CONSTITUTIVE MODELS FOR PREDICTING MECHANICAL PROPERTIES OF NATURAL POZZOLAN-BASED ALKALI ACTIVATED CONCRETE

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Mohammed Ibrahim ◽  
Megat Azmi Megat Johari ◽  
Muhammed Kalimur Rahman ◽  
Mohammed Maslehuddin ◽  
Hatim Dafalla Mohamed
Keyword(s):  
Compressive Strength ◽  
Flexural Strength ◽  
Modulus Of Elasticity ◽  
Constitutive Models ◽  
Engineering Properties ◽  
Strength Development ◽  
Natural Pozzolan ◽  
Material Development ◽  
Alkali Activated Concrete ◽  
Alkali Activated

A large variety of mix design variables and environmental conditions in which alkali activated concretes (AAC) are cured, influences the nature and intensity of the binder formed. Equations developed for OPC-based concrete in various codes and published work may not accurately predict engineering properties of these AAC. AAC in this study was synthesized utilizing natural pozzolan (NP) in the presence of alkaline activators. Nano-SiO2 was added for enhancing the strength development at room temperature curing as NP is a low calcium precursor material. Development of compressive strength, flexural strength and modulus of elasticity were investigated. Using the data generated, two constitutive models, relating the compressive strength to flexural strength and modulus of elasticity were developed and compared with the equations specified in international codes for OPC-based concrete and previous studies in the area. The results show that the ACI 318, underestimates the flexural strength and overestimates the modulus of elasticity of alkali activated concrete. However, constitutive models developed in this study are in good agreement with the equations proposed in the previous works for AAC. Only the limited data available to date on the engineering properties of AAC cannot be used to establish robust constitutive relationships and more research is required in this area.

scholarly journals Engineering Properties of Hybrid Fibre Reinforced Ternary Blend Geopolymer Concrete

2021 ◽  
Vol 5 (8) ◽  
pp. 203
Author(s):  
V. Sathish Kumar ◽  
N. Ganesan ◽  
P. V. Indira
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Flexural Strength ◽  
Modulus Of Elasticity ◽  
Engineering Properties ◽  
Ternary Blend ◽  
Geopolymer Concrete ◽  
Polypropylene Fibres ◽  
Hybrid Form ◽  
Steel Fibres

The primary aim of this research is to find an alternative for Portland cement using inorganic geopolymers. This study investigated the effect of steel and polypropylene fibres hybridisation on ternary blend geopolymer concrete (TGPC) engineering properties using fly ash, ground granulated blast furnace slag (GGBS) and metakaolin as the source materials. The properties like compressive strength, splitting tensile strength, flexural strength and modulus of elasticity of ternary blend geopolymer concrete. The standard tests were conducted on TGPC with steel fibres, polypropylene fibres and a combination of steel and polypropylene fibres in hybrid form. A total number of 45 specimens were tested and compared to determine each property. The grade of concrete considered was M55. The variables studied were the volume fraction of fibres, viz. steel fibres (0%, 0.5% and 1%) and polypropylene fibres (0%, 0.1%, 0.15%, 0.2% and 0.25%). The experimental results reveal that the addition of fibres in a hybrid form enhances the mechanical properties of TGPC. The increase in the compressive strength was nominal, and a significant improvement was observed in splitting tensile strength, flexural strength, and modulus of elasticity. Also, an attempt to obtain the relation between the different engineering properties was made with different volume fractions of fibre.

scholarly journals The potential use of pumice in mine backfill

2020 ◽  
Vol 1 ◽  
Author(s):  
Mohammed A. Hefni
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Mining Industry ◽  
Strength Development ◽  
Natural Pozzolan ◽  
Mine Backfill ◽  
Natural Pozzolans ◽  
Cemented Backfill ◽  
Compressive Strength Development ◽  
Potential Use

Abstract The use of natural pozzolans in concrete applications is gaining more attention because of the associated environmental, economic, and technical benefits. In this study, reference cemented mine backfill samples were prepared using Portland cement, and experimental samples were prepared by partially replacing Portland cement with 10 or 20 wt.% fly ash as a byproduct (artificial) pozzolan or pumice as a natural pozzolan. Samples were cured for 7, 14, and 28 days to investigate uniaxial compressive strength development. Backfill samples containing 10 wt.% pumice had almost a similar compressive strength as reference samples. There is strong potential for pumice to be used in cemented backfill to minimize costs, improve backfill properties, and promote the sustainability of the mining industry.

scholarly journals Strength and Durability Performance of Alkali-Activated Rice Husk Ash Geopolymer Mortar

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Yun Yong Kim ◽  
Byung-Jae Lee ◽  
Velu Saraswathy ◽  
Seung-Jun Kwon
Keyword(s):  
Compressive Strength ◽  
Rice Husk ◽  
Rice Husk Ash ◽  
Polymerization Reaction ◽  
Strength Development ◽  
Geopolymer Concrete ◽  
Portland Cement Concrete ◽  
Mix Proportion ◽  
Strength And Durability ◽  
Alkali Activated

This paper describes the experimental investigation carried out to develop the geopolymer concrete based on alkali-activated rice husk ash (RHA) by sodium hydroxide with sodium silicate. Effect on method of curing and concentration of NaOH on compressive strength as well as the optimum mix proportion of geopolymer mortar was investigated. It is possible to achieve compressive strengths of 31 N/mm2and 45 N/mm2, respectively for the 10 M alkali-activated geopolymer mortar after 7 and 28 days of casting when cured for 24 hours at 60°C. Results indicated that the increase in curing period and concentration of alkali activator increased the compressive strength. Durability studies were carried out in acid and sulfate media such as H2SO4, HCl, Na2SO4, and MgSO4environments and found that geopolymer concrete showed very less weight loss when compared to steam-cured mortar specimens. In addition, fluorescent optical microscopy and X-ray diffraction (XRD) studies have shown the formation of new peaks and enhanced the polymerization reaction which is responsible for strength development and hence RHA has great potential as a substitute for ordinary Portland cement concrete.

scholarly journals Influence of Hybrid Fibers on Toughness Behavior of High Strength Flowing Concrete

2011 ◽  
Vol 57 (3) ◽  
pp. 249-260 ◽  
Author(s):  
Eethar Thanon Dawood ◽  
Mahyuddin Ramli
Keyword(s):  
Compressive Strength ◽  
Flexural Strength ◽  
Modulus Of Elasticity ◽  
Hybrid Composite ◽  
High Strength ◽  
Steel Fibers ◽  
Hybrid Fibers ◽  
Static Modulus ◽  
Static Modulus Of Elasticity ◽  
Strength And Toughness

Abstract This study investigates the use of steel fibers and hybrid composite with a total fibers content of 2% on the high strength flowing concrete and determines the density, compressive strength, static modulus of elasticity, flexural strength and toughness indices for the mixes. The results show that the inclusion of more than 0.5% of palm fibers in hybrid fibers mixes reduces the compressive strength. The hybrid fibers can be considered as a promising concept and the replacement of a portion of steel fibers with palm fibers can significantly reduce the density, enhance the flexural strength and toughness. The results also indicates that the use of hybrid fibers (1.5 steel fibers + 0.5% palm fibers) in specimens increases significantly the toughness indices and thus the use of hybrid fibers combinations in reinforced concrete would enhance their flexural toughness & rigidity and enhance their overall performances

scholarly journals Effect of Recycled Coarse Aggregates in Properties of Concrete

2008 ◽  
Vol 3 (4) ◽  
pp. 130-137 ◽  
Author(s):  
R Kumutha ◽  
K Vijai
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Flexural Strength ◽  
Modulus Of Elasticity ◽  
Coarse Aggregate ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Split Tensile Strength ◽  
Coarse Aggregates ◽  
The Cost

The properties of concrete containing coarse recycled aggregates were investigated. Laboratory trials were conducted to investigate the possibility of using recycled aggregates from the demolition wastes available locally as the replacement of natural coarse aggregates in concrete. A series of tests were carried out to determine the density, compressive strength, split tensile strength, flexural strength and modulus of elasticity of concrete with and without recycled aggregates. The water cement ratio was kept constant for all the mixes. The coarse aggregate in concrete was replaced with 0%, 20%, 40%, 60%, 80% and 100% recycled coarse aggregates. The test results indicated that the replacement of natural coarse aggregates by recycled aggregates up to 40% had little effect on the compressive strength, but higher levels of replacement reduced the compressive strength. A replacement level of 100% causes a reduction of 28% in compressive strength, 36% in split tensile strength and 50% in flexural strength. For strength characteristics, the results showed a gradual decrease in compressive strength, split tensile strength, flexural strength and modulus of elasticity as the percentage of recycled aggregate used in the specimens increased. 100% replacement of natural coarse aggregate by recycled aggregate resulted in 43% savings in the cost of coarse aggregates and 9% savings in the cost of concrete.

scholarly journals Temperature Effect on the Compressive Behavior and Constitutive Model of Plain Hardened Concrete

Materials ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 2801 ◽  
Author(s):  
Ayman El-Zohairy ◽  
Hunter Hammontree ◽  
Eddie Oh ◽  
Perry Moler
Keyword(s):  
Experimental Data ◽  
Compressive Strength ◽  
Temperature Effect ◽  
Modulus Of Elasticity ◽  
Constitutive Models ◽  
Ultimate Strain ◽  
Effect Of Temperature ◽  
Hardened Concrete ◽  
Compressive Behavior ◽  
Stress Strain

Concrete is one of the most common and versatile construction materials and has been used under a wide range of environmental conditions. Temperature is one of them, which significantly affects the performance of concrete, and therefore, a careful evaluation of the effect of temperature on concrete cannot be overemphasized. In this study, an overview of the temperature effect on the compressive behavior of plain hardened concrete is experimentally provided. Concrete cylinders were prepared, cured, and stored under different temperature conditions to be tested under compression. The stress–strain curve, mode of failure, compressive strength, ultimate strain, and modulus of elasticity of concrete were evaluated between the ages of 7 and 90 days. The experimental results were used to propose constitutive models to predict the mechanical properties of concrete under the effect of temperature. Moreover, previous constitutive models were examined to capture the stress–strain relationships of concrete under the effect of temperature. Based on the experimental data and the proposed models, concrete lost 10–20% of its original compressive strength when heated to 100 °C and 30–40% at 260 °C. The previous constitutive models for stress–strain relationships of concrete at normal temperatures can be used to capture these relationships under the effect of temperature by using the compressive strength, ultimate strain, and modulus of elasticity affected by temperature. The effect of temperature on the modulus of elasticity of concrete was considered in the ACI 318-14 equation by using the compressive strength affected by temperature and the results showed good agreement with the experimental data.

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