Roughness of fracture surfaces and compressive strength of hydrated cement pastes

2010 ◽  
Vol 40 (6) ◽  
pp. 947-955 ◽  
Author(s):  
Tomáš Ficker ◽  
Dalibor Martišek ◽  
Hamlin M. Jennings
Keyword(s):  
Compressive Strength ◽  
Hydrated Cement ◽  
Cement Pastes ◽  
Fracture Surfaces

scholarly journals Surface Roughness and Porosity of Hydrated Cement Pastes

10.14311/1374 ◽  
2011 ◽  
Vol 51 (3) ◽  
Author(s):  
T. Ficker ◽  
D. Martišek ◽  
H. M. Jennings
Keyword(s):  
The Other ◽  
Porous Solids ◽  
Surface Irregularity ◽  
Hydrated Cement ◽  
Cement Pastes ◽  
Cement Ratio ◽  
Fracture Surfaces ◽  
Water To Cement Ratio ◽  
The One ◽  
Highly Porous

. Seventy-eight graphs were plotted to describe and analyze the dependences of the height and roughness irregularities on the water-to-cement ratio and on the porosity of the cement hydrates. The results showed unambiguously that the water-to-cement ratio or equivalently the porosity of the specimens has a decisive influence on the irregularities of the fracture surfaces of this material. The experimental results indicated the possibility that the porosity or the value of the water-to-cement ratio might be inferred from the height irregularities of the fracture surfaces. It was hypothesized that there may be a similarly strong correlation between porosity and surface irregularity, on the one hand, and some other highly porous solids, on the other, and thus the same possibility to infer porosity from the surfaces of their fracture remnants.

Microstructure and Porosity of Metakaolin Blended Cements

1988 ◽  
Vol 136 ◽  
Author(s):  
P. Bredy ◽  
M. Chabannet ◽  
J. Pera
Keyword(s):  
Compressive Strength ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Hydrated Cement ◽  
Cement Pastes ◽  
Blended Cements ◽  
Mercury Intrusion ◽  
Pozzolanic Cement

ABSTRACTFive compositions with 10% to 50% metakaolin for cement substitution were studied. The rate of hydration was studied from the compressive strength after up to 6 months of curing and from the hydrates formed (DTA-XRD). The metakaolin addition considerably reduced portlandite content in the hydrated cement and contributed to the formation of hydrated gehlenite which is not present in OPC paste. The microstructure study (SEM) shows that pozzolanic cement pastes were less crystallized than plain pastes. Mercury intrusion was used to measure porosity of hydrated cement pastes. The porosity with blended cements was higher than that with OPC, except for 10 and 20% metakaolin substitution. Evolution of the pore size distribution was studied: the pozzolanic pastes enhance small diameters.

Microstructure and Porosity of Metakaolin Blended Cements

1988 ◽  
Vol 137 ◽  
Author(s):  
P. Bredy ◽  
M. Chabannet ◽  
J. Pera
Keyword(s):  
Compressive Strength ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Hydrated Cement ◽  
Cement Pastes ◽  
Blended Cements ◽  
Mercury Intrusion ◽  
Pozzolanic Cement

AbstractFive compositions with 10% to 50% metakaolin for cement substitution were studied. The rate of hydration was studied from the compressive strength after up to 6 months of curing and from the hydrates formed (DTA-XRD). The metakaolin addition considerably reduced portlandite content in the hydrated cement and contributed to the formation of hydrated gehlenite which is not present in OPC paste. The microstructure study (SEM) shows that pozzolanic cement pastes were less crystallized than plain pastes. Mercury intrusion was used to measure porosity of hydrated cement pastes. The porosity with blended cements was higher than that with OPC, except for 10 and 20% metakaolin substitution. Evolution of the pore size distribution was studied: the pozzolanic pastes enhance small diameters.

scholarly journals Effect of Calcium Nitrate on the Properties of Portland–Limestone Cement-Based Concrete Cured at Low Temperature

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1611
Author(s):  
Gintautas Skripkiūnas ◽  
Asta Kičaitė ◽  
Harald Justnes ◽  
Ina Pundienė
Keyword(s):  
Compressive Strength ◽  
Cement Paste ◽  
Setting Time ◽  
Calcium Nitrate ◽  
Curing Temperature ◽  
Hardened Concrete ◽  
Cement Pastes ◽  
Initial Setting Time ◽  
Initial Setting ◽  
Early Strength

The effect of calcium nitrate (CN) dosages from 0 to 3% (of cement mass) on the properties of fresh cement paste rheology and hardening processes and on the strength of hardened concrete with two types of limestone-blended composite cements (CEM II A-LL 42.5 R and 42.5 N) at different initial (two-day) curing temperatures (−10 °C to +20 °C) is presented. The rheology results showed that a CN dosage up to 1.5% works as a plasticizing admixture, while higher amounts demonstrate the effect of increasing viscosity. At higher CN content, the viscosity growth in normal early strength (N type) cement pastes is much slower than in high early strength (R type) cement pastes. For both cement-type pastes, shortening the initial and final setting times is more effective when using 3% at +5 °C and 0 °C. At these temperatures, the use of 3% CN reduces the initial setting time for high early strength paste by 7.4 and 5.4 times and for normal early strength cement paste by 3.5 and 3.4 times when compared to a CN-free cement paste. The most efficient use of CN is achieved at −5 °C for compressive strength enlargement; a 1% CN dosage ensures the compressive strength of samples at a −5 °C initial curing temperature, with high early strength cement exceeding 3.5 MPa but being less than the required 3.5 MPa in samples with normal early strength cement.

Calorimetry, rheology and compressive strength of superplasticized cement pastes

1993 ◽  
Vol 23 (4) ◽  
pp. 939-950 ◽  
Author(s):  
M.-A. Simard ◽  
P.-C. Nkinamubanzi ◽  
C. Jolicoeur ◽  
D. Perraton ◽  
P.-C. Aïtcin
Keyword(s):  
Compressive Strength ◽  
Cement Pastes

Recycling of hydrated cement pastes by synthesis of α′H-C2S

2017 ◽  
Vol 100 ◽  
pp. 398-412 ◽  
Author(s):  
Ricardo Serpell ◽  
Franco Zunino
Keyword(s):  
Hydrated Cement ◽  
Cement Pastes

scholarly journals Hydration study of mechanically activated mixtures of Portland cement and fly ash

2007 ◽  
Vol 72 (6) ◽  
pp. 591-604 ◽  
Author(s):  
Gordana Stefanovic ◽  
Ljubica Cojbasic ◽  
Zivko Sekulic ◽  
Srdjan Matijasevic
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Portland Cement ◽  
Mechanical Activation ◽  
Early Period ◽  
Negative Effects ◽  
Early Hydration ◽  
Cement Pastes ◽  
Dta And Tg ◽  
Low Activity

Fly ash (FA) can be used in cement mixtures with certain limitations. The problem of the mentioned mixtures lies in the insufficient activity of the particles of FA in the reactions which are important for the establishment of the mechanical characteristics of cement. This is particularly true for the hydration reactions. As a result of this, cement pastes formed by mixing ash and clinker have worse characteristics compared to those of pure Portland cement (PC), especially in the early period of setting. As is well known, FA can be a good solution for the neutralization of the negative effects generated due to the creation of free Ca(OH)2 during the hydration of PC, provided that the problems with the low activity of FAare overcome. For the experiments in this study, a mixture of Portland cement and fly ash was used, the content of ash in the mixture being 30 % and 50 %. Mechanical activation was performed in a vibrating ring mill. The goal of this study was to demonstrate, through experimental results, that during the mechanical activation of a PC and FA mixture, the components in the mixture which mostly affect the direction, rate and range of hydration reactions occurring in the mixture had been activated. The values of the compressive strength of the activated and non-activated mixtures and the changes of their specific surface area proved that during the grinding process, the mixture PC+FA had been mechanically activated. The highest increase of compressive strength was achieved in the early period of setting, which indicates an improvement in the early hydration of the mixture. XRD, DTA and TG analyses showed that the alite (C3S) and belite (C2S) from the PC and a part of the fly ash were activated. .

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