Types Of Admixtures Research Articles

The effects of stabilizers on the thermal and the mechanical properties of rammed earth at various humidities and their environmental impacts

The overall behavior of rammed earth (RE) as a low embodied energy construction method can be enhanced by using stabilizers. Several studies have been performed on cement and lime stabilized RE. However, studies on other additives, especially the sustainable ones, are limited. In this research, the effect of stabilizers including cement, pozzolan, microsilica, fiberglass, guar gum and phase change material (PCM) was evaluated on the performance of RE mixtures. The mixtures were assessed by considering the durability, shrinkage, thermal conductivity, mechanical properties and their sensitivity to the humidity. Then, the correlations were determined between the mechanical properties and the non-destructive wave velocity. Scanning electron microscope (SEM) used to analyze the reaction and the bond between the stabilizers and aggregates. The improvement in ductility and energy absorption of RE is significant by limiting the guar gum content. Pozzolan, especially used in conjunction with microsilica, improved the mechanical behavior of the RE mixtures. Fiberglass significantly enhanced the ductility, the tensile strength, and the energy absorption. It was concluded that aggregate volume fracture and admixture type are the most effective parameters on the thermal conductivity. Furthermore, the wave velocity is a proper tool to evaluate the suitability of the RE. More durable, sustainable and eco-friendly mixtures can be achieved by using a sufficient amount of guar gum and pozzolan with microsilica to improve the mechanical behavior of RE materials and also reduce the carbon footprint of RE materials.

Synergistic Benefits of Using Expansive and Shrinkage Reducing Admixture on High-Performance Concrete.

High-performance concrete (HPC) is widely used in construction according to great mechanical properties, but it has a high risk of shrinkage cracking due to autogenous shrinkage stress. Therefore, the aim of this research was to investigate the effect of a combination of expansive admixture (EA) and shrinkage reducing admixture (SA) on the autogenous shrinkage of high-performance concrete without heat treatment. Two different EA to cement weight ratios of 0.0, 5.0%, and two different SA to cement weight ratios of 0.0, and 1.0% were combined and considered. To investigate the differences in the time-zero conditions effect on the autogenous shrinkage behaviors, four different initial points were compared. The test results indicate that the EA and/or SA content was conductive to a little bite increase compressive strength (22.6–37.9%) and tensile strength (<4.8%). According to the synergistic effect of the EA and SA on the HPC, the autogenous shrinkage significantly decreased (<50%), as compared to those specimens with only one type of admixture (EA or SA). Furthermore, all the specimens incurred restrained autogenous shrinkage cracks at an early age, except the specimen using the combined EA and SA. Therefore, it can be concluded that the combination of EA and SA is effective for improving the properties of HPC.

The Effect of Water-Cement Ratio on Sulfate Resistance of Self-Compacting Concrete with Bagasse Ash

Previous study showed so many factors will contribute to the durability of concrete, such as cement content, water cement ratio, admixtures to be used, compaction dan curing methods. Two types of admixtures for concrete mixture can be used, e.g. chemical admixture and mineral admixture. Materials can be categoried as mineral admixture such as fly ash, silica fume, risk husk ash, and bagasse ash. Sulfate resistance of concrete is one of the examples of chemical durability of concrete. Self-Compacting Concrete (SCC) known as concrete which can flow within its self-weight and without forming honeycombing, segregation and bleeding, even with no compaction. In this experimental work, bagasse ash was used in concrete mixture as partial replacement of cement with the percentage of 10%, 15% and 20%. The variation of w/b were used e.g 0.275, 0.300 and 0.325. For the purpose to stipulate the sulfate attack on concrete, the cylinder specimen with size of 100 x 200 mm and magnesium sulfate solution with 5% and 7% molarity were used. To observe the percentage of concrete weight loss, all the specimen were immersed in this solution within 28 days. The result showed that the value of compressive strength for the specimen with w/b = 0.275 and 15% bagasse ash was up to 67.240 MPa for 28 days and 68.096 MPa for 56 days without immersion in magnesium sulfate solution. The highest percentage of concrete weight loss is 3.030% yielded from the specimen with w/b = 0.325 and 0% bagasse ash which was immersed in 7% molarity of magnesium sulfate solution.

Analytical Study on the Flexural Behavior of Reinforced Concrete Beam with Mineral Admixture under Calcium Leaching Degradation

Calcium leaching degradation could be happened in reinforcement concrete member due to the contact with pure water in underground condition. Thus, it is needed to evaluate the resistance of calcium leaching for concrete mixed with mineral admixtures. So, in this paper, to evaluate the flexural behavior in RC member with mineral admixture under calcium leaching degradation, we investigated the effect of calcium leaching using the non-linear finite-element program. From the results, the load capacity and flexible rigidity of a degraded RC member decrease when the degradation level increases with leaching period. And, regardless of the type of mineral admixtures, finite-element-method analysis effectively showed the characteristics of calcium leaching damaged RC beam.

The effects of water-cement ratio and chemical admixtures on the workability of concrete

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.

Calculation of plastic viscosity of concrete mixture using the modified empirical formula

Nowadays various types of viscometers are being designed to measure the rheological properties of cement paste and fresh concrete. Most of them are very expensive and require specific knowledge about their usage. Then in practice usually the empirical formulas are used to calculate the main rheological properties – yield stress (Pa) and plastic viscosity (Pa·s). Therefore, in the literature, there are some formulas which can’t be used to calculate analytically plastic viscosity of concrete mixture, e.g. it cannot estimate the influence of different chemical admixture on plastic viscosity of concrete. The paper focuses on the modification of the empirical formula to calculate the plastic viscosity of fresh concrete mixture. In this paper the way of viscosity formula modification was described. For an empirical formula modification, the coefficients which describe the influence of different chemical admixture on plastic viscosity of concrete mixture were used. Coefficients Kcalc. were calculated as a ratio between different viscosity values of cement pastes obtained without and with certain chemical admixtures. Viscosity of cement paste was obtained by using rotational viscometer Rheotest RN4. Coefficients describe the change in cement pastes viscosity when adding different type (superplasticizer, viscosity modifying agent, air-entraining agent and air voids removing agent) and amount of chemical admixture.

Fresh properties of HPSCC containing SRA and expansive admixtures

Shrinkage-reducing admixture (SRA) and expansive admixture (EXA) were used in high performance selfcompacting concrete (HPSCC) to mitigate autogenous shrinkage. In order to evaluate the fresh properties of concretes, the rheological parameters were determined in a ICAR rheometer at 10, 25, 40, 60 and 90 min. The flow behavior of the mixtures was described by Bingham, Herschel-Bulkley, and modified Bingham models. Slump flow test, V-funnel test and J-Ring test were also carried out at 10 min. Slump flow test was performed also after 90 min of mixing. The test results showed that, at 10 minutes, all mixtures had similar performances, independently of the SRA and EXA contents. However, the slump flow test shows a reduction of up to 24% of its diameter at 90 min for mixtures with EXA. Mixtures with EXA revealed a gradual increase in dynamic yield stress with elapsed time. In contrast, concretes with SRA exhibited less variation in its rheological properties. Statistical analysis (ANOVA) showed that, regardless of the rheological model adopted, the admixture content was not a significant factor for the yield stress, while the type of admixture and the time of testing greatly influenced the concretes rheological response. Keywords: Shrinkage-reducing admixture (SRA), expansive admixture (EXA), rheological behavior, high performance self-compacting concrete.

Cement Kiln By-Pass Dust: An Effective Alkaline Activator for Pozzolanic Materials.

Cement kiln by-pass dust (CKD) is a fine-grained by-product of Portland clinker manufacturing. Its chemical composition is not suitable for returning back into feedstock and, therefore, it has to be discharged. Such an increasing waste production contributes to the high environmental impact of the cement industry. A possible solution for the ecological processing of CKD is its incorporation into alkali-activated blast furnace slag binders. Thanks to high alkaline content, CKD serves as an effective accelerator for latent hydraulic substances which positively affect their mechanical properties. It was found out that CKD in combination with sodium carbonate creates sodium hydroxide in situ which together with sodium water glass content increases the dissolution of blast furnace slag particles and subsequently binder phase formation resulting in better flexural and compressive strength development compared to the sample without it. At the same time, the addition of CKD compensates the autogenous shrinkage of alkali-activated materials reducing the risk of material cracking. On the other hand, this type of inorganic admixture accelerates the hydration process causing rapid loss of workability.

Experimental Study of Using Bentonite Concrete with and Without Crimbed Steel Fiber in Conventional Concrete.

Cement manufacturing pollutes atmosphere by release of greenhouse gases like carbondioxide and it depletes the ozone layer causing adverse affect on livings on earth by global warming. Due to this reason mineral admixtures are added to concrete to reduce carbondioxide emmision in concrete.various type of mineral admixtures are available fly ash, silica fume, rice husk, sea shell and a cheaper clay material bentonite is considered and used in this project.This paper presents the result of an experimental investigation carried out to evaluate the properties of concrete with bentonite and steel fiber bentonite in which ordinary portland cement was partially replaced with bentonite by weight for a mix of M25 grade concrete. Replacing of cement by bentonite and bentonite with steel fiber was carrird out, concrete was casted and tested for the compressive strength, split tensile strength and flexural strength. Mix of bentonite with conventional concrete for various percentage and the results have been tabulated and compared with conventional concrete. Then, the same properties were examined in concrete adding different percentages of crimed steel fiber by weight of concrete with constant amount of bentonite which in turn increases the strength of concrete

Development of conductive composite coatings with specific functional properties

The article presents the development results of advanced composite coatings with enhanced electric conductivity intended for detection of disruptions in the base material structure. Conductive coatings were prepared from a low viscosity epoxy resin and three types of admixtures - amorphous carbon black, micronized graphite and multi-walled carbon nanotubes (MWCNTs). Such multicomponent coatings were tested together with hand-applied graphite layers and commercial spray-applied colloidal graphite and copper-based electroconductive coatings, for comparison. The influence of the admixtures on electrical conductivity was evaluated. The course of impedance response of polymer coatings, graphite layers and copper layers was investigated during bending in press, drilling and high-speed loading by rifle projectiles. Conductive coatings showed a distinctive change in impedance under mechanical damaging by drilling and during dynamic testing. These functional coatings represent innovative direction for the development of new progressive ballistic and anti-blast shield systems.

APLIKASI MODIFIED PROCTOR PADA ROLLER COMPACTED NO-FINES CONCRETE DENGAN AGREGAT 5-10 mm

The usage of no-fines concrete as pavement currently was being utilized. It was constituted by diversity effort of concrete cement pavement construction material, besides no-fines concrete pavement having benefit that reduce water pond on pavement surface rapidly because of its pervious. Permeability character of no-fines concrete will recharge groundwater deposit therefore more environmental friendly. Problem faced is low strength of no-fines concrete as compared to conventional concrete. Therefore it is required the effort of increasing the strength of no-fines concrete by increase concrete density that is done by roller machine. No-fines concrete that is compacted by roller machine is called Roller Compacted No-fines Concrete (RCNC). &#x0D; This research analyzed the increase of concrete properties especially compression strength and split tensile strength effected by external compaction using modified proctor in creating the laboratory specimen. Materials of no-fines concrete utilized Clereng coarse aggregate with size 5-10 mm, Gresik Portland cement and the aggregate cement ratio is 4 and 6. To accelerating the hardening concrete utilized admixture type C which is sikaset accelerator with 20% of total water volume. The blow variation of modified Proctor per layer is 28, 42 and 56. Compression test and split tensile test been done at the age of 1 and 28 days. &#x0D; Result of research showed the increase of concrete specific gravity and compression strength in line with the increase of blow variation. RCNC specific gravity acquired ranging between 1,544 and 1,788. Compression strength at the age of 28 days acquired were (1) aggregate cement ratio 4 with 28, 42, 56 blows per layer were 21,47 MPa, 22,92 MPa, 26,55 MPa (2) aggregate cement ratio 6 each were 8,48 MPa, 10,51 MPa, 14,82 MPa. Split tensile strength at the age of 28 days were (1) aggregate cement ratio 4 with 28, 42, 56 blows per layer each were 2,27 MPa, 2,92 MPa, 3,13 MPa (2) aggregate cement ratio 6 each were 1,63 MPa, 1,83 MPa, 2,08 MPa.

Deterioration of concrete structures along with case studies in India

Concrete is used extensively in various types of construction works. However, the deterioration of reinforced-concrete structures is recognised as a major problem worldwide. Apart from requiring regular maintenance, many structures require extensive repair, rehabilitation and retrofitting. Over a period of time, as these structures become older, certain degradation or deterioration with resultant distress manifested in the form of cracking, splitting, delaminating and corrosion is found in them. Such deteriorated structures can be rehabilitated and retrofitted by using various types of admixtures and modern repair materials. This paper discusses the present state of concrete structures and the major areas where improvement is needed during the service life stage for sustainable development. It also discusses the method of carrying out repair, rehabilitation and retrofitting. This is detailed in the paper along with various case studies compiled by the author based on his field experience of direct involvement in the planning and execution of repair and rehabilitation jobs, which were successfully completed by using the latest repair materials and techniques.

Assessment of genetic diversity and population structure in gladiolus (Gladiolus hybridus Hort.) by ISSR markers.

ISSR (Inter simple sequence repeat) markers were used to assess the genetic diversity and population structure in 53 indigenous and exotic genotypes of gladiolus (Gladiolus hybridus Hort.). Molecular markers analysis showed PIC ranges from 0.42 (ISSR 861) to 0.99 (ISSR 855, ISSR 856 and ISSR 889) with an average 0.812, marker index ranged from 0.99 (ISSR 889) to 9.26 (ISSR 851) with an average 4.66 and resolving power of the primers ranged from 0.03 (ISSR 889) to 11.58 (ISSR 861) with an average value 3.80. The dendrogram based UPGMA clustering showed that all the 53 genotypes grouped into three main clusters. Nei's gene diversity (Na) varied from 0.929 to 1.717, effective number of alleles (Ne) varied from 1.262 to 1.369, Shannon's information index (I) ranged from 0.251 to 0.359 and gene diversity (He) was in the range from 0.167 to 0.229. Population structure analysis revealed three groups in which 32 genotypes were admixture types.

Synthesis, characterization and working mechanism of a novel sustained-release-type fluid loss additive for seawater cement slurry

Synthetic polymer fluid loss additive (FLA), an important type of admixture, was broadly applied in modern well cementation. However, the filter loss volume and fluidity of cement pastes containing polymer-FLA would deteriorate remarkably when sea water was used in mixing slurries instead of fresh water. In this study, a novel sustained-release-type fluid loss additive(S-FLA) was synthesized by means of anion-exchange intercalation reaction between an anionic type-copolymer and a calcium/aluminum type-Layered Double Hydroxide (Ca/Al-LDH). Based on the fluidity and compressive strength of experiments, it was found that in seawater mixing conditions, this composite material not only utilized its sustained release effect to significantly improve retention fluidity performance, but also the seed crystal effect of the Ca/Al-LDH effectively alleviated the declining in compressive strength of the slurries caused by the carboxyl group in the polymer. More interestingly, the realization of the slow release function increased actual adsorption capacity of the anionic polymer on the surface of cement hydrated particles, which made its controlling water loss effect was also better than that of the conventional FLA. The above advantages of this hybrid materials created the possibility to surmount the negative effect of electrolytes present in seawater, so as to provide some useful references for its practical application in the offshore well cement.

A Study on Porous Sealing Efficacy of hydrophilic Admixture on Blended Cement Concrete

The life of the concrete is strongly influenced by durability parameters. The permeability is one of the main characteristics influencing the durability of concrete. The concrete is more permeable due to the ingress of water, oxygen, chloride, sulphate, and other potential deleterious substances. The durability of concrete is mainly affected by pore structure system of concrete and addingthe supplementary cementitious materials (SCM), such as fly ash, slag cement, and silica fume can be decrease permeability. Crystalline technology enhances the strength of concrete by filling the poresand micro-cracks with non-dissolvable substances. To study the efficiency of crystalline formation in concrete in terms of more permeable should be guaranteed through a specific technique.The effectiveness of crystalline waterproofing system with partial replacement cement by GGBS is studiedin terms of strength and durability. The performance of the two different types of crystalline waterproofing integral admixtures has been studied for compressive strength, Split tensile strength, workability, water permeability, Rapid chloride permeability test and porosity in this paper.The early strength increased in GGBS with crystalline admixture concretes compare to the control concrete. No significant strength reduction is observed in GGBS concretes with crystalline admixture when replaced with 20% and 40% of cement than control concrete.

Evaluating Material Properties of Grout for PSC Bridge According to Admixture Type

This experimental study investigates material properties of prestressed concrete (PSC) grout depend on the combination of fly ash (FA), silica fume (SF) and zirconia silica fume (Zr). Based on the test results, when FA and Zr were included in grout mixtures, the fluidity, bleeding and volume change increased with less superplasticizer. The compressive strength of all grout mixtures was quite high at the age of 7 and 28 days, and the ternary mixtures had the excellent development of strength than binary mixtures. Furthermore, autogenous shrinkage properties of ternary grout combining shrinkage reducing agent (SRA) and expansive additive (EA) was evaluated. The 47~80% autogenous shrinkage was reduced by using SRA and EA. In addition, the effectiveness of using SRA and EA was higher for the grout mixture with SF than that with Zr. Keywords: PSC Grout, Bleeding, Autogenous Shrinkage, Silica Fume, Zirconia Silica Fume

Effects of re-curing on microstructure of concrete after high temperature exposure

Concrete contains many phases such as ettringite, portlandite, C-S-H etc. which undergo phase changes by forming some active products such as lime and calcium silicates during heating. These new active phases give reactions with water and carbon dioxide in air and affect the residual properties of concrete after subsequent days of cooling. In order to understand better these phase changes and their effects on residual properties, 3 different types of concrete were produced depending on mineral admixture type. Concrete specimens were heated to 1000 °C and one face heating procedure was applied in the furnace. Then concrete specimens were subjected to air and water re-curing processes. Microstructural investigations XRD, TGA and SEM/EDX were conducted on the samples obtained from concrete specimens.

Effect of high temperature on strength and mass loss of admixtured concretes

Chemical admixtures are used in concretes to prove some properties at ambient temperature. The admixtured concretes may present different behaviour at high temperature than at normal conditions. In this study, five different types of chemical admixtures – Superplasticizers (SP), hardening accelerators (HA), setting retarders (SR), air entrainers (AE) and water repellents (WR) – Were incorporated with different fraction of cement mass (0.5, 1.0, 1.5 and 2.0%), to investigate their influences on the strength and mass losses of concretes under high temperature. This study concerns the behaviour of admixtured concretes at ambient temperature 20 °C (normal conditions) and those subjected to temperatures 105 °C (oven dry) and 300 °C with a rate of 2 °C/min. Compressive-strength and mass loss tests were performed on the samples 10 × 10 × 10 cm3which were cooled up slowly to ambient temperature. It was concluded that among the chemical admixtures used, the superplasticizer (SP) significantly increased the workability of SPC. The tests results indicated that at a temperature of 300° C, the concrete with an air entrainer admixture caused the greatest loss of strength and mass when compared with others admixtured concretes. The lowest losses are those obtained for concretes with superplasticizers at this temperature.

The development of new empirical apparatuses for evaluation fresh properties of self-consolidating mortar: Theoretical and experimental study

Self-Consolidating Concrete (SCC) and Self-Consolidating Mortar (SCMO) contain unique properties such as filling ability, passing ability, and segregation resistance, differentiating them from ordinary concretes. Little changes in SCMO and SCC ingredients bring about major changes in their workability and segregation. The behavior of fresh SCMO depends on variable factors such as water to cement ratio, gradation and moisture content of aggregates, type of mineral additives, dosage and type of superplasticizer and other chemical admixtures. In addition, evaluation of fresh properties of the SCMO requires simple and fast methods.In this study, based on the flow velocity and volume to surface ratio method, new apparatuses were developed to evaluate the fresh properties of SCMO. Mini J-ring, mini U-box, and mini L-box were used to measure passing ability parameters. Mini slump, mini Orimet, new mini V-funnel and mini V-funnel were used to measure filling ability and mini column segregation was used to measure segregation of self-consolidating mortars. The relationships between critical areas of mentioned methods are considered. The Experimental set-up method was used to record the fresh properties. In addition, 27 different mortar mixtures were prepared to verify the test methods. Results show that flow velocity and volume to surface ratio were appropriate criteria to design new apparatuses to measure fresh properties of self-consolidating mortar.

Thermal Conductivity of Hydrated Paste in Cement-Based Foam Microstructure

Abstract This article presents the thermal constants of hydrated cement paste, which constitute the air-void wall of cement-based foam microstructure, and examines its influence on moisture, age, pozzolanic admixture type, and content. Along with the reference mix, containing portland cement only, six other mixes were prepared by replacing cement with fly ash, silica fume, and metakaolin, up to 20 % by mass in the binder. The Transient Plane Source, a thermal analyzer that conforms to ISO test standards, was employed to evaluate the thermal constants. Here, the measurements were made at 60, 120, 210, and 300 days. The results revealed that the drop in thermal conductivity for the cement paste was significant in the earlier age but progressively became insignificant as the hydration advanced. It was also found that adding fly ash and silica fume in higher dosages resulted in reducing the conductivity, while metakaolin exhibits a reverse trend. Furthermore, the reduction in the moisture content due to pozzolanic admixture was also noticed. Finally, an empirical formulation was developed to predict the thermal conductivity of the hydrated cement paste, which was also validated against the results of past research.