Microstructure of the interfacial zone between lightweight aggregate and cement paste

1990 ◽  
Vol 20 (4) ◽  
pp. 610-618 ◽  
Author(s):  
Min-Hong Zhang ◽  
Odd E. Gjørv
Keyword(s):  
Cement Paste ◽  
Lightweight Aggregate ◽  
Interfacial Zone

Water Absorbing and Releasing of Lightweight Aggregate and its Influence on Frost-Resistance of Combined Aggregate Concrete

2011 ◽  
Vol 217-218 ◽  
pp. 51-56 ◽  
Author(s):  
Li Xiong Gao ◽  
Li Juan Kong ◽  
Yong Ge
Keyword(s):  
Water Absorption ◽  
Cement Paste ◽  
Frost Resistance ◽  
Lightweight Aggregate ◽  
High Water ◽  
Interfacial Zone ◽  
Aggregate Concrete ◽  
High Water Absorption ◽  
Dense Shell ◽  
Curing Age

Water absorbing and releasing property of lightweight aggregate (LWA) in concrete and its influence on microstructure of interfacial zone as well as frost-resistance of combined aggregate prepared with different water absorption LWA and w/b ratios were investigated. The results show that, as for concrete with low w/b ratio, the 28d frost-resistance of concrete prepared with high water absorption LWA is worse, however with the increase of curing age, the 90d frost-resistance of concrete improves obviously, which is due to the water releasing of LWA that leads to the recovery of its air entraining effect as well as the densification and thicken of interfacial zone. So the LWA with moderate water absorption should be selected to prepare the low w/b ratio concrete. As for concrete with high w/b ratio, the frost-resistance of concrete prepared with low water absorption LWA is the best. This is account for the dense shell of ceramsite that could reduce the soakage from loose cement paste under frozen pressure.

Influence of Lightweight Aggregate on Durability of High Performance Concrete

2009 ◽  
Vol 405-406 ◽  
pp. 197-203
Author(s):  
Bao Sheng Zhang ◽  
Li Juan Kong ◽  
Yong Ge
Keyword(s):  
Pore Structure ◽  
Cement Paste ◽  
Frost Resistance ◽  
High Performance ◽  
High Performance Concrete ◽  
Bound Water ◽  
Lightweight Aggregate ◽  
Normal Weight ◽  
Lightweight Aggregate Concrete ◽  
Aggregate Concrete

High performance concrete (HPC) with a water/cement ratio (w/c) of 0.32 and different lightweight aggregate (LWA) contents (0%, 25%, 50%, 75%, 100%) were prepared, and the influence of LWA on concrete frost-resistance and impermeability at different ages were studied, as well as the hydration degree, hydrated product, pattern and pore structure of the paste around aggregate. The results show that, by replacing normal weight aggregate (NWA) with 50% and 100% volume contents of pre-wetted LWA respectively, the chemical bound water of the cement paste surrounding aggregate are increased 12.1% and 22.7% as compared to concrete mixed without LWA. And at 28 days, lightweight aggregate concrete has the highest Ca(OH)2 content, whereas the 90-day Ca(OH)2 content of normal weight concrete is the highest. This proves that, with the increase of LWA content in concrete, both of the internal curing effect of pre-wetted LWA and secondary hydration effect of fly ash (FA) are strengthened, this can also be verified by the SEM study. Furthermore, the pore structure of the cement paste around aggregate can be improved consequently. The performance of frost-resistance of HPC can be improved by mixing LWA, the 90 day-frost-resistance of lightweight aggregate concrete is about 2.5 times of that of concrete mixed without LWA. The influence of LWA on the impermeability of HPC is different from normal concrete. When LWA content is more than 50%, the HPC impermeability decreased obviously, however at later age the difference between them becomes minor.

scholarly journals Effect of Carbon Nanofiber Clustering on the Micromechanical Properties of a Cement Paste

Nanomaterials ◽  
2022 ◽  
Vol 12 (2) ◽  
pp. 223
Author(s):  
Lesa Brown ◽  
Catherine S. Stephens ◽  
Paul G. Allison ◽  
Florence Sanchez
Keyword(s):  
Cement Paste ◽  
Mechanical Response ◽  
Carbon Nanofiber ◽  
Homogenization Method ◽  
Indentation Modulus ◽  
Interfacial Zone ◽  
Micromechanical Properties ◽  
Significant Interest ◽  
Low Stiffness ◽  
Portland Cement Paste

The use of carbon nanofibers (CNFs) in cement systems has received significant interest over the last decade due to their nanoscale reinforcing potential. However, despite many reports on the formation of localized CNF clusters, their effect on the cement paste micromechanical properties and relation to the mechanical response at the macroscopic scale are still not fully understood. In this study, grid nanoindentation coupled with scanning electron microscopy and energy dispersive spectroscopy was used to determine the local elastic indentation modulus and hardness of a portland cement paste containing 0.2% CNFs with sub-micro and microscale CNF clusters. The presence of low stiffness and porous assemblage of phases (modulus of 15–25 GPa) was identified in the cement paste with CNFs and was attributed primarily to the interfacial zone surrounding the CNF clusters. The CNFs favored the formation of higher modulus C–S–H phases (>30 GPa) in the bulk paste at the expense of the lower stiffness C–S–H. Nanoindentation results combined with a microscale–macroscale upscaling homogenization method further revealed an elastic modulus of the CNF clusters in the range from 18 to 21 GPa, indicating that the CNF clusters acted as compliant inclusions relative to the cement paste.

Experimental Study on the Performance and Microstructure of Rubberized Lightweight Aggregate Concrete

2012 ◽  
Vol 28 (4) ◽  
pp. 147-156 ◽  
Author(s):  
Guiming Wang ◽  
Bin Zhang ◽  
Zhonghe Shui ◽  
Daoyi Tang ◽  
Yun Kong
Keyword(s):  
Mechanical Properties ◽  
Cement Paste ◽  
Lightweight Aggregate ◽  
Crumb Rubber ◽  
Bonding Interface ◽  
Lightweight Aggregate Concrete ◽  
Aggregate Concrete ◽  
Micro Level ◽  
Airport Runway ◽  
The Relationship

It is of great significance to improve the flexibility of concrete for specific applications, such as a tunnel pavement or an airport runway. This paper presents the structural properties of the rubberized lightweight aggregate concrete at the macro- and micro-level. The relationship between mechanical properties and microstructure features was further explored. An experimental programme was developed to use crumb rubber and shale ceramsite to produce a flexible concrete. Much attention was paid to the influence of the crumb rubber dosage. The compressive strength and elastic modulus of the rubberized lightweight aggregate concrete were measured. Furthermore, the corresponding microstructure was evaluated by microhardness assessment and microscopic observation. Experimental results show that with the increase of crumb rubber dosage, the bonding interface between the rubber and cement paste, as well as between the shale ceramsite and cement paste, gradually became weakened or flexible. In addition, the width of the weak bonding interface became wider. As a result the flexibility of lightweight aggregate concrete can be effectively improved by correctly adjusting the crumb rubber dosage.

A Method for Estimating the Dynamic Moduli of Cement Paste-Aggregate Interfacial Zones in Mortar

1994 ◽  
Vol 370 ◽  
Author(s):  
Menashi D. Cohen ◽  
Turng-Fang F. Lee ◽  
Ariel Goldman
Keyword(s):  
Portland Cement ◽  
Silica Fume ◽  
Cement Paste ◽  
Modulus Of Elasticity ◽  
Dynamic Modulus ◽  
Dynamic Shear Modulus ◽  
Interfacial Zone ◽  
Dynamic Moduli ◽  
Dynamic Modulus Of Elasticity ◽  
Cement Mortars

AbstractThe objective of this paper is to propose a method to estimate the average values of the dynamic modulus of elasticity and the dynamic shear modulus of cement paste-aggregate interfacial zones in mortar by applying the Logarithmic Mixture Rule (LMR). Both portland cement mortars (PC mortars) and portland cement mortars with silica fume (SF mortars) are investigated and compared, The influence of silica fume on the dynamic moduli of interfacial zone is also examined. Results indicate that for the specific ingredients and mix design used, the dynamic modulus of elasticity of interfacial zone falls between 0.4 and 2.0 (×10 6 psi) for PC mortar and 1.2 to 2.2 (× 106 psi) for SF mortar. These values are lower than the values obtained for PC mortar (4.2 ×106 psi), PC paste (2.7 ×106 psi), SF mortar (4.4 ×106 psi), and SF paste (2.5 × 106 psi).

scholarly journals Influencing Factors on the Interface Microhardness of Lightweight Aggregate Concrete Consisting of Glazed Hollow Bead

2015 ◽  
Vol 2015 ◽  
pp. 1-15 ◽  
Author(s):  
Gang Ma ◽  
Yu Zhang ◽  
Zhu Li
Keyword(s):  
Cement Paste ◽  
Lightweight Aggregate ◽  
Interface Structure ◽  
Interfacial Transition Zone ◽  
Lightweight Aggregate Concrete ◽  
Hydration Degree ◽  
Zone Structure ◽  
Interface Zone ◽  
Aggregate Concrete ◽  
Rational Control

Lightweight aggregate concrete consisting of glazed hollow bead (GHB) as lightweight aggregate is studied for the influence of nanosilica (NS) content, prewetting time for GHB, water-cement ratio, and curing humidity, on the interface structure between GHB and cement paste. This research analyzed the influences of various factors on the interface zone structure by measuring microhardness (HV) and hydration degree of cement paste (HD) nearby the interface zone (1 mm) between GHB and cement paste at different periods of aging. Due to the sampling limitation, the interface zone in this test is within 1 mm away from the surface of lightweight aggregate. The HD of cement paste was determined through chemically combined water (CCW) test. The results were expected to reflect the influence of various factors on the interface zone structure. Results showed that the rational control of the four factors studied could fully mobilize the water absorption and desorption properties of GHB to improve the characteristics of the interfacial transition zone.

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