Use of Off-ASTM Class F Fly Ash and Waste Limestone Powder in Mortar Mixtures Containing Waste Glass Sand

Developing sustainable concrete with less ordinary Portland cement is a growing issue in the construction industry. Incorporating industrial by-products (such as fly ash or slag) or municipal solid wastes (such as waste glass or recycled concrete aggregate) into the concrete becomes an effective way to reduce the consumption of natural sources and carbon dioxide emission if a proper mix design is provided. The present study examines the influence of the combined use of off-ASTM Class F fly ash (FFA) and waste limestone powder (LSP) on flowability, compressive strength, and expansion characteristics of mortar mixtures containing waste glass sand (WGS). FFA and LSP were used as cement replacement while WGS was used as partial reactive siliceous river sand replacement. Material variables included different WGS replacement ratios (25%, 50%, and 75%) with river sand, LSP contents (25%, 50%, and 75%), FFA contents (15%, 30%, and 45%), and different combinations of FFA-LSP (15–10%, 15–15%, 15–30%, and 15–35%). It is shown that the single use of FFA or LSP reduces both compressive strength and flowability of mortar mixture as its replacement level increases. However, mixtures combined with FFA and LSP provide higher or comparable strength to the single LSP or FFA mixture. For the expansion characteristics due to alkali-silica reaction, the single-use of more than 30% FFA or 75% LSP has less than 0.1% expansion, which is a non-reactive aggregate criterion based on the C1260/C1567 when the test period is extended to 56 days. Moreover, the combination of FFA and LSP has a considerable reduction in expansion rate compared to the single FFA or LSP mixture.

A Comparative Study on the Effect of Class C and Class F Fly Ashes on Geotechnical Properties of High-Plasticity Clay

Clays generally have a low strength and capacity, and additives are usually used to stabilize them. In recent years, using fly ash to stabilize soil has decreased environmental pollution while also having an economic benefit. The objective of this study is to perform a comparative investigation on the effect of class C and class F fly ashes on geotechnical properties of high-plasticity clay using the Atterberg’s limit, compaction, California Bearing Ratio (CBR), and unconfined compressive strength tests. The results showed that with an increase in the amount of fly ash, there was a decrease in the maximum dry density and an increase in the optimum moisture content. Moreover, an addition of fly ashes of up to 25% caused a reduction of the liquid limit and plasticity index, and an increase in the maximum unconfined compressive strength and CBR. Lengthening the curing time had a positive impact on the unconfined compressive strength of the soil. The soil samples with class C fly ash were seen to possess more efficient geotechnical properties as compared to class F fly ash.

Evaluation of Moisture Sensitivity Performance of Stone Mastic Asphalt Mixes with Additional Filler: A Laboratory Comparison of Dry and Wet Mixing Methods

Gap-graded mixtures are one of the areas of improving the permanent deformation strength of hot-mixed asphalt mixtures. Additional filler materials can be needed due to the high bitumen amount and the less fine aggregate amount in the mixture. In this study, the effects of filler additives on moisture susceptibility of the gap-graded hot-mixed asphalt mixtures and mixing methods are investigated. Filler additives such as class C and class F fly ashes and hydrated lime are used 0.5 %, 1.0 %, 2.0 %, and 4 % of the total weight of mixture instead of mineral filler. Design mixtures are prepared according to the Turkish Highway Technical Specifications (THTS). To determine the effect of mixing methods, dry and wet (slurry) methods are used to mix the filler materials. Modified Lottman method (AASHTO T283) are used to determine the moisture susceptibility. An indirect tensile strength test is the measurement of bitumen film thickness which is also conducted. Test results showed that class C fly ash is significantly improved the moisture susceptibility of mixtures. While the slurry method does not give the expected improvement on class C fly ash added mixtures, it shows a positive effect on class F fly ash and hydrated lime added mixtures.

A 6 GHz Integrated High-Efficiency Class-F−1 Power Amplifier in 65 nm CMOS Achieving 47.8% Peak PAE

This paper reports a “single-transistor” Class-F−1 power amplifier (PA) in 65 nm CMOS, which operates at the microwave center frequency of 6 GHz. The PA is loaded with a Class-F−1 harmonic control network, employing a new “parasitic-aware” topology deduced using a novel iterative algorithm. A dual-purpose output matching network is designed, which not only serves the purpose of output impedance matching, but also reinforces the harmonic control of the Class-F−1 harmonic network. This proposed PA yields a peak power-added efficiency (PAE) of 47.8%, which is one of the highest when compared to previously reported integrated microwave/millimeter-wave PAs in CMOS and SiGe technologies. The amplifier shows a saturated output power of 14.4 dBm along with an overall gain of 13.8 dB.