scholarly journals Comparison of influence of surfactants on thermokinetic characteristics of alkali-activated slag cement

2021 ◽  
Vol 6 (6 (114)) ◽  
pp. 39-48
Author(s):  
Pavlo Krivenko ◽  
Igor Rudenko ◽  
Oleksandr Konstantynovskyi
Keyword(s):  
Molecular Structure ◽  
Stressed State ◽  
Heat Release ◽  
Crack Resistance ◽  
Active Surface ◽  
Surface Active ◽  
Activated Slag ◽  
Thermally Stressed State ◽  
Alkali Activated ◽  
Active Substances

Increasing the durability of concrete and reinforced concrete structures according to the criterion of crack resistance is a relevant task of construction materials science. To solve this task, this paper proposes effective solutions for adjusting thermofinite characteristics of alkali-activated slag cement (ASC) by using surfactants of various chemical nature in order to control the thermally-stressed state of concrete based on it (ASC concrete). The method of calorimetry was applied to show that the problematic issue is to adjust the structure formation of ASC by anion-active surface-active substances based on complex polyesters. This is predetermined by the instability of the molecular structure of surfactants in the hydration environment of ASC due to the destruction of complex ester bonds as a result of alkaline hydrolysis. Thermokinetic analysis has demonstrated the effectiveness of using anion-active surfactants, which do not contain ester bonds, as regulators of crack resistance of ASC concrete. Simple polyesters and multi-atom alcohols provide the ability to adjust the duration of the induction period while ensuring the required completeness of ASC hydration within a time frame. The effectiveness of cation-active surface-active substances has been shown, which are characterized by the stability of the molecular structure in the hydration environment of ASC and an increased level of adsorbing capacity. The decrease in the effectiveness of surface-active substances has been shown, in terms of the effect on the heat release of ASC, in the following series: alkaline salt of carboxylic acid>salt of the quaternary ammonium compound>simple polyester> polyalcohol>complex polyester. The reported results are important in view of the possibility of effective adjustment of ASC heat release by influencing the structure formation of surfactant with a certain molecular arrangement in order to predictably reduce crack formation in a thermally-stressed state and a corresponding increase in the durability of structures

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 Thermal cracking resistance of stacking concrete blocks

2018 ◽  
Vol 245 ◽  
pp. 08005
Author(s):  
Albina Shaibakova ◽  
Kirill Semenov ◽  
Yurij Barabanshchikov
Keyword(s):  
Comparative Analysis ◽  
Stressed State ◽  
Crack Resistance ◽  
Concrete Structure ◽  
Concrete Block ◽  
Thermal Crack ◽  
Construction Period ◽  
Massive Concrete ◽  
Concrete Blocks ◽  
Thermally Stressed State

In massive concrete structures there is a danger of temperature cracks. One of the measures to get rid of these type of cracks is the breakdown of an array into concreting blocks. In this paper, we consider the provision of thermal crack resistance of a massive concrete structure during the construction period. A comparative analysis of the thermally stressed state of the structure erected by one and two blocks in height is carried out. The influence of the overlap intervals of the concrete block in the calculations of thermal crack resistance was evaluated. Thermal crack resistance is evaluated by the deformation criterion. The authors found that the breakdown of the concrete structure into concreting blocks reduces the elongation deformations by 37%. The results show that increasing the overlap interval of a concrete block more effectively ensures thermal crack resistance of the structure.

Modeling a Thermo-Stressed State of the Cast-in-Situ Low Carbon Footprint Alkali Activated Slag Cement Concrete Hardened under Hot Environment

2014 ◽  
Vol 525 ◽  
pp. 482-490
Author(s):  
Lu Qian Weng ◽  
Hai Lin Cao ◽  
Pavel V. Krivenko ◽  
Yue Guo ◽  
O.N. Petropavlovsky ◽  
...  
Keyword(s):  
Stressed State ◽  
Carbon Footprint ◽  
Low Carbon ◽  
Cement Concrete ◽  
Slag Cement ◽  
Alkali Activated Slag ◽  
Hot Environment ◽  
Activated Slag ◽  
Alkali Activated

Alkali activated slag cement concretes are low carbon footprint building mateirals, which can meet the requirements for sustainable development. The paper covers the results of modeling a thermo-stressed state of the cast-in-situ massive alkali activated slag cement concrete structure hardened under hot environment to meet the requirements for marine engineering application. The results show that alkali activated slag cement concretes have a substantially lower heat release than that of Portland, are suitable for cast-in-situ massive alkali activated slag cement concrete structure even under hot environment.

Performance evaluation of foaming agents in cellular concrete based on foamed alkali-activated slag

2017 ◽  
Vol 44 (11) ◽  
pp. 893-898 ◽  
Author(s):  
Azadeh Tarameshloo ◽  
Ebrahim Najafi Kani ◽  
Ali Allahverdi
Keyword(s):  
Molecular Structure ◽  
Compressive Strength ◽  
Hydration Product ◽  
Image Processing Technique ◽  
Lauryl Sulfate ◽  
Foaming Agents ◽  
Alkali Activated Slag ◽  
Activated Slag ◽  
Alkali Activated ◽  
Cellular Concrete

In this work, three different foaming agents were selected and their performance on density, compressive strength, pore structure, and molecular structure of alkali-activated blast furnace slag cellular concrete have been investigated. For this purpose, pre-formed foams based on sodium lauryl sulfate, protein-based foaming agent, and hydrogen peroxide were added to the alkali-activated slag paste with determined activator composition. After curing, density and compressive strength of cellular concretes were evaluated. Also, macroscopic pore size distribution was investigated by image processing technique for studying its relation with density and compressive strength. Results showed that with increasing the amount of foam, the density and the compressive strength decreased due to increases in both the number of pores per area and the pore average size. Samples containing protein-based foam showed higher mechanical strength, which could be due to its effect on the molecular structure of hydration product resulting in a stronger bond and hence higher compressive strength.

Effect of surface-active substances on the crack resistance of hard rock

1990 ◽  
Vol 26 (5) ◽  
pp. 411-414
Author(s):  
A. V. Starosel'skii ◽  
S. E. Chrikov ◽  
L. P. Shobolova ◽  
O. A. Édel'shtein
Keyword(s):  
Crack Resistance ◽  
Hard Rock ◽  
Surface Active ◽  
Active Substances ◽  
Effect Of Surface

scholarly journals The analysis of cracking risk by shrinkage restraint of an alkali-activated slag mortar

2020 ◽  
Vol 322 ◽  
pp. 01038
Author(s):  
Farah Rifai ◽  
Aveline Darquennes ◽  
Lavinia Stefan ◽  
Benoist Muzeau ◽  
Farid Benboudjema
Keyword(s):  
Tensile Strength ◽  
Heat Release ◽  
Risk Index ◽  
Thermal Strain ◽  
Basic Creep ◽  
Alkali Activated Slag ◽  
Activated Slag ◽  
Cracking Risk ◽  
Alkali Activated ◽  
Autogeneous Shrinkage

Alkali-activated slag (AAS) binders show in general larger autogeneous shrinkage strains than ordinary Portland cement (OPC) based binders. However, AAS can be a relevant alternative to OPC, if, for example low hydration heat release and fine pores, are required. This study proposes an evaluation of the advantage of using AAS materials in small-sized or massive structures with regard to cracking risk by autogeneous shrinkage and thermal strains. A cracking risk index is calculated; this risk is defined as the ratio between stress generated by full restraint and tensile strength. All required experimental data were investigated in an OPC and AAS mortar, these are: heat release, autogeneous shrinkage, Young’s modulus, tensile strength and basic creep evolutions. The material parameters of a rate-dependent model developed in 1D were then identified. Numerical simulations were then performed for different thicknesses in full-restraint conditions. These show that, as expected, basic creep is a very important material parameter to assess. Indeed, basic creep enables the significant reduction of the generated stresses. Besides, it is found that the more the structure is large (and sensitive to cracking by risk by thermal strain), the more the AAS material is becoming appropriate compared to the OPC material.

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