Search

Wollastonite is abundantly available in Rajasthan, Tamil Nadu, Uttarakhand, and Andhra Pradesh states of the Indian Union as a low-cost material. In this study, investigations were made on pastes and mortars to evaluate its potential as a new material for admixing with ordinary portland cement with or without microsilica. Its physical and chemical properties were analyzed. Wollastonite consists of 45.6% of CaO and 48% of Si[O.sub.2], mostly in amorphous form. It has an average specific surface area of 842.7 [m.sup.2]/kg and retention on 45-micron sieve of 3.20%. When ground to fine powder, it attains an average particle size of 4 microns which is about 4.5 times finer than ordinary portland cement. Scanning electron microscope images show that wollastonite particles were solid, acicular in shape, and have rough surfaces. Several cementitious mix proportions of ordinary portland cement, wollastonite, and microsilica were investigated for normal consistency, initial and final setting time of paste, and compressive strength of mortar. Test results indicate that the mortar, which contains 82.5% cement, 10% wollastonite, and 7.5% microsilica, as cementitious material attains the highest compressive strength. The mortar, which contains 77.5% cement, 15% wollastonite, and 7.5% microsilica, as cementitious material achieves compressive strength higher than the conventional OPC mortar along with rendering maximum cement replacement for better economy of concrete work. It was observed that the compressive strength of mortar varied logarithmically with the days of moist curing and linearly with the proportion of admixing. Suitable predictive models are presented accordingly. DOI: 10.1061/(ASCE)MT.1943-5533.0000019 CE Database subject headings: Mortars; Admixtures; Compressive strength; India. Author keywords: Wollastonite; Wollastonite-microsilica admixed mortar; Mineral admixtures; Consistency.

Recent studies have shown that potassium acetate based deicers are capable of triggering deleterious expansion and cracking in concrete specimens containing alkali-silica reactive (ASR) aggregates. This paper presents the results and analysis from a research study conducted to evaluate the effectiveness of fly ash and ground granulated blast furnace slag (slag) in mitigating expansions induced by ASR in the presence of a potassium acetate based deicer. Standard and modified ASTM C 1260 and 1567 tests were conducted on mortar specimens prepared with five aggregates to study the mitigation behavior of fly ashes and slag. In this study, fly ash was evaluated at 15, 25, and 35%, and slag at 40 and 50% by mass replacement of cement. Changes in length, dynamic elastic modulus, and microstructure of the mortar bars were studied. Results from these studies indicate that low- and intermediate-lime fly ashes were more effective than high-lime fly ash at 25 and 35% cement replacement levels. High-lime fly ash was ineffective even at a replacement level of 35%. Slag at 50% cement replacement was more effective in mitigating expansions compared to 40% dosage level. DOI: 10.1061/(ASCE)0899-1561(2009)21:1(19) CE Database subject headings: Deicing; Fly ash; Slag; Aggregates; Silica; Chemicals.

Researches at the Oak Ridge National Laboratory were able to create an amorphous silicon dioxide that has superhydrophobic properties. The material's production involves heating borosilicate glass and adding a weak acid solution after the glass is crushed into powder. The material has the potential use for improving powder coating to protect metal and extend the curing time of concrete.