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.

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 Eliminating the Shrinkage of High Strength Concrete by using Super Absorbent Polymer (SAP)

2018 ◽  
Vol 11 (4) ◽  
pp. 8-13
Author(s):  
Baidaa Khdheer Ahmed
Keyword(s):  
Compressive Strength ◽  
High Strength Concrete ◽  
Autogenous Shrinkage ◽  
Drying Shrinkage ◽  
High Strength ◽  
Super Absorbent Polymer ◽  
Strength Concrete ◽  
Group A ◽  
Group B ◽  
Absorbent Polymer

High Strength Concrete (HSC) is one of the  most popular types of concrete used in the world. This type of concrete has a low rapid  hydration of cementation materials with low  w/cm and the external surrounding  environment condition exposed the HSC to  high autogenous shrinkage. If this shrinkage is  not treated well that well led to cracking, in  this case HSC need to convenient curing  necessary at the earliest time. This study  presents the use of Super Absorbent Polymer  (SAP) as internal curing agent to eliminate  shrinkage. Two types of shrinkage are tested in  this study (Autogenous shrinkage and drying  shrinkage).  Two groups of concrete mixes(A and B) are  studied in this study each group have five types  of concrete mixes, four mixes with high and  ultra-high compressive strength (RPC, MRPC, HSC and SCC) and the last one with normal  compressive strength (NSC). Group A  represent concrete mixes without SAP addition  and group B for concrete mixes with SAP.  SAP was added for all mixes at 0.3% by  weight of cement and adding 20ml water for  each gram of SAP, specimens with dimensions  (40*40*160) mm were used for testing  shrinkage for each mix with and without SAP,  average values for two specimens was taken as  a results. It was found that concrete mixes of  group B have lower shrinkage than the  shrinkage of concrete mixes in group A at 28  days age with reduction of autogenous  shrinkage(AS) of (57%, 35%, 37%, 44.5% and  37.5%) respectively and for drying shrinkage  the percentage of reduction was (89.5%, 72%,  82%, 70% and 71%) respectively, addition of  SAP to concrete mixes proves to have active  effect in reducing the shrinkage of concrete.

scholarly journals Behavior of High Strength Concrete Subjected to Elevated Temperature

2019 ◽  
Vol 9 (2) ◽  
pp. 2997-3000
Keyword(s):  
Compressive Strength ◽  
High Strength Concrete ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
High Strength ◽  
Air Cooling ◽  
Split Tensile Strength ◽  
Strength Concrete ◽  
Hardened Properties ◽  
Compressive Strength Of Concrete

The High strength concrete defined as per IS 456 as the concrete having characteristic compressive strength more than 65 MPa. The concrete when subject to fire i.e. elevated temperatures loses its properties at a rapid rate. In the present investigation, ordinary vibrated concrete of M90 grade was developed as per the IS 10262. The hardened properties of concrete like compressive strength and split tensile strength were determined for concrete at ordinary temperature. The concrete specimens were subjected to elevated temperatures of 400oC, 600 oC, and 800 oC and then the specimens were brought to room temperature under different cooling regimes like air cooling and water quenching. The compressive residual strength of concrete was determined and a typical compared was made with the control specimen. The decrease in compressive strength of concrete at 800 oC was high compared to that at 400 oC.

scholarly journals Effect of Thermal Properties of Aggregates on the Mechanical Properties of High Strength Concrete under Loading and High Temperature Conditions

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6093
Author(s):  
Taegyu Lee ◽  
Keesin Jeong ◽  
Hyeonggil Choi
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Thermal Properties ◽  
High Temperature ◽  
High Strength Concrete ◽  
Room Temperature ◽  
Thermal Strain ◽  
High Strength ◽  
Transient Creep ◽  
Lightweight Aggregates

The effect of the thermal properties of aggregates on the mechanical properties of high-strength concrete was evaluated under loading and high-temperature conditions. For the concrete, granite was selected as a natural aggregate, and ash-clay and clay as lightweight aggregates. The mechanical properties of the concrete (stress–strain, compressive strength, elastic modulus, thermal strain, and transient creep) were evaluated experimentally under uniform heating from 20 to 700 °C while maintaining the load at 0, 20, and 40% of the compressive strength at room temperature. Experimental results showed that the concrete containing lightweight aggregates had better mechanical properties, such as compressive strength and elastic modulus, than that of the concrete with a granite aggregate at high temperature. In particular, the concrete containing lightweight aggregates exhibited high compressive strength (60–80% of that at room temperature) even at 700 °C. Moreover, the concrete containing granite exhibited a higher thermal strain than that containing lightweight aggregates. The influence of the binding force under loaded conditions, however, was found to be larger for the latter type. The transient creep caused by the loading was constant regardless of the aggregate type below 500 °C but increased more rapidly when the coefficient of the thermal expansion of the aggregate was above 500 °C.

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