Hot Water Curing Research Articles

Effect of curing regimes on the rheological, mechanical, hydration and microstructure of ultra-high-performance concrete (UHPC) using indigenous resources: progress towards sustainable construction practices

ABSTRACT Ultra-High-Performance Concrete (UHPC) was renowned for its exceptional mechanical strength and durability. While contemporary UHPC is made using high-quality materials and equipment, its enormous use of natural resources in construction has had global ecological impacts. Employing materials that are accessible locally without specialized procedures. This study concentrates on UHPC mixtures, formulated with indigenous materials, aiming to develop an economical product without the need for high-speed mixers or special fibers. The mixtures are designed with optimal proportions of various supplementary cementitious materials (SCM’s). The study begins with an analysis of flow behaviour, followed by an evaluation of mechanical properties using non-destructive techniques (NDT) under different curing conditions. The UHPC mixtures demonstrate compressive strengths from 70–85 MPa to 110–144 MPa under standard and hot water curing. Relationships between destructive and NDT test outcomes are also determined. The hot water curing process leads to the formation of calcium-silicate-hydrate(C – S – H) gel, with calcium-hydroxide (CH) crystals observed within the amorphous C – S – H gel. The use of high-temperature curing improves mechanical characteristics by (35–40%) and densifies the microstructure. Consequently, producing UHPC using widely accessible materials without further processing and common technologies like conventional casting and standard curing would increase its cost-effectiveness and environmental sustainability.

Study on mechanical properties and microstructure of manufactured sand reactive powder concrete with different curing methods

To prepare economical and environmentally friendly new cementitious composite materials – reactive powder concrete (RPC) that meets the requirements of field construction. In this paper, RPC was prepared by manufactured sand (MS) as fine aggregate, the compressive strength of MSRPC under natural curing (NC), standard curing (SC) and natural + heat curing (N + HC) were studied, and the microscopic mechanism of MSRPC was analyzed with different curing methods, revealing the relationship between mechanical properties and microstructure of RPC under different curing methods. It lays an important foundation for the widely used of RPC in practical engineering. The results showed that the MSRPC prepared under the three curing methods can meet the performance standards of the actual engineering components, and the compressive strength of the MSRPC under NC and N + HC could reach 85 %–95 % and 101 %–103 % of the SC, respectively. Hot water curing is helpful to the early hydration reaction and generates a large amount of CSH, which reduces the internal porosity of the MSRPC and has a great influence on the early strength.

Sustainable and cost-effective ultra-lightweight engineered cementitious composite: Design and material characterization

Lightweight ECC (LWECC) has been extensively concerned due to its superior tensile performance, durability and low self-weight. However, the high environmental impact and material cost of ECC impede its broader engineering applications. The objective of this research is to develop a novel sustainable and cost-effective ultra-lightweight engineered cementitious composite (ULECC) under the micro-mechanical design theory. Five lightweight ECCs were designed using different lightweight fillers (LF) and replacement ratios with three mixtures being categorized as ULECC. The impacts of LF content and curing regimes (standard or hot-water curing) on the density, mechanical, and microstructural properties were investigated. The proposed ULECC exhibited impressive tensile behavior and a low density of 950–1260 kg/m3. The specific tensile strengths (strength-to-density ratio) and strain capacities of ULECC were 110% and 70% higher than conventional M45-ECC. Compared to the conventional LWECC, ULECC offered the competitive strength and ductility with a substantial increase in sustainability and reduction of material cost. Hot-water curing played a vital role in improving ductility-related performance. The micro-mechanical design theory and SEM analysis of ULECC well explained the test results. This research lays the groundwork for developing the sustainable and economical ULECC for future structural application.

Modeling of Mechanical Performance from Concrete Made by Combining Iron Sand and Glass Powder Filler under Hot Water Curing Condition

The proportions of the concrete are critical for obtaining a high-strength, high-quality product. Different concrete grades may support varying loads and have varying ratios. Therefore, the objectivity of this research is to study mechanical performance from concrete treated with iron sand, glass powder, and hot water curing. The level of iron sand and glass powder treatment added to the SNI concrete composition is 2% to 10%, 1% to 5%, (w/w), respectively. The curing time and temperature were applied between 1 hr to 4 hr and 301 K to 343 K. The compressive strength of the concrete was tested on 0, 1, 3, 7, and 28 days after molding using UTM with a combination of linear regression and response surface models for optimization. The addition of iron sand and glass powder to increase the best compressive strength was 10%, 2.45%, respectively. Iron sand treatment of 10% combined with glass powder filler 3.04% was predicted to give the best compressive strength of 32.50 MPa. The compressive strength value of this treatment was 21.78% higher than that of SNI concrete. Treat the curing temperature, curing time, and age of the concrete which gives the best compressive strength (28.33 MPa) with SNI concrete composition of 301 K, 4 days, and 28 days. This research shows that the addition of iron sand, glass powder, and hot water curing to the composition of SNI concrete can increase its compressive strength.

Concrete compressive strength of mix proportioning cockle shell, glass powder and epoxy resin under hot water curing condition through response surface methodology

Nowadays, the significant demand for concrete has become a problem in concrete using aggregate from waste. Using standard concrete is recommended to reduce the breakdown of buildings. Unfortunately, standard materials used to produce previous concrete are not entirely environmentally friendly. As a result, many researchers have committed their awareness to identifying eco-friendlier substitutions in manufacturing concrete substitution aggregate from waste. In this respect, this paper discussed the proposed efficient procedure to indicate the compressive strength from mixed proportioning cockle shell, glass powder, and epoxy resin as concrete under hot water curing conditions (60°C, 4 hr) using response surface methodology. The experimental design used in this research uses a response surface methodology. There are three aggregates to be investigated, namely cockle shell powder, glass powder and epoxy resin under hot water curing condition (60°C, 4 hr). Under hot water curing conditions, this research discovered that adding 4.0% cockle shell powder and 10.0 % glass powder increased the compressive strength to 104.68 MPa. On the other hand, 4.0% cockle shell powder, 10.0% glass powder and 2% epoxy resin under hot water curing conditions improved the compressive strength to 115.70 MPa. It was therefore inferred that the use of both cockle shell powder and glass powder to produce cleaner and compressive strength concrete is applicable, both mechanically and environmentally.

Robustness to water and temperature, and activation energies of metakaolin-based geopolymer and alkali-activated slag binders

The aim of this paper is to evaluate the properties of four alkali-activated materials subjected to precasting and in situ concreting conditions: fluctuations in water content (±5%) and in temperature (10 °C, 20 °C, 30 °C). The initial slump and compressive strengths at 1, 2, 7, 28 and 90 days of a metakaolin-based geopolymer, and of sodium silicate-activated slag, sodium metasilicate-activated slag and sodium carbonate-activated slag mortars were determined, then compared to the properties of an ordinary Portland cement mortar (CEM I). A total of 50 mortars were cast for the five formulations studied and the different conditions. This paper reports that alkali-activated materials are as robust as CEM I in precasting and in situ concreting conditions. However, some adjustments should be made to offset the low reactivity in cold weather, such as hot water or hot curing, or reducing the water/binder ratio. The apparent activation energies were determined for the five pastes to explain these observations.

The Effects of Temperature Curing on the Strength Development, Transport Properties, and Freeze-Thaw Resistance of Blast Furnace Slag Cement Mortars Modified with Nanosilica.

This investigation studies the effects of hot water and hot air curing on the strength development, transport properties, and freeze-thaw resistance of mortars incorporating low-heat blast furnace slag cement and nanosilica (NS). Mortar samples were prepared and stored in ambient conditions for 24 h. After demolding, mortar samples were subjected to two different hot curing methods: Hot water and hot air curing (40 °C and 60 °C) for 24 h. For comparison purposes, mortar reference mixes were prepared and cured in water and air at ambient conditions. Strength development (from 1 to 180 days), capillary water porosity, water sorptivity, and freeze-thaw resistance were tested after 180 days of curing. The experimental results showed that both curing regimes accelerate the strength development of mortars, especially in the first seven days of hydration. The highest early strengths were reported for mortars subjected to a temperature of 60 °C, followed by those cured at 40 °C. The hot water curing regime was found to be more suitable, as a result of more stable strength development. Similar findings were observed in regard to durability-related properties. It is worth noting that thermal curing can more efficiently increase strength in the presence of nanosilica, suggesting that NS is more effective in enhancing strength under thermal curing.

Effects of curing types, fly ash fineness and fibre lengths on mechanical and impact properties of steel fibre reinforced concretes

ABSTRACT This paper presents the effects of fly ash fineness, steel fibre lengths and types of curing on the compressive strength and impact strength of steel fibre reinforced concrete (SFRC). To study these behaviour, the SFRC mixtures were prepared using class-F fly ashes with specific surface areas of 2320, 3320 and 5980 cm2/g and steel fibres with lengths of 8 , 13 and 16 mm. The SFRC samples were subjected to standard wet curing, steam curing and hot water curing. The compressive strength tests were carried out after 7-, 28-, 90- and 180-day curing periods and the impact strength test was carried out after 90 days of respective curing. Results show that the workability of SFRC decreases with increase in fly ash fineness and steel fibre lengths. Results also show that the compressive strength of SFRC increase with increase in fly ash fineness and increase in length of steel fibres at all ages and all curing conditions. However, steam curing shows significant improvement in compressive strength gains of all SFRC compared to hot water curing at all ages except at 180 days. Good correlations are also observed in compressive strength with increase in steel fibre lengths at 28 and 90 days.

Short- and Long-Term Structural Characterization of Cured-in-Place Pipe Liner with Reinforced Glass Fiber Material.

Cured-in-place pipe (CIPP), as a kind of trenchless sewer rehabilitation technology, is a method to repair sewer pipe using unsaturated polyester resin. This study develops a CIPP liner using hot water or steam curing as well as glass fiber, in contrast to traditional methods, which use nonwoven fabric. Composite material samples were fabricated by combining liner materials using various methods, and the structural characteristics of the liners were compared and analyzed through short- and long-term flexural strength tests. A long-term test was conducted for 10,000 h, and the results revealed 13.3 times higher flexural strength and 8 times higher flexural modulus than the American Society for Testing Materials minimum criteria for CIPP short-term properties. The maximum creep retention factor was 0.64, thereby reducing the design thickness of the CIPP by up to 54%. The structural characteristics also improved when glass fibers were mixed with traditional CIPP liner, making it possible to reduce the thickness by 30%. Glass fibers result in high structural strength when combined with unsaturated polyester resin. Structural strength increased, even when glass fibers were mixed with traditional CIPP liner. The main contribution of this research is the development of a high strength CIPP liner and improvement of the structural properties of CIPP lining without using the specially formulated resin or lining materials.

Combined Effects of Graphite Tailings and Curing Conditions on the Early‐Age Performances of Cement Mortar

In this study, the combined effects of different amounts of graphite tailings (GT) as a substitute for sand and three cure methods on the early‐age mechanical and material performances of cement mortar have been investigated. The results can be concluded that graphite tailings and hot‐water cure method can effectively improve the early strength of cement‐based materials and facilitate the formation of high‐density calcium silicate hydrate (C‐S‐H), more Ca(OH)2 (CH), and other hydration products. Simultaneously, the pore structure distribution in the cement mortar is improved to be finer. Finally, this paper explains the mechanism of GT and hot‐water curing (HWC) method on early‐age performances of the cement mortar through the graphic model and provides the basis for selecting the GT and HWC method on improving early performance requirements for special engineering or rapid repair engineering through the proposed comprehensive quantitative calculation model.

A Study of Mechanical Performance of Supplementary Cementitious Material using Hot Water Curing

This study aims to investigate mechanical properties of supplementary cementitious material (SCM) using different curing condition. The utilization of huge number of agricultural waste material due to amount type has been disposed-off and being hazardous to the environment. This problem lies into reuse and renew those wastes to be useful materials. The combination of industrial and agricultural waste materials were used up to 50% in order to replace the use of cement. The result showed that using different curing step could be an effective way to produce high mechanical performance of mortars using supplementary cementitious materials.

Experimental investigation on axial compressive behavior of ultra-high performance concrete (UHPC) filled glass FRP tubes

To investigate the axial compressive behavior of ultra-high-performance concrete (UHPC)-filled fiber-reinforced polymer (FRP) tubes, a total of 54 specimens, including 42 UHPC-filled glass FRP (GFRP) tubes and 12 unconfined UHPC specimens, were prepared and tested under axial compression. The effects of curing regime, steel fiber in the UHPC core, fiber orientation of the outer FRP tube, and specimen end condition during loading were examined. The test results indicate that UHPC-filled FRP tubes can exhibit highly ductile behavior and a significant enhancement in compressive strength, compared to the unconfined specimens. However, the axial compressive behavior of UHPC-filled FRP tubes is influenced by numerous factors. Hot-water curing can improve the performance of specimens unless the contribution from the enhancement of the UHPC core exceeds that from the damage of the outer FRP tube. Specimens without steel fibers experience a sudden strength loss in the transition region of the axial stress–strain relationship, and exhibit lower ultimate strength and strain than the steel-fiber-reinforced specimens. The test results indicate that aligning fibers in the hoop direction is the most effective way of improving the compressive performance of the specimens. Regarding specimens with thicker FRP tubes, loading the FRP tube can lead to a clear decrease in specimen ultimate strain; however, the influence of specimen end condition can be ignored for specimens with thinner FRP tubes.

UTILIZATION OF PUMICE OF BURDUR REGION AND ZEOLITE OF BIGADIC, BALIKESIR REGION AS FINE AGGREGATE IN CONSTRUCTION MATERIALS

Volcanic originated pumice and zeolite aggregates have low density owing to their considerable porous structure. Porosity is usually correlated with insulation properties. In order to examine the effects of this lightweight aggregates on dead load of structure and insulation properties of standard construction materials, samples were produced by using pumice and zeolite at varying percentages by volume and control samples were manufactured with crushed sand. The samples were exposed to normal (standard) curing, hot water curing and steam curing to observe the effect of different curing regimes on their behavior. Bulk density and thermal conductivity tests were carried out on samples. Both bulk density and thermal conductivity values of the lightweight mortar samples were smaller than those of control sample. Besides, chemical compositions of aggregates and cement, analyses were also performed. Silica content of pumice and zeolite were %54,09 and %75,14 by mass respectively.

Empirical Prediction Models for Strength Gain Properties of Fly Ash Based Concrete Subjected to Accelerated Curing

Experimental investigations on the early age, strength gain properties of fly ash blended cement concretes containing low and high volume fly ash replacement were studied. Concrete mixes were prepared with two different fly ash contents and varying concrete ingredients with water to binder ratio (w/b), fine to coarse aggregate ratio (F/c) and accelerator dosage. Five different curing techniques, namely controlled humidity curing; hot air oven curing, steam curing, hot water curing and normal water curing were adopted for curing the fly ash based concretes. Test results showed evidence the influence of accelerating admixtures and accelerated curing for obtaining the high early strength properties in fly ash mixed concrete. Most notably a maximum 1 day compressive strength of 40.20 MPa and 34.60 MPa with low (25%) and high (50%) volume fly ash concretes were obtained respectively in this study. Experimental results clearly indicated that the improvements on the strength gain properties with the careful selection of mix ingredients; accelerator addition and accelerated curing in fly ash based concrete mixes. Also, significant improvements on the flexural strength, elastic modulus, dynamic modulus and the ultrasonic pulse velocity test were noticed.

Combined curing as a novel approach to improve resistance of ultra-high performance concrete to explosive spalling under high temperature and its mechanical properties

The influence of a combined curing composed of precuring in hot water and heating in dry air on mechanical properties and explosive spalling of ultra-high performance concrete (UHPC) subjected to high temperature was investigated in this experiment. Meanwhile, the microstructure of UHPC was determined by means of X-ray diffraction (XRD) with Rietveld method, thermogravimetric analysis (TGA), scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP). The results indicate that the combined curing improves the mechanical properties of UHPC remarkably. More importantly, it is quite efficient to enhance the resistance of UHPC to explosive spalling under high temperature, which should be a novel approach to prohibit spalling occurrence, different from adding polypropylene fiber. During dry air heating in the combined curing, a high temperature steam environment is established in the dense structure framework of UHPC formed in the preceding hot water curing. Both further hydration of residual cement and pozzolanic reaction of mineral admixtures can be activated during the dry air heating, leading to not only the formation of a large amount of dense hydrates (such as C-S-H gels, katoite, tobermorite and xonotlite, etc.), which accumulate in the aforementioned existing framework, but also the consumption of most of internal free water. Therefore, both mechanical properties of UHPC and its resistance to explosive spalling under high temperature can be enhanced significantly.

Comparative study on flexural properties of ultra-high performance concrete with supplementary cementitious materials under different curing regimes

This study investigated the effects of curing regimes (standard, hot water, and steam curing) on mechanical properties of ultra-high performance concrete (UHPC) with different supplementary cementitious materials (SCMs). The flowability, compressive strength, flexural load-deflection relationship, ultimate flexural strength, and toughness of UHPC mixtures with 0, 20%, 40%, and 60% of either ground granulated blast-furnace slag (GGBS) or fly ash, by the mass of cement, were evaluated. Test results indicated that the increase in GGBS or fly ash content had limited or negative influence on the compressive strength of UHPC in terms of curing regime type . For the flexural strength, there existed an optimal SCM content, which was 40% for GGBS and 20% for fly ash. Excessed this dosage could result in a drop in flexural strength and toughness. The hot water and steam curing significantly improved the flexural properties. However, prolonging the standard curing over 28d led to comparable flexural properties as those under hot water and steam curing showed. The production of UHPC with appropriate GGBS or fly ash content with adequate standard curing, therefore, offers an effective way to obtain satisfactory flexural properties.

The effects of silica fume and hydrated lime on the strength development and durability characteristics of concrete under hot water curing condition

Sustainability is considered to be highly important for preserving continued industrial growth and human development. Concrete, being the world’s largest manufacturing material comprises cement as an essential binding component for strength development. However, excessive production of cement due to high degree of construction practices around the world frames cement as a leading pollutant of releasing significant amounts of CO2 in the atmosphere. To overcome this environmental degradation, silica fume and hydrated lime are used as partial replacements to cement. This paper begins with the examination of the partial replacement levels of hydrated lime and silica fume in concrete and their influence on the mechanical properties and durability characteristics of concrete. The effect of hot water curing on concrete incorporated with both silica fume and hydrated lime is also investigated in this paper. The results reported in this paper show that the use of silica fume as a partial replacement material improved both the mechanical properties and durability characteristics of concrete due to the formation of calcium silica hydrate crystals through the pozzolanic reaction. Although the hydrated lime did not significantly contribute in the development of strength, its presence enhanced the durability of concrete especially at long-term. The results also showed that hot water curing enhanced the strength development of concrete incorporated with silica fume due to the accelerated rate of both the hydration and pozzolanic reaction that takes place between silica fume and calcium hydroxide of the cement matrix particularly at early times. The results reported in this paper have significant contribution in the development of sustainable concrete. The paper does not only address the use of alternative binders as a partial replacement material in concrete but also suggest proper curing conditions for the proposed replacement materials. These practices play a vital role in the development of sustainable concrete.

Introducing an effective curing method for mortar containing high volume cementitious materials

This study reported an on-going research project of producing sustainable construction material for pre-cast industry. This paper studies the physical and chemical properties of materials, compressive strength, flexural strength, water absorption and porosity of multi blended cements under different curing methods. Fly ash (FA), ground granulated blast furnace slag (GGBFS) and rice husk ash (RHA) were used to replace with 50% ordinary Portland cement by mass. Specimens were cured in water (WC), air under room temperature (AC), the combination of hot-water at 60°C for 24h followed by curing in water (HWC), and air (HAC). The results showed that HAC could be an effective curing method with higher compressive and flexural strengths, lower water absorption and porosity for blended cement mortars. Mortars containing GGBFS in binder had higher enhancement on compressive strength under early hot water curing. While, at 24h hot water curing mortar containing OPC–RHA–FA binder showed better quality in properties compared to the other binders.

Effects of curing type, silica fume fineness, and fiber length on the mechanical properties and impact resistance of UHPFRC

The effects of silica fume fineness and fiber aspect ratio on the compressive strength and impact resistance of ultra high-performance fiber-reinforced concrete (UHPFRC) are investigated experimentally. To this end, UHPFRC mixtures are manufactured by combining silica fumes with different fineness (specific surface areas: 17,200, 20,000, and 27,600m2/kg) and hooked-end steel fibers with various aspect ratios (lengths: 8, 13, and 16mm). The samples are subjected to standard curing, steam curing, and hot-water curing. Compressive strength tests are conducted after 7-, 28-, 56-, and 90-day curing periods, and an impact resistance experiment is performed after the 90th day. A steam-cured mixture of silica fumes with a specific surface area of 27,600m2/kg and 16-mm-long fibers produce better results than the other mixtures in terms of mechanical properties. Moreover, impact resistance increases with the fiber aspect ratio.

Effect of Thermal-cured Hydraulic Cement Admixtures on the Mechanical Properties of Concrete

In the cement industry, researchers have worked on blending cement with supplementary cementitious materials (SCMs) to enhance the mechanical properties of concrete. For technical and environmental reasons, previous studies have recommended that concretes be designed with less ordinary Portland cement (OPC). Other researchers encourage the use of thermal treatments at the precast stage. In this work, high volumes of various SCMs other than OPC were used to prepare five cement formulations, including a control sample. Initial tests of three hydraulic binders were performed to check their suitability before mixing cement samples. The samples were treated in water, air, hot water, and hot air curing (HAC) conditions after demoulding. The study showed that a combination of rice husk ash (RHA) and fly ash (FA) with OPC in the binder matrix, cured under HAC conditions, gave the best compressive and flexural strength results with the lowest water absorption.