Papers by Keyword: Alkali Silica Reaction (ASR)

Abstract: In this article we treat a pathological problem for a better understanding of the phenomena of ASR; the modeling of ASR has been represented in a relative element of volume (REV) in mesoscopic scale. The method used to estimate the formation of ASG is the kinematic estimation of the ASR where it generates in the end an expansion, thus modeling leads to a better range of understanding of the rheological behavior of a concrete with ASR.The numerical model adopted to validate the effect of the expansion of alkali silica gel in terms of strain/stress is a phenomenological one, where it gives sustainable results with the rheological models.

Abstract: Raspberry Pi is a credit card sized Linux computer based on ARM11 architecture. Because of its small size, low power consumption and powerful performance, a robot controller is a suitable role for it to play. As a robot with artificial intelligence, speech recognition for controlling the robot and voice feedback to users is key parts of the entire system. In this essay, a robot called Lisa is assembled, and a speech control and interactive system is implemented based on Google voice API which is a voice recognition engine provided as a cloud service. In order to analysis complex voice commands, a semantic method is developed to catch key words from command sentences. Then try to make a pattern match between key words and instruction set build-in the robot control system. The speech recognition control and interactive system is effective and well behaved after experimental verification.

Abstract: This paper proposes a wheel slip control strategy for 4WD Electrical Vehicle with In-wheel Motors. In the first part of this paper, a brief introduction of sliding mode control for acceleration slip regulation is given. Consider that its control effect varies with road conditions, another algorithm which can automatically adapt to different roads is designed. This method takes advantage of the peculiarity of the longitudinal static tire force curve and regulates wheel slip ratio to the detected optimal value, aiming to maximize the traction force while preserving sufficient lateral tire force. Simulation results show that the slip rate can be regulated to a value around the optimal slip ratio, and the driving torque is very close to the maximum transmissible torque. The control strategy achieves stronger stability, shorter driving distance and hence better control performance.

Abstract: Slate has high alkali activity.When broken as aggregate, it produce high content of slate powder.In order to study the effect of slate powder on fly ash in suppressing alkali activity of slate aggregate and the possibility of making full use of the powder,we carried the experiment on rapid mortar bar method.The experimental results show that:1. When the content of slate powder is less than 15% , it has no adverse effect on fly ash in suppressing alkali activity of slate aggregate. When the content of slate powder is greater than 15%,it can increase the effect of suppression.2. For alkali-silica reaction,what really suppress it is the active SiO2 that comes from slate powder or fly ash.As long as the mineral admixture containing active SiO2 grinds fine to the fineness of cement particle, it can increase the effect of suppression on fly ash in suppressing alkali activity of slate aggregate, rather than reduces the suppressive effect.

Abstract: The study on metakaolins inhibit effect to alkali-silica reaction (ASR) of slate aggregate by the way of accelerated mortar-bar test (AMBT),the results show that when the gel contains 15% metakaolin,the 14d expansion ratio is less than 0.03%,the inhibit reach the wear goal. But when we add the content of metakaolin, the expansion ratios are similar at every age.

Abstract: The research uses Mortar bar rapid method. The experiment of single-doped mineral admixture such as fly, slag and silica fume has been done on the base of the theory of mineral admixture suppressing concrete alkali silica reaction (ASR).The effect of each mineral admixture on suppressing concrete ASR has been analysis ed. It shows that the inhibition for suppressing concrete ASR was the most beneficial when the addition of fly is 50% and the more the dosage is, the better the inhibition is. The silica fume is more beneficial for suppressing concrete ASR relatively and it also needs less addition. The effect of slag is the poorest and it also needs more addition.

Abstract: Test the alkali-silica reactivity of slate aggregate in Guizhou using mortar-bar method in JTG E42-2005of China and accelerated mortar-bar method in TB/T2922.5-2002 of China. The results show that the six months expansion is 0.11% with mortar-bar method, the aggregate has low alkali activity. The 14-days expansion exceeds 0.30% with accelerated mortar-bar method, according to the TB10005-2010, the aggregate has high alkali reactivity. Obviously, the accelerated mortar-bar method is safer than the mortar-bar method, but the test parameters and test conditions of accelerated mortar-bar method have some differences with the aggregate physical environments. According to the accelerated mortar bar method, the thesis proposes an improved test method for evaluating the alkali-silica reactivity of slate aggregate.

Abstract: In order to study the effect of manufactured-sand’s feature on the alkali activity of slate aggregate, refer to the accelerated mortar bar test in the “Standard for Constructional Quality Acceptance of Railway Concrete Engineering” TB 10424-2010. The text has studied the expansion of the specimens that are made from slate aggregate with different powder contents or different particle size distribution. The results show that: When the content of powder in slate aggregate is less than 10%, the powder dose not have adverse effects on the expansion of specimens, and when the powder content is 15% to 20%, the expansion has downward trend. Slate powder is an active powder. It can not suppress the alkali-aggregate reaction of slate aggregate, but it can reduce the expansion of specimens. Particle size has influence on the expansion of specimens. The most unfavorable particle size of slate aggregate for the alkali activity is 0.16~0.315(mm).

Abstract: The effects of Al₂O₃ and Al(OH)₃ on expansion due to alkali-silica reaction (ASR) were tested by using Accelerated Mortar Bar Test and through prolonging the curing age, and the ffect was compared with silicon fume and fly ash. The results show that ASR can be inhibited effectively by proper content of silicious admixtures within 14 days, but can not in long term, while it can be inhibited by proper content of Al₂O₃ and Al(OH)₃ not only within 14 days but also in long term. The composite of silicious admixtures and aluminous admixtures has synergetic effect on inhibiting ASR, and there exists a value of Al₂O₃/SiO₂ with which ASR is suppressed best. For the composite, ASR is suppressed mainly by silicious admixtures in early age and mainly by aluminous admixtures in long term.

Abstract: The alkali-aggregate reaction (AAR) in concrete is a group of chemical reactions that involves the reaction of certain minerals present in the aggregates with alkali and hydroxyl ions in the interstitial solution of cement paste in concrete. These reactions form an alkaline hygroscopic gel that absorbs water and expands causing internal stresses with cracking [1]. The AAR mitigation measures oblige the correct evaluation of the alkali reactivity of the aggregates. This is normally assessed by petrographic, chemical or expansion test methods. Several studies regarding alkali reactivity of aggregates for concrete structures in Portugal, including bridges and dams, indicated that their field performance does not correspond to the previously performed evaluation. Presently, Portuguese methodology is based on the LNEC Specification E461-2007, which shows some limitations regarding rock types such as granitoids [2]. This situation motivated the development of a research project, involving medium and long term expansion tests in different conditions, under accelerated and natural exposure conditions, as well as petrographic evaluation of the main Portuguese aggregates used/to be used in concrete. This paper presents the preliminary results of this research.