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.

Effect of Styrene-Acrylic Emulsion on Crack Resistance of Cement-Based Materials

2021 ◽  
Vol 1036 ◽  
pp. 288-300
Author(s):  
Jun Peng Mei ◽  
Hai Nan Li ◽  
Zhi Dong Xu
Keyword(s):  
Elastic Modulus ◽  
Crack Resistance ◽  
Autogenous Shrinkage ◽  
Drying Shrinkage ◽  
Cementitious Materials ◽  
Strength Ratio ◽  
Acrylic Emulsion ◽  
Cement Based Materials ◽  
Binder Ratio ◽  
Water Binder Ratio

In this paper, the brittleness coefficient, elastic modulus-to-strength ratio, drying shrinkage and autogenous shrinkage and cracking sensitivity were used to investigate the effect of styrene-acrylic emulsion (SAE) on crack resistance of cement-based materials under ultralow water binder ratio (0.22). Then the pore structures, hydration products and surface morphology were also studied to explore the mechanism of SAE on improving the crack resistance of cement-based materials. Results show that, the addition of SAE significantly reduces the elastic modulus, brittleness coefficient, elastic strength ratio, drying shrinkage and autogenous shrinkage of the specimen. The cracking susceptibility is also decreased by the incorporation of SAE and when the dosage of SAE was 5%, the initial cracking time would be extended by 43 hours. In addition, incorporation of SAE can reduce the amount of pores that have an adverse effect on shrinkage, refine the microstructure and decrease the calcium hydroxide formation and microcracks of cement-based materials. Such results would be expected to provide guidance on enhancing the anti-cracking ability of high-performance cementitious materials by the dosage of SAE under low water-binder ratio in practical engineering.

scholarly journals Influence of Concrete Mixture Composition on Acid Resistance of Concrete: A Review

2021 ◽  
Author(s):  
Chinnu Mariam Ninan ◽  
K P Ramaswamy ◽  
R Sajeeb
Keyword(s):  
Acid Resistance ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Concrete Mixture ◽  
Mixture Composition ◽  
Soluble Salts ◽  
Acid Attack ◽  
Related Factors ◽  
Binder Ratio ◽  
Water Binder Ratio

Cementitious materials are highly susceptible to rapid and severe degradation by a wide range of acids that are found immensely in ground water, sewage systems, industrial effluents, acid rain etc. which may cause microstructure deterioration. The factors influencing acid attack is generally categorised as material related factors and test related factors. Material related factors can be either related to acid solution or concrete mixture composition. Composition of concrete mixture greatly impacts the acid resistance of concrete. Factors related to composition of concrete mixture are type of cement, type and proportion of binders, water binder ratio, aggregate binder ratio and mineralogical nature of the aggregates. Even though the type of cement influences acid attack, the magnitude of variation is negligible. Consumption of calcium hydroxide and refinement of pore structure makes the use of supplementary cementitious materials favourable for acid resistance. Decrease in water binder ratio and increase in aggregate binder ratio reduces the porosity of concrete and thereby improves the acid resistance of concrete. Calcareous aggregates are preferred for concretes exposed to acids having less soluble salts and not preferred for acids forming soluble salts. This paper highlights the influence of composition of concrete mixture on acid resistance of concrete. A proper formulation of concrete is expected to enhance its acid resistance.

Effect of Nano-Silica Particles on the Fresh Properties of UHPC

2014 ◽  
Vol 629-630 ◽  
pp. 91-95
Author(s):  
Qian Qian Zhang ◽  
Jian Zhong Liu ◽  
Wei Lin
Keyword(s):  
Mechanical Properties ◽  
Cement Hydration ◽  
Physical And Mechanical Properties ◽  
Heat Evolution ◽  
Fresh Properties ◽  
Nano Silica ◽  
Cement Pastes ◽  
Binder Ratio ◽  
Nanosilica Particles ◽  
Water Binder Ratio

Nanotechnology is being used in UHPC for achieving more dense structural packing and better physical and mechanical properties. In this paper, nanosilica particles (0-1wt %) by cement were incorporated in cement pastes and mortars with water-binder ratio of 0.2, and their effect on fresh properties was addressed. The fresh properties of mixtures were investigated by spread, rheology and cohesiveness. In addition, effect of nanosilica on cement hydration was also investigated. The results show that significant increase of yield stress, viscosity and cohesiveness is observed with nanosilica above 0.005 wt% by cement, but nanosilica with content below 0.005% presents an improvement of workability especially with content of 0.002%. Moreover, the addition of nanosilica in cement pastes obviously accelerates the early cement hydration rate, but does not increase the cumulative heat evolution.

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.

Study on the Effect of Fly Ash or Silica Fume to Hydration Heat of Cement

2011 ◽  
Vol 250-253 ◽  
pp. 4001-4004 ◽  
Author(s):  
Li Guo Ma ◽  
Yun Sheng Zhang
Keyword(s):  
Fly Ash ◽  
Binary System ◽  
Silica Fume ◽  
Cement Paste ◽  
Heat Evolution ◽  
Hydration Heat ◽  
Dormant Period ◽  
Binder Ratio ◽  
Isothermal Calorimeter ◽  
Water Binder Ratio

The hydration heat evolution process is studied on the pure cement paste, the cement- fly ash binary system and the cement- silica fume binary system with water binder ratio(w/b) of 0.53, 0.35 and 0.23 by using isothermal calorimeter(TAM Air). The fly ash replacement in the cement-fly ash binary system is 10%, 30% and 50% respectively. The silica fume replacement in cement-silica fume binary system is 4%, 8% and 12% respectively. The experiments results indicate that w/b had great impact on the hydration heat evolution and the hydration heat decrease with the decrease in w/b. The addition of fly ash greatly decrease the exothermic rate and total hydration heat. The addition of silica fume shortens dormant period and increases the peak exothermic rate, but reduces the total hydration heat.

scholarly journals Early Hydration Heat of Calcium Sulfoaluminate Cement with Influences of Supplementary Cementitious Materials and Water to Binder Ratio

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 642
Author(s):  
Jun Zhang ◽  
Guoju Ke ◽  
Yuzhang Liu
Keyword(s):  
Critical Value ◽  
Cementitious Materials ◽  
Exothermic Peak ◽  
Hydration Heat ◽  
Supplementary Cementitious Materials ◽  
Calcium Sulfoaluminate Cement ◽  
Early Hydration ◽  
Calcium Sulfoaluminate ◽  
Granulated Blast Furnace Slag ◽  
Binder Ratio

Compared to ordinary Portland cement (OPC), calcium sulfoaluminate cement (CSA) displays very early-age strength and faster heat-releasing rate during hydration. In the present paper, the early hydration heat of CSA paste with influences of supplementary cementitious materials (SCMs) and water to cement (or binder) ratio (w/c) is systematically studied by measuring the heat-releasing rate using a calorimeter. Three traditional SCMs—silica fume (SF), fly ash (FA) and ground granulated blast furnace slag (SL)—were used in the study. A water to cement or binder ratio (w/c) between 0.19 and 0.73 was used in the mixtures. The results show that three exothermic peaks were presented during hydration—dissolution exothermic peak and two reaction exothermic peaks. With the w/c of 0.3, the first and second reaction peaks of the CSA paste are as high as 17.8 times and 4.1 times that of OPC paste, and the occurring time is much earlier than that of the OPC paste. The second reaction peak appears earlier, and the third reaction peak appears later in the pastes with addition of SF than in those without SF. Decreasing w/c can greatly reduce the two reaction peaks of the paste, and it looks that there is a critical value of w/c between 0.24 and 0.30. Above the critical value, the effect of w/c is minor, and below that the influence is obvious. An optimal use of SCMs in CSA pastes under different w/c can greatly decrease the heat releasing while maintaining the required strength.

scholarly journals Effect of the water/binder ratio on the hydration process of Portland cement pastes with silica fume and metakaolin

2022 ◽  
Vol 15 (1) ◽  
Author(s):  
Mara Monaliza Linhares Pereira ◽  
Ana Luiza Rocha de Souza ◽  
Valdirene Maria Silva Capuzzo ◽  
Rodrigo de Melo Lameiras
Keyword(s):  
Portland Cement ◽  
Silica Fume ◽  
Cementitious Materials ◽  
Hydration Process ◽  
X Ray Diffraction ◽  
Cement Pastes ◽  
X Ray ◽  
Binder Ratio ◽  
Water Binder Ratio ◽  
Mineralogical Phases

abstract: The microstructure of cement pastes is important to understand the effect of some parameters in the hydration process. In this context, this study had as objective to evaluate the effect of different water/binder (w/b) ratios in the hydration process of cementitious pastes produced with and without incorporation of silica fume and metakaolin. The pastes were obtained with water/binder ratios of 0.3, 0.4 e 0.5, with replacement, by weight, of Portland cement for silica fume and metakaolin, in the contents of 10% and 20%, respectively. It was performed the X-ray diffraction test of the pastes in the ages of 1, 3, 7, and 28 days, to evaluate the hydration evolution of the cementitious materials. According to the results obtained, it was observed that the cementitious pastes presented similar mineralogical phases, except for the pastes containing metakaolin due to the formation of new aluminate phases. With the increase of the water/binder ratio, the pozzolanic reactions and hydration occurred in greater proportion, standing out the metakaolin with greater reactivity.

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