Early-age Curing Research Articles

Use of recycled glass powder to improve the performance properties of high volume fly ash-engineered cementitious composites

High-volume fly ash (HVFA) Engineered Cementitious Composites (ECC) show reduced strength and physical properties, especially at early curing ages. The goal of this study was to improve their strength characteristics by incorporating recycled glass powder (RGP) for enhanced material sustainability. Composites containing 15, 30, 45 and 60% RGP as a replacement for FA, with FA to cement ratio of 2.2, were studied in HVFA-ECC. Standard ECC mixtures with FA to Portland cement (FA/PC) ratio of 1.2, and HVFA-ECC with FA/C ratio of 2.2 without RGP were also produced as control mixtures. The experimental results confirmed that incorporating RGP into HVFA-ECC significantly improves compressive and flexural strengths, chloride ion resistance and electrical resistivity, and results in a comparable ductility to standard ECC, based on FA to cement ratio of 1.2. Furthermore, self-healing of HVFA-ECC was accelerated and final recovery rate of strength and physical properties improved. Microstructural analysis showed high portlandite consumption and the formation of low Ca/Si ratio in new C-S-H structures near C-Na-Al-S-H as the main outcome of the binary admixture in ECC.

Early-Age Strength of Aeolian Sand-Based Cemented Backfilling Materials: Experimental Results

Cemented paste backfill (CPB) is used extensively in underground mining operations worldwide. However, CPB technology is not widely used in China’s western eco-environment frangible area because of the sources, costs, and mechanical properties of the material. This study aims to investigate and better understand the mechanical properties of aeolian sand-based cemented backfilling with different properties (water/cement ratio, aeolian sand content, fly ash content, and Portland cement content) at early-age curing times (1, 3, 7, 28 days). Based on microstructural analyses (e.g. X-ray diffraction and SEM studies) of tested CPB materials, an experiment was designed to study the early-age strength of nine different CPB materials. The obtained results reveal that water/cement ratio, aeolian sand content, fly ash content and Portland cement content can affect the properties of CPB materials. The experimental results can help to better assess and predict the mechanical properties of aeolian sand-based cemented backfilling materials. The findings of this study have significant implications for CPB practices in China’s western eco-environment frangible area.

Evaluation of the performance of eco-friendly lightweight interlocking concrete paving units incorporating sawdust wastes and laterite

Abstract This research investigates the performance of sawdust wastes and laterite as an alternative lightweight fine aggregate and cementitious material respectively in eco-friendly lightweight interlocking concrete paving units (ICPU) using a mix ratio of 1:2:4. The lightweight sawdust and laterite were studied due to their abundant availability as industrial waste and cheap local construction material. Eco-friendly ICPU is a low-strength concrete with compressive strengths of 6.02–7.57 and 3.66–4.52 N/mm2 at 5 and 10% sawdust replacements with bulk density ranges of 1,756.62–1,810.9 and 1,522.89–1,532.4 kg/m3 respectively which exceeded the minimum compressive strength requirement of 3.45 N/mm2 in non-load bearing concrete applications. Though air curing recorded higher compressive strengths at early curing ages, water curing was recommended to facilitate complete hydration owing to the hygroscopic nature of the sawdust. The packing and filling effects of the lightweight sawdust coupled with the combined pozzolanic properties of the sawdust waste and laterite seemed to have contributed to the slight increase in CS of the eco-friendly ICPU when heated. Effective partnerships among the State and Local Government Waste Management Authorities, sawmill operators and informal waste collectors were recommended for effective sawdust waste recovery, storage and usage in eco-friendly construction.

Concrete strength evaluation in an early-age curing process using SVM with ultrasonic harmonic waves

Concrete strength evaluation in an early-age curing process using SVM with ultrasonic harmonic waves

Viscoelastic response of an epoxy adhesive for construction since its early ages: Experiments and modelling

Abstract Epoxy adhesives have been extensively used in strengthening of reinforced concrete structures. In spite of that, research on the viscoelastic behaviour of these adhesives and its influence on the mechanical behaviour of strengthened concrete structures is scarce, particularly at the early ages of curing. The main goal of present work is to better understand the tensile creep behaviour of a specific commercial epoxy adhesive both at early ages and at long term. For this purpose, an experimental program comprising tensile creep tests was performed, in which epoxy specimens were subjected to: (i) equal stress levels but loaded at different ages, and; (ii) two different stress levels for a specific loading age. The results obtained have confirmed the viability of the principles of homogeneity and superposition, thus allowing the classification of this epoxy as linear viscoelastic. In addition, analytical simulations with Burgers model were carried out, and its predictive performance was considered insufficient at early ages, particularly upon unloading. In order to surpass some disadvantages of this model, a new framework is proposed to analytically evaluate the creep curing behaviour of this type of viscoelastic epoxy adhesives. The obtained results evidenced the capability of the proposed framework to predict the creep behaviour of an epoxy adhesive since its early ages.

Evaluating the early-age behaviour of full-scale prestressed concrete beams using distributed and discrete fibre optic sensors

This paper evaluates the results of a monitoring study that captures the early age behaviour of four 11.9m prestressed concrete bridge beams utilising both distributed and discrete fibre optic sensor (FOS) arrays. The performance of the beams is evaluated before they are placed in-service as part of new concrete railway bridges in the Midlands in the UK. Two types of prestressed beams were monitored, two TY7 internal beams and two TYE7 edge beams. The beams incorporated high strength (up to 90.7MPa) self-consolidating concrete. The entire manufacturing process which included early-age curing and the detensioning process was captured in great detail using the installed FOS system. An analysis of the curing strains within the beams revealed the significant effect that ambient temperature, curing duration, and formwork restraint has on the development of prestress losses prior to detensioning. Based on the distributed FOS readings, it was observed that the strain remained uniform along the length of the beams during the various beam monitoring stages. The measured strain data was then used to calculate prestress losses in the first six months after casting (prior to casting of the in-situ concrete bridge deck). The TY7 and TYE7 beams experienced losses that were 79% and 72% of the ultimate losses predicted using Eurocode 2 equations, respectively. Distributed strain measurements were used to provide estimates of the change in beam camber with time. The pre-camber values calculated using the recorded FOS strain data at the time of detensioning closely match the theoretically calculated values. However, camber values increased by up to 1.7 times in the first six months compared with the post-detensioning values and deviated significantly from the theoretically calculated values. The future aim of this research is to establish integrated FOS systems as viable tools for monitoring strain evolution in concrete bridges in order to establish comprehensive baselines to facilitate long term data-driven bridge monitoring programmes.

Evaluation of Thermal Properties of Early-Age Concrete Containing Fly Ash

Fly ash, a by-product of burning pulverized coal in electrical generating stations, is used as a supplementary pozzolanic material in the production of Portland cement concrete. It improves, e.g., workability of a concrete mixture, suppresses bleeding, reduces the rate of production of hydration heat and delays finishing operations. Consequently experimental research, theoretical analysis, incorporating available microstructural data, and efficient numerical simulations are needed to understand the influence of early-age curing on later macroscopic mechanical, thermal, etc. material properties. This paper presents a proper experimental and computational approach to the evaluation of time-variable thermal characteristics of a hardening mixture, based on the weak formulation of the evolution problem and on the least squares optimization. Results of such types are necessary for reliable prediction of behaviour, performance and durability of buildings and engineering structures.

Monitoring of the curing process in precast concrete slabs: An experimental study

In this paper a methodology for the quality control of the curing process in precast concrete plants is presented by non-destructive testing techniques. This methodology consists on a remote monitoring system and a method to estimate the strength gain of the precast elements during the curing process. The remote monitoring system is based on Wireless Sensor Networks (WSN) provided with temperature, humidity and ultrasonic sensors. The compressive strength is estimated using two different procedures, one based on temperature and the other one on ultrasonic velocity measurements. Comparing the compressive strength estimations obtained using temperature and ultrasonic velocity measurements, the concrete quality during early ages of curing can be controlled, and arising problems can immediately be detected. This methodology was tested in three different precast concrete plants in Spain.

Microstructure and mechanical properties of accelerated sprayed concrete

Considering the different hydration processes of concrete without accelerator, sprayed concrete with low-alkali accelerator not only presents short setting times and high early-age mechanical properties but also yields different hydration products. This study presents an analysis of the mechanical properties of concrete with and without accelerator and sprayed concrete with three water–binder (w/b) ratios and four dosages of fly ash (FA) after different curing ages. It also examines the setting time, mineral composition, thermogravimetric–differential scanning calorimetry curves and microscopic images of cement pastes with different accelerator amounts. Furthermore, the setting time and microstructure of accelerated sprayed concrete with different w/b ratios and FA contents are examined. Results show that the retarded action of gypsum disappears in the accelerated cement–accelerator–water system. C3A is quickly hydrated to form calcium aluminate hydrate (CAH) crystals, and a mesh structure is formed by ettringite, albite and CAH. A large amount of hydration heat improves the hydration rate of the cement clinker mineral and the resulting density, thereby improving mechanical properties at early curing ages. The setting times of the pastes increase with increasing w/b ratio and FA dosage. Thus, the hydration level, microstructure and morphology of the hydration products also change. Models of mechanical properties as functions of w/b, FA and curing age, as well as the relationship between compressive strength and splitting tensile strength, are established.

Effect of curing conditions on the hydration and performance of CFBC ash cementitious system

Circulating fluidized bed combustion (CFBC) ash can be used as supplementary cementitious material for concrete production for its high pozzolanic activity. We investigated the effect of curing conditions on the hydration and performance of CFBC ash-Portland cement system (30: 70, by mass) including hydration products, paste microstructure, linear expansion ratio, chemically combined water content and compressive strength. The results show that tobermorite rather than ettringite is generated under the condition of autoclaved curing. The expansion and mortar strength of the system cured in water is higher than those cured in air at a given age, and the strength and bulk volume may retract under the condition of air curing. In addition, autoclaved curing facilitates the increase of strength gain at early curing ages (the increase rate lowers down in the following ages) and the improvement of system volume stability. It is suggested that sufficient water is necessary for the curing of CFBC ash cementitious system, and autoclaved curing may be considered where volume stability is a primary concern.

Improvement Properties of Cohesion-Less Soil Using Recycled Bassanite

Solid waste management is a serious problem over the world. Therefore, reduction, re-use and recycling of waste have become major issues in recent days. Gypsum waste plasterboard is considered one example of these waste materials. This study evaluates the use of recycled bassanite, which is derived from gypsum waste plasterboard, to enhance the performance of two types of cohesion-less soil. Recycled bassanite was utilized as a stabilizing agent to improve both compressive and splitting strengths of the tested soil. The effect of bassanite content, soil type, water content and curing time were investigated to explore the behavior of treated soil with recycled bassanite. Test results showed that increase of bassanite content is associated with increase in optimal moisture content, while no significant increase in the dry unit weight was observed. Both compressive and splitting tensile strengths enhanced with the additives of recycled bassanite. The increase of bassanite content had a more significant effect on the compressive strength compared with the effect on tensile strength. The use of recycled bassanite to enhance the strength of sandy soil had a more significant effect compared with silty soil. The effect of curing time on the strength of treated samples was more significant in early curing ages compared with late curing ages. The strength decreased significantly in case of stabilized samples prepared with water content at the wet-side of the compaction curve. However, insignificant decrease in the strength of the stabilized sample was detected with moisture content at the dry-side of compaction curve. This research meets the challenges of our society to reduce the quantities of gypsum wastes, producing useful material from waste materials that will help to a sustainable society.

Palygorskite as an admixture to air lime–metakaolin mortars for restoration purposes

As mortars for rehabilitation purposes should have a similar composition to the historical materials, this work focussed on the preparation of mortars with binder:aggregate 1:3 volumetric ratio (vr) traditionally used in old buildings in central parts of Portugal. Mortars based on air lime binder with additions of 5mass% of palygorskite (Pal) and 20mass% of metakaolin (MKaol) were prepared to provide 1:3 vr, in which lime binder or sand was substituted.Needle-like Pal particles are functional as reinforcing fibres both in lime–Pal mortars and in air lime–MKaol–Pal systems. Chemical and mechanical properties of mortars were analysed at 28, 90 and 180days of curing. Pozzolanic activity of MKaol was revealed by the presence of tetracalcium aluminate hydrate C4AH13 and monocarboaluminate C4A C¯ H11 at early ages of curing. Top value of flexural strength at 180days shows lime–Pal mortar, in which sand was substituted by Pal, while the highest value of compressive strength was reached by lime–MKaol–Pal mortar, in which MKaol:lime mass ratio was 1:4.75. It was confirmed that differences in MKaol:lime mass ratios, even very small, cause considerable variances in the obtained mechanical properties.

Effect of Different Curing Conditions on the Mechanical Properties of UHPFC

Ultra-High Performance Fiber Concrete (UHPFC) is a new class of concrete. Because of its distinguished mechanical properties, UHPFC is considered as an ideal alternative material for use in developing new structural solutions. This paper discusses on influence of different curing conditions on mechanical properties of UHPFC. An experimental program was performed to study the mechanical properties of UHPFC which were cured under six different curing conditions. Test results indicated that steam and boil curing methods showed a promising performance particularly at early age of curing compared to other type of curing.

Effects of mineral admixtures and superplasticizers on micro hardness of aggregate-paste interface in cement concrete

This paper presents quantitatively the results of an experimental investigation on influence of mineral admixtures and superplasticizers on Vickers micro hardness (HV) of aggregate-paste interface in cement concrete. The HV was measured by Vickers hardness testing equipment. The results indicate that addition of fly ash decreases HV of the concrete. Although it decreases with the increase of ground granulated blast furnace slag (GGBS) replacement, the HV is higher than that of concrete containing fly ash at all replacements. The flying ash and GGBS composition increases HV in later curing ages, but does not improve it in early curing ages. Aminosulfonic acid based superplasticizer and aliphatic hydroxy sulphonate condensate superplasticizer can enhance HV in early curing ages. The HV of concrete with polycarboxylic acid superplasticizer is higher in later curing ages.

RETRACTED ARTICLE: Utilizing ANFIS for prediction water absorption of lightweight geopolymers produced from waste materials

In the present work, water absorption of lightweight geopolymers produced by fine fly ash and rice husk–bark ash together with palm oil clinker (POC) aggregates has been investigated experimentally and modeled by adaptive network-based fuzzy inference systems (ANFIS). Different specimens made from a mixture of fine fly ash and rice husk–bark ash with and without POC were subjected to water absorption tests at 2, 7, and 28 days of curing. The specimens were oven cured for 36 h at 80 °C and then cured at room temperature until 2, 7, and 28 days. The results showed that high amount of POC particles improve the percentage of water absorption at the early age of curing. In addition, the ratio of “the percentage of water absorption” to “weight” of the POC-contained specimens at all ages of curing was much higher than that of POC-free specimens, which make them suitable for lightweight applications. To build the model, training, validating, and testing using experimental results from 144 specimens were conducted. The used data in the ANFIS models are arranged in a format of six input parameters that cover the quantity of fine POC particles, the quantity of coarse POC particles, the quantity of FA + RHBA mixture, the ratio of alkali activator to ashes mixture, the age of curing, and the test trial number. According to these input parameters, the water absorption of each specimen was predicted. The training, validating, and testing results in the ANFIS models showed a strong potential for predicting the water absorption of the geopolymer specimens.

RETRACTED: Fuzzy logic for prediction water absorption of lightweight geopolymers produced from waste materials

Abstract In the present work, water absorption of lightweight geopolymers produced by fine fly ash and rice husk bark ash together with palm oil clinker (POC) aggregates has been investigated experimentally and modeled by fuzzy logic. Different specimens made from a mixture of fine fly ash and rice husk bark ash with and without POC were subjected to water absorption tests at 2, 7 and 28 days of curing. The specimens were oven cured for 36 h at 80 °C and then cured at room temperature until 2, 7 and 28 days. The results showed that high amount of POC particles improve the percentage of water absorption at the early age of curing. In addition the ratio of “the percentage of water absorption” to “weight” of the POC-contained specimens at all ages of curing was much higher than that of POC-free specimens which make them suitable for lightweight applications. To build the model, training, validating and testing using experimental results from 144 specimens were conducted. The used data in the fuzzy model are arranged in a format of six input parameters that cover the quantity of fine POC particles, the quantity of coarse POC particles, the quantity of FA + RHBA mixture, the ratio of alkali activator to ashes mixture, the age of curing and the test trial number. According to these input parameters, the water absorption of each specimen was predicted. The training, validating and testing results in the fuzzy model have shown a strong potential for predicting the water absorption of the geopolymer specimens.

Carbonation Curing versus Steam Curing for Precast Concrete Production

An investigation was conducted into the beneficial utilization of captured CO2 for early-age curing of precast concrete products. The performance of the carbonation-cured concrete was compared to that of steam curing to investigate the possibility of replacing steam curing with carbonation. The early-age carbonation curing was performed for a short period after an initial curing in a controlled environment. The effect of the carbonation curing was studied in terms of carbon uptake, accelerated strength, and durability. It was found that the short-term carbonation promoted early strength development, while subsequent hydration was essential to obtain later age properties. Durability performance of the carbonation-cured concrete was compared with steamed and normally hydrated references. The carbonation-cured concrete exhibited more resistance to chloride permeability, ion migration, sulfate attack, and freeze-thaw damage. The improved durability by carbonation is attributed to the significantly reduced calcium hydroxide content at the carbonated concrete surface. Despite a reduced pH at the carbonated zone, the alkalinity at the core was maintained above the threshold value needed to prevent carbonation corrosion.

Designing water resistant lightweight geopolymers produced from waste materials

In the present work, percentage of water absorption and pore structure of lightweight inorganic polymers (geopolymers) produced by fine fly ash, rice husk bark ash and palm oil clinker (POC) aggregates has been investigated. Different specimens, made from a mixture of waste materials, were subjected to permeability and porosimetry tests at 2, 7 and 28days of curing. The specimens were oven cured for 36h at 80°C and then water cured at room temperature until 2, 7 and 28days. The results showed that high amount of POC particles improve the percentage of water absorption at the early age of curing. In addition the ratio of “the percentage of water absorption” to “weight” of the POC-contained specimens at all ages of curing was much higher than that of POC-free specimens which make them suitable for lightweight applications. The total specific pore volume of the POC-contained specimens was smaller than POC-free specimens at early age of curing. Some empirical relationship was found to predict the total specific pore volume of the specimens by means of their percentage of water absorption at early age of curing with an acceptable approximation. The obtained results from Fourier transform infrared spectroscopy also confirm those results from permeability and porosimetry tests.

The effects of CuO nanoparticles on properties of self compacting concrete with GGBFS as binder

In this work, strength assessments and percentage of water absorption of high performance self compacting concrete containing different amounts of ground granulated blast furnace slag and CuO nanoparticles as binder have been investigated. Portland cement was replaced by different amounts of ground granulated blast furnace slag and the properties of concrete specimens were investigated. Although it negatively impacts the physical and mechanical properties of concrete at early age of curing, ground granulated blast furnace slag was found to improve the physical and mechanical properties of concrete up to 45 wt. (%) at later ages. CuO nanoparticles with the average particle size of 15 nm were partially added to concrete with the optimum content of ground granulated blast furnace slag and physical and mechanical properties of the specimens were measured. CuO nanoparticle as a partial replacement of cement up to 3.0 wt. (%) could accelerate C-S-H gel formation as a result of increased crystalline Ca(OH)2 amount at the early age of hydration and hence increase strength and improve the resistance to water permeability of concrete specimens. The increased the CuO nanoparticles' content more than 3.0 wt. (%), causes the reduced the split tensile strength because of the decreased crystalline Ca(OH)2 content required for C-S-H gel formation. Several empirical relationships have been presented to predict flexural and split tensile strength of the specimens by means of the corresponding compressive strength at a certain age of curing. More rapid appearance of the peaks related to hydrated products in X-ray diffraction results, all indicate that CuO nanoparticles could improve mechanical and physical properties of the concrete specimens.

RETRACTED ARTICLE: Effects of Al2O3 nanoparticles on properties of self compacting concrete with ground granulated blast furnace slag (GGBFS) as binder

In this work, strength assessments and percentage of water absorption of self compacting concrete containing ground granulated blast furnace slag (GGBFS) and Al2O3 nanoparticles as binder have been investigated. Portland cement was replaced by different amounts of GGBFS and the properties of concrete specimens were investigated. Although it negatively impacts the physical and mechanical properties of concrete at early ages of curing, GGBFS was found to improve the physical and mechanical properties of concrete up to 45 wt% at later ages. Al2O3 nanoparticles with the average particle size of 15 nm were added partially to concrete with the optimum content of GGBFS and physical and mechanical properties of the specimens were measured. Al2O3 nanoparticle as a partial replacement of cement up to 3.0 wt% could accelerate C-S-H gel formation as a result of increased crystalline Ca(OH)2 amount at the early ages and hence increase strength and improve the resistance to water permeability of concrete specimens. The increase of the Al2O3 nanoparticles’ content by more than 3.0 wt% would cause the reduction of the strength because of the decreased crystalline Ca(OH)2 content required for C-S-H gel formation. Several empirical relationships have been presented to predict flexural and split tensile strength of the specimens by means of the corresponding compressive strength at a certain age of curing. Accelerated peak appearance in conduction calorimetry tests, more weight loss in thermogravimetric analysis and more rapid appearance of the peaks related to hydrated products in X-ray diffraction results, all indicate that Al2O3 nanoparticles could improve mechanical and physical properties of the concrete specimens.