical admixtures on the workability of concrete
IOP Conference Series: Materials Science and Engineering
Concrete chemical admixtures are used to improve the fresh and hardened properties of mortar or concrete in different applications. Their addition can allow for the reduction of the water to cement ratio (w/c), without affecting the workability of the mixture. By reducing the amount of water, the cement paste will have higher density. However, the reduction of the water content in a concrete mixture should be done in such a way that complete cement hydration take place and sufficient workability is achieved. In order to maintain the workability of the concrete mix, the dosage of the admixture must be carefully calculated and must be taken into account in the calculation of the w/c ratio. In the present study, three types of chemical admixtures; Type A water-reducing, Type D water-reducing and retarding and Type F high range, water-reducing admixtures conforming to ASTM C 494/C 494M-04 standards, were used to optimize the percentage of the admixture with respect to the w/c ratio. The suitable time for the addition of the admixture is also investigated. Results show that using 1.5 % of Type A admixture with 0.45 w/c gives 45.6 MPa, 28 day compressive strength with an associated slump of 110 mm, compared to zero slump without admixture. 1.0 % Type A admixture with 0.52 w/c gives 33 MPa, 28 day compressive strength with an associated slump of 95 mm, compared to 35 mm slump achieved without admixture. For Type D admixture, using 1.5 % with 0.5 w/c the slump was 190 mm with 47 MPa, 28 day compressive strength, compared to 15 mm slump achieved without admixture. 1.0% of Type F admixture with 0.35 w/c and 0.45 w/c gave slumps of 25 mm, 225 mm and strength of 63.5MPa and 55.3MPa respectively. For all mixes, the best slump results were achieved when the admixtures were added during the initial mixing process, while maximum compressive strengths were achieved for different times of inclusion of the admixtures.
Effect of Low Mixing Speed on the Properties of Prolonged Mixed Concrete
Civil Engineering Journal, 2020
The mixing process of concrete consists of dispersing the constituent ingredients (i.e. cement, admixtures, sand, and gravel) in water to homogeneous and solid product. The properties of the final product depend on mixing parameters such as mixing time and mixing speed. Ready Mixed Concrete (RMC) should be mixed for a long time with limited speed until delivered to the working site. This long time depends on long transport distances and traffic conditions. The present study investigated the effects of long mixing time on the properties of concrete without any change in its proportions during the mixing process and the effects of using the chemical admixtures: super plasticizers and retarders on its effectiveness, using a drum batch mixer. It has two directions of rotation: one for mixing concrete and the other for discharging it. This research identified concrete mixtures with local available materials i.e. cement, sand as fine aggregates, dolomite as coarse aggregates, water and ch...