Influences on the Hydrophobicity of Concrete Surfaces Treated with Alkyl Trialkoxysilanes

2014 ◽  
Vol 20 (6) ◽  
pp. 405-412
Author(s):  
U. Antons ◽  
M. Raupach ◽  
O. Weichold
Keyword(s):  
Uv Radiation ◽  
Cement Hydration ◽  
Alkaline Media ◽  
Water Repellent ◽  
Portland Cement Concrete ◽  
Accelerated Carbonation ◽  
Surface Layers ◽  
Hydrophobic Layer ◽  
Furnace Slag

Abstract The paper focuses on how alkaline media, UV radiation, and carbonation as well as on-going cement hydration affects hydrophobic treatments of concrete and influences the properties of these water-repellent layers. Single-sided nuclear magnetic resonance measurements show that layers formed by impregnating samples with alkyl trialkoxysilanes are stable even under long-term exposure to alkaline solution and UV radiation, with the damage of the latter being limited to the topmost surface layers. Microstructural changes during accelerated carbonation of blast furnace slag cement based concrete have a major impact on the hydrophobic layer properties, while the carbonation of Portland cement concrete has no influence. On-going hydration additionally influences the hydrophobic layer properties.

scholarly journals Mechanisms Accompanying Chromium Release from Concrete

Materials ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1891 ◽  
Author(s):  
Anna Król
Keyword(s):  
Portland Cement ◽  
Building Materials ◽  
Portland Cement Concrete ◽  
Chromium Release ◽  
Granulated Blast Furnace Slag ◽  
Diffusion Controlled ◽  
Tank Test ◽  
Mineral Additives ◽  
Furnace Slag

The use of mineral additives from the power and metallurgy industries in the production of building materials still raises questions about the ecological safety of such materials. These questions are particularly associated with the release of heavy metals. The article presents research related to the leaching of chromium from concretes made of Portland cement CEM I and slag cement CEM III/B (containing 75% of granulated blast furnace slag). Concrete was evaluated for leaching mechanisms that may appear during tank test over the long term (64 days). It has been presented that the dominating process associated with the leaching of chromium from both types of concrete is surface wash-off. Between the 9th and 64th day of the test, leaching of Portland cement concrete can be diffusion controlled. It has been proven that the participation of slag in the composition of concrete does not affect the level of leaching of chromium into the environment from concrete.

scholarly journals Enhancing carbonation and chloride resistance of autoclaved concrete by incorporating nano-CaCO3

2020 ◽  
Vol 9 (1) ◽  
pp. 998-1008
Author(s):  
Guo Li ◽  
Zheng Zhuang ◽  
Yajun Lv ◽  
Kejin Wang ◽  
David Hui
Keyword(s):  
Cement Hydration ◽  
Mercury Intrusion Porosimetry ◽  
Hardened Concrete ◽  
Optimal Dosage ◽  
Hydration Products ◽  
X Ray Diffraction ◽  
Carbonation Depth ◽  
X Ray ◽  
Chloride Resistance

AbstractThree nano-CaCO3 (NC) replacement levels of 1, 2, and 3% (by weight of cement) were utilized in autoclaved concrete. The accelerated carbonation depth and Coulomb electric fluxes of the hardened concrete were tested periodically at the ages of 28, 90, 180, and 300 days. In addition, X-ray diffraction, thermogravimetry, and mercury intrusion porosimetry were also performed to study changes in the hydration products of cement and microscopic pore structure of concrete under autoclave curing. Results indicated that a suitable level of NC replacement exerts filling and accelerating effects, promotes the generation of cement hydration products, reduces porosity, and refines the micropores of autoclaved concrete. These effects substantially enhanced the carbonation and chloride resistance of the autoclaved concrete and endowed the material with resistances approaching or exceeding that of standard cured concrete. Among the three NC replacement ratios, the 3% NC replacement was the optimal dosage for improving the long-term carbonation and chloride resistance of concrete.

Water repellent room temperature vulcanized silicone for enhancing the long-term stability of perovskite solar cells

Solar Energy ◽  
2021 ◽  
Vol 218 ◽  
pp. 28-34
Author(s):  
Mahmoud Samadpour ◽  
Mahsa Heydari ◽  
Mahdi Mohammadi ◽  
Parisa Parand ◽  
Nima Taghavinia
Keyword(s):  
Solar Cells ◽  
Room Temperature ◽  
Perovskite Solar Cells ◽  
Water Repellent ◽  
Term Stability ◽  
Long Term Stability

scholarly journals Synthesis of Ambient Cured GGBFS Based Alkali Activated Binder Using a Sole Alkaline Activator: A Feasibility Study

2021 ◽  
Vol 11 (13) ◽  
pp. 5887
Author(s):  
Thandiwe Sithole ◽  
Nelson Tsotetsi ◽  
Tebogo Mashifana
Keyword(s):  
Silicate Solution ◽  
Environmental Footprint ◽  
Ambient Temperatures ◽  
Granulated Blast Furnace Slag ◽  
Naoh Solution ◽  
Alkaline Activator ◽  
Porous Morphology ◽  
Furnace Slag ◽  
Alkali Activated

Utilisation of industrial waste-based material to develop a novel binding material as an alternative to Ordinary Portland Cement (OPC) has attracted growing attention recently to reduce or eliminate the environmental footprint associated with OPC. This paper presents an experimental study on the synthesis and evaluation of alkali activated Ground granulated blast furnace slag (GGBFS) composite using a NaOH solution as an alkaline activator without addition of silicate solution. Different NaOH concentrations were used to produce varied GGBFS based alkali activated composites that were evaluated for Uncofined Compressive Strength (UCS), durability, leachability, and microstructural performance. Alkali activated GGBFS composite prepared with 15 M NaOH solution at 15% L/S ratio achieved a UCS of 61.43 MPa cured for 90 days at ambient temperatures. The microstructural results revealed the formation of zeolites, with dense and non-porous morphology. Alkali activated GGBFS based composites can be synthesized using a sole alkaline activator with potential to reduce CO2 emission. The metal leaching tests revealed that there are no potential environmental pollution threats posed by the synthesized alkali activated GGBFS composites for long-term use.

scholarly journals Long-term cement hydration studies with isothermal calorimetry

2021 ◽  
Vol 141 ◽  
pp. 106344
Author(s):  
O. Linderoth ◽  
L. Wadsö ◽  
D. Jansen
Keyword(s):  
Cement Hydration ◽  
Isothermal Calorimetry

scholarly journals LONG-TERM HYDRATION REACTION OF HIGH BLAST-FURNACE SLAG CEMENT

2010 ◽  
Vol 64 (1) ◽  
pp. 48-53
Author(s):  
Takeshi ANSAI ◽  
Makoto NISHIKAWA ◽  
Yosaku IKEO ◽  
Etsuo SAKAI
Keyword(s):  
Blast Furnace ◽  
Blast Furnace Slag ◽  
Hydration Reaction ◽  
Slag Cement ◽  
Furnace Slag

Synthesis and Characterisation of Slag Based Geopolymers

2010 ◽  
Vol 636-637 ◽  
pp. 155-160 ◽  
Author(s):  
C. Panagiotopoulou ◽  
Glykeria Kakali ◽  
Sotiris Tsivilis ◽  
T. Perraki ◽  
Maria Perraki
Keyword(s):  
Compressive Strength ◽  
Blast Furnace ◽  
Blast Furnace Slag ◽  
Starting Material ◽  
Alkaline Media ◽  
High Compressive Strength ◽  
Geopolymer Matrix ◽  
Furnace Slag ◽  
Alkali Ion

In the present work the geopolymerisation of blast furnace slag (GGBS) under varying conditions is being investigated. The experimental comprises the following parts: i) dissolution of slag in alkaline media and the investigation of the effect of the alkali ion (K or Na) on the dissolution of Al+3 and Si4+, ii) synthesis of slag based geopolymers and the investigation of the effect of the Si/Al ratio and the kind of alkaline ion on the development of the compressive strength and iii) characterization of geopolymers by means of XRD, FTIR and SEM/EDS measurements. As it is concluded, blast furnace slag geopolymers exhibit high compressive strength, with the maximum being 112.7±2 MPa. The Si/Al ratio of the starting material is found to affect strongly the development of the geopolymer compressive strength. The microstructure of slag–based geopolymers and the incorporation of Ca in the geopolymer matrix are also discussed.

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