scholarly journals Enhancement of alkali-activated slag cement concretes crack resistance for mitigation of steel reinforcement corrosion

2020 ◽  
Vol 166 ◽  
pp. 06001
Author(s):  
Pavlo Krivenko ◽  
Oleh Petropavlovskyi ◽  
Oleksandr Kovalchuk ◽  
Igor Rudenko ◽  
Oleksandr Konstantynovskyi
Keyword(s):  
Crack Resistance ◽  
Structure Formation ◽  
Water Glass ◽  
Sodium Metasilicate ◽  
Steel Reinforcement ◽  
Reinforcement Corrosion ◽  
Slag Cement ◽  
Alkali Activated Slag ◽  
Activated Slag ◽  
Alkali Activated

The paper is devoted to mitigation of steel reinforcement corrosion in alkali-activated slag cement (further, AASC) concretes, based on soluble sodium silicates (further, SSS’s), obtained from high consistensy concrete mixes. Enhancement of AASC fine concretes crack resistance due to modification by complex shrinkage-reducing additives (further, SRA’s) based on surfactants and trisodium phosphate Na3PO .12H2O (further, TSP) was proposed for mitigation of steel reinforcement corrosion. SSS’s were presented by sodium metasilicate (silica modulus 1.0, dry state) and water glass (silica modulus 2.9, density 1400 kg/m3). In case of sodium metasilicate the application of SRA composition “ordinary portland cement clinker – TSP – sodium lignosulphonate – sodium gluconate” provides enhancement of crack resistance starting from early age structure formation with restriction of drying shrinkage from 0,984 to 0,713 mm/m after 80 d. The effect is caused by reduction of water and by higher volume of crystalline hydrates. In turn, SRA presented by compositions “TSP – glycerol” and “TSP – glycerol – polyacrylamide” provide enhancement of AASC fine concretes fracture toughness during late structure formation with increasing ratio of tensile strength in bending to compressive strength up to 37 – 49 % if compare with the reference AASC when water glass is used.

scholarly journals Prevention of steel reinforcement corrosion in alkali-activated slag cement concrete mixed with seawater

2021 ◽  
Vol 280 ◽  
pp. 07004
Author(s):  
Pavlo Krivenko ◽  
Igor Rudenko ◽  
Oleksandr Konstantynovskyi ◽  
Olha Boiko
Keyword(s):  
Steel Corrosion ◽  
Steel Reinforcement ◽  
Passive State ◽  
Hardened Concrete ◽  
Reinforcement Corrosion ◽  
Alkali Activated Slag ◽  
Complex Additive ◽  
Activated Slag ◽  
High Consistency ◽  
Alkali Activated

Concretes mixed with seawater are characterised by enhanced performances, but action of chlorides and sulfates ensures the risk of reinforcement corrosion. Application of high consistency fresh concretes ensures changes in hardened concrete structure that causes the problem of steel reinforcement passive state ensuring. Thus mixing of plasticized concretes by seawater actualizes the search for means of steel corrosion prevention. Alkali-activated slag cements (further, AASC’s) reduce effect of ions Cl− and SO42− on steel reinforcement in concrete due to their exchange for ions OH− in the structure of zeolite-like alkaline hydroaluminosilicates. Complex additive «portland cement - calcium aluminate cement - clinoptilolite» was proposed to enhance the protective properties of AASC concretes to steel reinforcement. The results of DTA, X-ray diffraction, electron microscopy, microprobe analysis show that complex additive ensures to prevent steel reinforcement corrosion in AASC concrete mixed with seawater due to binding Cl− and SO42− ions in Kuzel’s salt in AASC hydration products and exchange of these aggressive ions with OH− ions in the structure of clinoptilolite. This effect of complex additive confirmed by surface state and the absence of mass loss of steel rebars embedded in plasticized AASC fine concrete mixed with seawater after 90 d of hardening.

Factors Influencing the Strength of Alkali-Activated Slag Cement

2011 ◽  
Vol 368-373 ◽  
pp. 3240-3245
Author(s):  
Zhi Jun Zhou ◽  
Hui Li ◽  
Qiang Song ◽  
Bao Jing Shen
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Silica Fume ◽  
Water Glass ◽  
Slag Cement ◽  
Alkali Activated Slag ◽  
Factors Influencing ◽  
Activated Slag ◽  
Alkali Activated

In this paper, water glass was chosen as activator to prepare Alkali-activated slag(AAS) cement. Effects of modulus and dosage of water glass, and admixture (fly ash, slag and silica fume) on the strength of AAS cement was investigated. It was found that the modulus of water glass had great effect on the strength of AAS cement when the mixing amount of water glass was less than 12%. With the incorporation of fly ash or slag, the strength of AAS cement decreased, however the incorporation of silica fume could promote the flexural and compressive strength of AAS cement slightly.

Adsorption of Naphthalene-Based Water Reducer on Alkali-Activated Slag Cement

2012 ◽  
Vol 226-228 ◽  
pp. 1747-1750
Author(s):  
Chang Hui Yang ◽  
Qun Pan ◽  
Jiong Zhu
Keyword(s):  
Zeta Potential ◽  
Rheological Properties ◽  
Water Glass ◽  
Slag Cement ◽  
Alkali Activated Slag ◽  
Absolute Value ◽  
Adsorption Of Water ◽  
Activated Slag ◽  
Alkali Activated ◽  
Over Time

In this work, the adsorption of naphthalene-based water reducer (FDN) on slag ground with or without the composite retarder YP-3 and PN (YP) in alkali-activated slag cement (AASC) activated by water glass (WG) has been studied in detail. The results show that the effect of the adsorption of water reducer on AASC depends directly on the dosage of the water reducer and on the composite retarder used. For example, mixed slag particles adsorb thrice as much water reducer FDN than pure slag particles at 1% mass of the slag, and the absolute value increment of the zeta potential of the AASC suspension containing the composite retarder is 8.61 mV, compared with 1.99 mV in the system without the composite retarder. Moreover, the AASC pastes activated by WG containing the retarder YP show better rheological properties and lower fluidity loss over time.

The Effect of Surfactant and Alkali on the Surface Tension of Simulated Solutions of Alkali Activated Slag Cement System

2011 ◽  
Vol 399-401 ◽  
pp. 1246-1250
Author(s):  
Xian Feng Liu ◽  
Jia Hui Peng ◽  
Chang Hui Yang ◽  
Yu Yan Shu ◽  
Da Chang Wu
Keyword(s):  
Surface Tension ◽  
Water Glass ◽  
High Viscosity ◽  
Heat Of Hydration ◽  
Slag Cement ◽  
Alkali Activated Slag ◽  
Cement System ◽  
Cement And Concrete ◽  
Activated Slag ◽  
Alkali Activated

Alkali activated slag cement and concrete are high strength, rapid hardening, low heat of hydration, good durability and so on. Whereas, too high viscosity and bad workability of the fresh mixture is the crux of the matter to embarrass application of alkali-activated slag cement and concrete. Development of special superplasticizer for alkali activated slag cement and concrete is a worth exploring way to solve the problem, and the study on the surface tension of simulated solutions of alkali activated slag cement system is one of the basic researches about the special superplasticizer. In this paper, the surface tension of surfactant-alkali-water was studied by Wilhelmy method. The results showed, first, water-glass had the best efficacity of several alkali activators, when the modulus of water-glass was 1.5 and dosage of water-glass by Na2O was 8%, the surface tension was reduced by 33 mN/m and reduced to 39.9mN/m; second, [CH3(CH2)9]2N(CH3)2Cl had the best efficacity of several surfactants, when the concentration of [CH3(CH2)9]2N(CH3)2Cl was 50g/L, the surface tension was reduced by 35.3 mN/m and reduced to 32.5 mN/m; finally, the effect of surfactant and alkali together on the surface tension of water was complex, surfactants had hardly effective in water glass.

Complex Shrinkage-Reducing Additives for Alkali Activated Slag Cement Fine Concrete

2021 ◽  
Vol 321 ◽  
pp. 165-170
Author(s):  
Pavlо Krivenko ◽  
Volodimir I. Gots ◽  
Oleh Petropavlovskyi ◽  
Igor Rudenko ◽  
Oleksandr Konstantynovskyi
Keyword(s):  
Cement Clinker ◽  
Reinforcement Corrosion ◽  
Sodium Gluconate ◽  
Slag Cement ◽  
Alkali Activated Slag ◽  
Granulated Blast Furnace Slag ◽  
Portland Cement Clinker ◽  
Activated Slag ◽  
Furnace Slag ◽  
Alkali Activated

Optimization of complex shrinkage-reducing additives (further, SRA’s), consisting of ordinary portland cement clinker (further, OPC clinker), salt-electrolyte and surfactants, is provided for prevention of steel reinforcement corrosion due to shrinkage mitigation in alkali-activated slag cement (further, AASC) fine concrete. Modification of AASC by SRA included 0.3 % sodium lignosulphonate, 0.15 % sodium gluconate, 1.4 – 2.0 % NaNO3 and 6.5 - 7.7 % OPC clinker (by mass of granulated blast furnace slag) provides shrinkage reduction from 0.984 up to 0.560 – 0.605 mm/m (t=202 °С, R.H.=65 %). Unlike, SRA presented by the mentioned system with 1.50 - 1.59 % Na2SO4 and 4.0 - 4.65 % OPC clinker causes shrinkage mitigation from down to 0.625 - 0.640 mm/m. In addition, SRA with 1.80 - 2.05 % Na3PO4 and 4.0 - 4.6 % OPC clinker minimizes shrinkage to 0.713 - 0.700 mm/m. Shrinkage mitigation in modified AASC fine concrete is explained by less water, higher crystallinity of hydrated phases as well as by formation of minamiit (Na,Ca0.5)Al3(SO4)2(OH)6, calcium hydronitroaluminate ЗСаО∙А12О3∙Са (NO3)2∙10Н2О and calcium hydroxylapatite Са10(РО4)6(ОН)2 crystals versus salt-electrolyte, i.e. Na2SO4, NaNO3 and Na3PO4 agreeably. The 28 day compressive strength of modified AASC fine concrete is not less than the reference one (48.0 - 56.0 МPа).

scholarly journals The influence of different parameters on the hydration process of binders based on alkali activated slag

2005 ◽  
Vol 70 (1) ◽  
pp. 97-105 ◽  
Author(s):  
Darko Krzan ◽  
Miroslav Komljenovic ◽  
Branislav Zivanovic
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Water Glass ◽  
Sodium Metasilicate ◽  
Hydration Process ◽  
Activator Concentration ◽  
Alkali Activated Slag ◽  
Activated Slag ◽  
Alkali Activated

The influence of certain types of activators (water glass Na2O.nSiO2 and sodium-metasilicate Na2SiO3.5H2O) on the hydration process of alkali activated slag was investigated in this study. The influence of activator concentration, specific surface area of the slag and the modulus n of the water glass (mass ratio between SiO2 and Na2O) on the kinetics of the hydration process i.e., the change of compressive strength were also investigated. Poorly crystallized low base calcium silicate hydrate C-S-H (I) is the main hydration product of alkali activated slag regardless of the activator used. This is the reason for the rapid increase in the strength of alkali activated slag and also of the very high strength values. The strength growth rate and strength values were significantly higher when sodium-metasilicate was used as the activator than when water glass was used. The specific surface area of the slag and the activator concentration are parameters which have a closely connected influence on strength and their action is cumulative. The modulus n of water glass does not have an explicit influence on the strength of alkali activated slag.

Effect of Dosage and Modulus of Water Glass on AC Impedance Properties of Alkali-Activated Slag Cement Mortar

2013 ◽  
Vol 423-426 ◽  
pp. 1018-1026
Author(s):  
Fu Qiang He ◽  
Xiao Peng An
Keyword(s):  
Compressive Strength ◽  
Water Glass ◽  
Cement Mortar ◽  
Ac Impedance ◽  
Slag Cement ◽  
Bulk Resistance ◽  
Alkali Activated Slag ◽  
Activated Slag ◽  
Alkali Activated

Compressive strength and AC impedance of mortar made with water-glass-activated slag were investigated as a dependence of modulus (0.5-2.0) and dosage (2-6%) of the water-glass. Results shown that when the dosage of water glass is 2- 4 %, the modulus of the water glass has a little effect on the compressive strength. In the case of the dosage of water glass is beyond 4 %, when modulus of the water glass change from 0.5-1.0, the compressive strength obviously increases with increase of modulus of water glass and when modulus of the water glass change from 1.0-2.0, the modulus of the water glass has a little effect on the compressive strength. The strength increases with increase of the dosage from 2 to 6%. In the case same dosage and modulus, there is a rather good power correlation between the bulk resistance and the activated age. With increase of the dosage, the bulk resistance significantly decreases when the dosage is below 4%. The decreasing degree is small when the dosage is beyond 4%. The decreasing degree derived from the dosage increases with the activated age. The effect of the modulus on the bulk resistance depends on range of the dosage. However, it can be regarded that when the dosage is 4% and 6%, the modulus has small effect on the bulk resistance in the case of all the dosages.

Design of Low Carbon Footprint Alkali Activated Slag Cement Concretes for Marine Engineering Application in China

2014 ◽  
Vol 525 ◽  
pp. 556-563
Author(s):  
Hai Lin Cao ◽  
Pavel V. Krivenko ◽  
Lu Qian Weng ◽  
Yue Guo ◽  
O.N. Petropavlovsky ◽  
...  
Keyword(s):  
Engineering Application ◽  
Steel Reinforcement ◽  
Low Carbon ◽  
Slag Cement ◽  
Alkali Activated Slag ◽  
Marine Engineering ◽  
Weather Resistance ◽  
Activated Slag ◽  
Reinforcement Bar ◽  
Alkali Activated

The paper covers the results of studies of the alkali activated slag cement concretes from the cements prepared under all-in-one technology to meet the requirements for concretes for marine engineering application. The compressive strength, weather resistance, biodegradability, bonding strength with steel reinforcement bar, steel reinforcement bar protection, chlorine ions diffusion parameters and resistance to corrosive exposure of 5% Na2SO4 solution were tested, which exhibit that alkali activated slag cement and concretes are very suitable for marine engineering applications.

FT-IR Study on Early-Age Hydration of Alkali-Activated Slag Cement

2011 ◽  
Vol 492 ◽  
pp. 429-432 ◽  
Author(s):  
Yong Hao Fang ◽  
Zheng Long Lu ◽  
Zhong Li Wang
Keyword(s):  
Water Glass ◽  
Glass Network ◽  
Early Age ◽  
Slag Cement ◽  
Alkali Activated Slag ◽  
Slag Powder ◽  
Ft Ir ◽  
Activated Slag ◽  
Ir Study ◽  
Alkali Activated

The hydration process of alkali-activated slag cement, especially at early-age, was studied by FT-IR, compared with that of Portland cement. The results show that during the hydration of alkali activated slag cement, two processes have taken place, the dissolution of Al3+ from the slag and then the recombination of Al3+ ions with the silicate anions. The former associated with the break of the glass network of slag and the later with the re-polymerization of the silicate and aluminosilicate anions. The rate of break of the glass network increases with the dosage of water glass, which completed in 24 h when the dosage of the water glass solution equivalent to Na2O exceeds 6% of the slag powder. It is confirmed by the IR study that Ca(OH)2 is absent in the hardened alkali activated slag cement paste.

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