A Study on the Development Mechanism of Early Strength in Cement Mortar Using an Early-Strength Polycarboxylated Agent

2007 ◽  
Vol 348-349 ◽  
pp. 473-476
Author(s):  
Won Jun Park ◽  
Han Seung Lee ◽  
Ki Bong Park
Keyword(s):  
Compressive Strength ◽  
High Performance ◽  
Cement Mortar ◽  
Early Age ◽  
Hydration Products ◽  
Degree Of Hydration ◽  
Exact Analysis ◽  
Mortar Strength ◽  
Early Strength ◽  
Micro Structures

It is well known that PC (polycarboxylate) agent is superior to other agents for the early-strength of concrete. Thus, this study investigates the development of mortar strength using various agents. To prove this, various factors were tested. Furthermore, this study measured compressive strength at the age of 18, 24, 36, 72, and 168 hours and gave a request text TG/DTA to observe minute structures. In addition, this study took pictures of minute structures using an SEM for each agent at the same age. According to the results, mortar using an early-strength PC agents is faster than a general water reducing AE agent, high performance PC agents, and other agents in the acceleration of hydration at the same early age. A TG/DTA test shows that the early-strength PC agents create more hydration products, such as Ca(OH)2, than others at the same age. The degree of pH in each agent is unrelated to the degree of hydration in mortar. An MIP analysis confirms these results. However, other methods are required the exact analysis of micro structures.

Studies on Exciting the Activity of Waste Glass Powder by Hydrothermal Activation

2013 ◽  
Vol 871 ◽  
pp. 171-178
Author(s):  
Qing Qiu Kong ◽  
Guo Jun Ke ◽  
Dan Wang
Keyword(s):  
Compressive Strength ◽  
Hydrothermal Treatment ◽  
Glass Powder ◽  
Cement Mortar ◽  
Waste Glass ◽  
Early Age ◽  
Cement Replacement ◽  
Waste Glass Powder ◽  
Temperature And Pressure ◽  
Optimal Strength

The effect of hydrothermal activation indifferent temperature and pressure conditions on the pozzolanic activity of waste glass powder was discussed. The waste glass powder was treated at 108°C, 0.15MPa, 116°C, 0.18MPa and 121°C, 0.2MPa for 2h in an autoclave respectively after milling to 4215cm2/g. Mortar was made with untreated and hydrothermal activated waste glass power replacement of cement at 20% respectively, then tested for compressive strength at 3, 7, 14 , 28 and 90 days. Results showed that compressive strength of cement mortar had varying degrees of decline when replacing cement with untreated waste glass powder, comparing to the control one. Decline amplitude was large at early age and small at late age. Activity of waste glass powder was significantly improved after hydrothermal treatment. Compressive strength of mortar improved as temperature and pressure elevated, obtaining optimal strength at 121°C, 0.2MPa. Compressive strength of mortar with hydrothermal activated glass powder was higher than that with untreated glass powder at all age with 20% cement replacement. Compressive strength increased 5.3% ~ 13.6% at 3 d, 6.8%~9.7% at 28 d, 9.7% ~ 17.7% at 90 d. The essence of hydrothermal activation was the corrosion of water in the glass.

Alkali Activation of Granulated Blast Furnace Slag

2010 ◽  
Vol 158 ◽  
pp. 1-11 ◽  
Author(s):  
Zi Qiao Jin ◽  
Xian Jun Lu ◽  
Shu Gang Hu
Keyword(s):  
Compressive Strength ◽  
Blast Furnace ◽  
Portland Cement ◽  
Blast Furnace Slag ◽  
Ordinary Portland Cement ◽  
Hydration Product ◽  
Early Age ◽  
Hydration Products ◽  
Granulated Blast Furnace Slag ◽  
Furnace Slag

In order to stimulate the potential cementitious property of granulated blast furnace slag (GBFS), the ground GBFS sample (Wei Fang Iron and Steel Corporation, China) was activated by lime and gypsum under different dosages. The results showed that lime is an effective activator for the slag, and the optimum dosage of lime is about 10% (w/w) of the slag. At the optimum dosage of lime, the 28 days compressive strength of the lime-slag paste is higher than that of 32.5 ordinary Portland cement (OPC). But, the early age strength (3 and 7 days compressive strength) of the lime-slag paste is lower than that of the OPC. Addition of gypsum can effectively improve the early age strength of the lime-slag paste. At the ratio of gypsum:lime:slag of 8.2:9.2:82.6 (w/w), both the early and long-term compressive strengths of the gypsum-lime-slag paste are higher than that of the OPC. According to XRD, TG-DTA and SEM detections of the hydration products of the lime-slag paste, the gypsum-lime-slag paste and the OPC paste, it reveals that the hydration process of the GBFS-based cementitious material is different from the ordinary Portland cement and the presence of ettringite (AFt) contributes to the early age strength of the pastes. The major hydration product of the OPC paste (<7 days) were measured as ettringite (AFt), but the AFt phase was not detected in the hydration product of the lime-slag paste and the major hydration product of the lime-slag paste was determined as amorphous CSH gel. However, AFt was detected in the hydration products of the gypsum-lime-slag paste in the early stages of hydration, and the formation of AFt is favorable for the early strength improvement of the material.

Critical Review of Early Age Cycling Effects on the Capacity of Pile to Sleeve Grouted Connections As Treated in ISO 19902

2019 ◽  
Author(s):  
Andi Merxhani ◽  
Jacob Fisker Jensen ◽  
Joao Caetano ◽  
Casper Klintø Christiansen
Keyword(s):  
Compressive Strength ◽  
Experimental Evidence ◽  
Structural Design ◽  
High Performance ◽  
Underlying Mechanism ◽  
Early Age ◽  
Design Code ◽  
Concrete Members ◽  
Jacket Structures ◽  
Shearing Mechanism

Abstract The treatment of early age cyclic loading (EAC) on pile-sleeve grouted connections is one of the challenging problems encountered in the design of offshore jacket structures. ISO 19902 appears to be the only offshore structural design code that quantifies the strength de-rating due to EAC. However, the mechanism of EAC considered in the ISO standard is little understood. Main provision is that the strength reduction due to EAC is considered to be linearly proportional to the compressive strength of the grout. This provision is conservatively applicable for medium strength grouts. However, it is over-conservative when modern high-performance grouts are used, and it can be further argued that it actually loses its physical meaning. Thus, a further investigation into the mechanics of the problem is deemed beneficial in order to understand better its underlying mechanism. Using existing experimental evidence and a simple mechanical model, it is shown that the EAC mechanism considered in ISO 19902 triggers the grout matrix failure mechanism of the grouted connections. This behavior is characteristic of segregating grout materials. The benefit of the approach followed is that it links the interpretation of EAC to the grout material properties. The phenomenon is then understood using methods and experimental results that are well established in concrete mechanics. After a comparison with existing experimental evidence on grouted connections and concrete members, it is suggested that the strength drop for the specific shearing mechanism is independent of the uniaxial compressive strength of the grout material.

Research on Multivariate Composite Super early Strength Grouting Materials

2013 ◽  
Vol 477-478 ◽  
pp. 990-995
Author(s):  
Xiao Ping Zhang ◽  
Chang Zheng Sun ◽  
Tong Feng Zhao
Keyword(s):  
Compressive Strength ◽  
High Performance ◽  
Ordinary Portland Cement ◽  
High Alumina ◽  
Flow Ratio ◽  
Initial Flow ◽  
Growth Structure ◽  
Grouting Material ◽  
Early Strength ◽  
Grouting Materials

Super early strength high performance grouting material was produced using high alumina cement, ordinary portland cement, gypsum and silica fume. The different glue sand ratio and the cement sand ratio 1.0 mix microstructure were studied systematically. The results showed that the system with a variety of admixture using hingh mortar ratio can be prepared for the initial flow ratio greater than 325{mm},, 30min flow greater than 280{mm}, 2h compressive strength 34.80{MPa}, 24h bending over 13.82{MPa}, 28d compressive strength greater than 99.90{MPa}, 28d compressive strength greater than 56d compressive strength. The system of early SEM microstructures showed good crystal growth, structure compact.

Design of Mix Proportion of Cement Mortar with High-Performance Composite Semi-Flexible Pavement

2013 ◽  
Vol 641-642 ◽  
pp. 342-345 ◽  
Author(s):  
Ya Jun Wang ◽  
Chang Ying Guo ◽  
Yan Feng Tian ◽  
Jian Jun Wang
Keyword(s):  
Compressive Strength ◽  
High Performance ◽  
Cement Mortar ◽  
Rupture Strength ◽  
Flexible Pavement ◽  
Mixture Ratio ◽  
Cement Ratio ◽  
Mix Proportion ◽  
High Performance Composite ◽  
The Relationship

Nine groups of cement mortar with different mix proportion were designed to measure their fluidity 0h, 0.25h, 0.5h, 0.75h and 1h later, compressive strength and rupture strength of 3d, 7d and 28d were also tested to find out the relationship between compressive strength, rupture strength, water-cement ratio and sand-cement ratio by software Origin. Considered the three factors above, the optimum mixture ratio was determined finally to meet the requirements.

Influences of Initial Curing Conditions on the Microstructure of Fly Ash Cement System

2010 ◽  
Vol 168-170 ◽  
pp. 532-536 ◽  
Author(s):  
Guo Li ◽  
En Li Lu ◽  
Peng Wang ◽  
Ou Geng ◽  
Yong Sheng Ji
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Cement Mortar ◽  
Early Age ◽  
Concrete Durability ◽  
Cement Concrete ◽  
Hydration Degree ◽  
Curing Conditions ◽  
Cement System ◽  
C 30

In order to study the influences of initial curing conditions on fly ash (FA) cement concrete durability, fly ash cement samples with 30% replacement ratio were fabricated and cured in water at 10°C, 20°C, 30°Cand 40°C for 3d, 7d, 14d and 28d respectively. Hydration degrees of fly ash at early age were measured using the selective dissolve method. Correspondingly the pore structure and morphology of FA-cement mortar and compared cement mortar were studied by using MIP and SEM methods. Then early age compressive strengths of FA-cement concrete and compared normal cement concrete were tested. Experimental results show that initial curing temperatures and ages are important factors to fly ash early age hydration degree, FA-cement system microstructure, morphology and early age compressive strength etc. High curing temperatures and longer curing time can lead higher fly ash hydration degree, and then higher compressive strength of FA-cement concrete, and make the micro-structures of fly ash-cement system denser.

scholarly journals Mechanical Performance and Microstructure of Ultra-High-Performance Concrete Modified by Calcium Sulfoaluminate Cement

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Meimei Song ◽  
Chuanlin Wang ◽  
Ying Cui ◽  
Qiu Li ◽  
Zhiyang Gao
Keyword(s):  
Compressive Strength ◽  
High Performance ◽  
Mechanical Performance ◽  
High Performance Concrete ◽  
Autogenous Shrinkage ◽  
Ultra High Performance Concrete ◽  
Maximum Heat ◽  
Degree Of Hydration ◽  
Calcium Sulfoaluminate ◽  
Shrinkage Property

High autogenous shrinkage property is one of the disadvantages of ultra-high-performance concrete (UHPC), which may induce early age cracking and threaten the safety of concrete structure. In the present study, different dosages of calcium sulfoaluminate (CSA) cement were added in UHPC as an effective expansive binder. Hydration mechanism, autogenous shrinkage property, and compressive strength of UHPC were carried out to investigate the effect of CSA addition on the mechanical properties of UHPC. Scanning electron microscopy was also employed to characterize the intrinsic microstructural reasons relating to the changes in macroproperties. Based on the XRD diagram, increasing formation of ettringite and Ca(OH)2 can be found with increasing CSA content up to 15%. In the heat flow results of UHPC with 10% CSA addition, the maximum heat release increases to 2.6 mW/g, which is 8.3% higher than the reference UHPC, suggesting a higher degree of hydration with CSA addition. The results in autogenous shrinkage show that CSA expansion agent plays a significantly beneficial role in improving the autogenous shrinkage of UHPC. The corresponding autogenous shrinkage of UHPC is −59.66 μ ε , −131.11 μ ε , and −182.31 μ ε , respectively, at 7 d with 5%, 10%, and 15% addition, which is 108%, 117%, and 123% reduction compared to the reference specimen without CSA. In terms of compressive strength, UHPC with 5%, 10%, 15%, and 20% CSA addition has 10.5%, 17.4%, 30.2%, and 22.1% higher compressive strength than that for the reference UHPC at 28 d. Microstructural study shows that there is an extremely dense microstructure in both the bulk matrix and interfacial transition zone of UHPC with 10% CSA addition, which can be attributed to the higher autogenous shrinkage property and can therefore result in higher mechanical performance.

scholarly journals Effect of Graphene Oxide/Graphene Hybrid on Mechanical Properties of Cement Mortar and Mechanism Investigation

Nanomaterials ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 113 ◽  
Author(s):  
Hongfang Sun ◽  
Li Ling ◽  
Zhili Ren ◽  
Shazim Ali Memon ◽  
Feng Xing
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Graphene Oxide ◽  
Flexural Strength ◽  
Pore Size Distribution ◽  
Cement Mortar ◽  
Underlying Mechanism ◽  
Mortar Specimen ◽  
Degree Of Hydration ◽  
Cement Mortars

This paper evaluated the effect of graphene oxide/graphene (GO/GR) hybrid on mechanical properties of cement mortar. The underlying mechanism was also investigated. In the GO/GR hybrid, GO was expected to act as a dispersant for GR while GR was used as reinforcement in mortar due to its excellent mechanical properties. For the mortar specimen, flexural and compressive strength were measured at varied GO to GR ratios of 1:0, 3:1, 1:1, 1:3, and 0:1 by keeping the total amount of GO and GR constant. The underlying mechanism was investigated through the dispersibility of GR, heat releasing characteristics during hydration, and porosity of mortar. The results showed that GO/GR hybrid significantly enhanced the flexural and compressive strength of cement mortars. The flexural strength reached maximum at GO:GR = 1:1, where the enhancement level was up to 23.04% (28 days) when compared to mortar prepared with only GO, and up to 15.63% (7 days) when compared to mortar prepared with only GR. In terms of compressive strength, the enhancement level for GO:GR = 3:1 was up to 21.10% (3 days) when compared with that of mortar incorporating GO only. The enhancement in compressive strength with mortar at GO:GR = 1:1 was up to 14.69% (7-day) when compared with mortar incorporating GR only. In addition to dispersibility, the compressive strength was also influenced by other factors, such as the degree of hydration, porosity, and pore size distribution of mortar, which made the mortars perform best at different ages.

scholarly journals Effects of Highly Crystalized Nano C-S-H Particles on Performances of Portland Cement Paste and Its Mechanism

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 816
Author(s):  
Yuli Wang ◽  
Huijuan Lu ◽  
Junjie Wang ◽  
Hang He
Keyword(s):  
Portland Cement ◽  
Cement Paste ◽  
Setting Time ◽  
Tricalcium Silicate ◽  
Strength Development ◽  
Early Age ◽  
Hydration Products ◽  
X Ray ◽  
Early Strength ◽  
Portland Cement Paste

In order to improve the early age strength of ordinary Portland cement-based materials, many early strength agents were applied in different conditions. Different from previous research, the nano calcium silicate hydrate (C-S-H) particles used in this study were synthesized through the chemical reaction of CaO, SiO2, and H2O under 120 °C using the hydrothermal method, and the prepared nano C-S-H particles were highly crystalized. The influences of different amounts of nano C-S-H particles (0%, 0.5%, 1%, 2% and 3% by weight of cement) on the setting time, compressive strength, and hydration heat of cement paste were studied. The hydration products and microstructure of the cement paste with different additions of nano C-S-H particles were investigated through thermogravimetry-differential thermal analysis (TG-DTA), X-ray powder diffraction (XRD), and scanning electron microscope (SEM) tests. The results show that the nano C-S-H particles could be used as an early strength agent, and the early strength of cement paste can be increased by up to 43% through accelerating the hydration of tricalcium silicate (C3S). However, the addition of more than 2% nano C-S-H particles was unfavorable to the later strength development due to more space being left during the initial accelerated hydration process. It is suggested that the suitable content of the nano C-S-H particles is 0.5%−1% by weight of cement.

The Preparation and Pozzolanic Activity of Metakaolin Admixtures

2013 ◽  
Vol 539 ◽  
pp. 230-234 ◽  
Author(s):  
Bao Min Wang ◽  
Yuan Zhang ◽  
Ming Li
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Cement Paste ◽  
Cement Mortar ◽  
Heat Treating ◽  
Ratio Method ◽  
Strength Ratio ◽  
Hydration Products ◽  
Burning Temperature ◽  
Optimum Proportion

The optimum burning temperature of kaolinite and the optimum proportion of metakaolin (MK) in cement paste were studied by the compressive strength ratio method. Metakaolin was obtained at different burning temperature of 700°C, 750°C, 800°C and 850°C for 4 hours, and mixed into cement with the incorporation of 0, 5wt.%, 10wt.%, 15wt.% and 20wt.%. At last, the mechanical properties were researched. The influence of different burning temperature on hydration products of metakaolin cement mortar were analyzed. The results show that the compressive strength ratio of metakaolin cement mortar and the metakaolin pozzolanicity reach the maximum when the metakaolin obtained by heat treating of 750°C, the optimum proportion of metakaolin in cement is 10%~15%.

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