Successful ASR Prevention in Germany: Influencing Factors and Adequate Measures

Alkali-Silica Reaction (ASR) in concrete pavements has become a real problem in Germany in the end of the 1990s / beginning of the 2000s. In an extensive research project, the background for such ASR-damaging has been examined intensively at the Ruhr University Bochum. ASR in concrete pavements is not only influenced by the reactivity of the aggregate, but rather by a superposition of different influencing factors. For concrete pavements for example, there are specific conditions that increase an ASR significantly. On the one hand, concrete pavements are microstructurally damaged by the superposition of cyclic stresses induced by traffic and climate changes, and on the other hand they are exposed to alkaline de-icing agents during the wintertime. Thereby, an ASR-promoting external alkali supply is given. Three absolute preconditions are necessary for an ASR to occur: potentially reactive aggregates, sufficient supply of alkalis and an adequate degree of moisture. In Germany, there have been numerous measures taken in the last 10 to 15 years in order to prevent ASR-damages in concrete pavements. Already in 2005 the alkali-content (Na₂O-Equivalent) allowed in cements for concrete pavements has been limited to 0.8% by mass. Additionally, in each case the aggregates intended to be used must be assessed beforehand in a special procedure. Since these requirements were established by the highway-authorities in 2005 (with modifications in 2013) there have been no new damages related to ASR observed on concrete pavements, which have been constructed in compliance with these guidelines.

The Characteristics of Liquid Soap with Additional Variations of Moringa Seed Extract (Moringa oleifera L.)

Soap is a cleaning compound formed from the reaction between fatty acid compounds and alkaline bases. Various types of soap have been circulating in the market, one of which is liquid soap. Liquid soap that has antibacterial abilities is needed by many people. Moringa seed extract is one of the natural ingredients that can be used as an active ingredient in making liquid soap because it can inhibit bacterial growth. This study aims to determine the effect of variations in the addition of extracts and to obtain the best extract concentration treatment on physical, chemical, and organoleptic. The addition of moringa seed extract used was administered at 3%, 5%, and 7%. Data analysis was carried out by applying the ANOVA (Analysis of Variance) with a significant level of 5%. The De Garmo method was used to formulate the best liquid soap recommendation among various treatments. The results showed that the addition of moringa seed extract had a significant effect on the parameters of free alkali content, viscosity, specific gravity, antibacterial activity, and organoleptic. The best recommendation for liquid soap is a soap with a concentration of 7% with specific gravity characteristics of 1.066 g/ml, the viscosity of 1.983 cP, pH value of 10.53, foaming power of 5.63 cm, foam stability of 94.64%, and free alkali content of 0.023%, and the antibacterial ability against S. aureus bacteria (clear zone) was 19.17 mm.

Raman spectra of MCl-Ga2S3-GeS2 (M = Na, K, Rb) glasses

Raman spectra of (MY) x (Ga2S3)0.2−0.2x (GeS2)0.8−0.8x pseudo-ternary glassy systems (M = Na, K, Rb; Y = Cl, Br, I) were investigated systematically as a function of MY nature and alkali content. Raman spectroscopy of the Ga3S3-GeS2 glassy matrix shows a complicated local structure: corner-sharing CS- and edge-sharing ES-GeS4/2 tetrahedra, Ga-S triclusters and ETH-Ga2S6/2 ethane-like units. The Ga2S6/2 population decreases with increasing x related to a substitution of some bridging sulfur atoms around central Ga by terminal Y species with a respective decrease of the network rigidity. The formation of mixed Ga-(S,Y) environment is affected by the M+ ion size and the MY concentration.

Use of jatropha seed oil and alkali solution obtained from its ash for soap making

The present study investigated the potential of Jatropha curcas L. seed oil and lye its ash for soapmaking. Oil was extracted from the seeds using Soxhlet extractor and n-hexane. Lye solution was obtained by boilingash of Jatropha with distilled water. The physicochemical properties (saponification value, Iodine value, acid valueand peroxide value) of the oil (and its blend with palm oil) were found to be consistent with reported values inliterature. The oil content and its relative density were also found to be 31.17% and 0.88g/cm3, respectively. Soapsamples were prepared by treating the oil and the prepared lye solution. Their physicochemical properties (moisturecontent, total alkali content, total fatty matter, pH, foam ability and cleansing ability) were found to be comparablewith reported properties for laundry soaps. The findings indicated that the lye solution from ash of Jatropha and itsseed oil result in soap materials that have acceptable qualities.

Effect of alkali content and slag content on the fresh and hardened properties of air-cured alkali activated mortar containing fly ash

Alkali Activated Material (AAM) is introduced as a pioneering construction material in the construction diligence to trim down the utilization of Ordinary Portland Cement (OPC) and to curtail the amount of carbon dioxide released during the production of OPC. Modestly refined industrial by products or natural materials rich in alumino silicates are the binding agents used in AAM. Generally, heat curing is needed for the alkali activated mortar to achieve the required hardened properties and this difficulty can be overcome by adding slag to the mix. In this experimental analysis, the alkali activated mortar mixes with different proportions of glassy granulated slag and Class F fly ash were prepared without the usage of superplasticizers, with alkali to binder (a/b) ratios of 0.7, 0.8 and 0.9. The rheological characteristics of mortar were studied using flow table apparatus and hardened properties were studied using compressive strength test and ultrasonic pulse velocity (UPV) test by testing cylindrical specimens of size 25 mm diameter and 50 mm height. The mortar specimens were air-cured, and the compressive strength and UPV test were conducted after 3 and 7 days. The test results showed that due to the presence of higher alkali content and the decrease in slag content, the workability of alkali activated mortar was improved, but the measure of strength decreased. The mix with 100% slag and a/b ratio of 0.8 had the best UPV value, indicating its quality among the various mortar mixes studied. This study portrays the significance of optimising the alkali and slag content in tailor making an alkali activated mortar system with good hardened properties.