Internal relative humidity and autogenous shrinkage of low water/binder ratio concrete

2006 ◽  
Author(s):  
Fazhou Wang
Keyword(s):  
Relative Humidity ◽  
Autogenous Shrinkage ◽  
Binder Ratio ◽  
Internal Relative Humidity ◽  
Water Binder Ratio

scholarly journals Autogenous Shrinkage, Strength, and Hydration Heat of Ultra-High-Strength Paste Incorporating Nano-Zirconium Dioxide

2020 ◽  
Vol 12 (22) ◽  
pp. 9372
Author(s):  
Guang-Zhu Zhang ◽  
Han-Seung Lee ◽  
Xiao-Yong Wang
Keyword(s):  
Relative Humidity ◽  
Room Temperature ◽  
Autogenous Shrinkage ◽  
High Strength ◽  
Hydration Heat ◽  
Experimental Device ◽  
Hydration Reaction ◽  
Hydration Products ◽  
Internal Relative Humidity ◽  
Two Stages

Ultra-high-strength paste (UHSP) combined with nanomaterials has been extensively studied. However, the research on nano-ZrO2 is limited. In this study, UHSP with various nano-ZrO2 contents is analyzed. The motivation of this study is to clarify the effects of nano-ZrO2 on the hydration products, strength, autogenous shrinkage, and hydration heat of UHSPs. The water-to-binder ratio (w/b) of the specimens is 0.2. The nano-ZrO2 content is 0, 1.5, and 3 wt.%. The strength is measured at the age of 3, 7, and 28 days. The hydration heat is measured from the mixing stage to 3 days. The hydration products are analyzed by X-ray diffraction (XRD) and thermogravimetric analysis (TG). The autogenous shrinkage is measured from the mixing stage for 7 days using a new experimental device. The new experimental device can measure autogenous shrinkage, internal relative humidity, and internal temperature simultaneously. The following conclusions can be drawn based on the experimental studies: (1) Two stages were noticed in the autogenous shrinkage of UHSPs: a variable-temperature stage and a room-temperature stage. The cut-off point of these two stages occurred in roughly 1.5 days. Furthermore, in the room-temperature stage, there was a straight-line relationship between the autogenous shrinkage and internal relative humidity. (2) With the increase of the nano-ZrO2 amount, the compressive strength at 3 days, 7 days, and 4 weeks increased. (3) With the nano-ZrO2 increasing, the flow decreased. (4) With the nano-ZrO2 increasing, the hydration heat increased due to the physical nucleation effect of the nano-ZrO2. Furthermore, the nano-ZrO2 used in this study was chemically inert and did not take part in the cement hydration reaction based on the XRD, differential thermal, and TG data. This paper is of great significance for the development of high-strength cementitious materials doped with nano-ZrO2.

scholarly journals Synthesis of a New Polycarboxylate at Room Temperature and Its Influence on the Properties of Cement Pastes with Different Supplementary Cementitious Materials

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Shuncheng Xiang ◽  
Yingli Gao ◽  
Caijun Shi
Keyword(s):  
Room Temperature ◽  
Autogenous Shrinkage ◽  
Drying Shrinkage ◽  
Cementitious Materials ◽  
Heat Evolution ◽  
Hydration Heat ◽  
Supplementary Cementitious Materials ◽  
Cement Pastes ◽  
Binder Ratio ◽  
Water Binder Ratio

Three polycarboxylates with different comb structures (i.e., the same degree of polymerization in side chains but different main chains) were synthesized via radical polymerization reaction at room temperature. The effect of polycarboxylates on the surface tension and the flowability in cement pastes was determined. The best product was selected to study its effects on the hydration heat evolution, compressive strength, autogenous shrinkage, and drying shrinkage of cement pastes with different kinds and contents of supplementary cementitious materials. The results showed that with the increase of molar ratio between AA and TPEG to 6 : 1, we could synthesis the best product. When the water-binder ratio was 0.4, with the increase of polycarboxylates, the cement hydration heat evolution had been slowed down, and the more the dosage was, the more obvious the effect was. Adding supplementary cementitious materials to cement under the same experimental conditions also played a mitigation role in slowing down the hydration heat. When the water-binder ratio was 0.3, supplementary cementitious materials could increase the strength of cement by 24.5% in maximum; its autogenous shrinkage and drying shrinkage could be decreased, respectively, by 60.1% and 21.9% in the lowest.

scholarly journals Internal Relative Humidity, Autogenous Shrinkage, and Strength of Cement Mortar Modified with Superabsorbent Polymers

Polymers ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 1074 ◽  
Author(s):  
Girum Urgessa ◽  
Ki-Bong Choi ◽  
Jung Yeon
Keyword(s):  
Relative Humidity ◽  
Coefficient Of Thermal Expansion ◽  
Autogenous Shrinkage ◽  
Thermal Characteristics ◽  
Cross Linking ◽  
Superabsorbent Polymers ◽  
Cracking Potential ◽  
Linear Relationships ◽  
Internal Relative Humidity ◽  
Compressive And Flexural Strengths

Laboratory evaluations were performed to investigate the effect of internal curing (IC) by superabsorbent polymers (SAP) on the internal relative humidity (IRH), autogenous shrinkage, coefficient of thermal expansion (CTE), and strength characteristics of low water-cement ratio (w/c) mortars. Four types of SAP with different cross-linking densities and particle sizes were used. Test results showed that the SAP inclusion effectively mitigated the IRH drops due to self-desiccation and corresponding autogenous shrinkage, and the IC effectiveness tended to increase with an increased SAP dosage. The greater the cross-linking density and particle size of SAP, the less the IRH drop and autogenous shrinkage. The trend of autogenous shrinkage developments was in good agreement with that of IRH changes, with nearly linear relationships between them. Both immediate deformation (ID)-based and full response-based CTEs were rarely affected by SAP inclusions. There were no substantial losses in compressive and flexural strengths of SAP-modified mortar compared to reference plain mortar. The findings revealed that SAPs can be effectively used to reduce the shrinkage cracking potential of low w/c cement-based materials at early ages, without compromising mechanical and thermal characteristics.

scholarly journals Effect of Nano-Silica on the Autogenous Shrinkage, Strength, and Hydration Heat of Ultra-High Strength Concrete

2020 ◽  
Vol 10 (15) ◽  
pp. 5202 ◽  
Author(s):  
Guang-Zhu Zhang ◽  
Hyeong-Kyu Cho ◽  
Xiao-Yong Wang
Keyword(s):  
Compressive Strength ◽  
Relative Humidity ◽  
High Strength Concrete ◽  
Room Temperature ◽  
Autogenous Shrinkage ◽  
High Strength ◽  
Silica Content ◽  
Nano Silica ◽  
Internal Relative Humidity ◽  
Two Stages

In this paper, the effect of nano-silica on the autogenous shrinkage, hydration heat, compressive strength hydration products of Ultra-High Strength Concrete (UHSC) is studied. The water/binder ratio (w/b) of UHSC is 0.2. The nano-silica replaces 2% and 4% of the mass fraction of the cement in UHSCs, respectively. A new instrument was developed to simultaneously measure the autogenous shrinkage, internal relative humidity, and internal temperature of UHSC. The following results were obtained from the analysis of the experimental data: (1) The trends in the autogenous shrinking of UHSC can be divided into two stages, which are the variable temperature stage and the room temperature stage. The dividing point between the two stages occurs at the age of approximately 2 days. During the room temperature stage, the internal relative humidity and autogenous shrinkage showed a good linear relationship. (2) The compressive strength of UHSC increased significantly with the increase of nano-silica content at 3 days, 7 days, and 28 days. (3) The total accumulated heat of UHSC increased during the 72 h, with the increasing of nano-silica content. (4) The XRD data at the age of 28 days showed that the Ca(OH)2 peaks of nS2 and nS4 have a tendency to weaken due to the pozzolanic reaction, compared with the peak of nS0.

Relationship between Internal Relative Humidity and Autogenous Shrinkage of Cement Paste with Supplementary Cementitious Materials (SCM)

2013 ◽  
Vol 539 ◽  
pp. 35-39 ◽  
Author(s):  
Yue Li ◽  
Qian Qian Yan
Keyword(s):  
Fly Ash ◽  
Relative Humidity ◽  
Autogenous Shrinkage ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Cement Pastes ◽  
Different Types ◽  
Influence Of Water ◽  
Internal Relative Humidity ◽  
Main Factor

The influence of water to binder (W/B), types and dosage of supplementary cementitious materials (SCM) on the internal relative humidity (IRH) and autogenous shrinkage (AS) of cement pastes caused by self-desiccation were investigated, and their relationship was discussed. The results show that, W/B is a main factor that affects IRH change and AS of cement pastes with SCM. With the decrease of W/B, IRH of cement pastes decreases, but AS of cement pastes increases. Different types and dosages of SCM affect the IRH differently; fly ash (FA) reduces AS, silica fume (SF) increases AS, and the effect of GBFS on AS is between FA and GBFS. The linear correlation between the change of IRH and AS of cement pastes with SCM is established.

scholarly journals Microstructure-Based Relative Humidity in Cementitious System Due to Self-Desiccation

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1214 ◽  
Author(s):  
Yong Zhang ◽  
Xiaowei Ouyang ◽  
Zhengxian Yang
Keyword(s):  
Relative Humidity ◽  
Cement Hydration ◽  
Pore Diameter ◽  
Limestone Powder ◽  
Average Pore ◽  
Binder Ratio ◽  
Internal Relative Humidity ◽  
Cementitious System ◽  
The Relationship ◽  
Cementitious Systems

The internal relative humidity (RH) plays a crucial role in most of the concrete properties. Self-desiccation caused by continuous cement hydration is a major factor affecting the RH of concrete. This paper investigates the relationship between RH and microstructure for cementitious systems in the case of self-desiccation. A series of paste specimens prepared with different binder and water-binder-ratio (w/b) were cured under sealed conditions from 1 day to 1.5 years. The RH and microstructure of the paste specimens were measured. The microstructure characteristics under study include porosity, pore size, evaporable and non-evaporable water content. The results reveal that the RH of cementitious system drops to a great extent in the first 105 days’ hydration and decreases slowly afterwards. The blended materials such as fly ash, slag or limestone powder have different influences on the RH. A mathematical model between RH and the average pore diameter is proposed for cementitious systems under self-desiccation, regardless of age, w/b or cement type.

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