A Study of Interfacial Transition Zone in Lightweight Aggregate Concrete

2011 ◽  
Vol 194-196 ◽  
pp. 935-941
Author(s):  
How Ji Chen ◽  
Chien Kuo Lin ◽  
Wen Po Tsai ◽  
Te Hung Liu
Keyword(s):  
Tensile Strength ◽  
Lightweight Aggregate ◽  
Normal Weight ◽  
Lightweight Aggregate Concrete ◽  
Lightweight Aggregates ◽  
X Ray Diffraction ◽  
Transition Zones ◽  
Different Types ◽  
Slight Downward Trend ◽  
High Absorption

If concrete is observed at the microscopic level, it can be seen to contain many interfacial transition zones (ITZ), resulting in the weakening of its mechanical properties; as the physical properties of lightweight aggregates (LWA), such as their high absorption, are clearly different from those of normal weight aggregates (NWA), they may lead to variations in the ITZ of lightweight aggregates concrete (LWAC), making its mechanical behavior different from that of normal concrete.This study takes three types of LWA with different rates of absorption as its subjects in order to examine the effects of LWA absorbency on ITZ. The main variables tested include water/binder (W/B) ratio, amount of fly ash substituted for cement, and the saturation states of the four types of LWA, with three different types of microscopic tests used to observe the microstructure of ITZ in concrete, and analyze and compare their differences with ITZ in concrete made with NWA. The results of the study indicate that in LWAC, ITZ with weaker tensile strength did not appear around highly absorbent LWA; only the sample group with a W/B ratio of 0.29 did not show apparent absorption due to the higher viscosity of the mortar, resulting in a slight downward trend in tensile strength, but it was still superior to the tensile strength of ITZ in typical NWA.Observation using scanning electron microscopy (SEM) found that inner pores and cracks of ITZ in LWAC were all smaller than in NWC; X-ray diffraction (XRD) tests indicated that the amount of CH crystals in ITZ was greater than LWAC; and microhardness testing found that microhardness values were higher closer to the surface of the LWA, with some even exceeding that of concrete. The increase in the tensile strength of ITZ in LWAC subsequent to the addition of pozzolanic materials was limited; their improvement of the weakness planes formed by ITZ in NWA concrete, however, was more apparent. An LWA has higher water absorbency capacity when in an absolutely-dry condition, which can markedly increase the strength of ITZ; conversely, if an LWA is in saturated surface dry (SSD) condition, its ITZ behave like those of concrete.

Structural Lightweight Aggregate Concrete by Incorporating Solid Wastes as Coarse Lightweight Aggregate

2015 ◽  
Vol 749 ◽  
pp. 337-342 ◽  
Author(s):  
Muhammad Aslam ◽  
Payam Shafigh ◽  
Mohd Zamin Jumaat
Keyword(s):  
Oil Palm ◽  
Lightweight Concrete ◽  
Negative Impact ◽  
Raw Materials ◽  
Lightweight Aggregate ◽  
Normal Weight ◽  
Lightweight Aggregate Concrete ◽  
Lightweight Aggregates ◽  
Aggregate Concrete ◽  
Structural Lightweight Aggregate Concrete

Structural lightweight aggregate concrete offers several benefits as compared to the normal weight concrete. Most common methods of producing structural lightweight concrete is by using artificial lightweight aggregates. However, the cost of the production of artificial lightweight aggregates is high due to energy and raw materials consumption. The use of waste and by-product materials as lightweight aggregate in concrete can provide a better solution to reducing the negative impact of the concrete industry. This paper reports an investigation to produce structural lightweight aggregate concrete by utilizing the locally available solid waste materials, namely oil palm shell (OPS) and oil-palm-boiler clinkers (OPBC) as coarse lightweight aggregates. Two different mix proportions were studied. In the first concrete mix, just OPS was used as coarse aggregate. However, 40% of OPS (by volume) of the first mix was replaced with OPBC in the second mix. The test results showed that by replacing OPS with OPBC, it directly affects the characteristics of the lightweight concrete. The 28-days compressive strength of the blended coarse lightweight aggregate concrete was significantly increased compared to OPS concrete.

scholarly journals The Effects of Additives to Lightweight Aggregate on the Mechanical Properties of Structural Lightweight Aggregate Concrete

2021 ◽  
Vol 31 (1) ◽  
pp. 139-160
Author(s):  
Mehdi Khoshvatan ◽  
Majid Pouraminia
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Specific Gravity ◽  
Lightweight Aggregate ◽  
Lightweight Aggregate Concrete ◽  
Lightweight Aggregates ◽  
Structural Concrete ◽  
Aggregate Concrete ◽  
Structural Lightweight Aggregate Concrete

Abstract In the paper, the effects of different percentages of additives (perlite, LECA, pumice) on the mechanical properties of structural lightweight aggregate concrete were tested and evaluated. For the research, 14 mixing designs with different amounts of aggregate, water, and cement were made. Experimental results showed that the specific gravity of lightweight structural concrete made from a mixture of LECA, pumice, and perlite aggregates could be 25-30% lighter than conventional concrete. Lightweight structural concrete with a standard specific gravity can be achieved by using a combination of light LECA with perlite lightweight aggregates (LA) and pumice with perlite in concrete. The results indicated that LECA lightweight aggregates show more effective behavior in the concrete sample. Also, the amount of cement had a direct effect on increasing the strength regardless of the composition of LAs. The amount of cement causes compressive strength to increase. Furthermore, the stability of different experimental models increased from 156 to 345 kg m 3 while increasing the amount of cement from 300 to 400 kg m 3 in the mixing designs of LECA and perlite for W/C ratios of 0.3, 0.35, and 0.4. For a fixed amount of cement equal to 300 kg, the compressive strength is reduced by 4% by changing the water to cement ratio from 0.5 to 0.4. The compression ratios of strength for 7 to 28 days obtained in this study for lightweight concrete were between 0.67-0.8. Based on the rate of tensile strength to compressive strength of ordinary concretes, which is approximately 10, this ratio is about 13.5 to-17.8 in selected and optimal lightweight concretes in this research, which can be considered good indirect tensile strength for structural lightweight concretes.

Performance of Lightweight Aggregate Concrete Containing Expanded Polystyrene, Cinder and Silica Fume

2020 ◽  
Vol 17 (9) ◽  
pp. 4311-4317
Author(s):  
M. L. Harish ◽  
H. Narendra ◽  
Md. Rizwan Tahashildar
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Silica Fume ◽  
Lightweight Aggregate ◽  
Normal Weight ◽  
Expanded Polystyrene ◽  
Lightweight Aggregate Concrete ◽  
Split Tensile Strength ◽  
Aggregate Concrete ◽  
Optimal Mix

Lightweight aggregate concrete is developed by substituting normal weight aggregate either fully or partially based on required strength and density. Expanded polystyrene (EPS) bead is a type of low density material, which also has good energy-absorbing characteristics and can be used as light weight aggregate in concrete. In the present study, Structural lightweight aggregate concrete (SLWAC) was produced by fully replacing normal weight aggregate with combinations of EPS beads to Cinder by the ratio 20:80, 40:60, 60:40, 80:20 respectively and Silica fume was used as supplementary cementitious material. The resulting concrete had strength variation between 24.85 to 12.01 MPa, and the density variation of 1896 to 1664 kg/m3. Considering strength and density criteria 40:60 ratios was observed as the optimal mix. The Compressive strength acquired by concrete was inversely proportional to the volume of EPS beads. Effect of fibres on mechanical properties such as flexural strength, compressive strength, and split-tensile strength was investigated on optimal mix by using polypropylene fibres, it was observed that a 13.24% increase in flexural strength at 1% fibres, 8.41% increase in Compressive strength at 1% fibres and 23.11% increase in split-tensile strength at 1% fibres. Along with these, durability tests such as water absorption and permeability tests were performed, the performance of this concrete in water absorption test and permeability is well within the acceptable limits as the EPS ratio in the concrete increased, the absorption and depth of penetration values increased considerably. Microscopic observations were also made to study the interface amongst the cement paste and aggregates. It was revealed that silica fume has influenced significantly in bonding with EPS beads.

Performance of Lightweight Aggregate Concrete Containing Expanded Polystyrene, Cinder and Ground-Granulated Blast-Furnace Slag

2020 ◽  
Vol 17 (9) ◽  
pp. 4304-4310
Author(s):  
M. L. Harish ◽  
H. Narendra ◽  
Md. Azam Afzal
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Flexural Strength ◽  
Lightweight Aggregate ◽  
Normal Weight ◽  
Expanded Polystyrene ◽  
Lightweight Aggregate Concrete ◽  
Split Tensile Strength ◽  
Aggregate Concrete ◽  
Optimal Mix

Lightweight aggregate concrete is developed by substituting normal weight aggregate either fully or partially based on strength and density required. Expanded polystyrene (EPS) bead is a type of low density material, which also has good energy-absorbing characteristics and can be used as light weight aggregate in concrete. In the present study, Structural lightweight aggregate concrete (SLWAC) was produced by fully replacing normal weight aggregate with combinations of EPS beads to Cinder by the ratio 20:80, 40:60, 60:40, 80:20 respectively. And GGBS was used as supplementary cementitious material. The resulting concrete had strength variation between 29.5 to 11.6 MPa, and the density variation of 2192 to 1701 kg/m3. Considering strength and density criteria 40:60 ratios was observed as the optimal mix. The Compressive strength acquired by concrete was inversely proportional to the volume of EPS beads. Effect of fibers on mechanical properties such as flexural strength, compressive strength, and split-tensile strength was studied on the optimal mix by using polypropylene fibers, it was observed that an 8.78% increase in flexural strength at 1% fibers, 16.5% increase in Compressive strength at 0.5% fibers, and 35.4% increase in split-tensile strength at 1% fibers. Along with this, durability tests such as water absorption and permeability tests were performed, the performance of this concrete in water absorption test is well within the limits but in permeability, it underperformed which confirms that as the EPS ratio in the concrete increased, the absorption and depth of penetration values increased considerably. Microscopic observations were also made to study the interface amongst the cement paste and aggregates. It was revealed that GGBS did not influence significantly on the bonding with EPS beads.

scholarly journals Quality Improvement on Properties of Concrete by using Lightweight Aggregates

2019 ◽  
Vol 8 (2) ◽  
pp. 4550-4554
Keyword(s):  
Coarse Aggregate ◽  
Lightweight Concrete ◽  
Lightweight Aggregate ◽  
Normal Weight ◽  
Partial Replacement ◽  
Lightweight Aggregate Concrete ◽  
Lightweight Aggregates ◽  
Slump Test ◽  
Test Compaction ◽  
Compaction Factor

This paper presents an investigation to make the study on workability and strength properties of concrete which is made by Lightweight Aggregates {i.e. Palm Oil Shell (POS) and Pumice Aggregate (PA)}as coarse aggregate. A series of tests conducted in lab containing Slump test, Compaction Factor test, Schmidt Hammer test and Compressive Strength test was led on concrete made by ordinary aggregate as normal weight sample and concrete formed by different ratios of POS and PA separately i.e. 10% to 50% of dry weight of coarse aggregate. All the specimens were underwater for 3, 7 and 28 days as curing stage. In this experimental study, an effort has been made to concentrate the properties of a lightweight concrete M30 using the lightweight aggregate (POS and PA) as a partial replacement to coarse aggregate. The test results indicate that with the increasing amounts of normal aggregates replaced by POS and PA, the slump test, compaction factor test and strength of the Lightweight Aggregate Concrete (LWAC) has reduced gradually. As water absorption of the LWAC has been increased step by step with the increasing amounts of aggregates replaced by POS and PA. Lastly, it is concluded that the use of POS has great future than compared to PA in the construction of structural lightweight concrete.

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.

scholarly journals Efficiency factor and modulus of elasticity of lightweight concrete with expanded clay aggregate

2010 ◽  
Vol 3 (2) ◽  
pp. 195-204 ◽  
Author(s):  
W.G Moravia ◽  
A. G. Gumieri ◽  
W. L. Vasconcelos
Keyword(s):  
Compressive Strength ◽  
Modulus Of Elasticity ◽  
Large Scale ◽  
Lightweight Concrete ◽  
Weight Ratio ◽  
Lightweight Aggregate ◽  
Normal Weight ◽  
Lightweight Aggregate Concrete ◽  
Empirical Methods ◽  
Normal Weight Concrete

Nowadays lightweight concrete is used on a large scale for structural purposes and to reduce the self-weight of structures. Specific grav- ity, compressive strength, strength/weight ratio and modulus of elasticity are important factors in the mechanical behavior of structures. This work studies these properties in lightweight aggregate concrete (LWAC) and normal-weight concrete (NWC), comparing them. Spe- cific gravity was evaluated in the fresh and hardened states. Four mixture proportions were adopted to evaluate compressive strength. For each proposed mixture proportion of the two concretes, cylindrical specimens were molded and tested at ages of 3, 7 and 28 days. The modulus of elasticity of the NWC and LWAC was analyzed by static, dynamic and empirical methods. The results show a larger strength/ weight ratio for LWAC, although this concrete presented lower compressive strength.

scholarly journals Behavior of high performance artificial lightweight aggregate concrete reinforced with hybrid fibers

2018 ◽  
Vol 162 ◽  
pp. 02001
Author(s):  
Wasan Khalil ◽  
Hisham Ahmed ◽  
Zainab Hussein
Keyword(s):  
Tensile Strength ◽  
Aspect Ratio ◽  
Steel Fiber ◽  
Fiber Type ◽  
Lightweight Aggregate ◽  
Plain Concrete ◽  
Splitting Tensile Strength ◽  
Lightweight Aggregate Concrete ◽  
Fiber Reinforced ◽  
Hybrid Fiber

In this investigation, sustainable High Performance Lightweight Aggregate Concrete (HPLWAC) containing artificial aggregate as coarse lightweight aggregate (LWA) and reinforced with mono fiber, double and triple hybrid fibers in different types and aspect ratios were produced. High performance artificial lightweight aggregate concrete mix with compressive strength of 47 MPa, oven dry density of 1828 kg/m3 at 28 days was prepared. The Fibers used included, macro hooked steel fiber with aspect ratio of 60 (type S1), macro crimped plastic fiber (P) with aspect ratio of 63, micro steel fiber with aspect ratio of 65 (type S), and micro polypropylene fiber (PP) with aspect ratio of 667. Four HPLWAC mixes were prepared including, one plain concrete mix (without fiber), one mono fiber reinforced concrete mixes (reinforced with plastic fiber with 0.75% volume fraction), one double hybrid fiber reinforced concrete mixes (0.5% plastic fiber + 0.25% steel fiber type S), and a mix with triple hybrid fiber (0.25% steel fiber type S1+ 0.25% polypropylene fiber + 0.25% steel fiber type S). Fresh (workability and fresh density) and hardened concrete properties (oven dry density, compressive strength, ultrasonic pulse velocity, splitting tensile strength, flexural strength, static modules of elasticity, thermal conductively, and water absorption) were studied. Generally, mono and hybrid (double and triple) fiber reinforced HPLWAC specimens give a significant increase in splitting tensile strength and flexural strength compared with plain HPLWAC specimens. The percentage increases in splitting tensile strength for specimens with mono plastic fiber are, 20.8%, 31.9%, 36.4% and 41%, while the percentage increases in flexure strength are 19.5%, 37%, 33.9% and 34.2% at 7, 28, 60, 90 days age respectively relative to the plain concrete. The maximum splitting tensile and flexure strengths were recorded for triple hybrid fiber reinforced HPLWAC specimens. The percentage increases in splitting tensile strength for triple hybrid fiber reinforced specimens are 19.5%, 37%, 33.9% and 34.2%, while the percentage increases in flexure strength are 50.5%, 62.4. %, 66.8% and 62.2% at 7, 28, 60 and 90 days age respectively relative to the plain concrete specimens.

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.

Mechanical Properties of Fiber Reinforced Lightweight Aggregate Concrete

2011 ◽  
Vol 477 ◽  
pp. 274-279 ◽  
Author(s):  
Yi Xu ◽  
Lin Hua Jiang ◽  
Hong Qiang Chu ◽  
Lei Chen
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Water Hyacinth ◽  
Steel Fiber ◽  
Polypropylene Fiber ◽  
Lightweight Aggregate ◽  
Splitting Tensile Strength ◽  
Lightweight Aggregate Concrete ◽  
Fiber Types

In this study, the effects of fiber types on the mechanical properties of lightweight aggregate concretes were investigated. Three types of fibers, namely, polypropylene fiber, steel fiber and water hyacinth (Eichhornia crassipes) fiber, and two types of lightweight aggregates, namely, expanded polystyrene and ceramsite were used. The compressive strength and splitting tensile strength of concretes were tested. The results show that both the compressive strength and the splitting tensile strength were improved by adding a reasonable volume of steel fiber and polypropylene fiber into LWAC. The addition of water hyacinth fiber had little effect on the compressive strength of LWAC, while a little increase was observed in the splitting tensile strength.

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