Concrete Admixtures Research Articles

Synthesis of sodium alginate-polycarboxylate superplasticizer and its tolerance mechanism on montmorillonite

Sodium montmorillonite (MMT) is a major mineral component of clay in manufactured sand which is an economical aggregate in concrete. Its lamellar structure has a negative effect on an important concrete admixtures polycarboxylate superplasticizer (PCE). In this study, sodium alginate (SA), a polysaccharide, was grafted with an unsaturated amide, having a double bond structure, to synthesize the acrylamide modified sodium alginate (Ugi-SA) through the Ugi reaction. Then, Ugi-SA, acrylic acid (AA), and isopentenol polyoxyethylene ether (TPEG) were used to synthesize sodium alginate-polycarboxylate superplasticizer (SPCE) by free radical copolymerization. The structures of Ugi-SA and SPCE were determined by gel permeation chromatography (GPC) and Fourier transform infrared (FT-IR). The fluidity of the montmorillonite (MMT) cement paste with SPCE and the traditional polycarboxylate superplasticizer (TPCE) was investigated. Furthermore, the adsorption behavior of SPCE on MMT was measured by X-ray diffraction (XRD), thermogravimetric analysis (TGA), total organic carbon analyzer (TOC) and the tolerance mechanism of SPCE on MMT was discussed. The FT-IR and GPC results showed that Ugi-SA and SPCE were synthesized successfully. The initial fluidity test results indicated that SPCE had a better dispersion effect and MMT tolerance than TPCE. TGA, TOC and XRD tests showed that the adsorption of SPCE on MMT was much lower than that of TPCE. This study demonstrated that the SA structure of SPCE appears to exhibit a large steric hindrance, which prevents the intercalation of SPCE into MMT.

Strength Behaviour of Geopolymer Concrete by using Different Mineral Admixtures

The world is developing rapidly and therefore the construction of buildings takes vital role. If we bear thoroughly the usage of concrete gets raised up so it ends up in the shortage of the natural resources. so as to save lots of our natural resources, by replacing a number of the proportions within the concrete with the subsequent measures. By using ash and GGBS as admixture in geopolymer concrete in equal percentages (50-50%). The results obtained from compressive strength, split durability test for the age of 7-and 28-days strength-polymer concrete is one among the building materials that became more popular in recent years thanks to the very fact that it's significantly more environment friendly than standard concrete-polymer concrete could be a variety of concrete that's made by reacting aluminates and silicate bearing materials with a caustic activator. Commonly, waste materials like ash or slag from iron and metal production are used, which helps result in a cleaner environment. Geo-polymer concrete completely replaces cement by ash, ground granulated furnace slag and therefore the polymer materials.

Study on Durability of Concrete under Alkali-Aggregate Reaction

The alkali-aggregate reaction has always had a great impact on the safety and durability of concrete projects. Therefore, the study of concrete failure mechanism under alkali-aggregate reaction has become a hot topic in the engineering field. This paper takes the Longtanqing debris flow ditch concrete treatment project as the background. Based on the alkali-aggregate reaction inhibition test under different conditions, regression analysis and trend surface analysis were used to study the correlation between fly ash content, expansion rate of concrete specimens, and curing age. And the engineering measures are put forward to effectively inhibit the alkali-aggregate reaction: (1) the optimum amount of fly ash appears at 30%-40%, fly ash has the strongest ability to inhibit alkali-aggregate reaction; when the content of fly ash is less than 20%, the fly ash ability to inhibit alkali aggregate reaction is weak. (2) To lower the height of the alkali content of concrete, there is 35% of the grade I class F coal ash as concrete admixture.

Effect of Hydration Process on Properties and Microstructure of Coal Gangue Admixture Concrete

The mineral of coal gangue is mainly kaolinite, which can be used as mineral admixture after activation. In order to study the effect of coal gangue on the hydration process of concrete, 20% coal gangue powder was used to replace cement to prepare concrete. The phase composition, microstructure morphology and pore structure of concrete hydration products at different ages were observed by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM) and nuclear magnetic resonance (NMR). At the same time, the experimental study on the compressive strength, splitting tensile strength and flexural strength of coal gangue admixture concrete with time and relationship was carried out. The results indicate that the addition of coal gangue powder significantly affected the hydration process of cement. In the cement-coal gangue powder-water system, coal gangue particles adsorbed a large amount of CH generated by cement hydration after curing for 14 d. The (AlO4)4− group in the coal gangue power replaced the (SiO4)4− on the calcium silicate hydrate (C-S-H) structure of the hydration product, thereby generating a new flocculated polymer calcium aluminosilicate hydrate (C-A-S-H). Until the curing age exceeded 56 d, the CH content in the slurry was less, and the hydration reaction rate of coal gangue became slowe. The unhydrated coal gangue particles played the “micro-aggregate effect”, filled in the pores and reduced the number of macropores and pores. The density of concrete microstructure increased, which promoted the continuous increase of concrete strength.

Durability of Reinforced Concrete Containing Biochar and Recycled Polymers

In the field of sustainable construction materials, the production of eco-friendly concretes, obtained by the addition of waste products such as biochar and recycled polymer particles, offers interesting alternatives to traditional materials. Biochar is a carbonaceous solid by-product obtained from the thermo-chemical conversion of biomass and its addition into concrete admixtures can offer an eco-friendly carbon sequestration solution, capable to slightly improve concrete properties. Recycled polymer materials can be used to partially replace conventional aggregates with the aim of obtaining lighter concretes that help to face the disposal challenge presented by this non-degradable plastic waste. However, the influence of these waste additions on the corrosion behavior of steel rebars embedded in these “eco-concretes” is still unexplored. Within this context, this work presents some results of an extensive study dealing with the concrete mechanical and physical properties and the rebar corrosion resistance during cyclic exposures to chloride-containing solutions.

Effect of highly dispersed colloidal olivine nano-silica on early age properties of ultra-high performance concrete

Nano-silica is an important admixture for ultra-high performance concrete (UHPC). However, complex production process and agglomeration problem of conventional nano-silica significantly limit its application in UHPC. In this study, a novel highly dispersed colloidal olivine nano-silica (C-OnS) is developed. The properties of C-OnS are characterized with laser light scattering, nuclear magnetic resonance and zeta-potential. The C-OnS is applied in UHPC to enhance the cement hydration and reduce the viscosity, while a commercial sol-gel colloidal nano-silica (C-nS) is used as a reference. The effects of C-OnS and C-nS on UHPC are investigated by calorimetry, thermal gravimetry, 29Si and 27Al nuclear magnetic resonance, nitrogen physisorption and mercury intrusion porosimeter. The results show that the performance of UHPC is enhanced by C-OnS at early ages thanks to its higher silanol content, surface area and dispersibility. The advantages of highly dispersive, strong pozzolanic reactivity and tailorable particle size provide new possibilities for application of C-OnS in cement-based materials.

Basalt Powder Waste Application as Affordable Concrete Admixture

Different weather conditions, like temperature and humidity influence on the performance of concrete structures to which they are normally subjected, especially at earlier stage of their service life. One of practical measures has been the regulation of the setting time of fresh concrete. Some admixtures are used in concrete to regulate the setting time and therefore increase structures performance under given situation. Almost all admixtures used in Rwanda are being imported from outside the country and this is one of factors affecting the construction cost. A big quantity of basalt powder at different sites in the country is left without being used and has been negatively impacting the environment. This study aimed at analyzing the potentials of basalt powder waste used in concrete as admixtures in different percentages, e.g. 0%, 5%, 10%, 15% and 20%. Different investigations on concrete incorporating basalt powder as admixture, such as the setting time, workability and compression tests were conducted. The results showed that the gradual incorporation of basalt powder waste as admixture up to 20%, accelerated the setting time more than 13 times, but decreased the compressive strength of concrete by around 24.5%, with comparison to normal concrete strength. The application of basalt waste in concrete would contribute not only to the reduction of environmental pollution but also to the provision of more affordable admixtures for mortar and concrete.

Rheological Properties of Cement Paste Containing Ground Fly Ash Based on Particle Morphology Analysis

Separating finer particles from raw fly ash is a popular method to produce high-performance admixture of concrete. However, the supply of separated fly ash is obviously behind the demand and the residue fly ash is difficult to be disposed. Ground fly ash is another method to improve the particle size and reactivity, but the change of particle morphology during grinding may affect the rheological properties of cement paste and concrete, which limits the application of ground fly ash in concrete projects. In this study, the raw fly ash, separated fly ash, and ground fly ash of the same particle size range were studied and the particle morphology was analyzed by Image-Pro Plus process and spherical particles proportion calculation. On this basis, the fluidity and rheological properties of cement paste with different fly ash content were tested and the mechanism was discussed by packing density and zeta potential analysis. The results showed that the total amount of spherical particles in fly ash-cement paste system was reduced due to the spherical particles of ground fly ash being destroyed during the grinding process. Thus, compared with the separated fly ash of similar particle size range, the fluidity of ground fly ash was significantly decreased while the yield stress and plastic viscosity increased significantly, which indicated that the rheological properties of fly ash cement paste are closely related to the particle morphology of fly ash. The results provide theoretical basis and technology support to the application of ground fly ash.

Study of self-compacting concrete containing coal bottom ash and fly ash

Abstract This paper consists of a detailed analysis of the use of industrial by-products(coal bottom ash and fly ash) as an admixture in the self-compacting concrete. The judicious use of industrial byproducts and the proper waste management can lead to a sustainable development in the field of infrastructure. This paper talks about the physical and chemical properties of these by products used in the self-compacting concrete. Critical and definite analysis has been carried out on the reviewed literature and further scope of work in the analysis and interpretation has been addressed. On a positive note, it can be stated that the use of industrial by-products in self-compacting concrete can lead to a sustainable development.

Capacity of Self-Sealing Concrete Embedding Crystalline Admixture

Concrete is one of the most intelligent and widely utilized man-made materials in the construction industry. Despite this, even high-quality concrete is susceptible to porosity, which reduces its serviceability period. Furthermore, there is an increasing need to increase longevity due to environmental exposure such as soil moisture, corrosive outside elements, or structural defects forming in the surface of concrete. The use of crystalline admixtures in concrete is one of the many approaches to reducing these risks. When crystalline admixtures come into contact with water, they form thin crystals that fill pores, capillaries, and micro fractures, as a result making concrete a self-sealing material. When the concrete has dried, the crystalline particles remain dormant until they come into contact with additional water, which causes them to crystallize once more. This research aims to analyze and compare the material properties between commonly used concrete and concrete where crystalline waterproofing is present. Furthermore, experiments are conducted to evaluate each of the concrete samples: compressive strength, water permeability and flexure strength. As a result, demonstrating benefits or negative aspects in the use of crystalline admixture in the early stages of concrete is important. It is not yet defined, weather this is the future of cutting-edge concrete and the impact that it will have in the Albanian building market.

Experimental Study on Sulfate Wetting–Drying Cycle of Metal Tailings Powder Concrete

In order to absorb a large amount of metal tailings powder and alleviate the shortage of mineral admixture in concrete, metal tailings powder can form a compound admixture with slag powder to prepare concrete. The sulfate wetting–drying cycle test of concrete with different contents of metal tailings powder was carried out to study the action law of metal tailings powder on the sulfate corrosion resistance of concrete. Scanning electron microscope, XRD, and nuclear magnetic resonance microscopic tests were used to reveal the deterioration mechanism of metal tailings powder concrete eroded by sulfate. The results show that proper addition of metal tailings powder can increase the sulfate corrosion resistance of C50 concrete. When the ratio of metal tailings powder to slag powder is 3:7 and 5:5, the sulfate corrosion resistance grade can reach KS180. There is a strong linear relationship between the relative ultrasonic velocity factor and relative compressive strength factor. The sulfate failure mechanism of metal tailings powder concrete is mainly the internal formation of corrosion products ettringite and gypsum. The introduction of metal tailings powder can reduce the alkalinity of concrete and improve the pore structure, thus improving the sulfate corrosion resistance of concrete.

Concrete admixtures - sustainable concrete

Durability of concrete, an important part of the sustainability theme, was, is, and will be one of the main topics for large infrastructure projects like the Gotthard base tunnel. For such important structures a service life of more than 80 years is expected. The prevailing underground conditions like water ingress, aggressive waters etc. will influence the choice of the concrete system and mix design. Therefore, a focus is on the potential damage mechanisms on the concrete like chloride ingress or sulfate attack. A well-designed concrete will be durable concrete which can withstand various external attacks and achieves or even extends the designed service life of the concrete structure. Based on the knowledge that the main damaging mechanisms for concrete are based on water penetration into the concrete, various measures can be taken to achieve concrete structures with significantly reduced permeability. These measure ranges from reduction of the water/binder-ratio, increasing the density of the concrete using silica fume, to the use of special admixtures in order to increase the durability of concrete. In an extensive research program, the influence of mix design components e.g. different admixture types, water/binder-ratio on hardened concrete properties like chloride resistance (chloride migration coefficient), sulfate resistance and water conductivity have been tested and analyzed.

Toward bioinspired polymer adhesives: activation assisted via HOBt for grafting of dopamine onto poly(acrylic acid).

The design of bioinspired polymers has long been an area of intense study, however, applications to the design of concrete admixtures for improved materials performance have been relatively unexplored. In this work, we functionalized poly(acrylic acid) (PAA), a simple analogue to polycarboxylate ether admixtures in concrete, with dopamine to form a catechol-bearing polymer (PAA-g-DA). Synthetic routes using hydroxybenzotriazole (HOBt) as an activating agent were examined for their ability in grafting dopamine to the PAA backbone. Previous literature using the traditional coupling reagent 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) to graft dopamine to PAA were found to be inconsistent and the sensitivity of EDC coupling reactions necessitated a search for an alternative. Additionally, HOBt allowed for greater control over per cent functionalization of the backbone, is a simple, robust reaction, and showed potential for scalability. This finding also represents a novel synthetic pathway for amide bond formation between dopamine and PAA. Finally, we performed preliminary adhesion studies of our polymer on rose granite specimens and demonstrated a 56% improvement in the mean adhesion strength over unfunctionalized PAA. These results demonstrate an early study on the potential of PAA-g-DA to be used for improving the bonds within concrete.

Investigation of the Efficiency of Ultra High Range Water Reducing Admixture in Roller Compacted Concrete Production

In this study, roller compacted concretes were produced by using polycarboxylate-based third generation high-performance mortar and concrete admixture, which provides ultra-high range water reduction and long workability time. In roller compacted concrete production, the chemical admixture dosage was 1%, which was the maximum dosage recommended by the manufacturer, and the amount of water used was reduced by 10, 20, 30 and 40% compared to the concrete produced without the use of concrete admixture. The physical and mechanical properties of the roller compacted concrete specimens were investigated. When the ultra-high range water reducer was used as 1% of the cement weight in the production of roller compacted concrete, optimum values in terms of unit weight, compressive strength, water absorption, ultrasonic pulse velocity and dynamic modulus of elasticity were obtained by reducing the mixing water by 10%. Although the water/cement ratio decreased, further reduction in water amount resulted in a decrease in compressive strength and affected the concrete quality negatively.

Durability Performance of Geopolymer Concrete: A Review.

Geopolymer concrete is produced from the geopolymerization process, in which molecules known as oligomers integrate to form geopolymer networks with covalent bonding. Its production expends less thermal energy and results in a smaller carbon footprint compared to Ordinary Portland Cement (OPC) concrete. It requires only an alkaline activator to catalyze its aluminosilicate sources such as metakaolin and fly ash, to yield geopolymer binder for the geopolymerization to take place. Because of its eco-friendly technology and practical application, current research interest is mainly concentrated on the endurance of geopolymer concrete to resist heat and chemical aggressions. As such, it is pertinent for this review article to provide critical insight into the recent progress in research on the durability of geopolymer concrete. One significant outcome of the review is that the admixture of geopolymer concrete could be blended with additives such as micro-silica and fibers such as polypropylene fibers, to enhance its durability. The review on the durability aspects of geopolymer concrete showed that it had high compressive strength at an optimal elevated temperature, low to medium chloride ion penetrability, and high resistance to acid attack and abrasion. This makes geopolymer concrete a viable candidate to replace OPC concrete in the construction industry.

Compressive resistance of concrete produced with recycled concrete aggregate and sugarcane vinasse waste-water

Vinasse is the main by-product of the sugar and alcohol industry. For each liter of ethanol produced from sugarcane, approximately 12–18 L of vinasse are generated. Being such, its use as a hydration agent in concretes may be useful to save drinking water. This work analyzed the compressive strength of concrete manufactured with vinasse and recycled concrete aggregates (RCA), as a substitute for water (100%) and sand (50 and 100%), respectively. At the initial periods (7 and 14 days), the compressive strength of specimens hydrated with water was higher than those hydrated with vinasse due to the delay in hydration of the cement caused by the sucrose present in the vinasse. Therefore, in these stages, the hydration agent is the main contributor for the differences in the compression strength ( p < 0.05, Two-way ANOVA). In the later stages (21 and 28 days), the RCA content was that which most contributed to the differences in the compressive strength. Specimens with 50% RCA showed the highest values ( p < 0.05), independently of the hydration agent; the specimens with vinasse reached the same resistance as that of the reference. After 63 days of curing, the concrete with water replaced by vinasse acquired higher resistance in relation to the reference due to continuity of curing. As both residues proved to be viable in the composition of concretes, they were applied in a precast concrete panel, that presented satisfactory results, enabling its use as a non-structural wall. It can be concluded that sugarcane vinasse with recycled concrete aggregate (RCA) is a suitable solution to achieve better reuse of construction and agroindustry waste as a new building materials compound. • Sugarcane vinasse waste water was used in concrete admixtures replacing water. • Concretes with vinasse and RCA acquired same compressive strength of reference at 28-days. • Concrete with vinasse reach higher compressive strength than reference at 63-days curing.

The Durability of Recycled Fine Aggregate Concrete: A Review.

With the rapid development of urbanization, many new buildings are erected, and old ones are demolished and/or recycled. Thus, the reuse of building materials and improvements in reuse efficiency have become hot research topics. In recent years, scholars around the world have worked on improving recycle aggregates in concrete and broadening the scope of applications of recycled concrete. This paper reviews the findings of research on the effects of recycled fine aggregates (RFAs) on the permeability, drying shrinkage, carbonation, chloride ion penetration, acid resistance, and freeze–thaw resistance of concrete. The results show that the content of old mortar and the quality of recycled concrete are closely related to the durability of prepared RFA concrete. For example, the drying shrinkage value with a 100% RFA replacement rate is twice that of normal concrete, and the depth of carbonation increases by approximately 110%. Moreover, the durability of RFA concrete decreases as the RFA replacement rate and the water–cement ratio improve. Fortunately, the use of zeolite materials such as fly ash, silica fume, and meta kaolin as surface coatings for RFAs or as external admixtures for RFA concrete had a positive effect on durability. Furthermore, the proper mixing methods and/or recycled aggregates with optimized moisture content can further improve the durability of RFA concrete.

Preparation of composite micro-slag based on the application of tailings slag in cement and concrete

To improve the application performance and utilization of tailings slag in building materials, a composite micro-slag composed of ultrafine tailings particles was prepared based on the chemical composition, phase composition, and surface morphologies of three tailings slags. Using of ball mill and horizontal sander combined with gradient grinding technology, the utilization rate of the composite micro-slag in the cement raw meal was as high as 60%, and the raw meal particle uniformity was good. When it was used as a concrete admixture, it can effectively reduce the amount of cement by 40%. The results showed that the grinding process improves the particle morphology of the tailings slag, thereby affecting the interaction between the particles, which not only promotes the particles to receive uniform energy during the calcination process, reduces the energy consumption of clinker firing, but also stimulates the activity of tailings slag so that improves the strength and workability of concrete. Moreover, the combination of cement kiln calcination and heavy metal solidification technology or hydration reaction solidification mechanism allows the heavy metal elements contained in the composite micro-slag to be solidified in cement and concrete, ensuring its safety in use.

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.

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.