Ta-Peng Chang

Hydration Process and Compressive Strength of Slag-CFBC Fly Ash Materials without Portland Cement

AbstractThis study mixed ground granulated blast-furnace slag (S) and circulating fluidized bed combustion (CFBC) fly ash (CA) without any portland cement or alkaline activator to produce an eco-binder, abbreviated as SCA binder. The hydration process, microstructure, and compressive strength of hydrated SCA materials were investigated. Although both the slag and CA had poor hydration with water, the SCA binder produced satisfactory hydration products with sufficient cementitious properties. These hydration products detected by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) were ettringite (AFt), calcium silicate hydrate (C-S-H), and calcium aluminosilicate hydrate (C-A-S-H). The scanning electron microscope (SEM) micrograph showed these hydration products formed dense microstructure for SCA pastes. As a result, the SCA materials had sufficient compressive strength for practical applications in building materials and civil engineering structures. The compressive strengths of th...

Circulating Fluidized Bed Combustion Fly-Ash-Activated Slag Concrete as Novel Construction Material

The performance of a novel concrete made with an eco-binder, referred to as SCA binder, that only contains raw slag (S) and raw circulating fluidized bed combustion (CFBC) fly ash (CA) without ordinary portland cement was evaluated. The major hydration products of SCA binders are ettringite, C-S-H, and C-A-S-H, which lead to SCA pastes with proper setting times, dense microstructures, and high compressive strengths up to approximately 80 MPa (11,600 psi). The SCA concrete, which is suitable for practical applications, has compressive and tensile strengths at 91 days of approximately 50 MPa (7250 psi) and nearly 5 MPa (725 psi), respectively. In addition, the SCA concrete shows moderate expansion at early ages and a low rate of shrinkage after 91 days of exposure. The regression equations that relate the splitting tensile strength, modulus of elasticity, and ultrasonic pulse velocity to the compressive strength are presented with a satisfactory coefficient of determination.

Mix Proportion and Engineering Behavior of San-Ho-Tu Building Material for Temples and Ancestral Clan Houses

The San-Ho-Tu building material is manufactured by adequately mixing a ternary mixture of sintered oyster shell ash, laterite and sand with water. It has been broadly used for construction and restoration of the ancestral temples and clan houses in China and Taiwan for hundreds of years due to its adequate engineering properties and easy availability of raw constituents. The main purpose of this study is aimed at understanding its engineering properties and proper mix proportioning. Cylindrical specimens of ϕ50 × 100 mm for nine sets of mixtures were cast, including three sets of traditional San-Ho-Tu building material (L-group), three sets of L-group mixtures with Portland cement (C-group) and three sets of single oyster ash paste an laterite paste (S-group). They were tested for compressive and tensile strengths at six ages of 7, 14, 21, 28, 56 and 90 days, respectively. Experimental results showed that at 90 days, the average compressive strengths of three specimens for S-group, L-group and M-group were 296.2, 2144.1 and 4915.4 kPa respectively. The ratios of the splitting tensile strengths to the corresponding compressive strength of San-Ho-Tu cylindrical specimens were between 16.1% and 19.9% which were higher than those of 10.0% and 14.0% for concrete cylinder made from the pure Portland cement paste.

Engineering Properties and Bonding Behavior of Self-Compacting Concrete Made with No-Cement Binder

AbstractThis study explores the engineering properties of a new self-compacting concrete (SCC), named as SFC-SCC, produced with a no-cement SFC binder and the bonding behaviors of embedded steel ba...

Factors affecting bond strength at early age between cladding plaster and concrete substrate

The bond strengths of two types of cylindrical composite specimens made of cladding plaster, concrete substrate with/without sticking slurry were evaluated by the splitting tensile strength. Two kinds of control factors, divided into two categories, were used for the investigation. The first is the constituents of concrete substrate including the fraction of fly ash to binder by weight (FL), the ratio of water to binder (W/B), the fraction of fine aggregate to total aggregate (FA) and the total volume of aggregate (Tot A). The second is the cladding plasters with or without sticking slurry in two curing conditions. The Taguchi method with L9(34) orthogonal array and the analysis of variance were used to analyse the experimental data. Experimental results show that raising either FL or Tot A, being the two most influential factors, tend to lower the bond strength at early ages. Whereas, an increase of W/B from 0.45 to 0.55 significantly lowers the bond strength for cladding plaster without sticking slurry, but only has a minor effect on those with sticking slurry. The composite concrete specimen with six-day-water-curing condition without sticking slurry shows an apparent decrease of bond strength after exposing to air condition for 7 days.

Effects of Activating Solution and Liquid/Solid Ratio on Engineering Properties of Metakaolin-Based Geopolymer

In this paper, the metakaolin is used as the raw material with aluminosilicate compounds to produce the geopolymer. The effects of three levels of two major controlling factors, the degree of polymerization of the activating solution (weight ratio of SiO2 to Na2O) of 0.4, 0.7 and 1.0 and the weight ratio of liquid to solid (L/S) of 0.7, 0.85 and 1.00 on the engineering properties of geopolymer are investigated. The experimental results show that, at age of 28 days, the compressive strength increases from the lowest 37.33 MPa (SiO2/Na2O = 0.4 and L/S = 0.7) to the highest 71.21 MPa (SiO2/Na2O = 0.7 and L/S = 0.7). While, the thermal conductivity increases from the lowest 0.39 w/mk (SiO2/Na2O = 0.4 and L/S = 1.0) to the highest 0.761 w/mk (SiO2/Na2O = 1.0 and L/S = 0.7).