scholarly journals Solidification Effect and Mechanism of Marine Muck Treated with Ionic Soil Stabilizer and Cement

Minerals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1268
Author(s):  
Xue-Ting Wu ◽  
Yi Qi ◽  
Jun-Ning Liu ◽  
Bin Chen
Keyword(s):  
Portland Cement ◽  
Clay Minerals ◽  
Setting Time ◽  
Environmentally Friendly ◽  
Hydration Products ◽  
High Increase ◽  
Soil Stabilizer ◽  
Effective Stabilizer ◽  
Solidification Speed ◽  
Cement Setting

In this study, an environmentally friendly ionic soil stabilizer (ISS) was adopted with combination of Portland cement to stabilize a marine muck. The macro and micro tests results demonstrated that the ISS was an effective stabilizer to improve the strength of marine muck when it was used combined with cement after adding the alkalizer NaOH. Except for the reduction in interlayer distance of clay minerals by ISS, Ca2+ and SO42− dissolved from ISS promoted the production of ettringite (AFt), pozzolanic and carbonation reactions of Portland cement in the presence of NaOH. Meanwhile, the hydration products of curing reaction notably agglomerated soil particles, which caused an obvious decrease of pores and a high increase of strength for solidified soils. Furthermore, this combination of stabilizers can not only save the dosage of cement, but also accelerate the solidification speed, decrease the cement setting time within 7 days to meet the curing requirements, and enhance the strength of solidified soils.

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.

scholarly journals Effect of Fly Ash Belite Cement on Hydration Performance of Portland Cement

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 740
Author(s):  
Yongfan Gong ◽  
Jianming Yang ◽  
Haifeng Sun ◽  
Fei Xu
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Setting Time ◽  
Hydration Heat ◽  
Hydration Reaction ◽  
Term Strength ◽  
Hydration Products ◽  
Composite Cement ◽  
Belite Cement

Fly ash belite cement is a green, low carbon cementitious material, mainly composed of hydraulic minerals of dicalcium silicate and calcium aluminate. In this study, we used fly ash belite cement to control the setting time, hydration heat, strength, composition and microstructure of hydration products in Portland cement. Results showed that incorporating fly ash belite cement into Portland cement can shorten the setting time, accelerate hydration reaction speed, enhance early hydration heat release rate of silicate minerals and reduce total hydration heat. Moreover, replacing composite cement with 30% FABC causes the 90 d compressive strength of pastes and mortars to reach 107 and 46.2 MPa, respectively. The mechanical properties can meet the requirements of P·F 42.5 cement. During the hydration reaction process, clinker and Portland cement have a synergistic hydration effect. Notably, hydration of fly ash belite cement promotes the formation of C-S-H gel, Ettringite and calcium hydroxide, thereby significantly enhancing long-term strength. With the increase of FABC contents, the long-term strength would be improved with the densification of hydration products. The porosity has a great influence on the strength, and the high porosity was the main cause of the low early strength of FABC pastes. FABC and its composite cement show promise for mass concrete applications and can be applied as a setting agent for Portland cement.

scholarly journals Influences of Waste Concrete Powder on the Strength Development and Hydration Products of Mortar Containing Fly Ash

2021 ◽  
Author(s):  
Huashan YANG ◽  
Yujun CHE
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Cement Mortar ◽  
Setting Time ◽  
Flow Index ◽  
Strength Development ◽  
Test Results ◽  
Hydration Products ◽  
Waste Concrete ◽  
Time Flow

During recycling waste concrete, a large amount of waste concrete powder (WCP) is generated. However, efficient utilization of WCP remains an unresolved issue. This paper investigates the influences of WCP on the properties and hydration products of cement mortar containing fly ash (FA). This study used two different types of WCPs. One was made from an ordinary Portland cement mortar, and the other was derived from a Portland cement mortar. WCP replaced 10%, 20%, and 30% of FA. The water requirement, setting time, flow index, strength, hydration products, and microstructure of FA mortar incorporating WCP were investigated. Test results indicate that the WCP has no significant influence on the performances and hydration products of FA mortar. By adequately combining WCP and FA, the FA mortar with required performances could be reached.

Research Progress on the Hydration of Portland Cement with Calcined Clay and Limestone

2021 ◽  
Vol 1036 ◽  
pp. 240-246
Author(s):  
Jin Tang ◽  
Su Hua Ma ◽  
Wei Feng Li ◽  
Hui Yang ◽  
Xiao Dong Shen
Keyword(s):  
Mechanical Properties ◽  
Portland Cement ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Research Progress ◽  
Hydration Reaction ◽  
Hydration Products ◽  
Early Hydration ◽  
Calcined Clay ◽  
Dense Microstructure

The use of calcined clay and limestone as supplementary cementitious materials, can have a certain influence on the hydration of Portland cement. This paper reviewed the influence of limestone and calcined clay and the mixture of limestone and calcined clay on the hydration of cement. Both limestone and calcined clay accelerate the hydration reaction in the early hydration age and enhance the properties of cement. Limestone reacts with C3A to form carboaluminate, which indirectly stabilized the presence of ettringite, while calcined clay consumed portlandite to form C-(A)-S-H gel, additional hydration products promote the densification of pore structure and increase the mechanical properties. The synergistic effect of calcined clay and limestone stabilize the existence of ettringite and stimulate the further formation of carboaluminate, as well as the C-(A)-S-H gel, contributed to a dense microstructure.

Utilization of Circulating Fluidized Bed Combustion (CFBC) Fly Ash and Coal-Fired Fly Ash in Portland Cement

2014 ◽  
Vol 629-630 ◽  
pp. 306-313 ◽  
Author(s):  
Mao Chieh Chi ◽  
Ran Huang ◽  
Te Hsien Wu ◽  
Toun Chun Fou
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Fluidized Bed ◽  
Building Materials ◽  
Circulating Fluidized Bed ◽  
Setting Time ◽  
Fluidized Bed Combustion ◽  
Initial Setting Time ◽  
Cfbc Fly Ash ◽  
Circulating Fluidized Bed Combustion

Circulating fluidized bed combustion (CFBC) fly ash is a promising admixture for construction and building materials due to its pozzolanic activity and self-cementitious property. In this study, CFBC fly ash and coal-fired fly ash were used in Portland cement to investigate the pozzolanic and cementitious characteristics of CFBC fly ash and the properties of cement-based composites. Tests show that CFBC fly ash has the potential instead of cementing materials and as an alternative of pozzolan. In fresh specimens, the initial setting time of mortars increases with the increasing amount of cement replacement by CFBC fly ash and coal-fire fly ash. In harden specimens, adding CFBC fly ash to replace OPC reduces the compressive strength. Meanwhile, CFBC fly ash would results in a higher length change when adding over 30%. Based on the results, the amount of CFBC fly ash replacement cement was recommended to be limited below 20%.

Influence of Aluminous Cement on the Hardening Rate of Cement-Based Stucco Mortars

2016 ◽  
Vol 865 ◽  
pp. 57-61 ◽  
Author(s):  
Wojciech Siemiński ◽  
Marcin Kaczmarczyk
Keyword(s):  
Portland Cement ◽  
Setting Time ◽  
Experimental Studies ◽  
Cellulose Ether ◽  
Hydrophobic Properties ◽  
Content Ratio ◽  
Flow Table ◽  
Aluminous Cement ◽  
Hydrophobic Nature ◽  
The Impact

Renovation mortars used to restore damaged stucco elements are materials with special physical properties due to the nature of the work and environment in which they are applied. They must be characterized by low shrinkage, relatively short setting time, appropriate working properties and hydrophobic nature of hardened mortar. This paper analyzes the impact of mortar stucco ingredients on these parameters. The analysis was performed by experimental studies. The effect of the content ratio of aluminate cement to Portland cement on the change in mortar setting time was studied. Suitable workability of fresh mortar is achieved by the use of consistence-modifying additives. To assess this parameter, flow table method was applied in accordance with PN-EN 1015-3: 2000. The additives used were a system of thickeners, which included: cellulose ether in the form of hydroxyethylmethylcellulose and modified starch ether (starch 2-hydroxypropyl ether). Hydrophobic properties were obtained by the addition of triethoxyoctylsilane. The results were presented as graphs and tables. It was found that the ratio of aluminous cement to Portland cement most beneficial in terms of the setting rate of the resulting stucco mortar is 25% (m/m). This amount accelerates the end of setting time to 2 hours, the beginning of the setting time being 20 minutes. Suitable working characteristics were obtained by the addition of 0.080% of hydroxyethylmethylcellulose and 0.025% (m/m in dry mix) of starch 2-hydroxypropyl ether. Best hydrophobic properties of the hardened mortar was obtained by the addition of 0.075% (m/m in dry mix) of triethoxyoctylsilane.

Setting Behaviour of Phosphate Cement

2011 ◽  
Vol 194-196 ◽  
pp. 853-857
Author(s):  
Zhong Hua Li ◽  
He Fei Gao ◽  
Shu Rong Feng ◽  
Chao Su
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Influencing Factors ◽  
Setting Time ◽  
Repair Material ◽  
Rapid Repair ◽  
Binder Ratio

For the situation that concrete engineering required rapid and timely repair after nature disaster, setting time and influencing factors of phosphate rapid repair material were studied in this paper. The results showed that setting time of phosphate rapid repair material increased a little with increase of water and binder ratio but the setting time was short. When water and binder ratio was less than 0.20 setting time was less than 3min. Setting time was shorted with reducing of P/M. Setting time was from 2min30s to 5min when P/M was reduced from 1:0.6 to 1:4. Setting time of phosphate cement increase a little mixed with fly ash, slag or portland cement but effect of their content on setting time was little. Setting time of phosphate rapid repair material increased with increase of B/M. When content was greated than 12% the setting time was longer than 20min. Fly ash, slag and portland cement can reduce setting time of phosphate cement with borax obviously.

scholarly journals MICRO-MECHANICAL PROPERTIES OF CEMENT AND SLAG COMPOSITES MEASURED BY NANOINDENTATION

2020 ◽  
Vol 26 ◽  
pp. 45-49
Author(s):  
Jiří Němeček ◽  
Jiří Němeček
Keyword(s):  
Mechanical Properties ◽  
Portland Cement ◽  
Modulus Of Elasticity ◽  
Volume Fraction ◽  
Blended Cement ◽  
Hydration Products ◽  
Granulated Blast Furnace Slag ◽  
The Difference ◽  
Portland Cement Paste ◽  
Furnace Slag

In this study, the micromechanical response of two cementitious composites was characterized by nanoindentation. Pure Portland cement paste and Portland cement with 50 vol. % replaced with granulated blast furnace slag (GBFS) paste were investigated at the age of 28 days. Grid nanoindentation, statistical deconvolution and scanning electron microscopy were used to characterize the main hydration products. Several grids with approximately 500 indents on each sample were performed to obtain modulus of elasticity, hardness and creep indentation parameter. Similar mechanical phases containing calcium silica hydrate, crystalline calcium hydroxide and un-hydrated clinker were found in both samples varying by volume fraction. Blended cement, moreover, contains a phase of slag hydration products with a significantly lower modulus of elasticity. This phase with a high portion of unreacted GBFS is mostly responsible for the difference of mechanical properties of the whole composite.

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