Papers by Keyword: Alkali-Silica Reaction

Abstract: This paper evaluates the properties of fly ash (FA) and ground granulated blast furnace slag (GGBFS) based geopolymer mortar mixtures with waste glass sand (WGS) obtained by crushing glass bottles. A total of seven mixtures, including the partial substitution of river sand (RS) with WGS (0%, 15%, 30%, and 45%) with two alkali activator solution to binder (AAS/b) ratio groups (0.4 and 0.3), were designed. Sodium silicate (Na₂SiO₃) and sodium hydroxide (NaOH) were used as the alkali activators. The experimental program evaluated compressive strength, hardened density, alkali-silica reaction (ASR), drying shrinkage, and thermal conductivity of geopolymer mortar mixtures. Test results indicated that the compressive strength of the geopolymer mortar increased with the addition of WGS for AAS/b = 0.4, but it had a negative effect for AAS/b = 0.3. The FA and GGBFS-based geopolymer mortar helps to reduce the ASR expansion of the mixture containing WGS. The drying shrinkage of the geopolymer mortar decreases with the increase of the WGS content. The increase of WGS decreases the thermal conductivity of geopolymer mortar in the case of mixtures with AAS/b = 0.4, but interestingly thermal conductivity value increases in the case of mixtures with AAS/b = 0.3. The findings of this study suggest that using WGS as partial RS substitution material in geopolymer mortar offers sufficient mechanical and thermal insulation properties without causing durability issues.

Abstract: The paper discloses results of durability studies of alkali activated concretes based on different alkali sources using aggregates capable to alkali-silica reaction (ASR). Active aggregates are representing by perlite, andesite, basalt and sandstone. It is shown that the alkali-reactive aggregates, in degree of their influence on expansion deformations occurring in the slag alkaline concretes may be placed in the following row: perlite< sand< sandstone< basalt< andesite, and a growth of expansion deformations is observed with increase in the active silica content in the aggregate. Also it is set that alkaline components, in degree of their influence on the rate of expansion deformations development in the slag alkaline concretes made with reactive aggregates, may be placed in the following sequence: Na₂CO₃<Na₂O SiO₂ < NaOH< Na₂O 2SiO₂.

Abstract: Alkali-aggregate reaction is one of the most serious concrete durability problems threating the safety of dam. Some accelerated test methods with high temperature and high alkalinity are usually used in laboratory to evaluate the reactivity of aggregates or the effectiveness of suppression measures. In this paper, an outdoor field exposure station was built to objectively assess the damage risk of real dam concrete suffering alkali-silica reaction. 25 concrete blocks measuring 450 by 450 by 450 mm in size were tested at first stage, all immersed into water to simulate the environment of dam concrete. The influences of the size of aggregate and the amount of cementing materials were tested at the same time. After 7 years field exposure testing, the results showed that: the crack risk of blocks was not proportional to the expansion rates, but influenced by the maximum diameter of aggregate. The block with bigger aggregate had smaller expansion rate, but cracked more easily. If the sizes of aggregate were the same, less cementing materials would cause bigger expansion. The constraint effect is bigger than the effect of alkali content increasing caused by increasing the amount of cementing materials.

Abstract: In this paper, ｍade a PC beam specimen using ASR reactivity aggregate made in Chinese Zhejiang Ministry and made them do an accelerated curing and the influence by which swell of ASR reactivity aggregate gives it to a PC beam specimen was evaluate. Moreover the PC beam specimen which degraded by swell was classified every degradation grade, a loading test was put into effect and the load carrying capacity was inspected. As a result, I got the following conclusion. ①The thing which classifies the degradation grade into 3 stages (incubation period, acceleration period and degradation period) from the accelerated curing results of the test piece performed in advance. In the incubation period, it was confirmed that the compressive strength and the modulus of static elastic tend to increase more than before accelerated curing. ②Expansion of PC beam specimen was inflated from the upper edge part with less influence of prestress, Moreover as the expansion stabilized, the tendency of the lower edge portion which is highly affected by the prestress to expansion could be confirmed from the strain behavior by monitoring.In addition, with expansion of the lower edge part the prestress amount of the PC steel material placed inside the PC beam specimen (The lower edge position) is increasing and as the prestress amount stabilizes the tendency of expansion of the lower edge part is stabilized can also be confirmed. ③When accelerated curing was further promoted, the expansion of the upper edge and lower edge turned to a decreasing trend, and it was confirmed that stabilize tendency at about 25 to 35% of the maximum expansion. ④The P-δ curve up to fracture was measured for PC beam specimen before accelerated curing and ② to ③. As a result, it was not possible to confirm a large difference at the P-δ curve before accelerated curing and ②, but a significant decrease in load bearing capacity was confirmed at ④.

Abstract: In the paper two existing roads in Austria were examined on the focus of alkali silica reaction of concrete. The two roads have different ages. One is more than 50 years old one is round about 20 years old. The exposition was ordinary highway and countryside highway in the mountains. As next the examination takes the stones from the origin and uses different types of cement to examine the background of the alkali silica guidelines for performance tests of alkali silica reaction. The results are very interesting because most of the performance tests are use test cements with ordinary alkali equivalent. Often the used stones not meet the maximum value of loss of mass under the condition of alkali-load. By using alkali reduced cement the results are less than the maximum value of loss of mass under the condition of alkali-load. One of the targets of the examination was the determination of good load conditions for examination of the alkali silica reaction of stones for use in concrete for road structures. The final paper shows all the examinations and the results between the compared cements and the compared test procedures.

Abstract: In the present paper the results of strength and creep of a specific pavement concrete after ASR performance test are reported and discussed. The FIB cyclic climate storage test was applied which was developed in Germany. The used specific pavement concrete was tested exposed to water and external alkalis such as NaCl solution as deicer. Concrete prisms (100 x 100 x 400 mm) were tested on length change. After 252 days of storage, strength properties, creep and shrinkage were determined. The results of the experimental study indicate that ASR affects not only expansion but also static modulus of elasticity and creep behavior of concrete. Furthermore the tested concrete exposed to NaCl solution shows higher level of creep strain than exposed to water.

Abstract: Among the test-methods for evaluation of aggregates reactivity towards alkali-silica reaction (ASR), linear dilatation of mortar bars or concrete prisms is often used in several tests under various conditions, criteria and procedures of measuring and accelerating the reaction. As reactivity is an essentially kinetic property, the expansion limits in such tests, or even tests results for the same aggregate, should be kinetically inter-related.

Abstract: A kinetic based comparison between expansion tests for alkali-aggregate reactivity was carried out deriving critical rates from test criteria, in an earlier paper. The present paper checks the assumptions and models of that earlier comparison against results with real aggregates varying in alkali reactivity. Using the same approach, for each aggregate, expansion rates for three expansion tests were estimated, corrected for alkalinity and depicted as an Arrhenius plot. The relationship used data from NF P18-590, ASTM C 1260 and ASTM C 227 expansion test-methods and shows linear Arrhenius plots for several aggregates, aligned almost parallel to the line obtained for test criteria. Aspects related to the different experimental conditions on test-methods and their effects are discussed. The proposed conclusion is that both standards and aggregate results, in the given conditions, are not inconsistent from the kinetic point of view. Some suggestions are made for improving the accuracy of the relationship obtained.

Abstract: The influence of the content of matekaolin powder and fly ash in cement on controlling ASR was evaluated using Accelerated Mortar Bar Test (AMBT). Replacing cement with matekaolin powder to the extent of 5%,10%,15%,20%,25%,and with fly ash to the extent of 10%,20%,30%,35%,40%, 45% respectively. The result show that matekaolin powder and fly ash both can control Alkali-aggregate activity but to different degrees. Small amount of metakaolin powder exerts significant influence, whereas only when the proportion of fly ash is up to 35%, can it control ASR effectively. The effect and mechanism of the control of the extension of glass aggregate activity was studied by means of SEM analysis.

Abstract: The furnace slag are the by-products of the steel industry, the main ingredients are the oxide of calcium, alumina and magnesium, and some silica. Slag used as concrete aggregate could cause the problem of the volume expansion of concrete. The expansion problem may be produced by ASR or free calcium oxide and magnesium oxide in slag. This research stabilizing the non-ASR reactive slag using steam treatment analyzes the effectiveness of steam treating technique inhibiting the expansive problem for slag used in concrete. And this paper also discusses the effect of the steam treating time on the performance of inhibiting the expansive problem.