Strength Development Of Concrete Research Articles

Deconvolution of main hydration kinetic peaks in properly sulfated Portland cements with boundary nucleation and growth models and relation to early-age concrete strength development

When the hydration kinetics of properly sulfated Portland cements is monitored by heat flow calorimetry, the initial dissolution peak and the dormant period is followed by the main hydration peak – formation of calcium-silicate-hydrates and portlandite, the so-called silicate peak. This main peak is superimposed by a peak associated to further tricalcium aluminate dissolution and a surge in precipitation of sulfoaluminates (the so-called sulfate depletion peak) right after sulfate added for setting control is depleted in the material system. In this paper strategies for the deconvolution of silicate peak and sulfate depletion peak are presented. Hereby, the boundary nucleation and growth model and the classical bulk nucleation and growth model serve as tools for deconvolution of calorimetric data. We discuss obtained kinetic parameters and their temperature dependency. The boundary nucleation and growth model for constant nucleation rate emerged as the most suitable model for the silicate reaction, the bulk nucleation and growth model with an order of three, indicating site saturation, as adequate for the sulfate depletion peak. The reaction enthalpy for tricalcium silicate hydration was obtained as 503 J/g, remarkably close to literature values. Calorimetric data related to the sulfate depletion peak is corroborated by X-ray diffraction analysis of formation history of crystalline hydration products. Furthermore, the history of the (silicate) degree of reaction as predicted by the boundary nucleation and growth model for different temperature histories is related to experimentally obtained early-age strength histories. • Investigation of hydration kinetics of commercial, well-sulfated Portland cement. • Main peak (C-S-H and portlandite formation) superimposed by sulfate depletion peak. • Strategies for deconvolution of peaks with Avrami–Cahn models as tools for analysis. • Degree of silicate reaction history is linked to early-age strength gain.

Influence of Ca2+ on Early Degradation of Cast-In-Situ Mortar Induced by Sulfate-Magnesium Multiple Combined Attack.

Early degradation of cast-in-situ concrete induced by multiple internal–external sulfate combined attacks significantly affects the development of concrete strength. An experimental study regarding the effects of Ca2+ on the early degradation of cast-in-situ mortars subjected to internal–external sulfate and magnesium combined attacks is investigated in this paper. In particular, a specific method for accurately simulating the degradation of cast-in-situ structures was proposed in this experiment. Physical properties (including weight, size changes, and porosity), mechanical properties (including flexural strength and compressive strength), sulfate concentration, and microstructural properties were monitored during 28 days of immersion. The results show that an internal sulfate and magnesium combined attack (ISA-IMA) obviously retards the development of early strength and accelerates the degradation induced by external sulfate attack (ESA). The diffusion path of sulfate ions from outside is blocked by flake-shaped magnesium hydrates, delaying the penetration of external sulfate attacks. However, it is far from neutralizing the strength loss induced by an internal magnesium attack (IMA) at an early age. Premixed excessive Ca2+ would improve the strength development and pore structure of concrete or mortar, enhancing durability against corrosive conditions.

Concrete strength development by using magnetized water in normal and self-compacted concrete

Abstract The main objective of this work was to adopt an environmentally friendly technology with enhanced results. The technology of magnetic water (MW) treatment system can be used in concrete mixture production instead of potable water (PW) to improve both workability and strength. Two types of concrete were adopted: normal concreter production with two grades 25 and 35 MPa and the self-compacted concrete (SCC) with 35 MPa grade. The concrete mixes containing MW instead of PW results showed that, for 25 MPa grade, an improvement in a compressive strength of 15.1, 14.8, and 10.2% was achieved for 7, 28, and 90 days, respectively. For 35 MPa grade, an improvement of 13.6, 11.5, and 9.1% was achieved for 7, 28, and 90 days, respectively. The mixture of SCC showed the highest improvement up to 16.2, 15.8, and 12.4% for 7, 28, and 90 days, respectively. The effect of MW is significant for 7 days compared to 28 and 90 days. An increase in the water content to cementitious material presents the more efficiency of MW, while the combined effect of MW and superplasticizer in SCC showed the best improvement with less water content for 35 MPa grade.

Preparation of Mineral Admixture from Iron Tailings with Steel Slag-Desulfurization Ash and Its Application to Concrete.

Iron tailing solid waste not only has a high annual output but also has a low comprehensive utilization rate. Low utilization rate of iron tailings seriously restricts the development of comprehensive utilization of solid waste. In order to prepare an iron tailings-based ternary solid waste admixture and to verify its application to concrete, first, the effect of solid waste synergy on the strength of an iron tailings-steel slag-desulfurization ash admixture (ISD) system was investigated. Second, the effect of chemical activator dosing on the strength of an ISD system was studied and the mechanism of chemical activator action on the ISD system was investigated by thermogravimetric analysis (TG-DTA) Then, the effect of this admixture on the strength of concrete was studied. Finally, the mechanism of the effect of this admixture on the strength of concrete was clarified by mercury intrusion porosimetry (MIP) and backscattering electron tests (BSE). The results showed that the 7 d and 28 d compressive strengths of the ISD admixture were significantly higher than those of iron tailings single admixture. The 7 d and 28 d compressive strengths of the ISD system reached 24.9 MPa and 36.1 Mpa, respectively, when the ratio of iron tailings:steel slag:desulfurization ash = 1:1:1. Na2SiO3 is suitable for the early strength agent of the ISD admixture, but the amount of admixture should not exceed 0.6% of the admixture. TG-DTA shows that Na2SiO3 is enhancing the early strength of the ISD system by promoting the consumption of Ca(OH)2 in the ISD system to produce C-S-H. However, in the late reaction of the ISD system, Na2SiO3 inhibits the late strength development of the ISD system by suppressing Ca(OH)2 production. Concrete with ISD dosing of 30% or less meets the C40 requirement. MIP and BSE show that ISD provides a filling effect to concrete, but also causes a reduction in the active reactants of concrete and the combined effect of microfilling and active effects affects the strength development of ISD concrete. This study provides a theoretical and scientific basis for the preparation of iron tailings-based ternary solid waste dopants, and, in addition, the study promotes the consumption of iron tailings solid waste and the development of multiple solid waste dopants.

Self-sensing reinforced concrete for damage assessment and real time strength development in smart structures

In this study, a self-sensing smart structure was developed with a novel approach. Electromagnetic wave based self-sensing structure designed by sending waves to the reinforced concrete structure through the reinforcement by using a coaxial cable. EM measurements were based on estimating the reflected EM waves through the reinforced concrete. Correlations between reflected EM wave, damage in reinforced concrete and strength development in concrete was estimated. According to test results, it was seen that with increasing crack width of reinforced concrete by applying monotonic load, reflection of EM wave through the reinforced concrete decreased. It was also seen that with strength development of the concrete, reflection of EM through the reinforced concrete increased. In the light of the findings of this study it can be said that, damage assessment and monitoring strength development of the reinforced concrete is possible in real time with applying the proposed novel technique.

A statistical models to predict strength development of eight molarity geopolymer concrete

Geopolymer concrete has emerged as a viable alternative to traditional concrete. Geopolymer is amorphous to semi-crystalline materials synthesized from materials generally containing SiO2 and Al2O3 compounds as a source of aluminosilicates. This study aims to develop and validate statistical models to predict the strength development of Geopolymer concrete with 8 molarity of NaOH using data from current experimental work as well as experimental data gathered from local and international literature with different R ratios; SiO2/Al2O3. The present experimental study used binary and ternary systems of source materials, Fly ash FA, Ground Granulated Blast-furnace Slag GGBS, and Metakaolin MK, to achieve different percentages of R ratios ranging from 1.42 to 3.6. Seven Geopolymer concrete mixes with varied R ratios were used in the current experimental portion of the inquiry. Compressive, splitting, and flexural strengths were the characteristics determined. Based on the findings of the trials, it was found that the R ratio has a considerable impact on the mechanical performance of the final product. Results showed that; the compressive strength, splitting tensile strength, and flexural strength at the highest value of R ratio of 3.6 used increased by 362%, 272%, and 333%, respectively, compared with those strengths at the lower R ratio of 2.01 used. Linear and non-linear regression analyses were performed by the Statistical Package for the Social Sciences (SPSS) software version 25 to generate the developed models. The statistical models indicated that the R ratio could reasonably estimate the geopolymer's strength with a statistical correlation coefficient of 0.86, 0.93, and 0.86 for compressive, splitting, and flexural strengths.

Early-age concrete strength development monitoring using piezoelectric self-emission and detection (SED) and coda wave energy (CWE)

The property of concrete is very significant to structural safety, and the early hydration process plays a critical role in the final concrete property. This paper develops a self-emission and detection (SED) principle with a single piezoelectric smart aggregate (SA) transducer, which is used as both an actuator and a sensor, to monitor the concrete early age strength development. The signal analysis is carried out by the coda wave energy (CWE). Experiments of concrete specimens with and without the SAs were conducted. Experimental results show a high correlation between the strength of early-age concrete and the CWE and non-linear fitting is used to establish the relationship between them. The proposed CWE features a simple analysis method, and the SED principle does not require consideration of the matching between the transmitting transducer and the receiving sensor, such as frequency range, sensitivity. Furthermore, the proposed method can be used as a reference for health monitoring of other structures and has good application prospects.

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.

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.

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.