Mortar Bar Method Research Articles

Study on Alkali-Reactivity of Aggregates Used in Projects in Kaifeng City

Investigation to the source of aggregates used in engineering in Kaifeng area was carried on. The aggregates used in experiment came from main places supplying concrete aggregates for projects in Kaifeng. By the Autoclaved Method, the ASTM C1260 Method, Accelerating Mortar-bar Method (10mm×10mm×40mm in dimension) to determine whether the concrete aggregates has alkali-reactivity. The results show that 14 days expansion rate of each sample is less than 0.1% and the aggregates have no activity.

The effect of mineral admixtures and micronized calcite on alkali silica reaction expansions in the usage of aggregates from different origin

This paper investigates the effectiveness of two zeolites with different reactive silica content, fly ash (FA), blast furnace slag (BFC), silica fume (SF), and micronized calcite (MC) in reducing expansion of concrete due to alkali-silica reaction. Also in this research, effects of three different cement usages were investigated by using accelerated mortar bar method, ASTM C1260. Five different aggregates, three natural sands, and two crushed sands were used for preparing mortar bars. All of these aggregates have been petrographically examined according to ASTM C295 standard and have been found out to be harmful to ASTM C 1260. Performances of the mineral admixtures were compared by examining the expansion due to alkali silica reaction (ASR). The aggregate and cement mixtures were tested with accelerated mortar bar test procedures including 10 and 20% replacement of mineral admixtures by weight of cement. 20% substitution levels of all admixtures were highly effective in inhibiting the ASR. The expansions of test specimens, in which mineral admixtures were used, were within the code-defined acceptable limits of ASTM C1260. According to the standard, different cement usage should not affect expansions in this accelerated test method. However, on contrary to ASTM C1260 statement, this research showed that the mixtures prepared with the same aggregate but different cements displayed different expansions at the end of 14 days. In addition, this different cement usage does not significantly affect the expansions. Key words: Alkali silica reaction (ASR), natural zeolite (NZ), fly ash (FA), blast furnace slag (BFC), silica fume (SF), micronised calcite (MC).

Analysis on Potential Alkali Reactivity of the Aggregate and its Inhibiting Method in Dam Concrete of a Hydro Project

The aim of this paper is to systematically investigate the alkali activity of the aggregate selected from a stockyard, and examine its supression method, before pouring roller compacted concrete into the hydro project in Lechang gorge. Samples of natural sand, sandstone and limestone will be analysed through comprehensive petrographic method and accelerate mortar bar method. The results showed that natural sand is the aggregate without activity; sandstone core contains some wave shape with extinction characteristics of deformation quartz, because of active alkali-aggregate and the harm expansion of mortar, which is the aggregate with potentially harmful alkali-silicate reaction; wave shape and elastic deformation of the alkali in limestone are also the harmful element in concrete. The addition of level 1 and level 2 fly ash both has the ability to inhibit the reaction between alkali and silicate, and can control expansion rate of sandstone under 0.1 %.

Use of waste glass as sand in mortar: Part II – Alkali–silica reaction and mitigation methods

Abstract Waste glass may be used in concrete provided that the potential deleterious expansion caused by alkali–silica reaction (ASR) could be mitigated. In this study, the influence of glass content, color and particle size on ASR expansion of mortar was determined by the accelerated mortar bar method. Two approaches to control ASR expansion were investigated for green, brown and clear glass sand mortar. They were: (1) by replacing cement with pozzolans, that is, 30% fly ash, 60% GGBS, 10% silica fume, or 20% glass powder; (2) by adding a suppressor, that is, plain steel fibers, and lithium chloride and lithium carbonate compounds. Test results showed that the ASR expansion increased with higher glass content in the case of clear glass sand mortar, but would decrease with increasing content for green and brown glass sand mortar. The ASR expansion also decreased with smaller glass particle size, regardless of glass color. Fly ash and GGBS were the most effective in mitigating ASR expansion, followed by silica fume, steel fibers and lithium compounds.

Study on Reducing ASR Expansion in Concrete Prepared with Iron Ore Tailings Sand

Iron ore tailings, wastes of mining industry, have been widely used as manufactured sand in concrete with absence of the natural sand. In present paper, the ASR reactivity of iron ore tailings sand was assessed with rapid mortar bar method (GB/T 14684-2001). Result of a preliminary study on ASR resistance was reported. The replacement of cement by 30% Fly ash (FA), 50% ground granulated blast-furnace slag (GGBFS), 10% metakaolin (MK) and replacement of sand by 15% ground iron ore tailings (GIOT) led to the ASR-expansion to below 0.10%. Compared with replacement of cement, replacement of sand led to better performance. Further more, the fine particles less than 75μm in iron ore tailings sand are beneficial to the reduction of expansion induced by ASR.

Reactividad potencial de las rocas andesíticas de Cabo de Gata (SE de España)

Andesitic rocks produce an alkali-silica reaction with the components of the interstitial phase of concrete. This reaction can be considered as belonging to the slow-kinetic type, since the incongruent dissolution of the rock-forming minerals leads to the late formation of siliceous calc-alkaline gel. As a conquence, the conventional mortar-bar method does not detect such reaction until 90 days later.

An Experimental Study on Evaluation of Suppression Effect Against ASR in Steam-Cured Fly Ash Concrete

It has been pointed out that the use of fly ash in concrete is effective in controlling the expansion due to ASR (alkali silica reaction). In Japan, the total amounts of alkalies in concrete has been kept up to 3.0kg/m3 as one of the major countermeasures for ASR suppression. Recently, it is reported that ASR may be accelerated by the steam curing of PCa concrete even in the case of low alkalies content of less than 3.0kg/m3. On the other hand, the effectiveness of fly ash on the suppression of ASR in concrete is often evaluated by means of the mortar bar method according to JIS A1146, however there are some problems that it takes the long time of 3 or 6 months in assessment, and that it can't take the pessimum content of reactive aggregate in mix proportions of mortar into considerations. In this study, the effectiveness of fly ash in steam-cured concrete was experimentally investigated. For this purpose, the steam-cured fly ash concrete with the replacement percentages by fly ashes was exposed to the accelerated test conditions which were selected as the factor, the temperature, the water supply, the immersion in saturated NaCl solution and so on. As the result of tests, it has been found that the accelerated condition exposed to the saturated NaCl solution at 50°C is most suitable as the rapid test method for the steam-cured fly ash concrete.

Effect of Portland Cement Fineness on ASTM C1260 Expansion

Abstract The present study is aimed at investigating the effect of portland cement fineness on the results of ASTM C1260 tests—Standard Test Method for Potential Alkali Reactivity of Aggregates (Mortar-Bar Method). The effects of clinker alkali content, aggregate reactivity, and sodium hydroxide (NaOH) solution concentration on the mortar expansion test results were also studied. In this study, high and low alkali portland cement clinkers were selected and ground with gypsum in a laboratory ball mill to three fineness levels: 300, 400, and 500 m2/kg (Blaine). Moderately- and highly-reactive aggregates were tested with these cements according to ASTM C1260. In addition to the standard 1 N NaOH solution, a 0.5 N NaOH soak solution was also used. The results show that mortar-bar expansion was promoted with increased cement fineness regardless of clinker alkali, aggregate reactivity, or soak solution normality. Clinker alkali had no or little effect on moderately reactive aggregate; whereas it had considerable effect on highly reactive aggregate. Highly reactive aggregate tended to be more sensitive to cement fineness and alkalinity. Although cement fineness and clinker alkali content did not affect the classification in terms of potential reactivity of the aggregates used in this study, they might change the classification for the aggregates near the boundary between reactive and nonreactive aggregates. Specification of fineness and alkali content of cement, or both, might be beneficial to further improve the reliability and reproducibility of ASTM C1260.

Expansion behaviour of glass aggregates in different testing for alkali-silica reactivity

The potential for reaction between amorphous silica in recycled glass used as aggregate in concrete and alkalis in cement is the subject of debate in current concrete literature. Whilst the ASTM C1260 accelerated mortar bar method is conventionally used for rapid ASR assessment, there is doubt about its suitability for glass aggregates. This paper reports upon a comparison of the relative ASR reactivity of various colours of recycled glass aggregates using the ASTM C1260 and C227 test methodologies. The results show that with limited exception the ASTM C1260 method does not cause glass aggregates to react by the end of the prescribed test period. In contrast, the ASTM C227 method causes all glass aggregates to react within 2 weeks, despite the test being designed for 12 months or even longer if necessary. This paper compares and contrasts the results of the two methods over a wide range of glass aggregate and cementitious systems made with two sizes of mortar bar, draws conclusions about the reasons for the differences observed and makes remarks on the expansion behaviour of glass aggregates in cementitious systems.

Characteristics of Alkali Silica Reaction of Siliceous Sedimentary Rocks

In this paper, alkali silica reactivity of chert and siliceous slate was investigated, and petrographic examination of these rocks was carried out. Petrological characteristics, JIS A1145 chemical method and mortar-bar method were examined on chert rock and siliceous slate which were included in the ASR damaged concrete structure in Aichi Prefecture. In the expansive test method of mortar and concrete, storage environment was changed in various types of conditions. The results of the chemical method became innocuousness, when the crystallinity index measured with X-ray diffraction exceeded 7.5. And in the JIS A1146 mortar bar method, the expansion of mortar made with chert and siliceous slate exceeded 0.1% in 2 months, and in comparison with both rock, the expansion of mortar using siliceous slate was higher than that of mortar using chert. Furthermore, the expansion of the mortar bar of the mixing use of siliceous slate and chert was higher than that of the single use.

유리 연마슬러지를 혼합한 모르타르의 알칼리-실리카 반응에 관한 고찰

After observing the alkali-silica reaction of the mortar that contains glass abrasive sludge, when evaluating it by a mineral or chemical point of view, it contained reactive silica (59~67%) and R₂0 elements (4.3~9.8%). Also, when evaluated by the mortar bar method, an addition of 5 wt% of CRT glass abrasive sludge is judged harmless. However when adding more, there appear severe contractions, thus carefulness is needed while using. Less than 0.10% of expansion was measured when adding up to 30wt% of flat glass abrasive sludge. However, after 30 days of the measurement, more than 0.1% rate of expansion was measured when adding more than 5 wt%. Therefore, more detailed experiments are needed in case of more than 5 wt%.

Influence of Alkali Contents of Cement and Testing Methods on Expansion of Mortar Bars due to Alkali-Silica Reaction

Some problems are pointed out about the examination method of evaluating the alkali reactivity of aggregate. For example, by the mortar bar method of JIS without supply of alkali from the exterior, and the method immersed in the NaOH solution defined by ASTM and the method immersed in saturation NaCl solution (Denmark method), the judgment result changes with kinds of aggregate. Then, in order to acquire broad knowledge about the factor influenced on an examination result in this research, the influence affect the result which alkali content of cement depends on the various examination methods was considered. Consequently, it became clear that the grades influenced alkali content and the kind and the amount of reactant mineral in aggregate by the examination method differ. Especially, a result, which supports indication that it is necessary to examine whether the Denmark method for having an advantage, like that it can judge for a short period of time and a judgment result becomes clear can apply to the aggregate of our country, was brought.

The effect of cement alkali content on ASR susceptibility of mortars incorporating admixtures

In this study, the effects of three types of plasticizing chemical admixtures (modified lignosulfonate, sulfonated naphthalene formaldehyde and polycarboxylate based) on deleterious expansion due to alkali–silica reaction (ASR) have been investigated. Two different types of cements with low (0.53 Na 2O eq.) and high (0.98 Na 2O eq.) alkali contents, a non-reactive crushed limestone as fine aggregate and a reactive river sand were used within the scope of the experimental program. ASR tests were conducted according to accelerated mortar bar method (ASTM C 1260). Additionally the flow value, dry unit weight, capillary water absorption and compressive strength tests were performed. Test results indicated that mortars prepared with inert fine aggregate caused no significant expansion, regardless of cement type, admixture type and dosage. However, for mixes containing reactive sand, admixtures increased or decreased the expansion values (compared to plain mortars) depending on the alkali content of cement used. The magnitude of change of expansion also depended on the type and amount of admixture incorporation which have a dominant effect on stability and compactability of mortars. The high-alkali cement usually revealed the ASR expansion augmentation behaviour of admixtures. In contrast, low alkali cement decreased the expansion values compared to the control specimens.

쇄석 골재의 알칼리-실리카 반응 방지 대책

In Korea, due to the insufficiency of natural aggregates and increasing needs of crushed stones, it is necessary to examine the alkali-silica reaction of the crushed stones. The reaction produces an alkali-silica reaction gel which can imbibe pore solution and swell to generate cracks that are visible In affected concrete. In general, crushed stones are tested by petrograptuc examination, chemical method and mortar-bar method, but the most reliable method Is mortar-bar test. This study tested alkali-silica reactivity of crushed stones of various rock types using ASTM C 227 and C 1260, and compared the results of two test methods. This study also analyzed effects of particle size and grading of reactive aggregate on alkali-silica reaction expansion of mortar-bar. The effectiveness of mineral admixtures to reduce detrimental expansion caused by alkali-silica reaction was investigated through the ASTM C 1260 method. The mineral admixtures used were nv ash, silica fume, metakaolin and ground granulated blast furnace slag. The replacement ratios of 0, 5, 10, 15, 25 and were commonly applied for all the mineral admixtures and the replacement ratios of 45 and were additional applied for the admixtures that could maintain workability. The results indicate that replacement ratios of for ay ash, for silica fume, for metakaolin or for ground granulated blast furnace slag were most effective to reduce alkali-silica reaction expansion under the experimental conditions.

Use of perlite powder to suppress the alkali–silica reaction

Reported below are the results from a study aimed at mitigating the deleterious alkali–silica reaction by using perlite powder as an admixture. The expansion of mortar bars containing various amounts of silica fume (SF), expanded perlite, and natural perlite was studied. Two kinds of reactive aggregates were used in the study: highly reactive river aggregate containing opal and marginally reactive monzo-diorite aggregate. Expanded perlite and silica fume were tested with both aggregate, separately; on the other hand, natural perlite was tested only with monzo-diorite aggregate. The bars were cast in accordance with ASTM C1260, accelerated mortar bar method, and were stored in NaOH solution for 30 days. Length changes were measured and reported. The results showed that both expanded and natural perlite powder (NPP) have potential to suppress the deleterious alkali–silica expansion.

A study on the alkali-aggregate reaction in high-strength concrete with particular respect to the ground granulated blast-furnace slag effect

The alkali-aggregate reaction (AAR) in high-strength concrete and the effect of ground granulated blast-furnace slag (GGBFS) were studied in this paper. From the results of this study, following conclusions can be drawn: (1) In high-strength concrete, because of high alkali content, the possibility of alkali-aggregate reaction is much higher than conventional concrete. (2) The occurrence of large expansion can be prevented by using nonreactive aggregate, which has been judged according to the mortar bar and chemical method's as specified in JIS A 5308, in high-strength concrete. (3) The replacement of cement by 30% of blast-furnace slag and using low-alkali cement can prevent the alkali-aggregate reaction from causing large expansion in high-strength concrete.

北陸地方の河川産骨材を使用したコンクリートのアルカリシリカ反応性の評価法の開発

The purpose of this paper is to develop an evaluation method for assessing the alkali-silica reactivity of concrete with a combination of the river sand and gravel used in the Hokuriku district. The 27 aggregate samples were collected from the stockpile of selected 8 ready-mixed concrete plants over the main river area in this district. The mineralogical features of the river sand and gravel, and their alkali-silica reactivity were tested by both the chemical method and the mortar bar method according to the specification by JIS A 1145-2001 and JIS A 1146-2001. Furthermore, a lot of cores were drilled from the concrete specimens, which were subjected to the accelerated curing condition of the immersion into 1N NaOH solution at 80°C or the saturated NaCl solution at 50°C in order to evaluate the alkali-silica reactivity of the concrete itself. By measuring the expansion behaviors of the cores in the accelerated curing condition, the rapid test method for the evaluation of the alkali-silica reactivity of the concrete itself was developed.

Proposed Universal Accelerated Test for Alkali-Aggregate Reaction The Concrete Microbar Test

Abstract The Concrete Microbar Test is modified after a Chinese test, for alkali-carbonate reactive aggregates. The protocol for the test is essentially the same as for ASTM C 1260, Standard Test Method for Determining the Potential Alkali-Silica Reactivity of Combinations of Cementitious Materials and Aggregate (Accelerated Mortar Bar Method), except for the size of the bars, the grading of the aggregate, the water to cement ratio and the length of the test. The concrete microbars are 40 by 40 by 160 mm. The aggregate is graded to pass a 12.5 mm sieve and be retained on a 4.75 mm sieve. The water to cement ratio is 0.33. The length of the test is 30 days in 1 M sodium hydroxide (NaOH) at 80°C. The test results show that the method is applicable to both alkali-carbonate and alkali-silica reactive aggregates. Moderate correlation was found between the expansions measured in this test at 30 days, and in the concrete prism test (CSA A23.2-14A) at 1 year. Alkali-carbonate reactive aggregates may be distinguished from alkali-silica reactive aggregates in this test by replacing a portion of the portland cement by a supplementary cementing material. The expansions of alkali-silica reactive aggregates, in this test, are significantly reduced by the presence of the supplementary cementing material but expansion of alkali-carbonate reactive aggregates is largely unaffected. It is tentatively suggested that the expansion limit to separate deleteriously alkali silica reactive siliceous limestones from innocuous limestones is 0.140 % at 30 days; the proposed limit for all other aggregates is 0.04 %.

骨材のアルカリシリカ反応性の評価方法に関する研究

Six kinds of coarse aggregates were used in order to evaluate the reactivity of alkali-silica reaction of aggregates by using JIS A 1145, 1146 and ASTM C 1260 methods. The evaluation obtained by the chemical or mortar bar of methods specified in JIS did not agree with that by the accelerated mortar bar method specified in ASTM. The expansion of mortar bar due to ASTM C 1260 was dependent on the type of aggregate. It was also observed that the expansions of mortar bar under the accelerated condition (in NaOH solution of 1mol/l at 80°C) were influenced by the size of specimen, added alkali content and alkali content intruded into specimen from the solution in test container during test period.

Alkali aggregate reaction in alkali slag cement mortars

By means of “Mortar Bar Method”, the ratio of cement to aggregate was kept as a constant 1∶2,25 the water-cement ratio of the mixture was 0.40, and six prism specimens were prepared for each batch of mixing proportions with dimensions of 10×10×60mm3 at 38±2°C and RH≧95%, the influences of content and particle size of active aggregate, sort and content of alkali component and type of slag on the expansion ratios of alkali-activated slag cement (ASC) mortars due to alkali aggregate reaction (AAR) were studied. According to atomic absorption spectrometry, the amount of free alkali was measured in ASC mortars at 90d. The results show above factors affect AAR remarkably, but no dangerous AAR will occur in ASC system when the amount of active aggregate is below 15% and the mass fraction of alkali is not more than 5% (Na2O). Alkali participated in reaction as an independent component, and some hydrates containing alkali cations were produced, free alkalis in ASC system can be reduced enormously. Moreover, slag is an effective inhibitor, the possibility of generating dangerous AAR in ASC system is much lower at same conditions than that in ordinary Portland cement system.