Factors Influencing the Hydration, Dimensional Stability, and Strength Development of the OPC-CSA-Anhydrite Ternary System

Due to the advantages of high early strength and rapid setting, ternary systems consisting of ordinary Portland clinker (OPC), calcium sulphoaluminate (CSA) clinker, and anhydrite have broad application prospects. However, further studies need to be undertaken to find a more optimal mixing proportion of this ternary binder in order to meet basic performance requirements. In this paper, isothermal calorimetric tests, chemical shrinkage tests, drying shrinkage tests, and compressive strength tests were carried out to systematically identify the effect of the OPC/CSA ratio and anhydrite dosage on the hydration, mechanical property development, and dimensional stability of ternary binders. It was found that a higher CSA content leads to a higher cumulative hydration heat, a shorter acceleration period, and a delayed induction period, which can be ascribed to the retardation of C3S at a high aluminate concentration. However, a higher addition of anhydrite can retard the main peak of hydration despite promoting the intermediate peak and improving the hydration reaction rate. The drying shrinkage of blends decreases first along with the CSA proportion and then increases. Moreover, a higher anhydrite content mitigates the drying shrinkage and hinders the strength development. Finally, considering the properties of both the fresh and hardened binder, the ternary blends with 5% anhydrite and OPC/CSA ratios ranging from 3/7 to 2/8 were identified as most suitable for applications that require a high early strength, stable late strength, and small level of shrinkage.

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Research on the Properties of High-strength Gypsum Based Tile Adhesive in Interior Decoration

E3S Web of Conferences ◽

10.1051/e3sconf/202016505015 ◽

2020 ◽

Vol 165 ◽

pp. 05015

Author(s):

Ji Xiu Zhang ◽

Ye Zhang ◽

Ji Kang Liu ◽

Yuan Chao Miao ◽

Sai Hong Duan

Keyword(s):

Bond Strength ◽

Dimensional Stability ◽

High Strength ◽

High Dimensional ◽

Strength Development ◽

Interior Decoration ◽

High Bond ◽

High Bond Strength ◽

Early Strength ◽

Interface Treatment

In this paper, a new early strength tile adhesive is prepared by using α- high strength gypsum and its properties are discussed. The research methods refer to relevant Chinese standards. The results show that the tensile bond strength of the adhesive can reach 0.6 MPa in one day and 1.5 MPa in 7 days, which is close to 80% of 28-day strength. It is indicating that the adhesive has high bond strength, rapid strength development, and high dimensional stability. It effectively solves the problems that the traditional cement-based tile adhesive is prone to hollowing, falling off, and cracking. Additionally, no interface treatment is required during the using process of this gypsum-based adhesive.

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Investigation on the Effect of Hydroxyapatite Nanorod on Cement Hydration and Strength Development

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2021.17387 ◽

2021 ◽

Vol 21 (3) ◽

pp. 1578-1589

Author(s):

Han Yan ◽

Qianping Ran ◽

Yong Yang ◽

Xin Shu ◽

Qian Zhang ◽

...

Keyword(s):

Isothermal Calorimetry ◽

Superior Performance ◽

Strength Development ◽

Hydration Reaction ◽

X Ray Diffraction ◽

Early Hydration ◽

Cement Pastes ◽

Supplementary Cementitious Material ◽

Acceleration Period

This work investigated the effect of hydroxyapatite (HA) nanorods on the strength development and hydration of cement. Undispersed HA nanorods (HA-UD) and dispersed HA nanorods (HA-DN) were prepared by atom-efficient neutralization. The strength of mortars modified by HA nanorods was tested, as well as their compatibility with supplementary cementitious material. The hydration of HA-modified cement pastes was characterized via in situ X-ray diffraction, isothermal calorimetry and scanning electron microscopy. As the results suggest, the undispersed HA-DN caused a considerable increase in superplasticizer demand to achieve the same level of flow. Both HA nanorods showed a significant accelerating effect on early hydration, with approximately 100% strength enhancement at 12 h at 2.0% dosage. The effect on early strength of the nanorods is retained in systems with up to 30% fly ash in the binder mass. According to the characterizations, the rate of the hydration reaction in the acceleration period was enhanced by HA nanorods, and C3S consumption was also increased. In all of the testing situations, HA-DN showed superior performance, likely due to improved spatial distribution of the hydroxyapatites. The results suggest that proper dispersion of the nanorods is necessary to optimize its performance.

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Research on Properties of High-Performance Cement Mortar for Semiflexible Pavement

Advances in Materials Science and Engineering ◽

10.1155/2018/4613074 ◽

2018 ◽

Vol 2018 ◽

pp. 1-10 ◽

Cited By ~ 3

Author(s):

Yazhen Sun ◽

Yuanyuan Cheng ◽

Min Ding ◽

Xuezhong Yuan ◽

Jinchang Wang

Keyword(s):

High Performance ◽

Cement Mortar ◽

Drying Shrinkage ◽

Pavement Performance ◽

Strength Development ◽

Working Ability ◽

Pavement Materials ◽

Optimum Formulation ◽

Different Types ◽

Early Strength

Cement mortar is one of the most important components of semiflexible pavement materials; however, the effects of cement mortar formulation on the performance and the grouting rate are rarely studied. Therefore, the optimum formulation of high-performance cement mortar (HPCM) for different types and contents was studied, and the grouting effect of the cement mortar was studied by rutting tests. The results show that polycarboxylate superplasticizer, expansion admixture, and accelerating admixture have different influences on the workability, the strength, and the drying shrinkage of HPCM, and the working ability of HPCM is good by adding these three admixtures. The strength at 7 days is 1.3 to 4 times that of the existing specifications, and the shrinkage rate is less than 0.2. The HPCM has higher early strength, and the strength development is stable in the later period compared with the other research studies. The semiflexible material has better pavement performance when the grouting rate is greater than 90%.

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Durable High Early Strength Concrete via Internal Curing Approach using Saturated Lightweight and Recycled Concrete Aggregates

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198120920882 ◽

2020 ◽

Vol 2674 (7) ◽

pp. 67-76

Author(s):

Faisal Qadri ◽

Christopher Jones

Keyword(s):

Cement Content ◽

Autogenous Shrinkage ◽

Drying Shrinkage ◽

Recycled Concrete ◽

Internal Curing ◽

Strength Development ◽

Freeze Thaw ◽

Strength Concrete ◽

Repair Materials ◽

Early Strength

Concrete pavements tend to degrade at joints when concrete gets exposed to freeze-thaw cycles in the presence of moisture. In Kansas, U.S., one common repair method for deteriorated concrete pavement involves patching with high early strength concrete (HESC). For heavily trafficked routes and intersections, this is often done at night, so that the pavement can be opened to traffic next morning. Often, patched concrete shows poor durability lasting for just few years. HESC mixtures often include high cement content and low water-to-cement ratio. These factors lead to shrinkage that creates cracks which, in turn, facilitate the ingress of detrimental substances that eventually degrade patches. Internal curing (IC) has been explored in this study to improve the durability of HESC repair materials. Saturated lightweight aggregates and recycled crushed concrete were used to replace a portion of the virgin fine aggregates. Both mixtures were compared with a control mixture. These three mixtures were replicated for low and high cement contents. The test program focused on assessing two main performance indicators—strength development and durability. Durability testing included autogenous and drying shrinkage, and freeze-thaw cycling where relative dynamic modulus of elasticity, expansion, and mass change were measured. Target strengths were achieved in all mixtures. Autogenous shrinkage test results showed that IC significantly improves shrinkage potential and durability. For these mixtures, low cement content also appears to improve durability.

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Effect of Sulphur-Containing Tailings Content and Curing Temperature on the Properties of M32.5 Cement Mortar

Materials ◽

10.3390/ma14195751 ◽

2021 ◽

Vol 14 (19) ◽

pp. 5751

Author(s):

Qian Chen ◽

Haiming Chen ◽

Pengju Wang ◽

Xiang Chen ◽

Jie Chen

Keyword(s):

Compressive Strength ◽

Substitution Rate ◽

High Speed ◽

Cement Mortar ◽

Curing Temperature ◽

Strength Development ◽

Hydration Reaction ◽

Replacement Ratio ◽

River Sand ◽

Early Strength

The effect of the dosage of sulphur-containing tailings (STs) and curing temperature on the properties of M32.5 cement mortar was studied in this work. An experimental study was conducted to evaluate the effects of STs with different substitution ratios (0, 10%, 20%, 30%, 40%) on the compressive strength experiment, fluidity, expansion ratio, and pore structure of M32.5 cement mortar. The results showed that the addition of STs reduced the fluidity of mortar, and the fluidity decreased with the increase of the STs dosage. The compressive strength of mortars increased at a lower substitution rate (0~20%) but decreased at a higher substitution rate (>20%). Ettringite peaks and new sulfate peaks were found by X-ray diffraction (XRD) analysis. Scanning electron microscope (SEM) observation of the microstructure showed that a large number of hydrated products, such as ettringite, formed and filled in the interstitial space, which was conducive to the development of strength. The optimal STs replacement ratio of river sand was 10%. Then, the performance of mortar at curing temperatures of 23 ± 1, 40, 60, and 80 °C was further investigated under the optimal STs replacement ratio. Under high-temperature curing conditions, the early strength of M32.5 cement mortar with STs increased greatly, but the late strength decreased gradually with the increase in curing temperature. The early strength development of the mortar mainly depended on the high speed of hydration reaction, and the late strength variation was mainly affected by hydration products and the pore size distribution. After comprehensive consideration, the optimal curing temperature of M32.5 cement mortar with STs was 40 °C.

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Effects of Shrinkage Reducing Agent and Expanded Cement on UHPC Fluidity, Mechanical Properties, and Shrinkage Performance

Advances in Materials Science and Engineering ◽

10.1155/2021/9045754 ◽

2021 ◽

Vol 2021 ◽

pp. 1-14

Author(s):

Tingyu Wang ◽

Jianqing Gong ◽

Bo Chen ◽

Xiao Gong ◽

Hongkui Luo ◽

...

Keyword(s):

Mechanical Properties ◽

Setting Time ◽

Autogenous Shrinkage ◽

Drying Shrinkage ◽

Reducing Agent ◽

Strength Development ◽

Study Results ◽

Binder Ratio ◽

Early Strength ◽

Shrinkage Reducing Agent

The purpose of this study was to evaluate the effects of a shrinkage reducing agent (SRA) and Portland expanded cement (PEC) on the fluidity, mechanical properties, and shrinkage performance of ultrahigh-performance concrete (UHPC). The results indicated that the fluidity of the fresh UHPC mortar initially decreased and then increases along as a function of SRA dosage. When the dosage of SRA was 1%, the UHPC mortar fluidity was at its minimum. For dosages exceeding 1%, the additional water-binder ratio of the mortar increased, which in turn increased the UHPC fluidity. That is, the SRA delayed the cement hydration and increased the setting time, which is not conducive for early strength development of UHPC. As the SRA dosage was increased (i.e., 0%–2%), the autogenous shrinkage of UHPC decreased significantly such that even a small dosage of about 0.5% SRA was able to effectively reduce drying shrinkage. From the study results, it was also observed that PEC accelerated the loss of fluidity in the fresh UHPC and concurrently promoted the early strength development of UHPC. At 75% PEC content, the strength enhancement effects tended to be stable. This means that although the addition of PEC will potentially increase the autogenous shrinkage of UHPC, it has the positive effect of inhibiting drying shrinkage provided that the PEC dosage is controlled within the 25%–50% range. Furthermore, morphological analyses using a scanning electron microscope (SEM) indicated that an increase in the SRA dosage loosens the UHPC microstructure, with the formation of the hydration products remaining incomplete, thus ultimately causing the UHPC strength to decrease. Overall, the study findings indicated that 2% SRA and 25%–50% PEC can effectively reduce the shrinkage of UHPC and are, therefore, recommended as the optimum dosages.

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Physicochemical Study on the Strength Development Characteristics of Cold Weather Concrete Using a Nitrite–Nitrate Based Accelerator

Materials ◽

10.3390/ma12172706 ◽

2019 ◽

Vol 12 (17) ◽

pp. 2706 ◽

Cited By ~ 3

Author(s):

Heesup Choi ◽

Masumi Inoue ◽

Hyeonggil Choi ◽

Jihoon Kim ◽

Yuhji Sudoh ◽

...

Keyword(s):

Calcium Nitrate ◽

Hydrate Formation ◽

Cold Weather ◽

Strength Development ◽

Early Age ◽

Hydration Reaction ◽

Wide Range ◽

Formation Behavior ◽

Early Strength ◽

Nitrite Nitrate

There has recently been an increased use of anti-freezing agents that are primarily composed of salt- and alkali-free calcium nitrite (Ca(NO2)2) and calcium nitrate (Ca(NO3)2) to promote the hydration reaction of concrete in cold weather concreting. Nitrite–nitrate based accelerators accelerate the hydration of C3A and C3S in cement more quickly when their quantities are increased, thereby boosting the concrete’s early strength and effectively preventing early frost damage. However, the connection between the hydrate formation behavior and the strength development characteristic over time has yet to be clearly identified. Therefore, in this study, a wide range of physicochemical reviews were carried out to clarify the relationship between the hydrate formation behavior and the strength development characteristics, both at an early age and at later ages, which results from the addition of nitrite–nitrate based accelerators to concrete in varying amounts. These accelerators also act as anti-freezing agents. The results show that an increased quantity of nitrite–nitrate based accelerators caused an increase in the early strength of the concrete. This was due to the formation of nitrite and nitrate hydrates in large amounts, in addition to ettringite containing SO42, which is generated during the hydration reaction of normal Portland cement at an early age. On the other hand, at later ages, there was a rise in nitrite and nitrate hydrates with needle crystal structures exhibiting brittle fracture behavior. A decrease in C–S–H gel and Ca(OH)2 hydrates, deemed to have caused a decline in strength on Day 3 and thereafter, was also observed.

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Use of Treated Non-Ferrous Metallurgical Slags as Supplementary Cementitious Materials in Cementitious Mixtures

Applied Sciences ◽

10.3390/app11094028 ◽

2021 ◽

Vol 11 (9) ◽

pp. 4028

Author(s):

Asghar Gholizadeh Vayghan ◽

Liesbeth Horckmans ◽

Ruben Snellings ◽

Arne Peys ◽

Priscilla Teck ◽

...

Keyword(s):

Mechanical Performance ◽

Cementitious Materials ◽

Supplementary Cementitious Materials ◽

Partial Replacement ◽

Strength Development ◽

Supplementary Cementitious Material ◽

Performance Requirements ◽

Metallurgical Slags ◽

Leaching Behaviour ◽

Kinetics Of

This research investigated the possibility of using metallurgical slags from the copper and lead industries as partial replacement for cement. The studied slags were fayalitic, having a mainly ferro-silicate composition with minor contents of Al2O3 and CaO. The slags were treated at 1200–1300 °C (to reduce the heavy metal content) and then granulated in water to promote the formation of reactive phases. A full hydration study was carried out to assess the kinetics of reactions, the phases formed during hydration, the reactivity of the slags and their strength activity as supplementary cementitious material (SCM). The batch-leaching behaviour of cementitious mixtures incorporating treated slags was also investigated. The results showed that all three slags have satisfactory leaching behaviour and similar performance in terms of reactivity and contribution to the strength development. All slags were found to have mediocre reactivity and contribution to strength, especially at early ages. Nonetheless, they passed the minimum mechanical performance requirements and were found to qualify for use in cement.

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