Yoon-moon Chun

PRECAST CONCRETE PRODUCTS USING INDUSTRIAL BY-PRODUCTS

This work aimed to help establish the use of high volumes of fly ash, bottom ash, and used foundry sand in manufacture of precast molded concrete products such as wet-cast concrete bricks and paving stones. ASTM Class F fly ash was used as a partial replacement for 0 (reference), 25, and 35% of portland cement. Bottom ash combined with used foundry sand replaced 0, 50, and 70% of natural sand. Tests for compressive strength, freeze-thaw resistance, drying shrinkage, and abrasion resistance were conducted on the wet-cast concrete masonry units manufactured at a commercial manufacturing plant. It was concluded that all wet-cast bricks could be used for both exterior and interior walls in regions where freezing and thawing is not a concern, and for interior walls in regions where freezing and thawing is a concern. No wet-cast paving-stone mixtures, including the reference mixture, met all ASTM requirements for paving stones.

Decing Salt-Scaling Resistance: Laboratory and Field Evaluation of Concrete Containing up to 70 % Class C and Class F Fly Ash

Laboratory mixtures, pilot mixtures, and field construction mixtures were made to evaluate salt-scaling resistance of concrete incorporating large amounts of either Class C fly ash obtained from several different sources or Class F fly ash. The laboratory mixtures that incorporated Class C fly ash up to a fly ash to cementitious materials ratio (FA/Cm) of 60 % by mass exhibited very slight to moderate scaling. Results from the pilot mixtures indicate that it is possible to produce structural-grade, salt-scaling resistant concrete using up to 56 % Class C fly ash. Specimens of a field mixture containing 50 % Class C fly ash showed moderate to severe scaling, and specimens of a field concrete with 40 % Class F fly ash showed slight to moderate scaling. These field mixtures exhibited satisfactory salt-scaling resistance in actual pavements. Comparisons of strength and scaling results suggest that it would be beneficial to allow sufficient time for high-volume fly ash concrete to develop strength before it is subjected to salt-scaling actions.

Concrete with Paper Industry Fibrous Residuals: Mixture Proportioning

The use of wood cellulose in concrete can improve its properties; pulp and paper mill fibrous residuals (sludge) could become an economical source of wood fibers for the microfiber reinforcement of concrete. This article reports on a study of concrete made with paper industry fibrous residuals. The researchers characterized seven sources of fibrous residuals generated from pulp and paper mills and added in concrete. Results showed that the addition of the residuals increased the water demand, and subsequently decreased the density and compressive strength of the concrete. The use of high-range water-reducing admixture (HRWRA) reversed these trends. By keeping the combined volume of mixing water, residual, and HRWRA constant, concrete mixtures containing up to 0.65% fibrous residuals (by mass of concrete) were produced that were equal in density, slump, and strength to a control concrete made without the residuals.

Use of Residual Solids from Pulp and Paper Mills for Enhancing Strength and Durability of Ready-Mixed Concrete

This research was conducted to establish mixture proportioning and production technologies for ready-mixed concrete containing pulp and paper mill residual solids and to study technical, economical, and performance benefits of using the residual solids in the concrete. Fibrous residuals generated from pulp and paper mills were used, and concrete mixture proportions and productions technologies were first optimized under controlled laboratory conditions. Based on the mixture proportions established in the laboratory, prototype field concrete mixtures were manufactured at a ready-mixed concrete plant. Afterward, a field construction demonstration was held to demonstrate the production and placement of structural-grade cold-weather-resistant concrete containing residual solids.

Properties of Flowable Self-Compacting Slurry Using Quarry By-Products and Ponded CCPs

This paper reports the properties of two series of flowable self-compacting slurry (SCS). In Series 1, a limestone quarry by-product, fine crushed sand (FCS), and ponded-CCPs were used. For Series 2, standard concrete sand and ponded-CCPs were used. For Series 1, five mixtures and for Series 2, six mixtures of flowable SCS were made. Ponded-CCPs and limestone quarry FCS content of the mixtures was expressed as a percentage of total fines. For Series 1 SCS mixtures, ponded-CCPs content was 100, 67, 53, 35, and 0%, and limestone quarry FCS content was 0, 33, 47, 65, and 100%, respectively. In Series 2 SCS mixtures, ponded-CCPs content was 100, 81, 60, 40, 20, and 4%, and standard concrete sand content was 0, 19, 40, 60, 80, and 96%, respectively. For both series of flowable SCS mixtures, tests were performed for flow, density, settlement, compressive strength, and permeability. Setting and hardening, bleeding, and ambient air and CLSM temperatures were also recorded.