Pre-soaked Lightweight Aggregate Research Articles

Execution of Internal Curing Method on Concrete using Pre-Soaked Light Weight Aggregate

Low water-cement proportion solid mixes have been progressively advanced for use in Civil Engineering foundation because of potential changes in quality and sturdiness. Notwithstanding their expanded quality and diminished porous nature, the structur

Effects of Presoaked Lightweight Aggregate Addition on Drying Shrinkage

AbstractIt is widely known that presoaked lightweight aggregate (LWA) is greatly beneficial for reducing autogenous shrinkage by providing additional water reservoirs for the mixture. However, in u...

Development of Autogenous Shrinkage Deformation and Strength Parameters in Self-Consolidating Concrete with Light and Natural Aggregate

The concrete during the curing exhibits volume changes caused by different factors: chemical reactions during hydration, surface drying, external temperature or carbonisation. Each aforementioned factor imposes different type of shrinkage that constitutes to the overall shrinkage of concrete. In case of the concretes with a low water/cement ratio, significant influence on the overall shrinkage has the autogenous shrinkage. This type of shrinkage is a result of self-desiccation that sucks out the water from capillary pores during the hydration.The article presents the results of the test on the autogenous shrinkage performer in accordance with modified ASTM C1581. To reduce the autogenous deformations caused by the shrinkage, the authors implemented internal curing by using presoaked lightweight aggregate. The tests were performed on cement mortars and self-consolidating concretes with water/cement ratio of w/c=0.28. The mortars were made with use of fine natural aggregate 0-2 mm and fly ash lightweight aggregate 0-4mm. To produce concrete authors used natural aggregate 0-2 mm and 2-8 mm and fly ash lightweight aggregates 0-4 mm and 4-8 mm. Designed self-consolidating mixes were tested to determine their rheological properties. The concrete compressive strength and tensile splitting strength was determined after 1, 3, 7 and 28 days. The autogenous deformations were registered every 500 s during 28 days. The shrinkage was determined on slab samples 35×150×1100 mm. The samples simulated linear expansion of ring specimen used in ASTM method. Study analyses the influence of the type of aggregate on the development of autogenous deformations and strength properties of young self-consolidating concretes. Studies have shown that presoaking of the light aggregate changes the development of deformation. Internal curing caused swelling instead of shrinkage during the hydration stage, reducing the overall autogenous shrinkage.

Effect of Impact Hot- Dry Weather Conditions on the Properties of High Performance Lightweight Concrete

The aim of this investigation is to produce high performance lightweight aggregate concrete in actual hot- dry weather conditions, and then study the combined effect of hot-dry weather conditions on the fresh properties of high performance lightweight aggregate concrete such as workability, initial and final setting time, measuring concrete temperature, and hardened concrete properties (compressive strength, splitting tensile strength and flexural strength, modulus of elasticity). The experimental program including the use of fixed mix proportions and was carried out in a typical Iraqi summer days (under actual conditions) of different times during the day, where the mean maximum temperature in shadow in July and August usually is more than 44° C and relative humidity of about 24 %, the results were compared with the specimens prepared and casted in laboratory and others in shadow site. The results indicate that as temperature rises, and relative humidity falls, the initial and final setting time were reduced, beside that actual drop in slump. The results also show that rising placing temperatures more than allowable concrete temperature that recommended in ACI 305 does not, as a rule, lead to lower strengths. The strength performance of concrete can remain unaffected by higher placing temperatures, or it can even improve over that at lower temperatures. Using pre-soaked lightweight aggregates (pumice) as internal water reservoirs for producing this type of concrete under actual hot-dry weather condition played positive role in improvement of concrete properties by compensate the evaporation of water due to the rising temperature and decreasing relative humidity, and provide additional moisture in concrete for a more effective hydration of the cement.

Evaluation of Shrinkage and Fracture Properties of Internal Cured 100-MPa Ultrahigh-Strength Steel Fiber–Reinforced Concrete

AbstractIn this paper, shrinkage and fracture properties of 100-MPa ultrahigh-strength steel fiber-reinforced concrete internally cured with presoaked lightweight aggregate (PSLWA) are evaluated th...

Test and simulation on moisture flow in earlyage concrete under drying

ABSTRACTIn this paper, moisture flow in two concrete with and without internal curing using presoaked lightweight aggregate (PSLWA) under surface drying is experimentally investigated by measuring the weight of the concrete samples. Mathematical modeling on moisture flow, especially moisture transfer coefficient between concrete and surrounding air, normally called surface factor is performed. The results show that moisture flow through the drying surface of concrete can be characterized by a constant moisture loss stage (I) followed by a gradually reducing moisture loss stage (II). For the given environmental condition, the length of stage I increases with a decrease in water-to-cement ratio. Internal curing with PSLWA will prolong the length of Stage I. Surface factor is a function of location along air flow direction, air flow speed, and temperature of air and concrete surface, while it is independent of mix proportions of concrete. Higher air flow rate, higher temperature of air and/or concrete will result in a larger surface factor. Element size along air flow direction significantly influences the value of surface factor. Smaller element size along the air flow direction will result in a larger surface factor. The comparison on surface factor between experimental determination and theoretical calculation is performed and a good agreement between them is obtained.

Effects of Presoaked Lightweight Aggregate on Deformation Properties of Ordinary Portland Cement-Calcium Sulfoaluminate Cement Blends

First Name is required invalid characters Last Name is required invalid characters Email Address is required Invalid Email Address Invalid Email Address

Effect of cementitious permanent formwork on moisture field of internal-cured concrete under drying

Drying shrinkage of concrete may still be the main source of cracking in concrete structures, even though the autogenous shrinkage of concrete can be effectively reduced by using internal curing. In the present paper, the effect of internal curing with pre-soaked lightweight aggregate and engineered cementitious composite permanent formwork (ECC-PF) on a moisture distribution in three kinds of concrete in a drying environment are investigated from both aspects of experiments and theoretical modeling. The test results show that the combination use of ECC-PF and internal curing can well maintain the humidity at a relatively high level not only at a place far from drying surface, but also at a place close to the drying surfaces. The developed model can well catch the characteristics of the moisture distribution in concrete under drying and the impacts of internal curing and ECC-PF can well be reflected as well. The model can be used for the design of concrete structures with combination use of internal curing and permanent formwork.

Efficacy of internal curing combined with expansive agent in mitigating shrinkage deformation of concrete under variable temperature condition

The benefits of internal curing (IC) have been confirmed by extensive laboratory studies under constant room temperature. In practical engineering, sidewall concrete undergoes a variable temperature evolution, which involves significant physical, chemical, and thermal changes during the hydration process at the early age and a high cracking risk at the temperature drop stage. Expansive agent (EA) has always been used to mitigate early-age cracking, but it has limited efficacy in the temperature drop stage and low mechanical properties. This study examines the efficacy of IC through pre-soaked lightweight aggregate (SLWA) and the combined use of SLWA and EA in mitigating shrinkage deformation under constant and variable temperature conditions. Results indicate that SLWA shows a higher efficacy than EA in mitigating shrinkage deformation during the temperature drop stage and can provide continuous expansion at the later stage. The combined use of SLWA and EA exhibits high efficacy in mitigating shrinkage deformation under constant and variable temperature conditions and can limit the reduction of mechanical properties caused by a single EA.

Shrinkage of high-strength calcium sulfoaluminate cement concrete with impact of pre-soaked lightweight aggregate internal curing

The effect of internal curing using pre-soaked lightweight aggregate in high-strength calcium sulfoaluminate cement concrete on shrinkage and internal humidity was investigated. Five mixture proportions with induced internal curing water (absorbed by lightweight aggregate) to cement (wIC/c) ratios of 0, 0·03, 0·06, 0·09 and 0·12 were used in the experiments. The experimental results show that the decrease of internal humidity is gradually reduced with an increase in wIC/c ratio. Accordingly, both autogenous and drying shrinkage of concrete also gradually decrease with an increase in wIC/c. Internal curing cannot eliminate the autogenous shrinkage completely because part of the autogenous shrinkage develops within the humidity-saturated stage for early-age concrete.

Shrinkage of high-strength calcium sulfoaluminate cement concrete with impact of pre-soaked lightweight aggregate internal curing

Shrinkage of high-strength calcium sulfoaluminate cement concrete with impact of pre-soaked lightweight aggregate internal curing

Simulation of moisture field of concrete with pre-soaked lightweight aggregate addition

Use of pre-soaked lightweight aggregate (PSLWA) as an internal reservoir to provide water as the concrete dries is an effective method to reduce shrinkage of concrete. In this paper, a moisture distribution model of concrete internal cured with PSLWA is developed based on the experimental measurement on internal relative humidity of concrete with and without internal curing under sealing status. The function of internal curing with PSLWA is considered in the model through a parameter called critically released water, Wc, that was experimentally determined from experiments. Meanwhile, self-desiccation and moisture capacity are taken into account in development of the diffusion equation. To verify the model, a series tests to measure the internal relative humidity of three kinds of internal cured concrete under drying and sealing conditions were conducted. Through comparing the model and test results of humidity profiles, the moisture dependent diffusivity of the three internal cured concretes is obtained. The developed moisture movement model and finite differential method can well predict the moisture distribution as well as its variations with time of concrete internal cured with PSLWA.

Reduction of the Early Autogenous Shrinkage of High Strength Concrete

The results of a laboratory investigation on the early autogenous shrinkage of high strength concrete, and the possibilities of its reduction, are presented. Such concrete demonstrates significant autogenous shrinkage, which should, however, be limited in the early stages of its development in order to prevent the occurrence of cracks and/or drop in the load-carrying capacity of concrete structures. The following possibilities for reducing autogenous shrinkage were investigated: the use of low-heat cement, a shrinkage-reducing admixture, steel fibres, premoistened polypropylene fibres, and presoaked lightweight aggregate. In the case of the use of presoaked natural lightweight aggregate, with a fraction from 2 to 4 mm, the early autogenous shrinkage of one-day-old high strength concrete decreased by about 90%, with no change to the concrete's compressive strength in comparison with that of the reference concrete.

Combination Effects of Internal Curing and Permanent Formwork on Shrinkage of High Strength Concrete

In this paper, the influences of internal curing using pre-soaked lightweight aggregate (PSLWA) and pre-fabricated fiber reinforced engineered cementitious composite (ECC) board as permanent formwork on shrinkage and internal relative humidity of high strength concrete were investigated. Three mixture proportions with induced curing water-to-cement ratios (WIC/C) of 0, 0.08 and 0.12 were utilized in the experiments. The test results show that the progress of the internal relative humidity of high strength concrete since casting exhibits first a vapor saturated stage (RH=100%, stage I), followed by a gradually reducing stage (RH<100%, stage II). As PSLWA is added, the reduction rate of internal relative humidity in stage II is greatly decreased. As ECC cover is used, the reduction on internal humidity of high strength concrete is further reduced. Shrinkage of high strength concrete decreases with increase of induced internal curing water. However, internal curing cannot completely eliminate the shrinkage of high strength concrete developed in the stage I. The combined effects of internal curing and ECC cover can reduce the shrinkage not only developed in the stage II, but also the shrinkage developed in stage I.

Physical properties of self-curing concrete (SCUC)

In this study the effect of two different curing-agents has been examined in order to compare them for optimizing the performance of concrete. The first used type is the Pre-soaked lightweight aggregate (leca) with different ratios; 0.0%, 10%, 15% and 20% of volume of sand, and the second type is a chemical agent of polyethylene-glycol (Ch.) with different percentages; 1%, 2% and 3% of weight of cement. In the test programme performed in this study, three cement content; 300, 400 and 500kg/m3, three different water-cement ratios; 0.5, 0.4, and 0.3, and two magnitudes of silica fume as a pozzolanic additive; 0.0% and 15% of cement weight, were used. The physical properties of concrete were evaluated at different ages, up to 28days. The concrete specimens are subjected to dry-air curing regime (25°c) during the experiment.The results show that the use of self-curing agent (Ch.) in concrete effectively improves the physical properties compared with conventional concrete. On the other hand, up to 15% saturated leca was effective while 20% saturated leca was effective for permeability and mass loss but adversely affects the sorptivity and volumetric water absorption. Self-curing agent Ch. was more effective than self-curing agent leca. In all cases, both 2% Ch. and 15% leca were the optimum values. Higher cement content and/or lower water–cement ratio leads to more effective results of self-curing agents in concrete. Incorporation of silica fume into concrete mixtures enhances all physical properties.

Mechanical properties of self-curing concrete (SCUC)

The mechanical properties of concrete containing self-curing agents are investigated in this paper. In this study, two materials were selected as self-curing agents with different amounts, and the addition of silica fume was studied. The self-curing agents were, pre-soaked lightweight aggregate (Leca); 0.0%, 10%, 15%, and 20% of volume of sand; or polyethylene-glycol (Ch.); 1%, 2%, and 3% by weight of cement. To carry out this study the cement content of 300, 400, 500kg/m3, water/cement ratio of 0.5, 0.4, 0.3 and 0.0%, 15% silica fume of weight of cement as an additive were used in concrete mixes. The mechanical properties were evaluated while the concrete specimens were subjected to air curing regime (in the laboratory environment with 25°C, 65% R.H.) during the experiment. The results show that, the use of self-curing agents in concrete effectively improved the mechanical properties. The concrete used polyethylene-glycol as self-curing agent, attained higher values of mechanical properties than concrete with saturated Leca. In all cases, either 2% Ch. or 15% Leca was the optimum ratio compared with the other ratios. Higher cement content and/or lower water/cement ratio lead(s) to more efficient performance of self-curing agents in concrete. Incorporation of silica fume into self-curing concrete mixture enhanced all mechanical properties, not only due to its pozzolanic reaction, but also due to its ability to retain water inside concrete.

Capillary absorption of structural lightweight aggregate concrete

The present study aims to characterize the capillary absorption of structural lightweight aggregate concrete (LWAC), taking into account different compositions with lightweight aggregates (LWA) of very distinct porosity. The influence of the following parameters is analysed: the volume and initial water content of LWA; the cement content and its replacement by fly ash or silica fume; the partial replacement of normal weight aggregate by lightweight coarse or fine aggregate; different curing conditions. It is shown that LWAC usually has higher initial and long-term absorption than normal weight concrete (NWC) of the same composition. However, the sorptivity tends to be similar in both concretes, regardless of the type and volume of aggregate and the water/cement of the surrounding paste. Moreover, the sorptivity is lower in LWAC than in NWC of the same strength. It is also shown that the coarser the porosity of the LWA the lower is the capillary action. The capillary absorption is higher in LWAC with pre-soaked LWA and increases as the percentage replacement of cement by fly ash increases and the percentage of silica fume decreases.

Experimental evaluation of cement mortars with phase change material incorporated via lightweight expanded clay aggregate

ObjectiveAn experimental evaluation on cement mortars with phase change material (PCM) incorporated via lightweight aggregate (LWA) is reported. Materials and methodsThree groups of LWA mortars were produced: one with pre-soaked LWA and the others with PCM-filled LWA combining two different impregnation processes and PCM dosages of 50, 75 and 100kg/m3 corresponding to the LWA contents of 242, 354 and 481kg/m3, respectively. Mechanical and thermophysical properties were evaluated. ResultsThe results showed that high thermal inertia and low mass are compatible in PCM-filled LWA mortars and that the thermal response increases with the PCM to a certain limit and then decrease.

Effect of internal curing on internal relative humidity and shrinkage of high strength concrete slabs

In the paper, the moisture content, in terms of relative humidity, inside of high strength concrete slab, with and without addition of pre-soaked lightweight aggregate (PSLWA), exposed to normal indoor environment is investigated by continually measuring the interior humidity of concrete immediately after slab casting until 28days. The effects of internal curing on the developments of internal relative humidity and free shrinkage in high strength concrete slab are analyzed. The experimental results show that the internal relative humidity of high strength concrete decreases with concrete age since casting. The developing tendency of the relative humidity inside of concrete with age follows a vapor-saturated stage with 100% relative humidity (stage I) and a stage that relative humidity gradually decreases (stage II). A humidity gradient along the thickness of slab exists in early age high strength concrete. As PSLWA is added, the reduction rate of interior humidity in stage II is obviously reduced and the reduction trend with age changes from non-linear pattern to almost linear pattern. The duration of the internal humidity-saturated stage I is noticeably prolonged by addition of PSLWA. The humidity gradient together with the corresponding shrinkage gradient along the thickness of the slab is reduced also. The highest reduction on internal humidity at 28days since casting in high strength concrete slab is changed from 46.5% to 26.2% with a medium PSLWA addition ratio, and finally to 7.9% with a high PSLWA addition level. Within present addition range, the more the PSLWA added, the stronger the above positive internal curing effects.

Integrative Study on the Effect of Internal Curing on Autogenous and Drying Shrinkage of High-Strength Concrete

High-strength concrete generally has a low water-to-cement ratio, which in turn increases the possibility of early-age cracking due to its high autogenous shrinkage. In this article, the effect of internal curing using presoaked lightweight aggregate (PSLWA) in high-strength concrete on shrinkage and interior humidity is investigated by continuously measuring the deformation and interior humidity of the test specimen under plastic film sealing and surface drying conditions since specimen cast. Four mixture proportions with an induced curing water-to-cement ratio (W IC/C) of 0, 0.04, 0.08, and 0.12 were used in experiments. The experimental results show that the decrease in interior humidity was gradually reduced with an increase in W IC/C. Accordingly, both autogenous and drying shrinkage of concrete gradually decreased with an increase in W IC/C. Internal curing cannot completely eliminate autogenous shrinkage because part of the autogenous shrinkage is developed within the humidity-saturated stage in early-age concrete.