Effect of Lightweight Aggregate Moisture Content on Pore Structure of Concrete

2010 ◽  
Vol 168-170 ◽  
pp. 647-651
Author(s):  
Shu Hui Dong ◽  
Yong Ge ◽  
Bao Sheng Zhang ◽  
Jie Yuan
Keyword(s):  
Moisture Content ◽  
Pore Structure ◽  
Transition Zone ◽  
Cement Paste ◽  
Lightweight Aggregate ◽  
Interfacial Transition Zone ◽  
Lightweight Aggregate Concrete ◽  
Aggregate Concrete ◽  
Water Rate ◽  
High Absorption

To understand the impacting law of lightweight aggregate moisture content on the cement paste pore structure and its relationship with humidity and deformation of the lightweight aggregate concrete, it is necessary to study the effect of water absorptivity and pre-wet moisture content of lightweight aggregate on the pore structure interfacial transition zone (ITZ) cement paste. The experimental results indicated that the species and moisture content of lightweight aggregate have a greater effect on the pore structure in interfacial transition zone of cement paste in low w/c concrete than that in high w/c concrete. With the saturation level of lightweight aggregate increased, the overall pore structure shows a refinement tendency. The porosity and the larger pore of ITZ in ordinary aggregate are notably higher than those in the basal body cement paste. Meanwhile, we find that the pore structure of ITZ in lightweight aggregate concrete is much different from that in ordinary aggregate concrete. Especially in the concrete using the lightweight aggregate with a high absorption–desorbtion water rate, the pore aperture in ITZ is significantly lower than that in the cement paste, the pore content below 50nm can reach as high as 80%.

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 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.

An Investigation on the Interfacial Transition Zone of Lightweight Aggregate Concrete

2013 ◽  
Vol 753-755 ◽  
pp. 610-615
Author(s):  
Hsi Chi Yang ◽  
Miao Ying Cheng
Keyword(s):  
Transition Zone ◽  
Lightweight Aggregate ◽  
Concrete Specimen ◽  
Pozzolanic Reaction ◽  
Normal Weight ◽  
Interfacial Transition Zone ◽  
Lightweight Aggregate Concrete ◽  
Hydration Products ◽  
Aggregate Concrete ◽  
Shihmen Reservoir

The technique of linking the SEM photographs taken around the interfacial transition zone area is applied to observe the development of hydration products for lightweight aggregate and paste at the different curing ages. This research first determines the mixture proportions of the two types of concrete specimens with different aggregate unit weights. The lightweight aggregate used is the sludge kilned aggregate from Shihmen reservoir. The very small SEM samples to be observed are taken from the concrete compressive test specimens and must include both aggregate and paste. The research then observes the hydration products (such as CH, C-S-H) of calcium ion and the pozzolanic reaction on the samples. Finally it assesses if the aggregate will produce ion exchange with cement and generate the hydration products. The hydration products on either side of the interface with a range of 100μm are observed using 2000x magnification. From the results, it is found that (1) the development of hydration products of the lightweight aggregate concrete is similar to that of the normal-weight aggregate concrete, (2) the failure at the 91 days age is that the lightweight aggregate is sheared, (3) the bond stress of aggregate and paste is controlled by hydration products of paste, (4) the aggregate has not interacted with cement paste to produce hydration products, and (5) the development of hydration products proves that the amount of binder used in the concrete specimen will affects its compressive strength.

Permeability of Lightweight Aggregate Concrete with Mineral Admixture

2013 ◽  
Vol 857 ◽  
pp. 105-109
Author(s):  
Xiu Hua Zheng ◽  
Shu Jie Song ◽  
Yong Quan Zhang
Keyword(s):  
Pore Structure ◽  
Lightweight Concrete ◽  
Chloride Ion ◽  
Lightweight Aggregate ◽  
Total Porosity ◽  
Normal Weight ◽  
Mineral Admixture ◽  
Mineral Admixtures ◽  
Lightweight Aggregate Concrete ◽  
Aggregate Concrete

This paper presents an experimental study on the permeability and the pore structure of lightweight concrete with fly ash, zeolite powder, or silica fume, in comparison to that of normal weight aggregate concrete. The results showed that the mineral admixtures can improve the anti-permeability performance of lightweight aggregate concrete, and mixed with compound mineral admixtures further more. The resistance to chloride-ion permeability of light weight concrete was higher than that of At the same strength grade, the anti-permeability performance of lightweight aggregate concrete is better than that of normal weight aggregate concrete. The anti-permeability performance of LC40 was similar to that of C60. Mineral admixtures can obviously improve the pore structure of lightweight aggregate concrete, the total porosity reduced while the pore size decreased.

Strength and Microstructural Study of Lightweight Aggregate Concrete (LWAC) Using Lightweight Expended Clay Aggregates (LECA)

2020 ◽  
Vol 1010 ◽  
pp. 678-683
Author(s):  
Khairul Nizar Ismail ◽  
Fatihah Halim
Keyword(s):  
Lightweight Aggregate ◽  
Interfacial Transition Zone ◽  
Lightweight Aggregate Concrete ◽  
Small Scale ◽  
Strength Development ◽  
Aggregate Concrete ◽  
Microstructural Study ◽  
Digital Microscope ◽  
Crushed Aggregate ◽  
Clay Aggregates

Concrete is a composite material that consists of a cement and aggregate particles. Microstructure is the small scale structure of a material, defined as the structure of a prepared surface of material as revealed by a microscope. There is strong evidence that aggregate type is a factor in the strength of concrete. The objective of this research is to investigate the properties of concrete that are containing the lightweight expanded clay aggregates (LECA). Digital microscope was used to analyses the formation mechanism of microstructure in concrete. LECA were used in production of lightweight aggregate concrete (LWAC) with the size 50 mm x 50 mm x 50 mm. This paper deals with observation of the concrete microstructure to point out some differences that would be responsible for strength of concrete. The results show that, LECA has several improvements when compared with conventional crushed aggregate. The concrete specimens were used to validate the existence of an interfacial transition zone (ITZ) in concrete. The microstructure features are discussed with respect to their influence on the strength development of concrete.

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.

scholarly journals Failure of Lightweight Aggregate Concrete in Compression under Stress Gradients

2019 ◽  
Vol 60 (1) ◽  
pp. 51-66
Author(s):  
Jelena Zivkovic ◽  
Jan Arve Øverli
Keyword(s):  
North Carolina ◽  
Moisture Content ◽  
Polyvinyl Alcohol ◽  
Lightweight Aggregate ◽  
Experimental Program ◽  
Lightweight Aggregate Concrete ◽  
Aggregate Concrete ◽  
Stress Gradients ◽  
The Third ◽  
Very High

Abstract The objective of this experiment is to investigate the behaviour of lightweight aggregate concrete (LWAC) under compression and with stress gradients. Experimental program contained three sets of LWAC which were used for production of 21 prisms. Lightweight aggregate argillite slate, called Stalite, from North Carolina had been used. The sets differed in using dry (0.10% moisture content) or saturated (7.9% moisture content) aggregate. The third set included a small amount of polyvinyl alcohol fibres (PVA). The geometry of the prisms were 100 × 140 × 480 mm (width × length × height). Prismatic samples were loaded centrically and eccentrically in compression. From the achieved experimental results, it is visible that the lateral deformation of the most stressed fibre is counteracted by the less stressed fibres that confine compressive stress and increase strains. The obtained strain level was much higher than expected, especially for the third set of concrete samples with PVA fibres. Recorded strains in prisms test was in range from 3.08‰ to 6.82‰). In general, LWAC with Stalite showed ductile behaviour followed with very high strains. The third set of samples included a small amount of polyvinyl alcohol fibres (0.5% of volume fractions) was even more ductile and non-brittle.

Experimental Study on Frost Resistance Durability of Lightweight Aggregate Concrete in Na2SO4 Solution

2010 ◽  
Vol 152-153 ◽  
pp. 1565-1569
Author(s):  
Jun Fang Huo ◽  
Hui Yang ◽  
Xiang Dong Shen ◽  
Xiao Xia Ji ◽  
Qi Cui
Keyword(s):  
Frost Resistance ◽  
Steel Fiber ◽  
Polypropylene Fiber ◽  
Lightweight Aggregate ◽  
Strength Loss ◽  
Interfacial Transition Zone ◽  
Lightweight Aggregate Concrete ◽  
Test Results ◽  
Aggregate Concrete ◽  
Resistance Durability

Pumice was used to make up lightweight aggregate concrete (LWAC). Frost resistance durability of LWAC in 5% Na2SO4 solution was studied. The test results showed that LWAC durability deteriorates more rapidly under freezing-thawing in salt solution than in water. The strength loss of LWAC was reduced by steel fiber and polypropylene fiber regardless of Na2SO4 solution and water. Fly ash and silica fume can improve Interfacial Transition Zone（ITZ）and the frost resistance of fibers reinforcement LWAC dramatically.

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