The Testing Method And Suppressing Measure Of Alkali Aggregate Reaction

Alkali aggregate reaction (AAR) is one of the important factors that affect the durability of concrete structures. It has caused large money consumption around the world in past decades. Because the crack damage caused by the AAR is hard to control, the AAR is called the "cancer" of the concrete. Alkali-silica reaction (ASR) is the main and most ordinary type of AAR. It has always been a hot topic in the area of AAR study to avoid ASR expansion. The research of how to evaluate the alkali reactivity of the aggregate and the preventing method is a main topic of the duration study of the concrete.ASR has a long potential reactivity time and will cause large damage, so it's very important to judge whether the aggregate has alkali reactivity. Many methods are dveloped to test the alkali reactivity internal and abroad but there is no recognizable method for assessing the alkali reactivity of the aggregate. Different methods get different resulets.Meanwhile, using mineral admixture to control ASR is the most economical and effective way in all the ASR preventing measure. Much experence is gained in using the blending material, however, there is no reliable method for assessing the effectiveness of mineral admixtureand a way to judge the how the mineral admixtureworks in suppressing ASR expansion.In practical constuction, we hope to quicken the testing process to estimate the alkali reactivity and the suppressing results when adopt the preventing measure. This article describes the scientific research item of the alkali aggregate reaction of the Qinghai-tibet railway headquarter. The research base on the lab experiment and the main results are summarized as follows:1. The concrete aggregate samples which are collected on the spot are examined by GB/T14684-2001 Quick Alkali-silica Reaction , GB/T 14684-2001 Alkali-silica Reaction and Petrographic Experimental Method respectively. The cause that leads to different test results are under analysis, and thus put forward the viewpoint of how to estimate the alkali reactivity of the aggregate.2. A new trial test method is introduced on the basis of consulting relative experimental methods. The article discusses how to establish a new method effectively by the comprehensive analysis of the test results.3. Contrast four types of mineral admixture under different replace level: the effectiveness and rules of the suppressing impact to the ASR.Thus put forward there is a 'critical range' of the mineral admixturereplacement.4. The analysis of the mechanism of how the mineral admixturesupress ASR:make a comprehensive survey of the macroscopical test results, we adopt SEM/EDS to study the characteristic of samples with blending material. We get the results that the suppress to the ASR of the mineral admixtureis mainly due to the chemical reaction and many other factors also have effects.