International Concrete Abstracts Portal

This paper reports the properties of two series of flowable self-compacting slurry. In Series 1, five mixtures of flowable slurry were made using ponded coal-combustion fly ash and quarry screenings (fine crushed sand). In Series 2, six mixtures of flowable slurry were made, the first five mixtures using the ponded coal-ash and natural sand, and the final one mixture using Class C fly ash and natural sand. Ash and quarry-screenings contents of the mixtures are expressed as percentages of the sum of the quantities of the ash and aggregate. For Series 1 flowable-slurry mixtures, ponded-ash content was 100, 67, 53, 35, and 0 percent, and quarry-screenings content was 0, 33, 47, 65, and 100 per-cent, respectively. In Series 2 flowable-slurry mixtures, ash content was 100, 81, 60, 40, 20, and 4 percent, and sand content was 0, 19, 40, 60, 80, and 96 percent, respectively. For both series of flowable-slurry mixtures, tests were performed for flow, density, settlement, compressive strength, and permeability. Ambient air and slurry temperatures were also recorded. Compressive strength of both Series 1 and Series 2 mixtures increased with age. Compressive strength of Series I mixture was higher than Series 2 mixtures. It was also observed that the permeability of flowable-slurry mixtures decreased with increase in age due to improvement in microstructure and increase in strength of the flowable-slurry mixtures. Mixtures containing quarry screenings were also less permeable.

This paper discusses the physical properties and leachate characteristics of a newly developed CLSM (Controlled Low Strength Materials) with a special type of cement as well as aggregate made from municipal solid waste. Eco-Cement, so-called in Japan, is the latest green cement made primarily from municipal refuse incineration ash and sewage sludge. Aggregate used in this paper was also made from the slag of municipal solid waste incinerator. High-volume off-specification fly ash was also used. This new type of green CLSM will he a promising sustainable material to reduce CO2 emissions. Test results showed an adequate strength development and reasonable flowability, especially when the mixture proportion is carefully designed. The leachate characteristics of this new CLSM are evaluated in this paper. Two types of standard tests showed acceptable leachate levels. From these tests results it was confirmed that a wide range of municipal solid waste may be applicable for the materials of the new green CLSM.

The influence of some pozzolanic additions—such as silica fume, fly ash and ultra-fine amorphous colloidal silica (UFACS)—on the performance of superplasticized concrete was studied. Superplasticized mixtures in form of flowing (slump of 230 mm) or self-compacting concretes (slump flow of 735 mm) were manufactured all with a water-cement ratio as low as 0.44, in order to produce high-performance concretes (HPC). They were cured at room temperature (20°C) or steam-cured at 65°C in order to simulate the manufacturing of pre-cast members. Concretes with ternary combinations of silica fume (15-20 kg/m3), fly ash (30-40 kg/m3) and UFACS (5-8 kg/m3) perform better—in terms of strength and durability—than those with fly ash alone (60 kg/m3) and approximately as those with silica fume alone (60 kg/m3). Due to the reduced avail-ability of silica fume on the market, these ternary combinations can reduce by 60-70% the needed amount of silica fume for each pre-cast HPC element at a given performance level. Moreover, at later ages the strength reduction in steam-cured concretes with respect to the corresponding concretes cured at room temperature, is negligible or much lower in mixtures with the ternary combinations of pozzolanic additions.

The development of fly ash based high-strength self-compacting (or self-consolidating) concrete is a positive contribution to sustainable concrete technology. The present work details a mixture proportioning methodology for such concretes based on four steps where simple test procedures are used. Self-compacting concrete with a 90-day compressive strength of about 100 MPa has been obtained. This concrete has been used satisfactorily in a demonstration project involving the manufacture of a prefabricated urban bench with a complex shape. Such applications are promising since they lead to a reduction in energy and labor requirements during the casting and surface finishing, and facilitate the use of complex designs, while improving the factory environment through noise and vibration reduction.

A new environment-friendly block, called "steel slag hydrated matrix", consisting mainly of steelmaking slag, ground granulated blast furnace slag, fly ash, and water was developed. Steel slag hydrated matrix has the following features: 1) Made from 100% recycled resources, 2) same strength performance as ordinary concrete, 3) excel-lent wear resistance, 4) low alkaline dissolution, and 5) excellent growth habitat for biofouling organisms in marine environments. In repair work at Mizushima Port, Okayama Prefecture, Japan, 150,000 tons of steel slag hydrated matrix material were used. The ease of use in construction and low impact on ecological systems of the new material were confirmed in the course of this work.