Three-Dimensional Multi-Phase Microscopic Simulation of Service Life of Recycled Large Aggregate Self-Compacting Concrete

Recycled large aggregate self-compacting concrete (RLA-SCC) within multiple weak areas. These weak areas have poor resistance to chloride ion erosion, which affects the service life of RLA-SCC in the marine environment. A three-dimensional multi-phase mesoscopic numerical model of RLA-SCC was established to simulate the chloride ions transportation in concrete. Experiments of RLA-SCC immersing in chloride solution were carried out to verify the simulation results. The effects of recycled large aggregate (RLA) content and RLA particle size on the service life of concrete were explored. The results indicate that the mesoscopic numerical simulation results are in good agreement with the experimental results. At the same depth, the closer to the surface of the RLA, the greater the chloride ion concentration. The service life of RLA-SCC in marine environment decreases with the increase of RLA content. Compared with the service life of 20% content, the service life of 25% and 30% content decreased by 20% and 42% respectively. Increasing the particle size of RLA can effectively improve the service life of RLA-SCC in chloride environment. Compared with the service life of 50 mm particle size, the service life of 70 mm and 90 mm increased by 61% and 163%, respectively. .

Prediction of Compressive Strength of Self-Compacting Concrete Using Intelligent Computational Modeling

In the present scenario,computational modeling has gained much importance for the prediction of the properties of concrete.This paper depicts that how computational intelligence can be applied for the prediction of compressive strength of Self Compacting Concrete(SCC).Three models,namely,Extreme Learning Machine(ELM),Adaptive Neuro Fuzzy Inference System(ANFIS)and Multi Adaptive Regression Spline(MARS)have been employed in the present study for the prediction of compressive strength of self compacting concrete.The contents of cement(c),sand(s),coarse aggregate(a),fly ash(f),water/powder(w/p)ratio and superplasticizer(sp)dosage have been taken as inputs and 28 days compressive strength(fck)as output for ELM,ANFIS and MARS models.A relatively large set of data including 80 normalized data available in the literature has been taken for the study.A comparison is made between the results obtained from all the above-mentioned models and the model which provides best fit is established.The experimental results demonstrate that proposed models are robust for determination of compressive strength of self-compacting concrete.

The Impermeability Mechanism of Self-compacting Water Proof Concrete

The impermeability mechanism of water-proof self-compacting concrete (WPSCC )w as studied. The mechanism and influential factors, such as water-cement ratio(w /c), dosage of powder, superplasticizer, sand content, aggregate conte nt, fly ash, UEA, PP fiber, on compactibility and crack resistance of WPSCC were analyzed. A type of WPSCC successfully applied in tunnel liner with its validit ies, conveniences and economies by mockup test was developed and optimized. Expe rimental results show that the WPSCC has good workability, mechanical properties and impermeability when reasonable requirements are fulfilled.

The Frost-resisting Durability of High Strength Self-Compacting Pervious Concrete in Deicing Salt Environment

A high strength self-compacting pervious concrete(SCPC) with top-bottom interconnected pores was prepared in this paper. The frost-resisting durability of such SCPC in different deicing salt concentrations(0%, 3%, 5%, 10%, and 20%) was investigated. The mass-loss rate, relative dynamic modulus of elasticity, compressive strength, flexural strength and hydraulic conductivity of SCPC after 300 freeze-thaw cycles were measured to evaluate the frost-resisting durability. In addition, the microstructures of SCPC near the top-bottom interconnected pores after 300 freeze-thaw cycles were observed by SEM. The results show that the high strength SCPC possesses much better frost-resisting durability than traditional pervious concrete(TPC) after 300 freeze-thaw cycles, which can be used in heavy loading roads. The most serious freeze-thaw damage emerges in the SCPC immersed in the 3% of Na Cl solution, while there is no obvious damage in 20% of Na Cl solution. Furthermore, it can be deduced that the high strength SCPC can be used for 100 years in a cold environment.

Self-compacting Concrete-filled Steel Tubes Prepared from Manufactured Sand with a High Content of Limestone Fines

To meet the requirements of construction of concretes filled in the steel tube arches,a C60 grade micro-expansive self-compacting concrete （SCC） was prepared from manufactured sand （MS）.The utilization of MS with a high content of quarry limestone fines was dealed for SCC applications.The workability,compressive and splitting strength,modulus of elasticity,restrained expansion and chloride ion permeability as well as freeze-thaw resistance of three MS-SCC mixes with fines content of 3%,7% and 10% were tested and compared with those of the natural sand （NS）-SCC mix.The experimental results indicate that the performances of the C60 MS-SCC with fines content of 7% are excellent and compared favorably with those of C60 NS-SCC.

Rheological Properties of Self-compacting Concrete Paste Containing Chemical Admixtures

Self-compacting concrete （SCC） was used for the filling layer of CRTSⅢ plate ballastless track, which needs excellent workability. The rheological properties of SCC cement paste containing chemical admixtures （CA） such as polycarboxylate-based superplasticizer （PCE）, air-entraining agent （AE） and defoamer （DF） were investigated using a Brookfield R/S SST2000 soft solid tester with a vane geometry spindle. The cementitious materials were designed as one, two and, three components systems by addition of ordinary portland cement （OPC） with these chemical admixtures. The rheological properties of one-component system （PCE paste） were improved with increasing the content of PCE. For two components systems of PCE-AE and PCE-DF, yield stress and plastic viscosity reduced firstly and increased afterward with the increasing of AE content. And the plastic viscosity reached the optimum when the content of AE is 0.004wt%. In general, the trend of yield stress and plastic viscosity decreased with the increasing of the DF content. For three components systems, PCE-AE-DF systems, the rheological properties were improved compared with the sample with AE or DF, which attributed to mixes of the active components mentioned above （CA） which could have a synergetic effect.

Design and Preparation of High Elastic Modulus Self-compacting Concrete for Pre-stressed Mass Concrete Structures

Requirements of self-compacting concrete （SCC） applied in pre-stressed mass concrete structures include high fluidity, high elastic modulus, low adiabatic temperature rise and low drying shrinkage, which cannot be satisfied by ordinary SCC. In this study, in order to solve the problem, a few principles of SCC design were proposed and the effects of binder amount, fly ash （FA） substitution, aggregate content and gradation on the workability, temperature rise, drying shrinkage and elastic modulus of SCC were investigated. The results and analysis indicate that the primary factor influencing the fluidity was paste content, and the main methods improving the elastic modulusof SCC were a lower sand ratio and an optimized coarse aggregate gradation. Lower adiabatic temperature rise and drying shrinkage were beneficial for decreasing the cement content. Further, based on the optimization of mixture, a C50 grade SCC （with binder amount of only 480 kg/ m3, fly ash substitution of 40%, sand ratio of 51% and proper coarse aggregate gradation （Vs.~0 mm： V10-16 ram： V16.20 mm= 30%： 30%：40%）） with superior workability was successfully prepared. The temperature rise and drying shrinkage of the prepared SCC were significantly reduced, and the elastic modulus reached 37.6 GPa at 28 d.

Effects of Stone Cutting Powder (Al-Khamkha) on the Properties of Self-Compacting Concrete

Most of the construction materials research now concerns on investigation of construction materials that is locally produced at a rate and cost compatible with the pace of construction. The present paper is concerned with investigation of fresh and hardened properties of self-compacting concrete (SCC) produced from local available materials in JORDAN. The produced SCC contains the local stone cut waste powder which is called Al-KHAMKHA in JORDAN with different replacement of (0%, 10%, and 25%) of fine silica aggregate;?the study also investigatesthe effects of SP33 super?plasticizer which is used by different doses (1%, 1.5% and 2%) for cement. The slump flow and the compressive strength of SCC were studied and the experimental results indicate the possibility of using Al-KHAMKHA in the production of SCC as the results showed that the compressive strength of the SCC with 10 % replacement by al-khamkha together with 1% SP33?super plasticizer was higher compared to pure SCC without al-khamkha;?the results also showed that as al-khamkha content increased the slump flow decreased.

Effect of Clay Fines on the Behavior of Self-Compacting Concrete

The technology of concrete has significantly increased in recent years through the use of super plasticizer and availability of mineral additions. One of the most recent materials used as an additive, replacing a portion of cement in concrete, is fine clay fired at a temperature of 800℃ to 900℃. This research is based on trials that complied with artificial pozzolan (waste crushed brick), and their effect on the rheological and mechanical behavior of mortar. The addition of 5% of a waste crushed brick has helped not only to improve the strength (tensile and compression), but also to foster a better rheological behavior in terms of fluidity and stability, with a low heat of hydration compared to control. However, tests of optimizing the content of self-compacting concrete (SCC) in coarse aggregates, sand and binder, led us to confirm that the combined mass of more optimal (better workability and stability) is that based on low in volumetric percentage of sand/paste with a granular skeleton richest gravel low dimensions (2/3 of G 3/8 and 1/3 of G 8/15).

Formulating for Innovative Self-Compacting Concrete with Low Energy Super-Sulfated Cement Used for Sustainability Development

This study proposed a new way to formulate a low energy super-sulfated cement (SSC) which can be used to produce self-compacting concrete (SCC) with high compressive strength and durability in terms of chloride penetration resistance. This innovative SSC, different from the traditional SSC, was purely produced with a ternary mixture of three industrial by-products of ground granulated blast furnace slag, low calcium Class F fly ash and circulating fluidized bed combustion (CFBC) fly ash and was denoted as SFC-SSC (super-sulfated cement made by mixture of slag, Class F fly ash and CFBC fly ash). Experimental results showed that the combination of a fixed amount of 15 wt.% of CFBC fly ash with various ratios of Class F fly ash to slag could be used to produce the hardened SCCs with high 28-day compressive strengths (41.8 - 65.6 MPa). Addition of Class F fly ash led to the resulting SCCs with lowered price and preferable engineering properties, and thus it was considered as state-of-the-art method to drive such type of concrete towards sustainable construction materials.

Investigation on the Free and Restrained Shrinkage of Self-compacting Concrete

A novel ellipsis-ring cracking apparatus with an automatic monitoring system was used to measure the restrained shrinkage and initial cracking time of self-compacting concrete (SCC). The free shrinkage, restrained shrinkage and strength were integrated to evaluate the effect of the mineral admixtures and content of cementitious materials on shrinkage of SCC. The experimental results show that the initial cracking time of SCC incorporating fly ash was delayed, the shrinkage value and rate was reduced. The hydration achievement of silica fume increased free shrinkage and reduced initial cracking time of FA-SCC comparing to control sample, but silica fume improved the mechanical properties of FA-SCC in early age. As same strength, with the reducing the content of cementitious materials, the initial cracking time of SCC delayed and cracking sensitivity decreased markedly, especially when the content of cementitious materials achieve 450 kg/m3.

Properties of Chemically Synthesized Nano-geopolymer Cement based Self-Compacting Geopolymer Concrete(SCGC)

The physical and mechanical properties of self-compacting geopolymer concrete(SCGC) using chemically synthesized nano-geopolymer cement was investigated. Nano-geopolymer cement was synthesized using nano-silica, alkali activator, and sodium aluminate in the laboratory. Subsequently, nine nanogeopolymer cement sbased SCGC mixes with varying nano-geopolymer cement content, alkali activator content, coarse aggregate(CA) content, and curing temperature were produced. The workability-related fresh properties were assessed through slump flow diameter and slump flow rate measurements. Mechanical performances were evaluated through compressive strength, splitting tensile strength, and modulus of elasticity measurements. In addition, rapid chloride penetration test, water absorption, and porosity tests were also performed. It was assessed that all mix design parameters influenced the fresh and hardened properties of SCGC mixes. Based on test results, it was deduced that nano-geopolymer cement SCGC performed fairly well. All the SCGC mixes achieved the 28-day compressive strength in the range of 60-80 MPa. Additionally, all mixes attained 60% of their 28-day strength during the first three days of elevated temperature curing. FTIR and SEM analyses were performed to evaluate the degree of polymerization and the microstructure respectively for SCGC mixes.

Expansive Performance of Self-stressing and Self-compacting Concrete Confined with Steel Tube

Combining with the technology of self-compacting concrete, self-stressing concrete and concrete-filled steel tube, we can get self-compacting and self-stressing concrete-filled steel tube. In order to study the expansive mechanism of self-stressing concrete, the continuous observation of 47 days on six specimens was carried on. The specimens have different steel area to concrete area ratio. The expansive process in hoop and axial direction were studied, and the expansive mechanism was discussed too. The experimental results identify that the creep and elastic deformation take a large proportion in effective free expansion. The calculating formulas of self-stress in hoop and axial directions were presented here.

Formwork lateral pressure of precast normal-concrete composite shear walls infilled with self-compacting concrete

Wall cracking and mold expanding due to concrete vibrations can be effectively solved through the application of precast normal-concrete composite shear walls infilled with self-compacting concrete(SCC). However, the high liquidity of SCC will induce a higher lateral pressure. Therefore, it is important to obtain a better understanding of the template lateral pressure. In this work, nine composite shear walls were experimentally investigated, focusing on the effects of two parameters, i.e., the casting rate and the section width of the formwork. The time-varying pressure was monitored during the SCC pouring. It is found that the increase of casting rate from 3.2 m/h to 10.3 m/h resulted in a higher maximum lateral pressure. The higher casting rate led to a longer time required for the lateral pressure to drop to a steady value. There was no correlation between the section width and the rate of decrease in the initial formwork pressure and stable value. Based on the test results, a formula considering the effect of casting speed for the calculation of SCC formwork pressure was established to fill the gap in the current standards and for engineering applications.

Preparation of Self-compacting Ultra-high Toughness Cementitious Composite

A self-compacting ultra-high toughness cementitious composite （UHTCC） reinforced by discontinuous short polyvinyl alcohol （PVA） fibers, which exhibits self-compacting performance in the fresh state and strain-hardening and multiple cracking behavior in the hardened state, was developed through controlling flow properties of fresh mortar matrix at constant ingredients concentrations determined by micromechanical design and ensuring uniform fibers dispersion. The superplasticizer was utilized to adjust its flow properties in the fresh state. A series of flow tests, including deformability test, flow rate test, and self-placing test, were conducted to characterize and quantify the fluidity performance of fresh mortar matrix and self-compactability of fresh UHTCC. It is revealed that the utilization of superplasticizer is efficient in producing the fresh mortar matrix with desirable fluidity and the resulting self-compacting UHTCC. In addition, results of four point bending tests on the developed self-compacting UHTCC confirm the insensitivity of mechanical performance of self-compacting UHTCC to the presence of external vibrations as well as the flexural characteristics of deformation hardening and multiple cracking.

Effect of molecular structure and slump loss resistance of polycarboxylate superplasticizers on self-compacting concrete

A new kind of polycarboxylate superplasticizer with high slump loss resistance was obtained by designing scheduled molecular structure.The number average molecular mass of the polymer was characterized by the gel permeation chromatography measurements.And chemical structure of the polymer was observed by the Fourier transform infrared spectroscopy(FT-IR).The results show that the good workable maintaining of self-compacting concrete could be achieved through direct adjustment of number average molecular mass and different unsaturated monomer in synthetic process.The FT-IR analysis illustrated that the high slump loss resistance of polycarboxylate superplasticizers with ester and carboxyl group and expectations of molecular structure were designed.

Comparison of Shrinkage, Creep and Elastic Shortening of VMA and Powder Type Self-Compacting Concrete and Normal Vibrated Concrete

Self-compacting concrete (SCC) is flowing in nature and hence viscosity modified agent (VMA) or higher amount of binder is used for stability of mix. The mix proportion of SCC is also different from normal vibrated concrete (NC). This modifies the properties of concrete at fresh as well as at hardened state. Three mixes, one VMA type SCC, one powder type SCC and one NC, are considered with identical water to binder ratio. Properties at fresh state such as workability and segregation resistance and at hardened stage such as compressive strength, elastic modulus, shrinkage, creep and elastic shortening are determined and compared. Powder type SCC shows superior properties at fresh stage. Also compressive strength of powder type SCC is found better than that of VMA SCC and NC. Observations show more shrinkage, elastic shortening and creep for powder type SCC as compared with VMA SCC and NC.

Properties and Thermal Stress Analysis of Blended Cement Self-Compacting Concrete

Self-Compacting concrete is a concrete that is able to flow and consolidate under its own weight, completely fill the formwork even in the presence of dense reinforcement, whilst maintaining homogeneity and without the need for any additional compaction. Self-Compacting concrete is achieved by using high proportions of powder content and super?plasticizers. Due to this, pronounced thermal cracking is anticipated. Thermal cracking in concrete structures is of great concern. The objective of this research is to carry out experiments and investigate fresh and hardened properties of SCC developed using a blend of ordinary Portland cement and ground granulated blast furnace slag (GGBFS), to evaluate the applicability of Japan Concrete Institute (JCI) model?equations and?to find out any similarities and differences between Self-?Compacting concrete and normal vibrated concrete—Portland blast furnace slag concrete class B. Thermal stress analysis of the proposed Self-Compacting concrete and normal vibrated concretes were investigated by simulation using 3D FEM analysis. To carry out these objectives, concrete properties such as autogenous shrinkage, adiabatic temperature rise, drying shrinkage, modulus of elasticity, splitting tensile strength and compressive strength were determined through experiments. From experimental results, it was observed that except for the fresh properties, the hardened properties of Self-Compacting exhibit similar characteristics to those of normal vibrated concrete at almost similar water to binder ratios. It was also established that Self-Compacting concrete at W/B of 32% with a 50% replacement of ground granulated blast furnace slag has better thermal cracking resistance than SCC with 30% GGBFS replacement. It is also found that provided the relevant constants are derived from experimental data, JCI model equations can be applied successfully to evaluate hardened properties of Self-Compacting concrete.

Evaluation of Fresh and Hardened Properties of Self-Compacting Concrete

This paper compared the rheological properties and compressive strengths of self-compacting concrete (SCC) and conventional cement concrete. The flowability and segregation resistance of freshly mixed concrete specimens were examined by the V-funnel apparatus, while the characteristics of passing ability were investigated with the L-box apparatus. Cylindrical concrete specimens of 100 mm diameter × 200 mm length were investigated for compressive strength. The rheological properties of SCC are incomparable with those of the conventional concrete due to their diverse testing methods and characteristics of individual flow. The compressive strength results of hardened concrete showed that SCC gained strength slowly compared to the conventional cement concrete due to the presence of admixtures and its 28 days strength was lower than conventional cement concrete, but SCC eventually had potentials of higher strength beyond 90 days. Finally, the effect of water-cement ratio on the plastic properties of self-compacting concrete was quite negligible compared to conventional concrete.

An Experimental Study of Self-Compacting Concrete Made with Filler from Construction and Demolition Waste

This study evaluated the influence of the Portland cement replacement by 0, 5%, 10%, 15% and 20% of Construction and Demolition Waste (CDW) filler contents in the production of self-compacting concrete (SCC). The SCC mixtures were evaluated on fresh state by slump flow, J-ring, resistance of segregation, specific gravity, and on hardened state by compressive and splitting tensile strength, specific gravity, air voids and absorption rate. The results indicated that all SCC produced with CDW filler met the limits established at any level of substitution without changes of the w/c ratio or superplasticizer content. It was possible to verify that the presence of CDW filler, in substitution of cement, by volume, improves the resistance to segregation and up to 5% of CDW filler decreases the loss of fluidity with time as compared to reference. It was found that all SCC mixtures, at 28 days, had the average compressive strength above 50 MPa, without showing significant loss with up to 20% of CDW filler. For splitting tensile strength, SCC recycled mixtures reached up to 92.5% of the SCC used as reference. Absorption rate and air voids index of SCC recycled mixtures had a maximum increase of 1.60%Compared to the reference one. So, it is possible to conclude that the use of the CDW filler up to 20% in substitution of cement, by volume, is feasible for SCC production.