scholarly journals Parameter Study of Superabsorbent Polymers (SAPs) for Use in Durable Concrete Structures

Materials ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1541 ◽  
Author(s):  
Laurence De Meyst ◽  
Els Mannekens ◽  
Maria Araújo ◽  
Didier Snoeck ◽  
Kim Van Tittelboom ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Cement Hydration ◽  
Setting Time ◽  
Concrete Structures ◽  
Parameter Study ◽  
Particle Sizes ◽  
Hydration Kinetics ◽  
Superabsorbent Polymers ◽  
Swelling Capacity ◽  
Cross Linker

Superabsorbent polymers (SAPs) can be added to a concrete mixture to provide internal curing and reduce the risk for early-age shrinkage cracking. Hence, they can help to increase the overall durability of concrete structures. The type, swelling characteristics, kinetics of water release, amount and particle size of the SAPs will dictate their effectiveness for this purpose. In this paper, SAPs with different cross-linking degrees, particle sizes and amount of solubles are investigated. By varying these parameters, insight can be gained on the influence of each of these parameters on SAP properties such as the swelling capacity. In a next step, the SAPs can be implemented in mortar to assess their influence on mortar properties like workability, compressive strength or hydration kinetics. Based on these results, the ‘ideal’ SAP with tunable properties for a specific concrete application can be selected. For this purpose, an anionic SAP was synthesized with varying amounts of cross-linker and ground to particle sizes with d50 varying between 10 and 100 µm. The swelling capacity in demineralised water of 40 µm SAP particles increased with a decreasing degree of cross-linker from 66 g/g SAP with 1 mol% cross-linker to 270 g/g SAP in case of 0.15 mol% cross-linker, and was about three to four times larger than the swelling capacity in the prepared cement filtrate. The SAPs were tested for their effect on mortar workability, cement hydration kinetics and mechanical properties of the hardened mortar. With proper compensation for the absorbed water by the SAPs, the mortar workability was not negatively affected and the reduction in flow over the first two hours remained limited. The SAPs with the lowest swelling capacity, resulting in the smallest total amount of macro pores formed, showed the smallest negative effect on mortar compressive strength (a reduction of 23% compared to the reference after 28 days for an addition of 0.5 m% SAP) and a negligible effect on cement hydration. The difference in strength with the reference decreased as a function of mortar age. When using SAPs with particle sizes in the range of 10–100 µm, no significant differences between the studied particle sizes were found concerning the mortar properties. With the ease of upscaling in mind, the need to purify the SAPs and to remove the non-cross-linked soluble fraction was further investigated. It was shown that the solubles had no effect on the mortar properties, except for increasing the setting time with almost 100%.

scholarly journals Effect of Morphologically Controlled Hematite Nanoparticles on the Properties of Fly Ash Blended Cement

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 1003
Author(s):  
Pantharee Kongsat ◽  
Sakprayut Sinthupinyo ◽  
Edgar A. O’Rear ◽  
Thirawudh Pongprayoon
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Size Distribution ◽  
Cement Hydration ◽  
Blended Cement ◽  
Spherical Shape ◽  
Particle Sizes ◽  
Fe2o3 Nanoparticles ◽  
Structure And Properties ◽  
Hematite Nanoparticles

Several types of hematite nanoparticles (α-Fe2O3) have been investigated for their effects on the structure and properties of fly ash (FA) blended cement. All synthesized nanoparticles were found to be of spherical shape, but of different particle sizes ranging from 10 to 195 nm depending on the surfactant used in their preparation. The cement hydration with time showed 1.0% α-Fe2O3 nanoparticles are effective accelerators for FA blended cement. Moreover, adding α-Fe2O3 nanoparticles in FA blended cement enhanced the compressive strength and workability of cement. Nanoparticle size and size distribution were important for optimal filling of various size of pores within the cement structure.

scholarly journals Cement-Based Renders Manufactured with Phase-Change Materials: Applications and Feasibility

2016 ◽  
Vol 2016 ◽  
pp. 1-6 ◽  
Author(s):  
Luigi Coppola ◽  
Denny Coffetti ◽  
Sergio Lorenzi
Keyword(s):  
Compressive Strength ◽  
Phase Change ◽  
Phase Change Materials ◽  
Residential Buildings ◽  
Setting Time ◽  
Drying Shrinkage ◽  
Hydration Kinetics ◽  
Mechanical Performances ◽  
Entrapped Air ◽  
Kinetics Of

The paper focuses on the evaluation of the rheological and mechanical performances of cement-based renders manufactured with phase-change materials (PCM) in form of microencapsulated paraffin for innovative and ecofriendly residential buildings. Specifically, cement-based renders were manufactured by incorporating different amount of paraffin microcapsules—ranging from 5% to 20% by weight with respect to binder. Specific mass, entrained or entrapped air, and setting time were evaluated on fresh mortars. Compressive strength was measured over time to evaluate the effect of the PCM addition on the hydration kinetics of cement. Drying shrinkage was also evaluated. Experimental results confirmed that the compressive strength decreases as the amount of PCM increases. Furthermore, the higher the PCM content, the higher the drying shrinkage. The results confirm the possibility of manufacturing cement-based renders containing up to 20% by weight of PCM microcapsules with respect to binder.

scholarly journals Evaluation of Strengths from Cement Hydration and Slag Reaction of Mortars Containing High Volume of Ground River Sand and GGBF Slag

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Punnaman Norrarat ◽  
Weerachart Tangchirapat ◽  
Smith Songpiriyakij ◽  
Chai Jaturapitakkul
Keyword(s):  
Particle Size ◽  
Compressive Strength ◽  
Cement Hydration ◽  
High Volume ◽  
Inert Material ◽  
Early Age ◽  
Particle Sizes ◽  
River Sand ◽  
Reactive Material ◽  
Median Particle

This paper investigates the cement hydration, and the slag reaction contributes to the compressive strengths of mortars mixed with ground river sand (GRS) and ground-granulated blast furnace (GGBF) slag with different particle sizes. GRS (inert material) and GGBF slag (reactive material) were ground separately until the median particle sizes of 32 ± 1, 18 ± 1, and 5 ± 1 micron and used to replace Portland cement (PC) in large amount (40–60%) by weight of the binder. The results showed that, at the early age, the compressive strength obtained from the cement hydration was higher than that obtained from the slag reaction. The results of compressive strength also indicated that the GGBF slag content and particle size play important roles in the slag reaction at the later ages, whereas cement hydration is more prominent at the early ages. Although the results could be expected from the use of GGBF slag to replace PC in mortar or concrete, this study had presented the values of the compressive strength along with ages and the finenesses of GGBF slag that contributed from cement hydration and from GGBF slag reaction.

scholarly journals The Influence of Superabsorbent Polymers and Nanosilica on the Hydration Process and Microstructure of Cementitious Mixtures

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5194
Author(s):  
Gerlinde Lefever ◽  
Dimitrios G. Aggelis ◽  
Nele De Belie ◽  
Marc Raes ◽  
Tom Hauffman ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Isothermal Calorimetry ◽  
Autogenous Shrinkage ◽  
Hydration Process ◽  
Microstructural Development ◽  
Self Healing ◽  
Hydration Kinetics ◽  
Superabsorbent Polymers ◽  
Water To Cement Ratio ◽  
Supplementary Material

Superabsorbent polymers (SAPs) are known to mitigate the development of autogenous shrinkage in cementitious mixtures with a low water-to-cement ratio. Moreover, the addition of SAPs promotes the self-healing ability of cracks. A drawback of using SAPs lies in the formation of macropores when the polymers release their absorbed water, leading to a reduction of the mechanical properties. Therefore, a supplementary material was introduced together with SAPs, being nanosilica, in order to obtain an identical compressive strength with respect to the reference material without additives. The exact cause of the similar compressive behaviour lies in the modification of the hydration process and subsequent microstructural development by both SAPs and nanosilica. Within the present study, the effect of SAPs and nanosilica on the hydration progress and the hardened properties is assessed. By means of isothermal calorimetry, the hydration kinetics were monitored. Subsequently, the quantity of hydration products formed was determined by thermogravimetric analysis and scanning electron microscopy, revealing an increased amount of hydrates for both SAP and nanosilica blends. An assessment of the pore size distribution was made using mercury intrusion porosimetry and demonstrated the increased porosity for SAP mixtures. A correlation between microstructure and the compressive strength displayed its influence on the mechanical behaviour.

scholarly journals Effect of Cr6+ on the Properties of Alkali-Activated Slag Cement

2021 ◽  
Vol 8 ◽  
Author(s):  
Fu Bo ◽  
Cheng Zhenyun
Keyword(s):  
Compressive Strength ◽  
Setting Time ◽  
Cement Stone ◽  
Slag Cement ◽  
Hydration Kinetics ◽  
Alkali Activated Slag ◽  
Dual Beam ◽  
Press Method ◽  
Activated Slag ◽  
Alkali Activated

In order to investigate the effect of Cr6+ on the properties of alkali-activated slag cement (AAS), the effects of added dosage of Na2Cr2O4 on the setting time and compressive strength of AAS were measured. The leaching concentration of Cr6+ from AAS cement stone was measured using dual-beam UV-visible spectrophotometry. The effect of Na2Cr2O4 on the hydration kinetics of AAS cement was monitored by microcalorimetry and the corresponding kinetic parameters were analyzed. The pore solution from AAS was collected and analyzed using the high pressure press method. The effects of Na2Cr2O4 on the hydration products of AAS cement were observed and compared using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The experimental results showed that the AAS hydration process was markedly affected by Na2Cr2O4 dosage. The setting time of AAS pastes was increased and the compressive strength of cement stones was reduced with increasing dosage of Na2Cr2O4. With the development of AAS hydration, the leaching concentration of Na2Cr2O4 gradually decreased. Na2Cr2O4 did not affect the dissolution of slag particles, but impeded the formation of C-S-H gel. The Cr6+ was immobilized chemically in the form of needle-like CaCrO4 particles formed by the chemical reaction between Na2Cr2O4 and Ca2+ leaching from the slag.

Effect of Anhydrite on the Early Hydration Performance of Rapid Setting and Hardening Belite Sulfoaluminate Cement

2017 ◽  
Vol 898 ◽  
pp. 1990-1995 ◽  
Author(s):  
Ming Zhang Lan ◽  
Bin Feng Xiang ◽  
Jian Feng Wang ◽  
Xu Dong Zhao ◽  
Xiao Ying Wang
Keyword(s):  
Compressive Strength ◽  
Setting Time ◽  
High Strength ◽  
Cement Clinker ◽  
Hydration Kinetics ◽  
Early Hydration ◽  
Free Lime ◽  
Calcium Sulfoaluminate ◽  
Setting Times ◽  
Rapid Setting

In order to investigate the early hydration behavior of rapid setting and hardening belite sulfoaluminate cements, the methods of X-ray Diffraction, Scanning Electron Microscope, Compressive Strength test and Setting Times test were used to identify and quantify the hydration kinetics and microstructure of this new-found cements in China. The results showed that the main mineral compositions of high belite sulfoaluminate cement clinker included calcium sulfoaluminate (4CaO·3Al2O3·CaSO4), belite (2CaO·SiO2), ferrite phase, free gypsum and free lime. It was found that not only the setting time and compressive strength but also the composition of hydration products were influenced by anhydrite to some extent. Meanwhile, a mass of AFt and AFm generated along with the hydration process at different ages, overlapped, crossed and penetrated through calcium silicate hydrate gel and aluminum oxide to form a relatively dense structure which could contribute to the high strength of cement.

Investigations on Degradable and Figuline Calcium Alkaline Phosphate Cements with Multimodal Particle Size Distribution

2011 ◽  
Vol 493-494 ◽  
pp. 355-360
Author(s):  
F. Dombrowski ◽  
R. Hoffmann ◽  
Ute Ploska ◽  
Heidi Marx ◽  
Georg Berger
Keyword(s):  
Particle Size ◽  
Compressive Strength ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Setting Time ◽  
Volume Ratio ◽  
Particle Sizes ◽  
Powder Mixtures ◽  
Setting Reaction ◽  
Tap Density

The paper presented here deals with rheological and hardening properties during the setting reaction, and density and compressive strength after the final setting of a figuline composite consisting of Ca2KNa(PO4)2and 2wt% medium gel strength gelatin. Compared to the composite with monomodal particle size distribution (d50=7.18µm; span=3.9) and its properties during and after setting reaction, the goal of this work is to increase the resulting product compressive strength by mixing different particle sizes in order to obtain bi- and trimodal distributions. For the bimodal powder mixtures the ratio in diameter (dcourse/dsmall) was chosen with 7/1 and volume ratio dcourse/dsmallwas 70/30%. For the trimodal powder mixtures the ratio in diameter (dcourse/dmedium/dsmall) was chosen with 70/7/1 and volume ratio dcourse/dmedium/dsmallwas set to 44/28/28%.After establishing an adequate crushing and sieving process the tap density and powder density of each fraction was determined. Subsequently, the different particle sizes were mixed and the densities and the Hausner ratio were determined again. The mixtures show an increase in both densities especially the tap density increased significantly. Rheological investigations show that the graphs of storage and loss moduli of the multimodal powder mixtures respectively are similar. The characteristic setting times show a slight decrease compared with the monomodal composite but not significantly different data. When comparing the resulting compressive strength of cylindrical samples, which were stored direct after reaching the initial setting time under physiological conditions, the studies illustrated in all cases for the multimodal mixtures a significant increase in compressive strength and a higher density.

scholarly journals The effects of seawater on the hydration, microstructure and strength development of Portland cement pastes incorporating colloidal silica

2019 ◽  
Vol 10 (8) ◽  
pp. 2627-2638 ◽  
Author(s):  
Pawel Sikora ◽  
Krzysztof Cendrowski ◽  
Mohamed Abd Elrahman ◽  
Sang-Yeop Chung ◽  
Ewa Mijowska ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Synergistic Effect ◽  
Portland Cement ◽  
Colloidal Silica ◽  
Cement Hydration ◽  
Pozzolanic Reaction ◽  
Strength Development ◽  
Hydration Kinetics ◽  
Cement Pastes ◽  
Noticeable Improvement

AbstractThis contribution investigates the effects of seawater and colloidal silica (NS) in the amounts of 1, 3 and 5 wt%, respectively, on the hydration, strength development and microstructural properties of Portland cement pastes. The data reveal that seawater has an accelerating effect on cement hydration and thus a significant contribution to early strength development was observed. The beneficial effect of seawater was reflected in an improvement in compressive strength for up to 14 days of hydration, while in the 28 days compressive strength values were comparable to that of cement pastes produced with demineralized water. The combination of seawater and NS significantly promotes cement hydration kinetics due to a synergistic effect, resulting in higher calcium hydroxide (CH) production. NS can thus react with the available CH through the pozzolanic reaction and produce more calcium silicate hydrate (C-S-H) gel. A noticeable improvement of strength development, as the result of the synergistic effect of NS and seawater, was therefore observed. In addition, mercury intrusion porosimetry (MIP) tests confirmed significant improvements in microstructure when NS and seawater were combined, resulting in the production of a more compact and dense hardened paste structure. The optimal amount of NS to be mixed with seawater, was found to be 3 wt% of cement.

scholarly journals Property Improvement of Cement Emulsified Asphalt Paste Modified by Graphene Oxide

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Yu-wei Ma ◽  
Hong-yan Zhao ◽  
Gang Li ◽  
Zhen-jun Wang ◽  
Hua Tang ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Graphene Oxide ◽  
Flexural Strength ◽  
Building Material ◽  
Cement Hydration ◽  
Setting Time ◽  
Hydration Products ◽  
Hummers Method ◽  
The Stability ◽  
Emulsified Asphalt

Cement emulsified asphalt paste (CEAP) is widely used as a construction and building material by combining the advantages of cement rigidity and asphalt flexibility. However, the properties of CEAP can be evidently reduced due to the addition of emulsified asphalt. In this work, graphene oxide (GO) was prepared by the Hummers method and was innovatively used to improve the workability and strength of CEAP. The viscosity of CEAP was tested by Brookfield viscometer. In addition, the effects of GO on the setting time of CEAP were studied. The adsorption between cement and asphalt with GO was tested through an ultraviolet-visible spectrophotometer and the stability of CEAP was tested by zeta potentiometer. The effects of GO on the strength of CEAP were studied. The reinforcement effects of GO on CEAP were analyzed. The results show that the viscosity of CEAP and cement hydration products can increase after adding a reasonable dosage of GO to CEAP. The setting time of CEAP first decreases and then increases with the increase of GO dosage. The adsorption and viscosity of cement and asphalt increase with the increase of GO dosage. GO can reduce CEAP stability and make the paste easier to agglomerate. The flexural strength and the compressive strength of CEAP at 28 curing days first increase and then decrease with the increase of GO dosage, but excessive GO can hinder cement hydration. The reasonable dosage of GO in CEAP can be determined as 0.06% in asphalt weight.

scholarly journals Influence of component fineness on hydration and strength development in ternary slag-limestone cements

2019 ◽  
Vol 4 ◽  
pp. 81-88 ◽  
Author(s):  
Samuel Adu-Amankwah ◽  
Susan A Bernal Lopez ◽  
Leon Black
Keyword(s):  
Compressive Strength ◽  
Setting Time ◽  
Cementitious Materials ◽  
Particle Packing ◽  
Simultaneous Optimization ◽  
Strength Development ◽  
Heat Of Reaction ◽  
Hydration Kinetics ◽  
Compressive Strength Development ◽  
Furnace Slag

The quest for sustainable alternatives to Portland cement has led to the exploration of a range of materials or their combinations, often with the aim of exploiting synergies in reactions or particle packing to maximize performance. Simultaneous optimization of both presents a viable option to increase the efficiency of cementitious materials. The objective of this study was to evaluate the effect of varying the fineness of the constituents in ternary blends of CEM I – granulated ground blast furnace slag (GGBS) - limestone on hydration kinetics and strength development. Eight (8) ternary cement mixes were tested at 0.5 water/binder (w/b) ratio. Hydration was followed by isothermal conduction calorimetry and setting time. In addition, X-ray powder diffraction, thermogravimetric analysis and compressive strength development up to 180 days of curing were assessed. The efficiency associated with changing the fineness of each component was evaluated in terms of the net heat of reaction and compressive strength. The results show that fine CEM I is critical for hydration at early age, and this is reflected in the compressive strength accordingly. The benefits associated with finer GGBS and similarly limestone depend on the fineness of the other constituents in the blend. Optimization of these should consider the inter-dependencies in terms of kinetics and microstructure development.

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