Shrinkage Of Self-compacting Concrete Research Articles

Estimation of drying shrinkage in self-compacting concrete containing micro- and nano-silica using appropriate models

Estimation of drying shrinkage in self-compacting concrete containing micro- and nano-silica using appropriate models

Behavior improvement of self-compacting concrete in hot weather

The main aim of this research is studying the effect of hot weather on the properties of self-compacting concrete and conventional concrete in both fresh and hardened state. Also, this research extends to improve the behavior of self-compacting concrete in hot weather. The main parameters were surrounding weather temperature (5°C, 20°C and 35°C), concrete materials temperatures’ (25°C, 50°C), curing temperatures (25°C and 50°C) and admixtures (using a retarder). Two stages were carried out to achieve the research aim. The behavior of self-compacting concrete compared to conventional concrete was evaluated in the first stage. Based on the first stage, attempts to enhance the concrete properties were evaluated in the second stage. Precautions on mixing and placing concrete in these climates are considered. Results are a drive in terms of; workability tests, compressive strength, splitting tensile strength, and flexural strength. Test results showed that self-compacting concrete behavior and strengths were better than conventional concrete. Slump test, J-ring and V-funnel test were used to evaluate the fresh properties of the self-compacting concrete. Drying shrinkage of self-compacting concrete in hot weather were also evaluated.

Experimental determination of the influence of additives on shrinkage in self-compacting concrete

The paper deals with the influence of additives on the progress of shrinkage and mass losses in self-compacting concrete. Limestone and fly ash at varying amounts were used as an additive in the production of four types of self-compacting concrete. Volume changes were observed from an early stage of setting (the measurement was commenced within 1 hour of mixing) using shrinkage drains with a moveable wall, followed by a long-term manual measurement using an external strain gauge. For the first 48 hours the volume-change measurement was continuous, and for the next few months it was performed manually. Mass losses were determined simultaneously with shrinkage – during the first 48 hours by weighing on a special weighing table capable of continuous recording, and manually afterwards.

Influence of calcined mud on the mechanical properties and shrinkage of self-compacting concrete

The use of SCC has a particular interest in terms of sustainable development. Indeed, their specific formulation leads to a greater volume of dough than for common concretes, thus, a larger quantity of cement. However, for economical, ecological and technical reasons, it is sought to limit their cement content [1]. It is therefore necessary to almost always use mineral additions as a partial replacement for cement because the technology of self-compacting concretes can consume large quantities of fines, in this case calcinated mud issued from dams dredging sediments that can give and/or ameliorate characteristics and performances of this type of concretes. Four SCCs had been formulated from the same composition where the only percentage of calcinated mud of Chorfa (west of Algeria) dam changed (0%, 10%, 20% and 30%). The effect of calcinated mud on characteristics at fresh state of SCC according to AFGC was quantified. Mechanical strengths and shrinkage deformation (total, autogenous, drying) were evaluated. The results show the possibility to make SCCs with different dosages of calcinated mud having strengths that can defy those of the control SCC. The analysis of free deformations indicates the beneficial impact of the mud by contributing to decrease the amplitudes of the shrinkage compared to those of the control SCC.

Influence of calcined mud on the mechanical properties and shrinkage of self-compacting concrete

The use of SCC has a particular interest in terms of sustainable development. Indeed, their specific formulation leads to a greater volume of dough than for common concretes, thus, a larger quantity of cement. However, for economical, ecological and technical reasons, it is sought to limit their cement content [1]. It is therefore necessary to almost always use mineral additions as a partial replacement for cement because the technology of self-compacting concretes can consume large quantities of fines, in this case calcinated mud issued from dams dredging sediments that can give and/or ameliorate characteristics and performances of this type of concretes. Four SCCs had been formulated from the same composition where the only percentage of calcinated mud of Chorfa (west of Algeria) dam changed (0%, 10%, 20% and 30%). The effect of calcinated mud on characteristics at fresh state of SCC according to AFGC was quantified. Mechanical strengths and shrinkage deformation (total, autogenous, drying) were evaluated. The results show the possibility to make SCCs with different dosages of calcinated mud having strengths that can defy those of the control SCC. The analysis of free deformations indicates the beneficial impact of the mud by contributing to decrease the amplitudes of the shrinkage compared to those of the control SCC.

Shrinkage of self-compacting concrete. A comparative analysis

Self-compacting concrete (SCC) is a concrete type that does not require vibration for placing and compacting. SCC possesses special technical features and properties that recommend its application in many jobs. Nevertheless, in some situations, it has been observed an inadequate behaviour of the material at early ages due to shrinkage. The existing shrinkage prediction models were developed for standard concrete. In this paper three SCC mixtures, with different compressive strength, are studied in terms of autogenous and total shrinkage. The results are compared with the Eurocode 2 model. For the studied mixtures it was found that this model underestimates the autogenous shrinkage, while the total shrinkage is generally overestimated.

EFFECT OF ADMIXTURES ON SHRINKAGE PROPERTIES IN SELF COMPACTING CONCRETE

With the rapid advancement in concrete technology, demand for sustainable building materials has increased manifold in last few decades. High strength concrete such as Self compacting concrete (SCC), also known as Self consolidated concrete, is considered one of the finest and highly modified concrete material. SCC represents a major evolution in the building industry. The increased use of SCC for construction and repair purposes lies in the fact that it is semi-flowable in nature and possess several advantages such as environmental, human, technological and economical. This paper mainly focuses on the effect of various shrinkage properties such as drying shrinkage, autogenous shrinkage and plastic shrinkage on performance of SCC. Detailed literature review suggests that early age shrinkage in SCC has been a major setback in attaining it’s desired strength. Expansive cracking and capillary tension are considered as two main phenomena behind shrinkage in SCC. It is found out that factors like lower water/cement ratio or decreasing limestone filler/cement ratio leads to reduction in autogenous shrinkage. It is considered that cracks are one of the pivotal reasons behind the poor durability of concrete as they help in entering hazardous fluids. Hence cracks causes specific problems like plastic shrinkage. The effect of shrinkage reducing admixtures (SRA) on SCC was observed to be positive. SRA along with paraffin based curing compounds helps in reducing cracks. It was observed from rheological tests conducted on concrete as well as fresh SCC that, as far as drying shrinkage is concerned usage of SRA was found out to be effective while hydrophobizing admixtures tends to be useless. Along with addition of such admixtures, limestone fines in SCC mixes shows a reduction in autogenous shrinkage in SCC as compared to normal vibrated concrete (NVC). More importantly results show that total shrinkage in SCC mixed with limestone filler is slightly higher (not >9.2%) than in NVC, while SCC made with viscous Modifying Agents (VMA) shows 7.7% less shrinkage than in NVC, due to lower autogenous and drying shrinkage.

Effect of High Volume Fly Ash on Shrinkage of Self-compacting Concrete

Self-compacting concrete (SCC) has been produced incorporating fly ash as cement replacement at 35%, 55% and 65% by weight. The flowability, fillingability and passingability of these concrete were assessed by combination of the following test methods: flow table, J-Ring, L-Box, Box Type and V-funnel test. For each mix proportion of SCC, six cylinder specimens (75mm x 275mm) were cast for shrinkage measurements following the RILEM Recomendation. Three of them were used for measurement of drying shrinkage while the other three were used for autogenous shrinkage. The results show that a higher cement replacement by fly ash tends to decrease both drying and autogenous shrinkage. Estimations of shrinkage using ACI 209R, CEB-FIP 1990 and Ross's method suggest that ACI 209R and CEB-FIP 1990 provide accurate prediction than Ross's model.

Compensation Effect of Expansive Agent on Shrinkage of Self-Compacting Concrete

The compensation effect of expansive agent on shrinkage of self-compacting concrete (SCC) are studied. The deformation of Concrete was tested by concrete comparator, and the qualitative and quantitative analysis of hydration products were done by X-ray diffractometer (XRD). The results show that the dosages of mineral admixture and curing conditions affect the application results of expansive agents markedly. SCC samples containing expansive agent cured in the water are expanding within the test time. In the case of watering condition and natural curing condition, the samples are always shrinkage within test time, but mineral admixtures have a good effect to resist the shrinkage of SCC. Microstructure analysis show that ettringite content is reduced slightly due to the reduction of the alkalinity of SCC resulted by more mineral admixture. However, when at water curing condition, humidity inside SCC is much higher, which makes ettringite content larger even though with more mineral admixture. So, curing is the most important factors for the micro-expansion of SCC containing expansive agent.

Combined effect of expansive and shrinkage reducing admixtures to control autogenous shrinkage in self-compacting concrete

Self-compacting concrete possesses special properties that recommend its application in many repair jobs. However, in some practical cases, inappropriate performance of the repair material has been observed in the early stages of hydration, including cracks or delamination due to shrinkage. This study presents laboratory test results on the autogenous shrinkage of self-compacting concrete. Taking into account the typically high autogenous shrinkage of concrete mixtures with low W/C, associated with this type of concrete, the efficiency of different shrinkage-compensating products was evaluated. Two shrinkage reducing admixtures and one expansive binder have been studied.The results show the efficiency of the individual use of each product and put in evidence a synergistic effect on the autogenous shrinkage reduction when shrinkage reducing admixture and expansive agent were combined.The results also show a potential for achieving a predefined shrinkage range, by using the combined effect of a set retarder and an expansive admixture.

Creep and Shrinkage of Self-Compacting Concrete with and without Fibers

Fiber-reinforced self-compacting concrete (FRSCC) is a high-performance building material that combines positive aspects of fresh properties of self-compacting concrete (SCC) with improved characteristics of hardened concrete as a result of fiber addition. Considering these properties, the application ranges of both FRSCC and SCC can be covered. To produce SCC, either the constituent materials or the corresponding mix proportions may notably differ from the conventional concrete (CC). These modifications besides enhance the concrete fresh properties affect the hardened properties of the concrete including creep and shrinkage. Therefore, it is vital to investigate whether all the assumed hypotheses about conventional concrete are also valid for SCC structures. In the present paper, a numerical and experimental study about creep and shrinkage behavior of FRSCC and SCC is performed. Two new creep and shrinkage prediction models based on the comprehensive analysis on the available models of both CC and SCC are proposed for FRSCC and SCC structures. In order to evaluate the predictability of the proposed models, an experimental program was carried out. For this purpose, four SCC mixes plain SCC, steel, polypropylene, and hybrid FRSCC are considered in the test program. Several specimens were loaded and deformation in non-loaded specimens was also measured to assess shrinkage. All specimens were kept under constant stress during at least 364 days in a climatic chamber with temperature and relative humidity of 22oC and 50%, respectively. Results showed that the new models were able to predict deformations with good accuracy, although providing deformations slight overestimated.

Influence of limestone filler and viscosity-modifying admixture on the shrinkage of self-compacting concrete

The aim of this experimental work is to study shrinkage evolution with age in self-compacting concretes (SCC) made with w/c=0.6 and different limestone filler and viscosity-modifying admixture (VMA) contents. The results show that limestone fillers speed up hydration reactions and provide a finer porous structure. As a result, when specimens are hardened under water, SCC made with limestone fillers tends to shrink, since the water only penetrates the outer layers of the specimen, while the interior is subject to self-desiccation. If the concrete contains substantial air content (3.2%) the water finds it easier to penetrate and the concrete swells. When hardening takes place in the open air, autogenous shrinkage in SCC is lower than in normally-vibrated concretes (NVC) and the higher the fines content, the lower the shrinkage. This is more than likely due to the use of limestone filler as addition, finer porous structure and higher amount of absorbed water from the aggregate which compensates for the auto-desiccation of the concrete. On the whole, drying shrinkage in SCC is greater than in NVC. However, when filler is replaced by VMA the porous structure is coarser and shrinkage is reduced by 33%, thanks to the lower capillary pressure. This means that due to the reduction in autogenous and drying shrinkage, SCC made solely with VMA presents 7.7% lower total shrinkage than NVC. In SCC made with limestone filler, total shrinkage is only slightly higher than in NVC, the differences being under 9.2%.

Numerical modeling of drying shrinkage behavior of self-compacting concrete

Self-compacting concrete (SCC), characterized by the high flowability and resistance to segregation, is due to the high amount of paste (including cement and mineral admixtures) in contrast with normal concrete (NC). However, the high amount of paste will limit the volume fractions of coarse aggregate,and reduce the tendency of coarse aggregate to suppress drying shrinkage deformations. For this reason, SCC tends to produce higher values of drying shrinkage than NC for the most part. In order to assess the drying shrinkage of SCC quantitatively for application to offshore caisson foundations, the formulas presented in the literatures (ACI 209 and CEB-FIP) are used to predict the values of drying shrinkage in SCC according to the corresponding mix proportions. Additionally, a finite element (FE) model, which assumes concrete to be a homogeneous and isotropic material and follows the actual size and environmental conditions of the caisson, is utilized to simulate stress distribution situations and deformations in the SCC caisson resulting from the drying shrinkage. The probability of cracking and the behavior of drying shrinkage of the SCC caisson are drawn from the analytic results calculated by the FE model proposed in this paper.

Experimental Study on Cracking Property of Self-Compacting Concrete

Taking free shrinkage as the key parameter in evaluating cracking of concrete, the cracking properties of self-compacting concrete with strength grade of C35 and C50 were investigated based on ring and slab restraint tests. Meanwhile, the ultimate tensile strain of self-compacting concrete was studied by using flexural test. Experimental results show that the shrinkage of self-compacting concrete is lower than that of normal concrete. Self-compacting concrete cracks later than normal concrete with the same strength grade. Although the ultimate flexural tensile strains of self-compacting concrete in 7 d and 28 d are a little bit lower than that of the normal concrete, it can still be concluded from the research that the cracking property of self-compacting concrete can be greatly improved by using proper mix proportion.

A comparison between mechanical properties of self-compacting concrete and the corresponding properties of normal concrete

An experimental and numerical study on mechanical properties, such as strength, elastic modulus, creep and shrinkage, of self-compacting concrete (SCC) and the corresponding properties of normal compacting concrete (NC) is outlined in this article. The study included eight mix proportions of sealed or air-cured specimens with water–binder ratio (w/b) varying between 0.24 and 0.80. Half of the mixes studied were based on NC. The age at loading of the concretes in the creep studies varied between 2 and 90 days. Four different stress to strength levels were studied. Parallel studies were performed on strength ( f c) and relative humidity (RH). The results show that elastic modulus, creep and shrinkage of SCC did not differ significantly from the corresponding properties of NC. The ongoing study was started in 1997.