Effect Of Chemical Admixtures Research Articles

Effect of Chemical Admixtures on the Working Performance and Mechanical Properties of Cement-Based Self-Leveling Mortar

In this work, the effect of cellulose ether (CE), tartaric acid (TA), and polycarboxylate superplasticizer (PCE) on the working performance and mechanical properties of cement-based self-leveling mortar is investigated. According to the orthogonal experiment analysis, TA is identified as the most influential factor affecting the working performance, as indicated by factors such as fluidity, fluidity loss, and viscosity. Upon conducting a comprehensive assessment of the working performance and mechanical properties, the optimal parameters are found to be CE = 0.6 wt.‰, TA = 0.5 wt.‰, and PCE = 2.0 wt.‰. A univariate test highlights that that the working performance improves with the higher TA dosages. Specifically, the exponential reduction of fluidity loss corresponds with an increased TA content. Regarding the mechanical properties of cement-based self-leveling mortar, the compressive and flexural strength exhibit enhancement when the TA dosage remains below 0.4 wt.‰ at the early stage, implying that TA has some influence on the hydration process. Impressively, the 1 d compressive and flexural strengths surpass 7 MPa and 2 MPa, respectively, ensuring the viability of subsequent construction activities. Through an analysis of hydration heat, the effect mechanism of TA on the cement-based self-leveling mortar is derived. The result shows that the addition of TA decelerates the hydration process within the initial 10 h, followed by acceleration in the subsequent 20 h to 30 h. Consequently, this delayed formation of the early hydration product, ettringite, contributes to a more porous structure in the slurry, with low friction leading to a better working performance. A large number of hydration products, such as alumina gel and calcium–silicon–hydrate gel, presented in the hardened paste results in the good mechanical properties at 1 d. This study may lay a foundation for the optimization of the dosage of chemical admixtures in the self-leveling mortar and high-performance cement-based materials, and also impart valuable insights for practical applications extending to the realm of building construction and decoration.

A review on the effects of chemical admixtures on Autoclaved Aerated Concrete (AAC) blocks

AbstractAutoclaved Aerated Concrete (AAC) is a special composite and widely accepted construction material owing to good durability, raw material availability, and environmentally friendly nature. Nevertheless, the continuing focus of the industry remains in cost optimization and maximizing the performance of blocks. The investigations related to the effects of admixtures in AAC are continuing globally with the objective of improving the productivity and strength improvement of AAC blocks. It is now well documented that the behavior of admixtures in conventional concrete and AAC is different, partly due to the low quantities of cement in a mix design and production systems. Hence it is essential to conduct a detailed investigation for finding the suitability of chemical admixtures. This review paper shows the trend of admixtures used in AAC and describes how they affect the rheological characteristics, setting time, and mechanical properties. From the review, it is clear that the performance of admixtures mainly depends on the type of binder, type, and dosage of admixtures. PCE‐based superplasticizers and performance enhancers are generally recommended to provide incremental improvement in flow behavior and mechanical strength. However, it is important to note the mix design and complex interplay of various materials have a large impact on the performance of any admixture employed. The investigations thus far indicate that chemical admixtures also impact the initial curing times without sacrificing the mechanical properties of AAC. In general, the usage of admixtures can enhance the strength of blocks between 5% and 15% depending on the type and quantity of admixture.

The role of iron in cement hydration process: From perspective of chemical admixture

The post-peak decelerating hydration progress plays a significant role for concrete technology to assure durability of concrete. The effect of chemical admixture on cement hydration, hydration products, pore structure and moisture diffusion process are conducted by various experiments and the controlling factor on deceleration period of cement hydration and the effect of iron ion on microstructure are revealed. When the chemical admixture is added into cement paste, more ferrite phase is consumed and the iron dissolved in the pore solution modifies the initial hydration product layer and accelerate the hydration process, causing more C-S-H gel generated and denser microstructure. In addition, it is also proved that single diffusion control factor occurs at 80 h for the later deceleration period of cement hydration.

Effect of Chemical Admixtures on Mechanical and Degradation Properties of Metallurgical Sludge Waste Concrete.

This study extends the development of concretes with metallurgical sludge waste (MSW) by determining the effect of superplasticizers and air entrainment admixture (AEA). The MSW is a very fine powdery material, and in this case, it was used as a partial replacement of fine aggregate in the mixture. The reference ordinary concrete mixtures without MSW were created for evaluation. The results of concrete density, compressive strength, electrical resistivity, and rapid chloride permeability were obtained and some of them were measured continuously to determine the influence of the chemical admixtures on these characteristics over time. It was found that in general, the MSW substitution slightly lowers the mechanical and durability parameters, but MSW in combination with the chemical admixtures improves the compressive strength in comparison to the reference concrete with the addition of AEA.

Improving the Rheological and Mechanical Properties of Oil Well Cement Slurries Using Multiple Chemical Admixtures for Enhancing Zonal Isolation: A Laboratory Evaluation

Abstract The study uses chemical and mineral admixtures to understand the critical processes affecting the cement slurry characteristics, including rheological properties, free water, compressive strength, and thickening time. Using alternate mineral admixtures to replace cement slurry partially has environmental and economic benefits. The mechanisms behind the effects of chemical admixtures on the parameters of cement slurry were investigated at different temperatures using cutting-edge experimental equipment. The binder's compatibility and reactions with chemical admixtures were examined. When temperature and chemical admixtures are combined, it has a major effect on the flow characteristics of slurries. The results suggested that present technical data for chemical admixtures must be confirmed for use in oil well cementing; admixtures that are efficient at raised temperatures in conventional cementing work may become ineffective at elevated temperatures in oil well cementing. Finally, the new mixture can be employed in the desired oil field due to this new material generation (4200–6900 feet and pressure and temperature range of 4100–4800psi and 140–170 °F, respectively). Because this mixture enhances the rheological properties of cement slurry, the end product will be better than the current version. After all, the plastic viscosity, apparent viscosity, and yield stress diagrams of mixture #3*-A are lower than the desired oil field. The other mixtures in this study lead to a decrease in cement slurry viscosity and have the highest compressive strength. Finally, mixture #3*-A was the optimal blend.

A review on the effects of chemical admixtures on alkali activated concrete

Alkali activated concrete (AAC) is a cement-free concrete and widely accepted as a construction material by researchers due to its high strength, durability, raw material availability, low construction cost and energy cost. Nevertheless, the main issues associated with the practical implementation of AAC are high shrinkage, low workability and quick setting behaviour. The use of chemical admixtures is the only solution for improving the workability of AAC, and it modifies the properties of concrete. The behaviour of admixtures in conventional concrete and AAC are different. Hence it is essential to conduct a detailed literature survey for finding the suitability of chemical admixtures in AAC. This review paper shows the trend of admixtures used in AAC and describes how they affect AAC's rheological characteristics, setting time, and mechanical properties. From the review, it is clear that the use of admixtures in AAC mainly depends on the activator solution used, type of binder, type and dosage of admixtures and the need for the admixtures in concrete. The investigations related to the effects of admixtures in AAC are continuing globally. PCE and SNF- based superplasticizers are generally recommended for AAC, with PCE suited for low alkaline AAC and SNF for high alkaline AAC. Lignosulphonates also show good compatibility with AAC, but their effects for improving the mechanical behaviour in AAC are lesser than SNF.

Mechanical and electrical properties of MWCNTs - high early strength cement - mortars composite: Dispersion of CNTs and effect of chemical admixtures.

The objectives of this research were to study (1) the dispersion of MWCNTs in an aqueous system by three commercial admixtures (CAds) for concrete, and (2) the effect of CAds and MWCNTs on indirect tensile strength and electrical conductivity of MWCNTs-high early strength (HE) cement-mortar composites. To achieve the objectives, we dispersed MWCNTs in an aqueous system with (1) hydroxylated polymers-based water reducing plasticizer (HPs), a nonionic compound, (2) Naphthalene based superplasticizer (SNF), an anionic compound, and (3) calcium chloride-based accelerating agent (CC) a neutral amphoteric salt. We prepared a total of 242 samples grouped in three sets: (1) Plain mortar [PM] (water + HE cement + Sand), (2) [PM+CAd], and (3) [PM+CAd+MWCNTs]. The three CAds dispersed MWCNTs in an aqueous solution. The CC and HPs admixtures have a two-time bigger dispersing power than the SNF. They demand half of SNF's ultrasound energy for optimal dispersion. Although the SNF (anionic) based superplasticizer resulted incompatible with the HE cement, it improved the indirect tensile strength of [PM+SNF+MWCNTs] composite. In contrast, the CC (amphoteric) based accelerating agent was compatible with the HE cement; the CC adsorption on the MWCNTs surface favors an improvement in the electrical conductivity of [PM+CAd+MWCNTs] composite.

Effects of slag and superplasticizers on alkali activated geopolymer paste

Geopolymers are a type of amorphous alumino-silicate product, and can be synthesised by the polycondensation reaction of geopolymeric precursor and alkali polysilicates. The binder is prepared by the alkaline activation of industrial by-product materials like fly ash, slag, metakaolin, rice husk ash, etc. as a source for aluminosilicate. The most commonly used alkaline activator is the combination of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). Chemical admixtures are indispensable in alkali activated systems owing to its poor fresh properties such as workability, too quick setting etc. In this study, the chemical admixture – alkali activated binder interactions were carried out by using latest generation superplasticizers, such as Polycarboxylic ether admixture (PCE) and Sulphonated naphthalene formaldehyde (SNF). Mini slump test, initial and final setting time tests were conducted in alkali activated slag blended fly ash based geopolymer paste and the test results were analyzed with respect to parameters such as alkali to binder ratio (a/b), proportion of slag in blended geopolymer paste, type and dosage of superplasticizers. The test results indicated that the workability and setting time of alkali activated geopolymer paste enhanced due to the increase in alkali content and the reduction in slag content. Based on the effect of chemical admixtures in geopolymer mix, SNF performed better than PCE admixture with regards to mini slump test for all the mixes; whereas in the case of setting time test, SNF showed better results only for the mix with 100% slag. In the case of slag blended fly ash based geopolymer paste, both PCE and SNF showed similar effects, and also it was observed that, the flow of the paste got enhanced when the dosage of superplasticizers is increased from 0 to 3% by weight of binders.

Effects of Chemical Admixtures on the Working and Mechanical Properties of Ordinary Dry-Mixed Mortar

The effects of hydroxypropyl methyl cellulose ether, starch ether, bentonite, and redispersion emulsoid powder on the working and mechanical properties of fresh dry-mixed mortar were studied. The results show that hydroxypropyl methyl cellulose ether has the greatest impact on the consistency and water retention of ordinary dry-mixed mortar and that redispersion emulsoid powder reduces the water action and starch ether has essentially no effect on water retention. It also shows that the time of mortar condensation when mixed with hydroxypropyl methyl cellulose ether is the longest, followed by redispersion emulsoid powder and bentonite. Starch ether can slightly, but not obviously, extend the setting time of cement mortar. Hydroxypropyl methyl cellulose ether has the greatest impact on the mechanical properties of ordinary dry-mixed mortar, followed by redispersion emulsoid powder, starch ether, and bentonite. As the water retention increases, the setting time of the mortar also increases. The use of water as a thickening material has a retarding effect on the mortar, increases the water-retention rate, and increases the retarding effect. Moreover, increasing the content of the chemical admixtures decreases the strength of cement mortar.

Crack remediation in mortar via biomineralization: Effects of chemical admixtures on biogenic calcium carbonate

Limited research on biomineralization in cement-based systems suggested that self-healing of surface cracks could be obtained by triggering biogenic calcium carbonate (CaCO3) precipitation within the cracks. While this is encouraging, there is not enough information regarding the influence of admixtures on crack remediation and durability of the biogenic CaCO3 against weathering conditions. In this study, the microorganisms were introduced to mortar with their growth medium, which included corn steep liquor (CSL) and urea. With this approach, the cracks on mortar surface were sealed with the CaCO3 and the water absorption capacity of the so-called self-healed mortar decreased compared to its counterpart cracked mortar samples. The biogenic CaCO3 precipitate was found to be durable against freeze-thaw; however the precipitate was unstable under rain water and light. While the addition of air entraining agents (AEA) did not influence the self-healing ability of cells, use of superplasticizers improved the self-healing ability in terms of crack sealing, water absorption, and durability of the precipitate.

Effect of chemical admixtures on concrete’s electrical resistivity

PurposeThe purpose of this paper is to verify the influence of superplasticizer and air entrainment admixtures (AEs) in the electrical resistivity of concrete.Design/methodology/approachTen different types of concrete have been studied. Three levels of superplasticizer and air AEs have been used (0.20, 0.35 and 0.50 per cent). Concrete samples were cast and the electrical resistivity was monitored at the ages of 28, 63 and 91 days. Compressive strength and density tests have also been executed.FindingsThe superplasticizer admixture presented an optimal level of 0.35 per cent that significantly increased the electrical resistivity. The air AEs at the same dosage caused a considerable decrease in the electrical resistivity. The concrete with air AEs showed highest resistivity/MPa ratio.Research limitations/implicationsThe results should be carefully extrapolated for other materials and admixtures.Practical implicationsThe usage of chemicals admixture in concrete is extremely common nowadays. However, only a few authors have studied the impact of such materials on the concrete’s electrical resistivity. Since many other researchers have already correlated electrical resistivity with other concrete’s properties, such as strength, setting time and corrosion probability, it is important to better understand how superplasticizers and air-entraining agents, for instance, impact the resistivity.Originality/valueThe vast majority of studies only tested the resistivity of cement paste or mortar and usually for short period of time (up to 28 days), which seems not to be adequate since the cement reaction continues after that period. This paper fills this gap and studied the impact of admixture on concrete and for a period of 91 days.

Effect of chemical admixtures on borogypsum containing cement mortar

Effect of chemical admixtures on borogypsum containing cement mortar

Improvement of workability and early strength of calcium sulphoaluminate cement at various temperature by chemical admixtures

Effects of chemical admixtures on the workability and strength development of calcium sulphoaluminate cement (CSA) at various temperature were researched, of which mechanisms were analyzed by XRD and TG. The setting time and early strength of CSA were significantly improved by lithium carbonate-aluminum sulfate (LC-AS) at 0 °C and sodium gluconate-borax (SG-B) at 40 °C. LC-AS not only enhanced ettringite formation, but also accelerated belite hydration, and the amounts of ettringite was significantly increased at 0 °C. However, the formation of ettringite was retarded by SG-B, and the reduction of the amounts of ettringite can be achieved at 40 °C.

The effects of chemical admixtures and physical factors on the treatment of dispersive soils

Dispersive soils are very abundant around the world; upon contact with water, the clay minerals in dispersive soils become strongly repulsed by each other and remain suspended apart from each other, a dangerous trend which has led to a number of irreparable damages. The soil used in this test was completely virgin and could be classified as a dispersive soil. In the first section of this study, the pinhole test was conducted on more than 20 selected additives; the results of these tests demonstrated that the best amending agents were calcium oxide and calcium hydroxide salts, in addition to polymer and cement compounds. A closer examination of the results obtained from the pinhole test for the six ideal additives, used at different percentages, revealed that even low percentages of lime, cement, and calcium hydroxide would dramatically reduce soil dispersivity. The combined effect of lime compounds with any of the (high pH) additives, including aluminum sulfate, pozzolan, and sulfur, at identical ratios represents their cumulative effect on the amendment intensity. The second section simultaneously explores the effects of several physical parameters of the amended soil including density, moisture, and time, through the test design method. The results obtained from this phase suggested that both increasing soil density and time would effectively amend the soil if used within their respective ranges, the former directly and the latter to a certain extent.

Effects of chemical admixtures on the rheology of fresh recycled aggregate concretes

Air-entrainers and super-plasticizers are among the most used chemical admixtures that affect the rheological parameters of fresh cement-based materials. In this work, their influence on fresh properties of recycled aggregate concrete (RAC) is investigated through an experimental campaign, where Bingham rheological parameters, i.e. plastic viscosity µ and yield stress τ0, were analyzed. Ten concrete mixtures were prepared, varying w/c ratio, admixtures content, recycled coarse aggregate substitution ratio and aggregates proportioning methods. In this regard, a particular attention was paid on the Equivalent Mortar Volume (EMV) method for RAC designing. Results were then compared to ones obtained in a previous experimental campaign carried out by the same authors, where further twenty concretes were prepared with the same materials and under the same conditions. From the results achieved in this work, it is possible to conclude how the admixtures addition and aggregates proportioning method influence yield stress and plastic viscosity values.

Effect of Chemical Admixture on Durability of Concrete

In this paper, the effect of the polynaphthaene sulphonate type water reducer (PSWR) and new type polycarboxylate water reducer (PAWR) on the internal pore structure, internal defects and forces of resistance to external environmental of concrete are fully compared and analyzed. The effect of PAWR on improving the durability of concrete was revealed. The test result showed that compared with PSWR, PAWR can improve the pore structure and pore size distribution of concrete grout, improve the density of concrete, reduce the adiabatic temperature rise of concrete, optimize the hydration heat curve of cement, reduce the shrinkage and deformation of concrete, improve concrete anti-cracking performance and volume stability, to reduce the internal defects of concrete; at the same time, but also to improve the ability of the concrete, including anti- carbonation, frost resistance, chloride ion erosion resistance and steel protection in different degree, as well as to enhance the resistance of concrete to the external environment, thereby greatly improving the durability of concrete.

Effect of chemical admixtures on setting time, fluidity and mechanical properties of phosphorus gypsum based self-leveling mortar

Phosphorus Gypsum (PG) based Self-Leveling mortar (GSL) is a green and efficient material for floor construction. Its hydration kinetics, rheology property and their effect on mechanical strength of hydrated GSL were crucial to its final application. This study analyzed the effect on setting time of three retarders, namely Protein Salt (PS), Citric Acid (CA), and Sodium Tripolyphosphate (STPP). The fluidity of GSL was investigated individually using three different types of superplasticizer, namely naphthalene (FDN), polycarboxylate (PCE) and melamine (MSF). Finally, the effect of these chemical admixtures on mechanical properties of GSL hardened was examined. Results showed that the optimal contents of PS were 0.1%-0.15% by weight. With 0.1% PS, setting time of GSL retarded to 80min. To reach a maximum fluidity of GSL to 350mm, the optimal contents of PCE, MSF and FDN were 0.2%, 0.6% and 1.0% respectively and corresponding compressive strength of GSL were 54.25MPa, 53MPa and 52.25MPa. Suggesting PCE is the most effective dispersant in PG based GSL system.

Effects of chemical admixtures and curing conditions on some properties of alkali-activated cementless slag mixtures

This paper reports the results of an investigation on the influences of admixtures and curing conditions on some properties of Alkali-Activated Slag (AAS) mixtures with no cement. In the study, Shrinkage-Reducing (SRA) and superplasticizing and setretarding (WRRe) admixtures were used. For the slag activation, sodium metasilicate was used at two sodium concentrations, 4% and 6% by mass of slag. Setting time, flow loss of fresh mixtures, and shrinkage strain, carbonation, flexural and compressive strength of hardened mixtures were measured. The test results showed that the admixtures generally had no impact on the setting times of AAS pastes. WRRe increased the flow rate of AAS mortars while SRA partially affected the flow values of AAS mortars. WRRe and SRA did not produce an important difference on the carbonation depths of AAS mortars. However, WRRe and especially SRA admixtures decreased the shrinkage values of AAS mortars. Additionally, curing conditions had a significant effect on the mechanical behavior in the hardened state of AAS mortars compared to Normal Portland Cement (NPC) mortars, and the strength development of AAS mortars at early ages was very fast in comparison with NPC mortars when subjected to elevated temperature.

Effect of Chemical Admixtures on the Strength of Dian Chi Peat Soil

This article focuses on peat soil ofthe region of the Dian Chi Lake inKunming, the peat soil as research subject. This paperstudy on unconfined compressive strength test of solidifiedpeat soil mainly. In the experimental study of chemical admixtures curing peatsoil, the test hadeight groups. The experimental study of cement soil of different kindsof additives, and study the impact of additives on curing peat soil. It was concluded that the regularof cement soil compressive strength with the increases of chemical admixtureand curing time.

Light Weight Geopolymer Paste Made with Sidoarjo Mud (Lusi)

This paper presents the efforts of how to use the solid form of Sidoarjo mud as a base material of lightweight-geopolymer paste. The mud, which is called Lusi was mixed with a class F fly ash. Some experimental results have shown that mixing mud with fly ash and alkali was potential to become a binder in concrete, instead of Portland cement. Alkaline solutions used in the mixture were NaOH of 12 M and 14 M and Na2SiO3combined in the ratio of 1:2.5 by weight. Aluminum powder was applied as a foaming agent. It showed that the strength of paste made with mixing Sidoarjo mud and fly ash was influenced by mud content. The effect of chemical admixture and curing temperature was observed as well. A steam curing method at 60°C was applied to the paste for three and six hours. Test results showed that the compressive strength of the paste varied with the concentration of alkaline solution, mud content, admixture and curing temperature. The maximum strength of the lightweight paste at 21 days was 2.8 MPa with the density of 722 kg/m3.