Green High Performance Concrete Research Articles

A novel high-performance lightweight concrete prepared with glass-UHPC and lightweight microspheres: Towards energy conservation in buildings

Improving energy conservation of buildings and promoting wastes recycling contribute to reducing CO2 emissions. This work developed a green high-performance lightweight concrete (HPLC) with good thermal insulation for energy-saving purposes. The HPLC was comprised of lightweight microspheres and sustainable ultra high-performance concrete (UHPC), which was prepared with a large volume of waste glass. For the glass-based UHPC, the use of glass cullet led to mechanical decrement, while the workability and mechanical properties were improved with the replacement of 50% cement by glass powder. Combining glass aggregates and powder in UHPC significantly enhanced its thermal insulation properties. Meanwhile, incorporating two kinds of lightweight microspheres in the glass-based UHPC further lowered the density and thermal conductivity of HPLC. The performance of HPLC was dependent on the physical characteristics of lightweight microspheres rather than their chemical reaction based on molecular dynamics simulation. The developed HPLC exhibited a low density (<2000 kg/m3) and excellent mechanical properties (compressive strength >100 MPa and flexural strength >35 MPa). The superior performance of HPLC was ascribed to the high pozzolanic reactivity of glass powder and its promotion on cement hydration, the low thermal conductivity of glass, the chemical reactivity of microspheres as well as their hollow nature for impeding heat transfer. The good flexure and thermal insulation performance would make this eco-HPLC a promising material for applications in energy efficient buildings and long-span lightweight structures.

Early-Age Performance Analysis of Sludge Water Incorporation in High-Temperature Steam Cured Green High-Performance Concrete.

Sludge water (SW) with abundant sulfate ions (SO42−) was utilized in this work to replace freshwater (FW) to prepare green high performance concrete (GHPC). A comprehensive investigation was conducted to evaluate the early-age performance of GHPC specimen mixed with SW incorporation (GHPC-SW). High temperature steam curing (HTS) has been presented to prepare GHPC-SW specimens. The compressive strength of the GHPC-SW specimen cured by HTS curing for 2 days is 85.2 MPa, which is 34% higher than the compressive strength of the GHPC-SW specimen cured by 3 days standard curing as the reference. The mechanical property results reveal that the incorporation of SW makes no harmful effects on the strength formation of HPC specimens, compared with FW added specimens under the same curing methods. Moreover, XRD and TG analyses indicate that HTS curing can effectively improve the hydration degree of GHPC-SW specimens. MIP analysis has been conducted and the specimens cured by HTS curing exhibit a more refined pore structure with fewer harmful pores. This work lays a solid foundation for the utilization of SW in the concrete construction industry, which is resource saving and environmentally friendly.

Strength and Durability of High Performance Concrete Doped New Low Clinker Cementing Material

A new low clinker cementing material applying to different concrete strength is developed in this paper. The experiential results show that standard consistency water consumption of the new material is less than the ordinary material; and the particle size is better than the ordinary material. And the cracking performance of the concrete made by the new material is far better than the performance of the concrete made by the ordinary material. Furthermore, the shrinkage of the concrete made by new material is less; and the resistance ability to carbonation is higher. Especially, our proposed new material could make the gel body dense and become six components of concrete into four, which simplifies the production process of concrete mixing station. At the same time, the prepared concrete made by the new material has better construction performance, volume stability and high durability. Unfortunately, the initial and final setting time of the new material are slightly longer. However, the initial and final setting time are still able to meet the national requirements. And most of all the new material meets the requirements of green high performance concrete.

Green High Performance Concrete Based on Sustainable Development

Green high performance concrete is concrete materials which can reduce the load of the earth's environment, coordinate development with the ecosystem and create comfortable living environment. The relationship between the construction materials and the sustainable development and the characteristic of green high performance concrete were introduced, the measures of green concrete production was analyzed and the work essential for the development of green high performance concrete was proposed in this paper. The research shows that the development of green high performance concrete is the inevitable way for the sustainable development of concrete.

Experimental Study on Workability and Strength of Green High Performance Concrete with High Volume Fly Ash

A great deal of experiments have been carried out in this study to reveal the effect of the water-binder ratio and fly ash content on the workability and strengths of GHPC (green high performance concrete). The workability of GHPC was evaluated by slump and slump flow. The strengths include compressive strength and splitting tensile strength. The results indicate that the increase of water-binder ratio can improve the workability of GHPC, however the strengths of GHPC were decreased with the increase of water-binder ratio. When the fly ash content is lower than 40%, the increase in fly ash content has positive effect on workability of GHPC, while the workability begins to decrease after the fly ash content is more than 40%. The addition of fly ash in GHPC has adverse effect on the strengths, and there is a tendency of decrease in the compressive strength and splitting tensile strength of GHPC with the increase of fly ash content.

Study Progress on Modern Green High Performance Concrete at Domestic and Foreign

Recycled concrete is one of the main measures to develop ecological and green concrete, also it is one of the useful ways to obtain sustainable development of buildings, resources,and environment . Conforming to this idea , it is increasingly being valued by engineering and became one of the hot concrete research. In this paper, we start with the concept of green high performance concrete , taking high performance concrete in green cementitious materials, aggregates and admixtures point to cut in ,and describing the characteristics of green high performance concrete and its research situation in details. Besides,on the basis of combining the domestic and foreign development of green concrete,I will point out the problems in the currentre research of recycled concrete .Then Ill give the corresponding countermeasures and propose sustainable research and development proposals by emphatically analyzed the research status and application of recycled concrete at domestic and foreign .

Evaluation on Compressive Strength and Workability of Green High-Performance Concrete by Grey Relational Grade

Applying grey relational analysis method, this paper calculated the relational grades between the mix proportion parameters and the compressive strength, the slump of green high-performance concrete (GHPC) respectively. Besides, the sequence results of influencing degree of the factors affecting the compressive strength and workability were obtained. The results indicate that the compressive strength and slump of GHPC are affected by various mix proportion factors with different sensitivity, and the sensitivity could be well analyzed by the grey relational analysis. Among the four selected parameters of mix proportion such as water to binder ratio, cement dosage, fly ash dosage and sand ratio, the water to binder ratio and the cement dosage greatly influence on the compressive strength of GHPC, the water to binder ratio and the sand ratio greatly influence on the workability of GHPC.

Test and Study on Green High-Performance Marine Concrete Containing Ultra-Fine Limestone Powder

In order to solve the environment pollution of limestone powder during production of limestone manufactured sand and gravel and problem of lack of high quality fly ash or slag powder in ocean engineering, ultra-fine limestone powder was selected for preparation of green high-performance marine concrete containing fly ash and limestone powder and that containing slag powder and limestone powder for tests on workability, mechanical performance, thermal performance, shrinkage, and resistance to cracking and chloride ion permeability. And comparison was made between such green high-performance concrete and conventional marine concrete containing fly ash and slag powder. Moreover, the mechanism of green high-performance marine concrete was preliminary studied. Results showed that ultra-fine limestone powder with average particle size around 10μm had significant water reducing function and could improve early strength of concrete. C50 high-performance marine concrete prepared with 30% fly ash and 20% limestone powder or with 30% slag powder and 30% limestone powder required water less than 130kg/m3, and showed excellent workability with 28d compressive strength above 60MPa, 56d dry shrinkage rate below 300με, cracking resistance of grade V, 56d chloride ion diffusion coefficient not exceeding 2.5×10-12m2/s. Mechanical performance and resistance to chloride ion permeability of limestone powder marine concrete were quite equivalent to those of conventional marine concrete. But it had better workability, volume stability and cracking resistance. Moreover, it can serve as a solution to the lack of high quality fly ash and slag powder.

Development of Green High Performance Concrete

As the world's largest building materials production, the mechanical properties of concrete prominent and construction is simple, inexpensive features. Concrete production and construction sectors also exists a very serious problem of environmental pollution, people have to consider how to enhance the environmental protection of concrete, namely, the production and use of "green concrete". Since the past one-sided pursuit of high strength concrete, while ignoring the the durability issues brought a series of questions, allowing people to put forward the concept of a high-performance concrete. The paper by exploring the current development of high-performance green concrete, summary of the proposed method to achieve green high performance concrete.

Study and Application of a Modified Agent GHPC-1 for Green High-Performance Concrete

A modified agent GHPC-1 for green high-performance concrete was composed of the strength-increasing groups of organic alcohol amine, the slump-retaining groups of carboxylate polymer and the workability-stabilizing groups of amide. It could be used through substituting some of polycarboxylate water-reducers or combining with polycarboxylate water-reducers to modify the workability of fresh concrete and to increase the strength of hardened concrete. The adaptability tests of cementing materials with admixtures show that the dispersing ability was almost not influenced but the retaining ability of paste flowing was evidently enhanced if the substitution of polycarboxylate water-reducers have been to 20 %. The comparative tests of concrete indicated that as 20 % content of GHPC-1 was added in polycarboxylate water-reducers, it could modify the concrete workability. If adding 0.6 % with polycarboxylate water-reducers it could save water by 5 % and cement 10 % and simultaneously modify the workability and to enhance the strength, or to reduce water by 2.5 % and increase the strength of 28 d by 5~8 MPa.

Evaluating the Influence of Mix Proportion Parameters on Anti-Permeability of Green High Performance Concrete with Grey Relational Analysis

The aim of this study was to evaluate the influence of mix proportion parameters on anti-permeability of green high performance concrete (GHPC) and find out the main influencing factors. Applying grey relational analysis method, the relational grades between the influencing factors and diffusion coefficient of Cl- of GHPC were calculated. Besides, the sequence result of influencing degree of the factors to affect the anti-permeability was obtained. The result shows that the importance of the factors affecting anti-permeability of GHPC has following sequence: water-binder ratio&gt; sand ratio &gt; dosage of cement&gt; dosage of water reducing admixture &gt; dosage of mineral fillers &gt; dosage of fly ash. In order to improve anti-permeability of GHPC, water-binder ratio and sand ratio must be controlled strictly.

The influence of mineral admixtures on resistance to corrosion of steel bars in green high-performance concrete

In this paper, the influences of the types, amount and adding approaches of mineral admixtures on pH values, electrical resistance of concrete, anodic polarization potential and mass loss ratio of steel bars in concrete subjected to 50 immersion–drying cycles were investigated. The testing results showed that the addition of mineral admixtures reduced the pH values of the binder pastes in green high-performance concrete (GHPC), especially when two or three types of mineral admixtures were added at the same time (double- or triple-adding approaches), whereas the final pH values were still above the critical breakage pH value of passivation film on the steel bar surface (11.5). Double- and triple-adding approaches also greatly increased the electrical resistance of concrete, which led to a delay in the initial time of corrosion and a decrease in the corrosion rate of steel bars. Additionally, double- and triple-adding mineral admixtures, instead of single-adding, fly ash can reduce the corrosion of steel bars when a large amount of fly-ash replacement was used. All the details of this paper provided a method to reduce or prevent the corrosion of steel bar in concrete, especially for the application in aggressive marine environments.

The permeability and strength of green high performance concrete

The permeability, alkali-silica reaction, workability and strength of GHPC (green high performance concrete) were studied in this paper. The results show that GHPC has an excellent durability and the effects of mass ratio of flyash to high calcium slag, water-binder ratio, content of water reducer, and crushed coarse aggregate type on the workability and strength of GHPC were considerably evident. A new path for the concretes continuous development was put forward.