Strength Development Of Concrete Research Articles

Application of machine learning algorithm to assess the efficacy of varying industrial wastes and curing methods on strength development of geopolymer concrete

The contribution of geopolymer concrete is irrefutable and imperative in the context of sustainable construction practices. The current study highlights the relevance of red mud and glass powder in conjunction with fly ash as the aluminosilicate source material for geopolymer concrete production. The performance of the designed binders was evaluated accentuating the function of fly ash replacement levels (10%-40%), curing time, and curing method (ambient, external exposure, and oven curing). Experimental results affirm that the mix containing 10% red mud and glass powder in equal proportions depicted the highest compressive strength at 28 days under external exposure (48 MPa) and oven curing (75 MPa). The study also revealed allowable leachability of geopolymer composites as per relevant standards. Analysing the 28 days compressive strength data using machine learning algorithms showed that the relationship between the dependent and the set of independent variables could be best predicted by a non-linear model, substantiated by the highest level of accuracy (98.79%).

Strength Development of LC3 Concrete Containing Grade 100 Ground Granulated Blast-Furnace Slag (GGBFS)

To decrease greenhouse gas emissions and maintain sustainable economic growth, the cement industry has developed limestone calcined clay cement (LC3). Many researchers have started to investigate the performance of LC3 as a construction material. However, the strength development of LC3 has diverging or opposite views. In this research, the strength development characteristics of ordinary Portland cement (OPC) and LC3 with different combinations of medium reactive ground granulated blast furnace slag (GGBFS) have been compared using compressive strength and ultrasonic pulse velocity, and maturity tests. The test result shows that the LC3 concrete has a similar 28-day compressive strength to OPC concrete despite developing a lower early age. Ultrasonic pulse velocity test results have matched compressive strength test results. The predicted compressive strengths using 7-day maturity data were comparable to actual strength results.

Short-term and long-term behavior of RC beams strengthened by galvanized steel mesh laminate

Steel reinforced polymers (SRP) are useful in a wide range of applications, including strengthening of existing reinforced concrete (RC) structures, due to their numerous advantages like high strength, low maintenance, light weight and low cost. As such, galvanized steel mesh (GSM) has emerged as an option in the strengthening of RC structures. Although numerous studies were performed on GSM strengthened RC beams, the durability of such strengthening systems is yet to be fully understood. This paper presents an experimental and numerical study to investigate the strengthening effect of GSM on RC beams as well as the time-depended behavior of RC beams with and without strengthening. Reinforced concrete beams without strengthening were used as control beams. For the strengthened beams, both high cord density galvanized steel mesh (HSM) and medium cord density galvanized steel mesh (MSM) were used after which the beams were exposed to Qatar atmospheric environment for different periods of time following 28 days of water curing. Finite element analyses using ABAQUS software were conducted to predict the mechanical behavior of the RC beams with and without strengthening. The results showed an improvement ranging from 46% ∼ 57% in the ultimate load of GSM strengthened beams, with a higher initial cracking load ranging from 3% ∼ 35% when compared to the unstrengthened beams. On the other hand, the time-dependent effect of the concrete has limited influence on the initial cracking load of both systems (before and after strengthening) while the ultimate load increased gradually with time due to the strength development of concrete. The results obtained from this study are useful in improving the design, construction, and maintenance of RC beams strengthened with GSM laminates.

Compressive Strength Development of Dune Sand Reactive Powder Concrete (RPC) Under Different Curing Conditions

Reactive powder concrete (RPC) is a special type of concrete with remarkable properties, particularly compressive strength. Some of its main disadvantages include its high cement and SF content, fine quartz with a preferred size of 150 μm - 600 μm, and low water-to- binder ratio. These characteristics increase the cost of RPC production and affect sustainable development. Because of this, researchers have resorted to exploring substitutes to cement and quartz to produce an eco-friendlier type of RPC. Accordingly, this research aims to study the compressive strength development of RPC prepared with dune sand and supplementary cementitious materials (SCM). Three main factors were investigated including 1) replacing cement with 30% ground granulated blast furnace slag (GGBS), 2) using ternary blends of GGBS and fly ash (FA) in RPC, and 3) applying 100°C hot air curing (HAC) to RPC. Overall, the results showed that the compressive strength of HAC and water cured specimens exceeded 120 MPa after 12 hours and 28 days, respectively. Moreover, the compressive strength development of the mixes incorporating SCM was slower than that of the control mix incorporating cement only under HAC conditions.

Role of silica fume on hydration and strength development of ultra-high performance concrete

Silica fume (SF) is the most commonly used ingredient in ultra-high performance concrete (UHPC) due to its inherited properties, which can effectively improve the rheology and mechanical performance. However, investigations with regard to its filler effect and pozzolanic reaction on UHPC are limited. To assess the contribution from SF, a chemically inert filler of titanium dioxide (TD), with a comparable particle size distribution and specific surface area (per unit volume), was selected as a reference ingredient to eliminate the influence of packing effect. Results showed the addition of SF will accerate the early hydation of UHPC and it is controlled by the combined effect of seeding effect and preferential adsorption. Moreover, the SF’s surface characteristic controlling the concentration of adsorption sites provided for hydration product is the key factor influencing the early hydration rather than surface specific area. Furthermore, the enhancement of compressive strength of UHPC after 3 days is attributed to the pozzolanic reaction of SF and its promoting effect on cement hydration degree. The total contribution is less than 20%, and it will enhances with the decrease of W/C ratio.

Performance buildup of concrete cured under low-temperatures: Use of a new nanocomposite accelerator and its application

Although revealed with some benefits, the use of traditional accelerators in concrete indeed encounter some issues such as the deterioration of concrete durability. Therefore, this study proposed a new nanocomposite accelerator (NCA), whose influences on the fresh (e.g., workability) and hardened properties (e.g., strength and durability) of C60 high-strength concrete (HSC) under low temperature curing (i.e., 16 °C and 6 °C) were studied. The experimental results revealed that although low curing temperatures damage the overall fresh and hardened performances of concrete, their performances were compensated via the use of the proposed NCA. The slump and slump flow were increased and the workability loss over time was reduced. The setting time was significantly shortened whereas negligible effects were revealed by NCA on the air content of fresh concrete. The addition of NCA significantly enhanced the compressive strength of HSC under low-temperature curing, especially in an early age (i.e., 3 days). The HSC with NCA could reach the standard of impermeable concrete, and no visible cracks were found in the annular crack resistance test. It belonged to low-permeability concrete and could be applied to extreme chloride ion environments. The content of chloride ion and alkali also met the design specifications. The enhanced workability, strength development and durability of concretes with NCA enabled the overall indicators of the high strength concretes to meet the corresponding requirements even when they were cured in low-temperatures.

Delayed Absorption Superabsorbent Polymer for Strength Development in Concrete.

Superabsorbent polymers (SAPs) are used as internal curing agents in cementitious materials, which reduce autogenous shrinkage in concrete as they have a low water-to-cement ratios and improve the freeze–thaw resistance. However, the compressive strength of concrete may also be reduced due to additional voids in the hydrated cement matrix. In this study, we fabricated a delayed absorption type of SAP (I-SAP) composed of cross-linked modified acrylate and studied its absorption characteristics and effect on compressive strength after 28 days. Furthermore, the effect of curing conditions on the strength of concrete and hydrated cement paste with SAP were investigated. The absorption capacity of I-SAP in the synthetic pore solution and deionised water was examined and compared with that of a conventional SAP, and the former was absorbed more by I-SAP. The results revealed that the compressive strength of concrete increased with the addition of I-SAP, particularly with the curing condition of 60% RH. Although the compressive strength of hydrated cement paste with I-SAP reduced in water or sealed curing conditions, no loss of strength in the paste cured at 60% RH was seen. The cement matrix densification due to hydration of belite around the SAP surface is the main mechanism for strength development in concrete cured at sealed and 60% RH. However, the voids formed by SAP control the compressive strength of hydrated paste.

Review on the Relationship between Nano Modifications of Geopolymer Concrete and Their Structural Characteristics.

The main objective of this review is to study some important nanomaterials and their impact on the performance of geopolymer concrete. This paper is an investigation into trends and technology in the development of different nanomaterials to develop higher structural performance geopolymer concrete. The effect of the alkaline to binder and sodium silicate to sodium hydroxide ratio on the performances of geopolymer performances is studied. The relationship between setting time and slump is evaluated through the ternary plot, the variation in compressive strength values is evaluated using the kernel density plot, and the relationship between split tensile and flexural strength is investigated using the scattering interval plot. Regression analysis is carried out among water absorption and bulk-density result values obtained from previous literature. As the molarity and alkaline to binder (A/B) ratios increase, the strength development of geopolymer concrete increases up to a specific limit. The addition of a small quantity of nanomaterials, namely, nano silica, nano alumina, carbon nano tubes, and nano clay, led to the maximum strength development of geopolymer concrete. Incorporating these nanomaterials into the geopolymer significantly refines the structural stability, improving its durability. The various products in GP composites emerging from the incorporation of highly reactive SEM, XRD, and FTIR analysis of nanomaterials reveal that the presence of nanomaterials, which enhances the rate of polymerization, leads to better performance of the geopolymer.

Pemanfaatan Agregat Sungai Mata Allo Enrekang Sebagai Campuran Beton

Mata Allo River is located in Enrekang, South Sulawesi. a river that has a fairly abundant source of aggregate material that has been used by the local community as a concrete-making material in the construction of small-scale construction. This study aims to determine the development of concrete strength based on concrete compressive strength, split tensile strength, flexural strength, and modulus of elasticity in normal quality concrete mixtures based on variations in the Water Cement Factor (FAS), namely Variations 0,49, 0,52 and 0,55 where the variation with the highest compressive strength is used to further testing. The Mix Design method used is the American Concrete Institute (ACI) method with a design concrete quality of 25 MPa. From the results of the study, the highest strength value was found in the FAS variation of 0,49 with an average compressive strength of 7 days, 14 days, 21 days, and 28 days, respectively, with a compressive strength of 16,977 MPa, 23,301 MPa, 25,276 MPa, and 26,691 MPa. The results of the research carried out, the characteristics produced from the Mata Allo river meet the SNI specification standard to be used as a concrete mixture.

Molarity activity effect on mechanical and microstructure properties of geopolymer concrete: A review

The purpose of this paper is to discuss the effect of different molarity, Alkaline to Binder ratio (A/B), and Sodium silicate to sodium hydroxide (SS/SH) ratios on the enhancement of fresh and mechanical properties of geopolymer concrete. In addition, it also reveals the investigation of recent trends and technology of developments of geopolymer concrete in recent years. The fresh and hardened properties like, slump, compressive, split tensile and flexural strength, water absorption, and bulk density of geopolymer concrete data for molarity variations ranging from 5, 8–18 M, with A/B ratios ranging from 0.30 to 0.5, and SS/SH ratios. These data further assessed using kernel density plot. Molarity and A/B ratio maximum the strength development of geopolymer concrete is computed from the graph. The various binding materials used and tests performed on geopolymer concrete by the researchers are also highlighted in this paper. Increasing the molarity and A/B ratios results in the strength development of geopolymer concrete up to a specific limit.Further increment of these parameters will not significantly affect the performance. The optimal value of molarity and A/B ratios at which give better performance is discussed in this paper. Structural performances of geopolymer concrete are higher than traditional concrete.

Effect of superplasticizer on the strength of fly ash based geopolymer concrete

In this research, the effect of a polycarboxylate based superplasticizer on the strength of Geopolymer Concrete (GPC) was investigated. A fixed amount of superplasticizer (1.5 % of Fly Ash weight) was utilized along with alkali activators Sodium Hydroxide (NaOH) and Sodium Silicate (Na2SiO3). The Ultrasonic Pulse Velocity Test determined the strength development of concrete. The quality of the GPC improved when a higher concentration of alkali activator was applied based on the Concrete Quality Designation. In detecting the color development of GPC, samples were put through MATLAB and specimens became lighter as time passes due to dehydration (a process where water escapes from the sample). Stress strain diagrams were generated which generally indicate that GPC specimens are ductile. The researchers were able to assess the workability of the mix designs using a rating from 1 to 5, with 1 being the least workable and 5 being the most workable.

Influence of Curing Practices and Environment on Compressive Strength De-velopment of High Strength Concrete

The paper presents the impact of practicing curing techniques on the compressive strength evolution of ternary blended high strength concrete under local prevailing environmental conditions. Initially the control mix was designed using the guidelines of IS: 10262:2009, whose compressive strength at 28 days is greater than 70 MPa. Later mechanical properties of high strength concrete after incorporating the alternative binder materials was evaluated. For all mixtures water to cement ratio was kept as 0.25. For the purpose of improving the mechanical properties of control mix and to achieve the economy slag, fly ash, quartz powder and silica fume were incorporated in the mix as partial substitution of cement. Total replacement with supplementary binders was kept at 20% by its weight of cement. Among all the combinations, silica fume and slag combination performed well in respect to the hardened properties. Subsequently, the same mix was considered in order to study the influence of practicing curing methods. From the results it was concluded that although type of curing regime on strength development both in indoor and outdoor environment at early ages was not considerable but at the later ages the effect was considerable. Compressive strength of specimens subjected to sprinkling, burlap and plastic cover curing in outdoor environment are significantly affected than the corresponding specimens in indoor environment.

A Statistical Model to Predict the Strength Development of Geopolymer Concrete Based on SiO2/Al2O3 Ratio Variation

Geopolymer Concrete (GPC) is a new class of concrete that presents a vital improvement in sustainability and the environment, particularly in recycling and alternative construction methods. Geopolymers offer a sustainable, low energy consumption, low carbon footprint, and a 100% substitute for the Portland cement binder for civil infrastructure applications. Furthermore, many aluminosilicate materials can be obtained as by-products of other processes, such as coal combustion or the thermal pulping of wood. In addition, slag and fly ash are necessary to source materials for geopolymer. Therefore, geopolymer is considered a solution for waste management that can minimize greenhouse gas emissions. In this statistical study, the present experimental work and found experimental data were collected from local and international literature and were used to build and validate the statistical models to predict the strength development of Geopolymer concrete with binary and ternary systems of source materials. The main independent variable was R, representing the ratio of SiO2/Al2O3by weight in the source material. The investigated range of R was 1.42–3.6. Nine concrete geopolymer mixes with R in the above range represent the experimental part carried out. The targeted properties were compressive, splitting, and flexural strengths. The experimental results showed that the R ratio significantly influences the mechanical performance of the final product. The compressive strength improved by 82, 86, 93, and 95%, when metakaolin content was partially replaced by fly ash and GGBS by percentages of 30, 70, 72, 90, and 95% for mixes 2, 3, 5, 7, and 8 respectively. Also, when GGBS partially replaced fly ash content by 36% and 100% for mixes 6 and 9, compressive strength improved by 10.6% and 41.8%, respectively, compared to mix4. Furthermore, the statistical study revealed that the R ratio might be utilized to determine geopolymer strength with reasonable accuracy. The built models were developed by linear and non-linear regression analysis using SPSS software, version 25. Doi: 10.28991/CEJ-2022-08-03-04 Full Text: PDF

Monitoring strength development of concrete using the wave propagation technique: A practical study

Concrete is one of the most commonly used materials in the construction industry for structural members such as slabs, beams, columns and foundations due to its low cost, high durability and long service life. When concrete is freshly mixed it is in a paste form, which eventually develops into a hard solid once it has cured over time. Concrete typically takes 28 days for full-strength development. In bottom-up concrete construction, it is important to monitor the strength development of concrete under curing to ensure the concrete members are strong enough before casting additional structural elements above. In this study, an attempt is made at a construction site to monitor the strength development of concrete under curing with the non-destructive piezoelectric-based wave propagation (WP) technique. The WP technique employs two piezoelectric sensors and offers the capability of real-time monitoring on the strength development of concrete. The pressure wave (P-wave) velocity can be acquired after applying voltage to the sensor. The P-wave velocity can then be related to the strength of concrete at different curing durations. Based on the on-site experimental study, the P-wave velocities correlate well with the compressive strength of concrete from destructive compressive tests. This on-site experimental study shows the applicability of the WP technique for predicting the strength of concrete in a practical application.

Effect of calcium formate on the compressive strength, and hydration process of cement composite containing fly ash and slag

The replacement of Portland cement (PC) by fly ash (FA) or slag will cause low early age strength development of concrete. However, the addition of chemical additives can eliminate the well-known drawbacks above. The effect of calcium formate (CF) on the compressive strength development of ternary cement (containing FA and slag) was studied based on simplex centroid design in this paper. Results show that CF can be safely used to increase the strength of ternary cement composite. In addition, the influence of CF on the hydration process and microstructural features of PC and PC-FA/slag blends was investigated using isothermal calorimetry, X-ray diffraction, thermal analysis, and scanning electron microscopy. These results show that the addition of CF can enhance the strength of PC and PC-FA/slag blends at early curing ages, which is mainly because of a kind of calcium aluminate silicate hydrate called gismondine (CaAl2Si2O8·4H2O) and more formation of ettringite (AFt). Furthermore, at later ages of hydration, CF can promote the silicate reaction of PC and PC-FA/slag blends and accelerate the pozzolanic reaction of FA in order to improve the strength.

Study of Fly Ash Concrete Exposed to Elevated Temperature

The ability to improve the tendency of hardened concrete in compression at elevated temperature was studied. Five mixes of fly ash were cast with a replacement amount of 0%, 10%, 20%, 30%, and 40% by cement mass. They were exposed to 400°C and held for 2 hours after water curing. The specimens have been cooled down to room temperature and then undergo a compressive test. This research aims to study the physical and mechanical properties of fly ash concrete after being exposed to elevated temperatures. A digital microscope was used to analyse the formation mechanism of microstructure in concrete. Fly ash was used to produce high fire resistance concrete with 100 mm x 100 mm x 100 mm concrete cube. Sample 4 with 30% fly ash has the highest compressive strength with 26 MPa after 28 days and 21 MPa after exposed to 400°C. The results show that concrete containing a high amount of fly ash has several improvements when exposed to elevated temperature. The concrete specimens were used to validate an interfacial transition zone (ITZ) in concrete. The microstructure features were discussed concerning their influence on the strength development of concrete.

Development of sintered aggregate derived from POFA and silt for lightweight concrete

The decline in available natural resources and generation of waste materials has brought about a high environmental impact. A potential solution is artificial aggregate fabrication from waste materials. Comprehensive findings have been reported on the performance of industrial waste modified as geo-polymer or cementitious substitution for concrete application. Furthermore, some commercial artificial aggregates made from waste such as LECA, Lytag and others form the basis for further exploitation. A valuable area of investigation is using known cementitious POFA activated by binary activator combined with silt to produce an artificial aggregate. Thus, the present study investigates the physical, mechanical, thermal properties and microstructure of optimised sintered POFA-silt (S-POFA) aggregate on lightweight concrete (LWC). Firstly, characterisation analysis of raw materials, POFA and silt is conducted. Then, the effect of different mix proportion ratios of POFA and silt on the S-POFA aggregate properties is studied with sintering temperature (1150 °C) defined from a preliminary study. Then, the selected optimised sintered S-POFA aggregate is applied as coarse aggregate for concrete production to determine its performance. Based on the result, the increase of POFA proportion increases the density and mechanical properties but shows a declining trend in water absorption. This observation is due to the formation of a dense matrix for the internal microstructure of S-POFA aggregate. Sintered S-POFA aggregate with 40% POFA shows better strength performance with optimum results and is therefore used for concrete mix. Besides, the density of the S-POFA aggregate shows that all the samples are categorised as lightweight aggregate. S-POFA LWC with 28 d strength of more than 30 MPa with density less than 2000 kg/m3 is obtained. Moreover, this concrete provides a low coefficient for capillary absorption and shrinkage. Internal curing allows further hydration to enhance strength development in concrete. In conclusion, this result indicates that S-POFA LWC with both acceptable workability and strength can be achieved through incorporation with sintered S-POFA aggregate.

Evaluation of the Effect of Granite Waste Powder by Varying the Molarity of Activator on the Mechanical Properties of Ground Granulated Blast-Furnace Slag-Based Geopolymer Concrete.

Industrial waste such as Ground Granulated Blast-Furnace Slag (GGBS) and Granite Waste Powder (GWP) is available in huge quantities in several states of India. These ingredients have no recognized application and are usually shed in landfills. This process and these materials are sources of severe environmental pollution. This industrial waste has been utilized as a binder for geopolymers, which is our primary focus. This paper presents the investigation of the optimum percentage of granite waste powder as a binder, specifically, the effect of molar and alkaline to binder (A/B) ratio on the mechanical properties of geopolymer concrete (GPC). Additionally, this study involves the use of admixture SP-340 for better performance of workability. Current work focuses on investigating the effect of a change in molarity that results in strength development in geopolymer concrete. The limits for the present work were: GGBS partially replaced by GWP up to 30%; molar ranging from 12 to 18 with the interval of 2 M; and A/B ratio of 0.30. For 16 M of GPC, a maximum slump was observed for GWP with 60 mm compared to other molar concentration. For 16 M of GPC, a maximum compressive strength (CS) was observed for GWP with 20%, of 33.95 MPa. For 16 M of GPC, a maximum STS was observed for GWP, with 20%, of 3.15 MPa. For 16 M of GPC, a maximum FS was observed for GWP, with 20%, of 4.79 MPa. Geopolymer concrete has better strength properties than conventional concrete. GPC is $13.70 costlier than conventional concrete per cubic meter.

Validation of slag-binder fiber-reinforced self-compacting concrete with slag aggregate under field conditions: Durability and real strength development

The environmental conditions to which a concrete may be exposed will condition its real range of use. Thus, concrete behavior must, at all times, be verified under a wide variety of environmental conditions, in order to ensure its real applicability. In this study, the real strength development and durability behavior of a fiber-reinforced self-compacting concrete is analyzed. This particular concrete incorporates 100% coarse (4/12 mm) and fine (0/4 mm) Electric Arc Furnace Slag (EAFS) as aggregate, as well as limestone fines as aggregate powder (0/1.18 mm). Furthermore, Ground Granulated Blast Furnace Slag (GGBFS) was also added as binder. Four mixtures with and without either metallic or synthetic fibers, and different GGBFS contents were designed. Real strength development was evaluated in all the mixes by comparing the strength development of both cores extracted from full-scale beams and wet-cured laboratory specimens. The durability behavior was analyzed by Mercury Intrusion Porosimetry (MIP), freeze/thaw, moist/dry, sulfate-attack, chloride-penetration, carbonation, and SO2-attack tests. On the one hand, the long-term mechanical properties of the cores (real conditions) were similar to the properties of the specimens cured in a moist chamber for 90 days in all the mixes. On the other, the increase in water content when adding fibers to maintain flowability, as well as the addition of GGBFS, resulted in an increase in MIP porosity. Therefore, the use of fibers, both metallic and synthetic, slightly worsened the durability behavior of the concrete, facilitating the entry of aggressive external agents. Nevertheless, the increased flexibility of the cementitious matrix when adding GGBFS was beneficial against moist/dry and sulfate-attack phenomena, despite the increase in porosity. Overall, the mixes complied with the regulatory requirements for use in aggressive environments, although the amounts of fibers and GGBFS should be carefully studied.

Statistics and Analysis of the Relationship between Strength and Age of Coral Concrete

In this study, based on the experimental results of this study and from the previous research, it is concluded that the compressive strength of coral concrete at 3, 7, 14, 21, 60, and 90 days reaches about 71%, 84%, 92%, 96%, 104%, and 110% of that at 28 days, respectively, indicating that the early strength development of coral concrete is significantly faster than that of ordinary concrete but slower in the later stage. A new model to characterize the strength‐age relationship of coral concrete is proposed in this study, which is in good agreement with the experimental result, but for the long‐term strength prediction of coral concrete in actual engineering, it is recommended to adjust the prediction results according to the environment and working conditions of coral concrete, and the adjustment coefficient could be approximately taken as 0.88. In addition, the effects of water‐binder ratio (w/b), total dosage of cementitious materials (b), supplementary cementitious material (SCM) content, and aggregate properties, on the age strength development of coral concrete are studied.