Effect Of Shrinkage Reducing Admixture Research Articles

Prediction of Restrained Shrinkage of New-to-old Concrete Interface

The focus of this study is on the shrinkage differences between new and old concrete, which can cause cracks at the bonding surface of the interface. The effects of various factors on shrinkage, such as the content of shrinkage reducing admixtures (SRA) the content of basalt fibers (BF) and the roughness at the new-to-old concrete interface (RI) are also examined. In this research, nine groups old-new concrete composite specimens were tested for shrinkage to gather experimental data. The restrained shrinkage mechanical model (RSMM) was deduced, and the restrained shrinkage model based on grey correlation analysis (RMGC) was proposed. The effectiveness and convenience of both prediction methods were evaluated by comparing their results to the experimental data. It was determined that the RMGC was more effective and convenient. Additionally, the research found that as the content of SRA and BF increases, shrinkage decreases. The effect of SRA was found to be more significant. As RI increases, shrinkage undergoes an initial increase and then decreases. The study can be used to inform the design and construction of structures that use both new and old concrete.

Effects of Shrinkage Reducing Admixture and Polypropylene Fiber Utilization on Some Fresh State, Mechanical and Durability Properties of Khorasan Mortar

ABSTRACT This study aimed to improve the mechanical and durability properties of Khorasan mortar, a type of lime-based mortar, using polypropylene shrinkage reducing admixture (SRA) and fiber. In addition to the control mixture without fiber and chemical admixture, three series of mixtures were prepared. The first series contains 0.4–0.6-0.8% polypropylene fiber by total volume; the second series contains SRA at the 0.05–0.1-0.15% by binder weight; the third series consists of mixtures containing both fiber and the SRA. Within the scope of the study, some fresh state, mechanical and durability properties were determined. The results show that utilization of fiber and SRA reduced the length change depending on drying-shrinkage and mass loss due to abrasion compared to the control mixture. In addition, the 90-day flexural and compressive strength values for all mixtures were lower than the 28-day results. It was determined that the decrease in strength values is less than the control mixture with the utilization of fiber and SRA because of the degradation in drying-shrinkage.

Reduction of shrinkage of self compacting concrete using polycarboxylate ether as shrinkage reducing admixture

The advancements in concrete and building technology have led to the demand for sustainable building materials over the last few decades. Various types of modified concrete like SCC or Self Compacting Concrete or Self Consolidated Concrete have also been developed and are considered as a new age highly modified concrete material. Self Compacting Concrete is considered a major evolution in the recent developments of the building industry. The semi-flow-able nature of SCC helps in construction and repair works along with several other advantages in terms of environmental, technological, economical and human. This work focuses on the effects of numerous types of shrinkage like drying shrinkage, plastic shrinkage and autogenous shrinkage on the performance of SCC. Many studies suggest that the excessive shrinkage properties in SCC provide a major hindrance to achieving the desired strength of the modified concrete. Capillary tension and expansive cracking are generally considered to be responsible for the shrinkage in SCC and lowering the water/cement ratio or reduction in filler/cement content leads to reduced levels of autogenous shrinkage. Cracks resulting from the excessive shrinkage are generally responsible for the substandard durability of the modified concrete as they provide spaces for hazardous fluids enter the concrete member resulting in an excessive plastic shrinkage. The effect of SRA or Shrinkage Reducing Admixtures is generally shown to have positive results and SRAs used in conjunction with compounds based on paraffin help in reduction of cracks. This paper also includes the experimental studies using Poly Carboxylate Ether (PCE) as SRA to combat the shrinkage of the modified concrete. This work included the use of poly carboxylate ether (PEC) over the use of commercially available shrinkage reducing admixtures (SRA) because it is locally available in many parts of the world where self compacting concrete has still not gained precedence over the normally vibrated concrete. The results obtained show that the use of PCE has similar effect to the lowering of shrinkage as the use of SRAs.

Rheological behaviour of low-heat Portland cement paste with MgO-based expansive agent and shrinkage reducing admixture

The combined use of low heat Portland cement (LHC), MgO-based expansive agent (MEA) and shrinkage reducing admixture (SRA) is beneficial to reduce the cracking risk of concrete. In this study, the effects of MEA and SRA on the rheological behaviour of LHC paste were investigated using dynamic and static shearing tests. The response surface methodology was used to estimate the effects of MEA, SRA, and superplasticizer on dynamic rheological parameters, while the zeta potential, calorimetric, and solid phases tests were conducted to explore the mechanisms of time-dependent rheological behaviour. Results indicate that MEA contributes to higher dynamic yield stress and plastic viscosity, while the effect of SRA is dependent on its dosage. MEA promotes the static yield stress development for accelerating the hydration of blends and the formation of Mg(OH)2. SRA retards the hydration of LHC and blended paste and reduces the number of main hydration products. However, the static yield stress is further increased by SRA, showing a consistent changing trend with the surface area of hydrated particles.

Effect of Shrinkage Reducing Admixture on Drying Shrinkage of Concrete with Different w/c Ratios.

The reduction of the moisture content of concrete during the drying process reduces the concrete’s volume and causes it to shrink. In general, concrete shrinkage is a phenomenon that causes concrete volume to dwindle and can lead to durability problems. There are different types of this phenomenon, among them chemical shrinkage, autogenous shrinkage, drying shrinkage including free shrinkage and restrained shrinkage, and thermal contraction. Shrinkage-reducing admixtures are commercially available in different forms. The present study investigates the effect of liquid propylene glycol ether on mechanical properties and free shrinkage induced by drying at different water-cement (w/c) ratios. Furthermore, the effect of shrinkage-reducing admixtures on the properties of hardened concrete such as compressive and tensile strength, electrical resistivity, modulus of elasticity, free drying shrinkage, water absorption, and depth of water penetration was investigated. The results indicated that shrinkage reducing agents performed better in a low w/c ratio and resulted in up to 50% shrinkage reduction, which was due to the surface reduction of capillary pores. The prediction of free shrinkage due to drying was also performed using an artificial neural network.

Effect of shrinkage reducing admixture on drying shrinkage and durability of alkali-activated coal gangue-slag material

This paper studied the effect of shrinkage reducing admixture (SRA) on drying shrinkage and microstructure of alkali-activated coal gangue-slag (AACGS). Concrete was prepared by using calcined coal gangue as coarse aggregate. The effect of SRA on the compressive strength and durability of concrete under different calcined coal gangue coarse aggregate (CCGCA) content was investigated, and the action mechanism of SRA was also systematically analyzed. The research results showed that the addition of 3% SRA can reduce the drying shrinkage of AACGS mortar by 47.5%. The 28d compressive strength of concrete can be reduced by mixing with SRA, which has limited effect on the 90d compressive strength. SRA can significantly improve the frost resistance durability of concrete (water freezing and salt freezing conditions can increase the number of freeze–thaw cycles by about 50 and 25, respectively) and sulfate attack resistance (90d testing). With the increasing content of CCGCA, the effect of adding SRA on the improvement of anti-chloride penetration has become more obvious. SRA caused changes in the pore size distribution, reaction rate and interfacial bond strength of AACGS concrete. Moreover, the present study also provides the experimental and detailed theoretical basis for the action mechanism of SRA in alkali-activated materials concrete.

Effect of Shrinkage Reducing Admixture on Shrinkage and Crack Properties of Cement Based Materials

In order to improve the dimensional stability of cement based materials, the effects of shrinkage reducing admixture (SRA) dosage on the shrinkage and crack properties of cement based materials were investigated. The hydration process of the cement pastes was tracked and monitored by hydration calorimeter and adiabatic temperature rise apparatus respectively. The action mechanism of SRA on hydration process of the cement based materials was characterized by differential scanning calorimeter (DSC). The shrinkage and crack results show that the ability of resist cracking of concrete can be effectively improved by SRA. The results of hydration calorimeter and adiabatic temperature rise indicate that the appear time of hydration temperature peak at early age was delayed and the development of hydration heat changed gently at later period by doped SRA. The results of DSC show that the release amount of hydration heat and the production of early calcium hydroxide can be delayed by SRA, however, there has no effects of SRA on the formation of cement hydration products like calcium hydroxide at the later period.

Effect of Shrinkage Reducing Admixture on the Strength and Shrinkage of Alkali Activated Cementitious Mortar

The effect of a shrinkage reducing admixture (SRA) on the mechanical properties and drying shrinkage of a proprietary alkali activated cementitous material (AACM) was investigated. Five AACM mortar mixes were prepared. SRA replaced the liquid activator at a dosage of 0%, 1%, 2%, 4% and 7%. The liquid/binder ratio was 0.38. The samples were cured in water. The flexural and compressive strengths of all mixes were determined at 1day, 2 days, 7 days and 28 days and the drying shrinkage was determined up to 80 days. The results show that SRA reduced the shrinkage of AACM mortar by up to 69% after 80 days at 7% dosage. However, SRA also reduced the compressive and flexural strengths of AACM mortars. Increasing dosages of SRA reduced the compressive and flexural strength while recording less shrinkage. Regardless of the dosage of SRA, a unique relationship exists between flexural strength and compressive strength, which correlates with the data of previous research. The AACM mortar maintained strength of over 43MPa (greater than 75% of the control mix at 0% SRA dosage) at 7% SRA dosage, which is classified as high strength in accordance with British Standard PAS 8820:2016.

Influence of alkali ions on the efficiency of shrinkage reduction by polypropylene glycol in alkali activated systems

Alkali-activated materials, especially when activated by water glass, exhibit substantial drying shrinkage that hinders their broader industrial application. The effect of shrinkage-reducing admixtures (SRA), based on polypropylene glycol, on drying shrinkage of alkali-activated blast furnace slag (BFS) mortars was examined. The determination of SRA efficiency and the influence of potassium alkali activators with varying silicate modulus on drying shrinkage characteristics were studied. It was observed that a high amount of alkalis positively affected the effect of SRA. The higher the amount of alkalis was, the lower was the drying shrinkage. The paper further discusses and underlines the role of the amount of alkali ions on the properties of alkali-activated BFS systems.

Effect of shrinkage-reducing admixture and expansive agent on mechanical properties and drying shrinkage of Engineered Cementitious Composite (ECC)

In order to reduce the drying shrinkage strain of traditional ECC and diminish the shrinkage differences between concrete and PVA (PolyVinyl Alcohol) fiber, this paper designs eighteen groups mix proportions based on Taguchi Methods. The influences of water-binder ratio, sand-binder ratio, fly ash content, expansive agent content, shrinkage-reducing agent content and PVA fiber volume content on the compressive strength, tensile properties and drying shrinkage are researched. In addition, the effect of PVA fiber on the crack resistance is investigated. The results indicate that the shrinkage strain of ECC increases with the raising of water-binder ratio, and decreases with the increasing of sand-binder ratio, fly ash content, expansive agent, and shrinkage-reducing agent; The anti-cracking performance is significantly improved along the fiber volume content changes, but it has little effect on ECC shrinkage strain. The compressive and tensile strength of ECC will greatly reduce with the increasing of shrinkage-reducing agent, rather, the compressive strength of ECC will enhance with the increase of expansive agent; But the expansive agent will lower the tensile strength and ultimate tensile strain. In the scope of this research, the water-binder ratio, sand-binder ratio, and fly ash content is about 0.25–0.33, 0.33–0.45, and 65% respectively. The research generated a set of reliable and valuable test data for the researchers and practical structural engineers in the field of ECC drying shrinkage.

Büzülme engelleyici katkıların su azaltıcı katkı varlığında harç karışımlarının basınç dayanımına, su emmesine ve kuruma-büzülmesine etkisi

Bu çalışmada, kuruma büzülme engelleyici (KBE) katkı içeren harç karışımlarının basınç dayanımı, su emme oranı ve kuruma büzülmesi incelenmiştir. Bu amaçla,4 farklı fabrika ürünü 9 adet toz ve sıvı halinde katkı kullanılmıştır. Tüm harç karışımlarında bağlayıcı olarak CEMI 42.5 R tipi çimento ve agrega olarak standart kum kullanılmıştır. KBE katkı içermeyen kontrol karışımına ilaveten çimento ağırlığının %2'si kadar KBE katkı kullanılarak toplamda 10 seri karışım hazırlanmıştır. Üretilen tüm harç karışımlarında, kum/bağlayıcı oranı, su/çimento (S/Ç) oranı ve yayılma değeri sırasıyla, 2.75, 0.485 ve 230±20 mm olarak sabit tutulmuştur. Hedeflenen yayılma değerlerini sağlamak için tek tip polikarboksilat-eter esaslı yüksek oranda su azaltıcı katkı kullanılmıştır. Hazırlanan harç karışımlarının 1, 3, 7 ve 28 günlük basınç dayanımları ve 28 günlük su emme oranı elde edilmiştir. Ayrıca söz konusu karışımların 28 günlük kuruma büzülme davranışı incelenmiştir. Deney sonuçlarına göre, kontrol karışımına kıyasla, KBE katkı kullanımı ile harç karışımlarının basınç dayanımı ve geçirgenlik özellikleri genel olarak olumlu etkilenmiştir. Ancak, 2 farklı KBE katkı kullanımı harç karışımlarının priz almamasına sebep olmuştur. Söz konusu karışımlarda su azaltıcı katkı kullanılmamıştır. Ayrıca, KBE katkı kullanımı ile harç karışımlarının kuruma büzülme değerlerinde %10-%45 oranında azalmalar tespit edilmiştir. Sıvı halinde olan KBE katkılar genel olarak toz halinde olan katkılara kıyasla kuruma-büzülme davranışı açısından daha başarılı olmuştur.

Investigation on the Effect of Shrinkage Reducing Admixtures on Shrinkage and Durability of High-Performance Concrete

Abstract Because of the advances in material science, new materials are launched to market that make it possible to produce concretes with more desirable properties for technical applications. These new concretes that cannot be made using the common materials and mixing ratios are called high-performance concretes. High-performance concretes are usually made with a low water-to-cement (w/c) ratio and high cement contents. High-performance concrete and its properties have gained the attention of engineers in recent years. One of the major shortcomings of cement-based materials such as concrete is their shrinkage. In this study, the effect of shrinkage-reducing admixture (SRA) on the shrinkage and durability of concrete is investigated. To examine SRA effects on shrinkage, free and constrained shrinkage tests are carried out while taking into account the impact of changing w/c ratio and cement content. Moreover, to study the durability of high-performance concrete, tests are carried out on durability parameters, including electrical resistance, depth of water penetration under pressure, and the percentage of water absorbed by the concrete. The results show that the use of shrinkage-reducing material decreases free shrinkage of concrete. When applying a lower w/c ratio and higher contents of cementitious materials, the use of this substance has a greater impact. Constrained shrinkage test results also indicate that the use of SRA additive causes a significant increase in the time of shrinkage crack formation during the test. The results of the durability tests indicate significantly improved durability properties of concrete aged 28 days.

Combined Use of Shrinkage Reducing Admixture and CaO in Cement Based Materials

The combined addition of a Shrinkage-Reducing Admixture (SRA) with a CaO-based expansive agent (CaO) has been found to have a synergistic effect to improve the dimensional stability of cement based materials. In this work, aimed to further investigate the effect, mortar and self-compacting concrete specimens were prepared either without admixtures, as reference, or with SRA alone and/or CaO. Their performance was compared in terms of compressive strength and free shrinkage measurements. Results showed that the synergistic effect in reducing shrinkage is confirmed in the specimens manufactured with SRA and CaO. In order to clarify this phenomenon, the effect of SRA on the hydration of CaO as well as cement was evaluated through different techniques. The obtained results show that SRA induces a finer microstructure of the CaO hydration products and a retarding effect on the microstructure development of cement based materials. A more deformable mortar or concrete, due to the delay in microstructure development by SRA, coupled with a finer microstructure of CaO hydration products could allow higher early expansion, which might contribute in contrasting better the successive drying shrinkage.

Combined effect of shrinkage reducing admixtures (SRA) and superabsorbent polymers (SAP) on the autogenous shrinkage, hydration and properties of cementitious materials

This paper examines the combined effect of superabsorbent polymers (SAP) and shrinkage reducing admixtures (SRA) on the autogenous shrinkage, hydration, microstructure, and properties of cementitious materials. The addition of SRA was found to reduce the absorption of SAP in the extracted pore solution as well as in the cement pastes. It was shown that the cement pastes with both SAP and SRA exhibited a higher shrinkage than the cement paste with SAP, more notably at the early age. The hydration temperature peak of the cement paste with both SRA and SAP occurred sooner than that of the cement paste with SRA at early age. The non-evaporable water content measurement indicated a higher degree of hydration for the cement paste with both SRA and SAP than the cement paste with SRA due to the internal curing effect of SAP. The compressive strength and electrical resistivity of the cement paste with both SRA and SAP were shown to be lower than those of the cement paste with SAP and the cement paste with SRA. Addition of SAP appeared to promote increased Ca(OH)2 formation in the hydration product. SEM examination indicated a distribution of microvoids in the range of 10–20μm in the microstructure of the cement paste with SAP and SRA at 28days, which could be responsible for a lower compressive strength of the cement paste with SAP and SRA compared to the cement paste with SAP at this age.

Design and control shrinkage behavior of high-strength self-consolidating concrete using shrinkage-reducing admixture and super-absorbent polymer

In the present study, self-consolidating concrete (SCC) with 28 days compressive strength of 110 MPa was fabricated. Its workability, hydration heat evolution, chloride penetration resistance, and mechanical properties were analyzed. To enhance its volume stability, shrinkage-reducing admixture (SRA) and super-absorbent polymer (SAP) were used, and their effect on autogenous shrinkage, drying shrinkage, and strength of the concrete were evaluated. The results indicate that high-strength SCC can be achieved using a carefully designed ternary binder system (made with cement, fly ash, and silica fume), water-reducing admixture, and low water-to-binder ratio (W/B = 0.20). Addition of SRA and SAP into the concrete significantly reduced autogenous shrinkage and slightly reduced drying shrinkage. SAP is more effective in reducing autogenous shrinkage at later age, and the effect of SRA is better than that of SAP for drying shrinkage reduction.

Effects of Shrinkage Reducing Admixture (SRA) on the Tensile Behavior of Strain-Hardening Cement Composite (SHCC)

This research investigates the influence of shrinkage reducing admixture (SRA) on the tensile behavior of strain-hardening cement composite (SHCC). SHCC materials with specified compressive strength of 50MPa were mixed and tested. All SHCC mixes with different dosage of shrinkage reducing admixtures were reinforced with 2.2 % polyvinyl alcohol (PVA) fibers at the volume fraction. A special SRA, i.e. strontium (Sr)-based SRA, used in this study was based on a phase change material (PCM) that has the ability to absorb or release the hydration heat of cement composite. This paper focuses on the tensile behavior and cracking characteristics of SHCC materials under direct tension. The effect of a special SRA on the fresh properties, such as flow and air content, and hardened properties of SHCC materials was investigated. Test results showed that SRA reduces the air content of SHCC material. The SRA can also improve the tensile strength of SHCC material.

Effect of Shrinkage Reducing Admixture on Properties of Pumping Concrete

In order to improve the crack resistance of pumping concrete, effect of shrinkage reducing admixture on the performance of pumping concrete was stuied, the results showed that dry shrinkage decreased obviously when shrinkage reducing admixture was added into pump concrete , and 28d shrinkage can be reduced by over 40% when the dosage of shrinkage reducing admixture was 1.5% , while the shrinkage reducing admixture can significantly improve the fresh pumping concrete workability, improve compressive strength of 28d, but the flexura strength decreases slightly.

Effect of shrinkage reducing admixture on flexural behaviors of fiber reinforced cementitious composites

The use of shrinkage reducing admixture (SRA) at various concentrations was investigated in fiber reinforced cementitious composites. Both mortar and high strength concrete (HSC) matrices were tested. Two types of fibers—steel and polypropylene—were assessed. The effect of SRA was measured on the fundamental properties such as surface tension of the bulk fluids and the contact angle developed between the fibers and the bulk fluids, on the fresh properties such as the air content and the density, and finally on the hardened mechanical properties, specially the flexural behaviors. It was noted that SRA enhances the wettability of fibers and reduces the air content of fiber reinforced cement mortars, while critical SRA concentrations are existing. SRA with critical concentration can significantly improve the flexural toughness and residual strength of steel fiber reinforced cement mortar. In the case of polypropylene fiber, SRA is not as effective in enhancing the flexural behaviors as it is in the case of steel fiber. SRA is generally ineffective in reducing the air content of HSC and the properties of steel fiber reinforced HSC with SRA are inferior to those without SRA.

Synergistic Effect of MgO-Based Expansive Agent and Shrinkage Reducing Admixture on Compensating the Shrinkage of Cementitious Materials

In order to improve dimensional stability of cementitious materials, synergistic effect of shrinkage reducing admixtures (mixture of glycol ethers and siloxane, SRA) and MgO-based expansive agent (MEA) burned at 850 °C, 950 °C, 1050 °C and 1200 °C for 1 h on the deformation of cement paste was investigated while being cured in water of 20 °C, 40 °C and 60 °C, sealedly by polyethylene sheet at 20 °C, 40 °C and 60 °C as well as in simulated using environment. The results illustrated that combined use of SRA and MEA (burned at 850 °C and 950 °C) could compensate the shrinkage of cement paste effectively, and MEA also could make up for the shortage of SRA whose shrinkage-reducing ratio decreased at later age. In the simulated using environment, the paste both with SRA and MEA (burned at 850 °C and 950 °C) was in micro-expansion condition, and the average deformation increased slowly till 240d, and the deformation amplitude reduced to the half of the control sample. Then hydration of MEA in the present of SRA was examined by gravimetry. The results indicated that the presence of SRA retarded the hydration of MEA, but with prolonged curing, the hydration degree of MEA with or without SRA tended to be the same.

Effect of shrinkage-reducing admixtures on the properties of alkali-activated slag mortars and pastes

The effect of a shrinkage-reducing admixture (SRA) based on polypropylenglycol on the dimensional stability of waterglass-activated slag mortars was studied. The analysis also showed the effect of the admixture on pore structure of the mortars as well as on the mineralogical composition and microstructure of the alkali-activated slag pastes. The SRA reduced the shrinkage by up to 85 and 50% when the alkali-activated slag mortar specimens were cured at relative humidities of 99 and 50%, respectively. The mechanism primarily involved in shrinkage reduction is the decrease in the surface tension of pore water prompted by the admixture. The SRA also modified the pore structure – under both curing conditions – increasing the percentage of pores with diameters ranging from 1.0 to 0.1 μm. Capillary stress is much lower in these pores than in the smaller capillaries prevailing in mortars prepared without admixtures. Microstructurally, the SRA occasioned a slight increase in the proportion of Si units Q 2 in the CSH gel and a decrease in the percentage of Al replacing the Si in the gel structure. The admixture did not, however, modify the mineralogical composition of the pastes. Finally, the SRA admixture retarded the alkaline activation of the slag, more intensely at higher admixture dosages. While the admixture did not significantly alter the degree of reaction in pastes cured for 7 days at RH = 99%, the value of this parameter dropped by 7% in the presence of the admixture in pastes cured at 50% relative humidity.