Chemical Admixtures In Concrete Research Articles

Eupatorium Adenophorum Spreng as a green additive in cementitious materials for sustainable infrastructure

The use of natural admixtures as a sustainable alternative to cement and chemical admixtures in concrete has gained significant attention. Eupatorium adenophorum Spreng (EAS), commonly known as the ‘forest killer’ in Nepal, is a perennial and herbaceous invasive plant. This prompted an experimental investigation aimed at assessing the potential utilization of its liquid and burnt ashes as additives in cement mortar. EAS leaves were dried, burnt at wooden coal fire, and sieved through a 90 μm sieve to obtain EAS powder. EAS liquid was produced by hammering the fragmented leaves, followed by squeezing and filtering. The control mortar had a water-cement ratio of 0.35 and a cement-sand ratio of 1.0. EAS powder content ranged from 0 % to 15 % and EAS liquid from 0 % to 0.4 %, by weight of cement. The optimal content (10 %) of EAS powder resulted in decreases in flow table value, density, and elastic modulus of mortar by 2.3 %, 4.2 %, and 10.6 %, respectively, while increasing compressive strength and water absorption by 2.3 % and 14.6 %, respectively. As for EAS liquid, its optimal content (0.3 %) led to increases in flow table value, density, compressive strength, elastic modulus, flexural strength, and splitting tensile strength by 11.0 %, 1.4 %, 13.0 %, 25.4 %, 28.4 %, and 33.0 %, respectively, while decreasing water absorption by 2.7 %. The observed increase in the compressive strength of mortar with the incorporation of EAS powder suggests its potential to substitute mineral admixtures. This can be achieved through improvements in the burning process, grinding to finer particles, and thorough micro-characterization, followed by detailed investigations into mortar properties. Additionally, the effectiveness of EAS liquid in replacing chemical admixtures to enhance various mortar properties has been confirmed. The collaborative use of EAS powder and liquid holds promise for supporting future sustainable infrastructure development, facilitating the production of eco-friendly green concrete.

3D-printable quaternary cementitious materials towards sustainable development: Mixture design and mechanical properties

Development of 3D-printing technologies for cementitious materials becomes one of the driving forces to accelerate innovation in modern construction. The use of mineral and chemical admixtures in concrete has been found to benefit fresh and hardened properties and reduce the carbon footprint of portland cement. Towards this aim, four different supplementary cementitious materials, including metakaolin, silica fume, blast furnace slag, and sodium metasilicate, were utilized in binary, ternary, and quaternary cementitious blends. Flowability, setting, and compressive strength were measured to investigate the effects of different admixtures and their combinations on materials properties of printable mixtures. Selected mixtures were 3D-printed into cylinder specimens to assess their printing quality. The optimal mixture with up to 32.5% cement replacement was 3D-printed to evaluate mechanical properties (i.e., compressive strength and elastic modulus) based on prism specimens. The anisotropic behavior under compression load was observed. 3D-printed specimens tested under perpendicular direction showed the lowest compressive strength but the highest elastic modulus.

Comparative study on using chemical and natural admixtures (grape and mulberry extracts) for concrete

There is a general belief that admixture can improve some important properties of concrete, and different kinds of admixtures are in use worldwide. In the current investigation, a comparative experimental study has been performed on using grape and mulberry extracts as a natural admixture and chemical admixture for concrete. Increasing of workability and reduction in water absorption were observed due to the addition of natural admixtures to concrete. There was an enhancement of concrete compressive strength tested at 3, 7, and 28 days and the 28 days modulus of elasticity as a result of using different admixtures, but reduction of splitting tensile strength was observed. In general, using the two natural admixtures has a beneficial effect to improve both fresh and hardened properties of concrete and they have a superiority on the chemical admixture with regard the cost and producing environmental-friendly construction material.

Optimization of multifunctional nano cement composite for self – sensing

Abstract The invent of new construction materials and extensive research in concrete technology and cement chemistry has proved that apart from proportioning concrete for high strength it is very important to design a concrete mix for high performance in terms of diagnosing damage like smart materials. The use of mineral and chemical admixtures in concrete has facilitated the material scientists to invent special types of concrete to suit the current application. Materials that are used in concrete like steel fibres, carbon nano fires (CNF) and carbon nano tubes (CNT) with appropriate dosage, can impart this self-sensing property in concrete. These multifunctional smart materials have resulted in assessing the damage to structures without the need for any external sources like sensors or any structural health monitoring device like optical fibres. The inclusions of nano materials in cementitious matrix that are conductive in nature provide a new type of self-sensing composite. Self-sensing material have the ability to sense their own conditions like stress, strain, temperature and damage. This property of the material which enables itself to assess its own damage and deformation has made it a smart material for health monitoring. Appropriate use of this smart material with a well-defined sensing scheme can enhance the sensitivity of damage detection in micro level which can prevent the collapse of the structure. CNT and CNF were used in 0.1 to 0.3% by weight of cement and their electrical conductivity was measured which gives a good relation of the self-sensing properties of the material. Cyclic compressive load was conducted and the response to the piezoresistive properties of the nano composite was tested. It was observed that 0.1% of these carbon nano materials had better electrical properties.

Ductile cementitious composite with copper slag as fine aggregate

The invent of new construction materials and extensive research in concrete technology and cement chemistry has proved that, apart from proportioning concrete for high strength it is very important to design a concrete mix for ductile behaviour to be used in earthquake prone areas. The use of mineral and chemical admixtures in concrete has facilitated material scientists to invent special types of concrete to suit the current application. This research work is one such attempt in characterizing cement composite that is ductile and durable. Apart from using only Portland cement, mineral admixtures which are industrial by-products are used in this composite which makes this material a sustainable construction material. Concrete is a brittle material and this disadvantage in concrete was overcome by the addition of fibres in the matrix improving the flexural toughness of the material. Ductile Cementitious Composite (DCC) is different from the conventional fibre reinforced concrete (FRC) which is characterized by high tensile strain capacity and strain-hardening behaviour under uniaxial tensile loading. This property is accomplished by the fiber content, matrix proportion and the interface between the matrix and fibre. The formation of closely spaced multiple micro cracks in the matrix enables this composite to have the ductile behaviour. The self healing ability of these composites is another added advantage which enables the durability of the material. The autogenous healing of crack by the formation of additional calcite and CSH are responsible for the self healing capacity of these composites. The materials used for this composite is a blend of Portland cement, class F fly ash, silica fume, pulverized copper slag and PVA(Polyvinyl acetate) fibres. The concrete had a compressive strength of 64 to 72 MPa and flexural strength of 4 to 6 MPa. Durability parameters were also studied to ascertain the permeability characteristics of concrete.

Effect of Natural Organic Materials as Admixture on Properties of Concrete

Objectives: To study the influence of natural organic materials (i.e. gram-flour, ghee and triphala) as admixture on the durability of concrete. A new method was proposed with 70% loading of average compressive strength to know the durability of concrete under practical conditions. Methods/Statistical Analysis: Use of chemical admixtures in concrete is a common practice in modern construction. Although chemical admixtures improve properties of concrete but also create leaching problem. The paper presents, the various experiments performed to identify the influence of natural organic materials as admixture on durability of concrete. Electrical resistivity, ultrasonic pulse velocity (UPV) and carbonation tests were performed on hardened concrete for 0.4 and 0.45 w/c ratios. Findings: Based on the above results it was found that addition of gram flour provided better durability in terms of electrical resistivity, UPV and carbonation for both the w/c ratios over normal concrete. Even under 70% loading, better durability results were noticed for concrete with gram flour. Although for concrete with ghee and triphala poor results were noticed. Most of the previous work were performed on cement and lime mortar. The present work is performed on the concrete with use of advanced equipment. Application/Improvements: Utilisation of waste food grain causing environmental problems in concrete as admixture in place of chemical admixtures. Research shall discourage use of chemical admixtures in concrete as they are responsible for environmental pollution.Keywords: Carbonation, Electrical Resistivity, Proposed Durability Method, UPV

Effect of Superplasticizer Dosage on Workability and Strength Characteristics of Concrete

The use of chemical admixtures in concrete is a common solution to achieve full compaction particularly where reinforcement congestion and shortage of skilled workers. The past researchers have been underscored the use of chemical admixtures imparts the desirable properties to concrete in both fresh and hardened state. This paper has been made an attempt to study the influence of superplasticizer dose of 400ml, 600ml, 800ml, 1000ml and 1200ml/100 kg of cement on performance of Concrete. The experimental tests for fresh and hardened properties of concrete for three mixes of 30 MPa grade are studied and the results are compared with normal concrete. The tests considered for study are, slump test, slump loss, flow table and compressive strength test The results show that for the constant water cement ratio, increase of superplasticizer dose in properties of concrete leads to gain of good workability. Moreover, there is also increase in compressive strength than that of normal concrete mix.

The Use of Chemical Admixtures in Concrete. Part II: Admixture-Admixture Compatibility and Practical Problems

Different combinations of admixtures can produce concretes having high flow, good cohesion, and self-leveling properties; they can be placed underwater, can expand and induce compressive stresses or reduced shrinkage, and can be placed and cured at sub-zero temperatures. Thus, correct combinations of admixtures produce custom-made concrete for particular jobs. This article, the second in a series, explores admixture-admixture compatibilities; the first article in this series discussed admixture-cement compatibilities. Topics include compatibility problems with viscosity-enhancing admixtures, compatibility problems with water reducing admixtures (WRA) or damproofing admixture combinations, shrinkage compensating concretes for flat slab applications, accelerated setting in concrete containing calcium nitrite and superplasticizers, and decreased air contents in silica fume concrete. The authors also consider problems caused by admixture side effects and poor practice, including surface finishing problems, plastic shrinkage, and the effect of retempering of concrete on the air void system. The authors conclude that it is vital to understand both admixture-cement and admixture-admixture interactions so that the best use of materials can be achieved, field problems are avoided, and more accurate prediction of concrete properties is made possible.

The Use of Chemical Admixtures in Concrete. Part I: Admixture-Cement Compatibility

Concrete incorporates chemical and mineral admixtures. These interact with cement constituents to influence cement hydration. This article focuses on admixture-cement compatibility and provides examples of the results of incompatible admixtures. These include abnormal setting and loss of workability due to the type of gypsum in the cement, the influence of soluble alkalis on the stability of the air void structure of concrete, suppressed strength development in sulfate-resistant concrete, and cement-superplasticizer incompatibility in high-performance concrete.

JIS A 6204 (コンクリート用化学混和剤) 改正の背景とその概要

JIS A 6204 (コンクリート用化学混和剤) 改正の背景とその概要

The zeta-potential of cement: Pt. V: Effect of surfactants

The zeta-potential of cement and fly ash has been measured in solutions of various anionic and cationic surfactants. The results obtained are in excellent agreement with the model of the reactive double layer on cement. Further, they are a contribution to a better understanding of the action of chemical admixtures in concrete containing fly ash.

Tests of Water-Reducing Agents Respecting their Efficacy in Conformity with“The JSMS Tentative Specification for the Chemical Admixtures for Structural Concrete”

“The JSMS Tentative Specification for the Chemical Admixtures for Structural Concrete” was drafted in 1968 by the Committee on the Chemical Admixtures for Concrete, Japan Society of Materials Science, and has since been put into practice. It was in conformity with this Tentative Specification that tests were carried out of thirty-five kinds of water-reducing agents generally on the market throughout Japan including both of accelerating sort and of retarding one. Double objects were intended in these tests, to examine the efficacy of these agents on one hand, and on the other to collect technical data for deliberation of possible requirement in future for revision of the“Tentative Specification”currently in practice.