scholarly journals Review of Carbonation Resistance in Hydrated Cement Based Materials

2019 ◽  
Vol 2019 ◽  
pp. 1-6 ◽  
Author(s):  
Joseph Mwiti Marangu ◽  
Joseph Karanja Thiong’o ◽  
Jackson Muthengia Wachira
Keyword(s):  
Environmental Benefits ◽  
Partial Substitution ◽  
Cement Matrix ◽  
Hardened Cement ◽  
Hydrated Cement ◽  
Blended Cements ◽  
Carbonation Process ◽  
Carbonation Resistance ◽  
Cement Based Materials ◽  
Process Factors

Blended cements are preferred to Ordinary Portland Cement (OPC) in construction industry due to costs and technological and environmental benefits associated with them. Prevalence of significant quantities of carbon dioxide (CO2) in the atmosphere due to increased industrial emission is deleterious to hydrated cement materials due to carbonation. Recent research has shown that blended cements are more susceptible to degradation due to carbonation than OPC. The ingress of CO2 within the porous mortar matrix is a diffusion controlled process. Subsequent chemical reaction between CO2 and cement hydration products (mostly calcium hydroxide [CH] and calcium silicate hydrate [CSH]) results in degradation of cement based materials. CH offers the buffering capacity against carbonation in hydrated cements. Partial substitution of OPC with pozzolanic materials however decreases the amount of CH in hydrated blended cements. Therefore, low amounts of CH in hydrated blended cements make them more susceptible to degradation as a result of carbonation compared to OPC. The magnitude of carbonation affects the service life of cement based structures significantly. It is therefore apparent that sufficient attention is given to carbonation process in order to ensure resilient cementitious structures. In this paper, an indepth review of the recent advances on carbonation process, factors affecting carbonation resistance, and the effects of carbonation on hardened cement materials have been discussed. In conclusion, carbonation process is influenced by internal and external factors, and it has also been found to have both beneficial and deleterious effects on hardened cement matrix.

Elucidation of block boundaries as the dissolution channels in hydrated cement

1978 ◽  
Vol 36 (1) ◽  
pp. 484-485
Author(s):  
N.V. Belov ◽  
U.I. Papiashwili ◽  
B.E. Yudovich
Keyword(s):  
Liquid Phase ◽  
Grain Boundaries ◽  
Benzoyl Peroxide ◽  
Phase Contrast ◽  
Active Role ◽  
Point Of View ◽  
Hardened Cement ◽  
Hydrated Cement ◽  
Hardened Cement Paste

It has been almost universally adopted that dissolution of solids proceeds with development of uniform, continuous frontiers of reaction.However this point of view is doubtful / 1 /. E.g. we have proved the active role of the block (grain) boundaries in the main phases of cement, these boundaries being the areas of hydrate phases' nucleation / 2 /. It has brought to the supposition that the dissolution frontier of cement particles in water is discrete. It seems also probable that the dissolution proceeds through the channels, which serve both for the liquid phase movement and for the drainage of the incongruant solution products. These channels can be appeared along the block boundaries.In order to demonsrate it, we have offered the method of phase-contrast impregnation of the hardened cement paste with the solution of methyl metacrylahe and benzoyl peroxide. The viscosity of this solution is equal to that of water.

Research on Properties of Low Grade Cement-Based Composite Materials Modified by Silica Fume

2012 ◽  
Vol 174-177 ◽  
pp. 751-756
Author(s):  
Zi Fang Xu ◽  
Ming Xu Zhang ◽  
Jin Hua Li
Keyword(s):  
Silica Fume ◽  
Mechanical Performance ◽  
Raw Materials ◽  
Cement Matrix ◽  
Hardened Cement ◽  
Low Grade ◽  
X Ray ◽  
Matrix Microstructure ◽  
Nano Powder ◽  
Strength And Durability

In order to notably improve the mechanical properties and durability of low-grade cement-based material, superfine silica fume was used to modify the cement-based composite based on special perfomance and effects of nano powder. The mechanical performance and durability were investigated.Then the phase compositions,microstructure and morphologies of as-received cement-based composite were studied by X-ray Diffractometer、TGA-DTA and SEM. The results show that： the best formula of raw materials is 1:1:0.025:0.015, and hydration can be accelerated and increasing of hydration products is observed after modification. In the hardened cement matrix, microstructure is very compacted and C-S-H gel forms densed structure, so the structure defect is notably reduced. This means that both strength and durability of cement-based composite are notably improved by the addition of superfine silica fume.

A feasibility study of municipal solid waste incineration fly ash utilisation in Estonia

2017 ◽  
Vol 35 (9) ◽  
pp. 904-912 ◽  
Author(s):  
Hakan Berber ◽  
Ruedi Frey ◽  
Viktoria Voronova ◽  
Arina Koroljova
Keyword(s):  
Environmental Management ◽  
Fly Ash ◽  
Municipal Solid Waste ◽  
Solid Waste ◽  
Feasibility Study ◽  
Current Situation ◽  
Environmental Benefits ◽  
Management Options ◽  
Carbonation Process ◽  
Msw Incineration

The purpose of this paper is to discuss the alternative environmental management options for the utilisation of municipal solid waste (MSW) incineration fly ash (FA), which is generated at Iru Power Plant where MSW is incinerated in Estonia. To determine sustainable and economically feasible environmental management options for MSW incineration FA in Estonia, CO2 sequestration with a further carbonation process was examined. A partial Cost & Benefit Analysis has been conducted to compare the carbonation process to the current situation. Two carbonation options were developed. Option 1 is to use carbonated FA in any other processes based on the waste-to-product principle. Option 2 is to send carbonated FA to the non-hazardous landfill in Tallinn, Estonia. Important parameters, such as Net Present Value (NPV), Internal Rate of Return (IRR), Benefit–Cost Ratio (BCR) and Break Even Point (BEP), have been calculated for carbonation options and the current case. In addition, a sensitivity analysis has been conducted to examine its robustness. The results showed that the best option is carbonation Option 1 with NPV of 9,209,662 EUR, IRR of 43%, BCR of 2.63 and BEP between 2018 and 2019. Both Options 1 and 2 constitute more sustainable and environmentally friendly management options compared to the current situation. It can be concluded that this preliminary feasibility study showed that running a carbonation plant may be profitable and sustainable for Estonia. Currently, there is no treatment technology for MSW incineration FA in Estonia and FA is sent to a neighbouring country for further utilisation. This is the first study to demonstrate FA management options with economic and environmental benefits.

Influence of Cementitious Capillary Crystalline Waterproofing Material on the Water Impermeability and Microstructure of Concrete

2019 ◽  
Vol 953 ◽  
pp. 209-214
Author(s):  
Yi Teng Zhang ◽  
Lian Zuo ◽  
Jin Chao Yang ◽  
Wei Xia Zhao ◽  
Xiang Xiong Zeng
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Differential Scanning Calorimetry ◽  
Cement Matrix ◽  
Hardened Cement ◽  
Hydration Products ◽  
Hardened Cement Paste ◽  
Scanning Calorimetry ◽  
Chinese Standard ◽  
Scanning Electron

The main objective of this study is to investigate the effect of cementitious capillary crystalline waterproofing (CCCW) material on the water impermeability and microstructure of concrete. The water impermeability of concrete covered with or without CCCW material was tested according to the Chinese standard GB 18445-2012. The results indicate that concretes coated with CCCW material showed much higher water impermeability than blank ones, and the ratio of water impermeability pressure between them reached 275. The samples obtained in various depths of hardened cement paste specimens with or without CCCW coating were analyzed through scanning electron microscopy (SEM) and thermogravimetry-differential scanning calorimetry (TG-DSC), to study the differences in microstructure and hydration products. The results present that after a 28-day standard curing, there were lots of ettringite crystals and CaCO3 formed in the paste in 1 cm from the coating, but the action depth of the CCCW coating could not reach 3 cm. The ettringite and CaCO3 is precipitated in the pore structure of cement matrix and filling the voids, which leads to the significant enhancement in water impermeability.

scholarly journals Cement-based materials destruction under the action of deicing salts

2019 ◽  
Vol 298 ◽  
pp. 00053 ◽  
Author(s):  
Ekaterina Potapova ◽  
Ivan Korchunov
Keyword(s):  
Aqueous Solution ◽  
Pore Solution ◽  
Colorimetric Method ◽  
Chloride Ions ◽  
Cement Matrix ◽  
Chloride Solutions ◽  
Deicing Salts ◽  
Cement Based Materials ◽  
Destructive Processes

The results of chloride ions with aqueous solution penetrating into the cement structure were determined with the colorimetric method. Some tendencies of chloride solutions migration in different conditions were established. The article suggests the possible ways of the prevention of destructive processes occur during the excessive pore solution saturation in cement matrix with chloride ions.

Einfluss der elektrochemischen Doppelschicht auf die Sorption und den Transport von Chlorionen im Zementstein / Influence of the electrochemical double layer on sorption and transport of chlorides in hardened cement paste

2000 ◽  
Vol 6 (4) ◽  
pp. 415-428
Author(s):  
O. Wowra ◽  
M.J. Setzer
Keyword(s):  
Double Layer ◽  
Cement Paste ◽  
Building Materials ◽  
Pore Solution ◽  
Chloride Ions ◽  
Transport Processes ◽  
Cement Matrix ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
Electrochemical Double Layer

Abstract Besides the formation of Friedel salt the transport and binding of chlorides in concrete is mainly defined by the electrochemical double layer at the interface between cement matrix and pore solution. Due to the alkaline pore solution the surface of hardened cement paste is negatively charged which may change to positive values by the potential regulating calcium ions. Inverting of the surface charge leads to an attraction of anions and therefore, to an adsorption of chloride ions in the diffuse part of the electrochemical double layer. Influence from outside like sulphates and carbon dioxide may lead to a decomposition of Friedel salt. Apart from these effect temperature, pH-value and certain environmental conditions affects the electrochemical double layer as well. The chloride equilibrium is mainly controlled by adsorbed ions in the electrochemical double layer. The model presented here is relevant for the assessment of ion transport processes in mineral building materials. Continuing investigations may lead to optimize transport models and a better evaluation of the critical chloride threshold value in reinforced concrete.

Influence of the partial substitution of fine aggregate by granite powder in mortar on the process of natural carbonation

2019 ◽  
Vol 38 (3) ◽  
pp. 254-262 ◽  
Author(s):  
Júlio Lopes da Silva ◽  
Daniel Baracuy da Cunha Campos ◽  
Alberto Casado Lordsleem ◽  
Yeda Vieira Povoas
Keyword(s):  
Particle Size ◽  
Exposure Time ◽  
Time Variable ◽  
Partial Substitution ◽  
Fine Aggregate ◽  
Carbonation Depth ◽  
Experimental Planning ◽  
Carbonation Process ◽  
Granite Powder ◽  
Natural Carbonation

This article presents an evaluation of the influence on the natural carbonation process of the use of granite cutting residue as a replacement for fine aggregate in mortars. The methodology adopted consisted of replacing the fine aggregate with granite cutting residue, analysing the carbonation depth with the aid of an experimental planning matrix of 23 + 3 repetitions at the central point. The influence of the exposure time, the percentage of residue in the mixture, and the particle size of the residue used were evaluated. The exposure time variable was found to have the greatest influence on the carbonation process. Under the conditions analysed, granite residue was found to be beneficial, reducing the carbonation depth.

Sign in / Sign up

Export Citation Format

Share Document