Alkali-Silica. Reaction Of Foamed. Concrete Containing. Waste Glass as Aggregate

This research focused on examining Alkali-Silica. Reaction (ASR) of foamed concrete mixes containing1different1types of1crushed waste glass (CWG) with different chemical compositions. The reactivity was determined in sodium hydroxide solution by adopting mortar bar test. Four types of waste glass with different particle sizes and different percentages content were used. From the test results of recorded expansion of these mixes, it was noticed that the coarse glass resulted in more expansion than that of fine glass. Lead-silicate1glass (CR) exhibits the maximum expansion followed by1soda-lime1glass (SL) and boro-silicate glass (BS), while less expansion was recorded in mixes with green glass (GG). As compared to reference mix (FC), it was noted that the mixes with crushed waste glass (SL), (BS), and (CR) undergo notable expansion, while the expansion of the mixes with (GG) slightly increased compared to the reference mix (FC).

Long-term alkali-silica mitigation of high-alkali concrete with cement replacements

The impact of high-alkali Portland cements on the prescribed level of supplementary cementitious materials required in the Canadian standard for akali-silica reaction mitigation was evaluated. Based on the results, for concretes containing aggregates exhibiting moderate reactivity, the maximum allowable cement alkali limit was raised from 1.00% to 1.15%. For all levels of aggregate reactivity, cement alkali contents could be allowed up to 1.25% provided the recommended level of mitigation by supplementary cementitious materials was increased. In the initial laboratory study, mortar bars and concrete prisms were cast and monitored using two different reactive aggregates and recommended levels of fly ash and slag. For the concrete prism tests, the alkali contents of the cements were increased to 1.25%, as per the standard, or were increased by 0.25%. Instrumented outdoor exposure concrete blocks, along with additional concrete prisms stored at different temperatures, were cast from numerous mixtures made with cement alkali equivalents ranging up to 1.22%. This paper report on the long-term performance of the prisms and concrete blocks after 12 and 27 years. The performance of the outdoor blocks is also compared to predicted performance based on the accelerated mortar bar and concrete prism test results.

The Efficacy of Accelerated Test Methods to Evaluate Alkali Silica Reactivity of Recycled Concrete Aggregates

The effectiveness of accelerated tests in evaluating the Alkali-Silica Reactivity of Recycled Concrete Aggregates was evaluated. The Accelerated Mortar Bar Test was found effective for evaluating potential alkali-reactivity when the test variables, such as crushing method and absorption, are carried out in a well-defined process. The method of crushing was found to have significant impact on the expansion. The Concrete Microbar Test (CMBT) provides good correlation to the expansion of Concrete Prisms incorporating Supplementary Cementing Materials when an expansion limit of 0.10% at 56 days or 0.04% at 28 days were used, based on the limited number of tests carried out here.

The Efficacy of Accelerated Test Methods to Evaluate Alkali Silica Reactivity of Recycled Concrete Aggregates

The effectiveness of accelerated tests in evaluating the Alkali-Silica Reactivity of Recycled Concrete Aggregates was evaluated. The Accelerated Mortar Bar Test was found effective for evaluating potential alkali-reactivity when the test variables, such as crushing method and absorption, are carried out in a well-defined process. The method of crushing was found to have significant impact on the expansion. The Concrete Microbar Test (CMBT) provides good correlation to the expansion of Concrete Prisms incorporating Supplementary Cementing Materials when an expansion limit of 0.10% at 56 days or 0.04% at 28 days were used, based on the limited number of tests carried out here.

The Application of a New Oxidation Mortar Bar Test to Mixtures containing Different Cementing Systems

The effects of different cementing systems on the expansion of mortars containing iron sulphide-bearing aggregate was studied. Using a recently developed oxidation mortar bar test, the results showed that cementing systems containing low-calcium fly ash, metakaolin, slag, high-sulphate resisting Portland cement, or low heat of hydration Portland cement could reduce the expansion by 50–85%. The main suggested mechanisms behind the reduced expansion is the more refined pore structure of samples with SCMs, and the reduced C3A of low heat of hydration Portland cement. The refined pore structure reduces the permeation of the oxidizing solution into the samples. The similarity of this to penetration of oxygen into concrete under field exposure needs to be determined. Soaking the samples for >3 h in the oxidizing agent can produce excessive expansion – not related to oxidation of iron sulphide phases – in samples with cementing blends containing reactive alumina such as metakaolin.

Sulphide oxidation mortar tests for evaluation of the oxidation potential of sulphide-bearing aggregate

This paper proposes two new sulphide mortar bar tests. The two tests involve two exposure conditions: the first one relies on soaking the sample in an oxidizing agent (6% sodium hypochlorite) for three hours at room temperature to promote oxidation while the other test adopts a range of temperatures and relative humidity that promote oxidation and sulphate attack. Both tests were effective in discriminating between aggregates with oxidizable sulphide and those without. Moreover, the use of low-calcium fly ash at 25% and slag at 30% reduced the expansion but not to the level of samples with non-sulphide aggregates. On the contrary, 10% of metakaolin produced more expansion.<br>

The Application of a New Oxidation Mortar Bar Test to Mixtures containing Different Cementing Systems

The effects of different cementing systems on the expansion of mortars containing iron sulphide-bearing aggregate was studied. Using a recently developed oxidation mortar bar test, the results showed that cementing systems containing low-calcium fly ash, metakaolin, slag, high-sulphate resisting Portland cement, or low heat of hydration Portland cement could reduce the expansion by 50–85%. The main suggested mechanisms behind the reduced expansion is the more refined pore structure of samples with SCMs, and the reduced C3A of low heat of hydration Portland cement. The refined pore structure reduces the permeation of the oxidizing solution into the samples. The similarity of this to penetration of oxygen into concrete under field exposure needs to be determined. Soaking the samples for >3 h in the oxidizing agent can produce excessive expansion – not related to oxidation of iron sulphide phases – in samples with cementing blends containing reactive alumina such as metakaolin.

The Application of a New Oxidation Mortar Bar Test to Mixtures containing Different Cementing Systems

The effects of different cementing systems on the expansion of mortars containing iron sulphide-bearing aggregate was studied. Using a recently developed oxidation mortar bar test, the results showed that cementing systems containing low-calcium fly ash, metakaolin, slag, high-sulphate resisting Portland cement, or low heat of hydration Portland cement could reduce the expansion by 50–85%. The main suggested mechanisms behind the reduced expansion is the more refined pore structure of samples with SCMs, and the reduced C3A of low heat of hydration Portland cement. The refined pore structure reduces the permeation of the oxidizing solution into the samples. The similarity of this to penetration of oxygen into concrete under field exposure needs to be determined. Soaking the samples for >3 h in the oxidizing agent can produce excessive expansion – not related to oxidation of iron sulphide phases – in samples with cementing blends containing reactive alumina such as metakaolin.

Sulphide oxidation mortar tests for evaluation of the oxidation potential of sulphide-bearing aggregate

This paper proposes two new sulphide mortar bar tests. The two tests involve two exposure conditions: the first one relies on soaking the sample in an oxidizing agent (6% sodium hypochlorite) for three hours at room temperature to promote oxidation while the other test adopts a range of temperatures and relative humidity that promote oxidation and sulphate attack. Both tests were effective in discriminating between aggregates with oxidizable sulphide and those without. Moreover, the use of low-calcium fly ash at 25% and slag at 30% reduced the expansion but not to the level of samples with non-sulphide aggregates. On the contrary, 10% of metakaolin produced more expansion.<br>

Sulphide oxidation mortar tests for evaluation of the oxidation potential of sulphide-bearing aggregate

This paper proposes two new sulphide mortar bar tests. The two tests involve two exposure conditions: the first one relies on soaking the sample in an oxidizing agent (6% sodium hypochlorite) for three hours at room temperature to promote oxidation while the other test adopts a range of temperatures and relative humidity that promote oxidation and sulphate attack. Both tests were effective in discriminating between aggregates with oxidizable sulphide and those without. Moreover, the use of low-calcium fly ash at 25% and slag at 30% reduced the expansion but not to the level of samples with non-sulphide aggregates. On the contrary, 10% of metakaolin produced more expansion.<br>