International Concrete Abstracts Portal

International Concrete Abstracts Portal

The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.

Showing 1-5 of 83 Abstracts search results

Document: 

SP114-70

Date: 

May 1, 1989

Author(s):

K. Byfors, G. Klingstedt, V. Lehtonen, H. Pyy, and L. Romben

Publication:

Symposium Papers

Volume:

114

Abstract:

Durability properties of concrete and mortar based on a special type of alkali-activated slag called F-cement have been studied. The microstructure was found to possess a high occurrence of microcracks that had an obvious influence on the flexural strength and rate of carbonation. The rate of chloride-ion diffusion was about 30 times lower than in the portland cement concrete. Salt scaling was found to depend solely on the water-to-binder ratio and is independent of the air content. Early freezing takes place when the strength exceeds 5 MPa, and F-mortar shows high chemical resistance against solutions of sodium, calcium, and magnesium chloride.

DOI:

10.14359/1827


Document: 

SP114-23

Date: 

May 1, 1989

Author(s):

N. Hara, H. Yamada, K. Inoue, N. Inoue, S. Tsunematsu, and H. Noma

Publication:

Symposium Papers

Volume:

114

Abstract:

Usability of rice husk ash was investigated as a siliceous material for calcium silicate products manufactured by hydrothermal reaction. It is concluded that rice husk ash can be used as a superior siliceous material for manufacture of calcium silicate insulating materials with good thermal durability up to 1000 C. Characteristics of rice husk ash, namely, high SiO2 content, reactive silica phase comprising amorphous silica, cristobalite and/or tridymite, and high surface area, are favorable to the formation of well-grown xonotlite which forms bodies of insulating materials. Trial products with bulk densities ranging from 0.11 to 0.41 g/cm3 prepared from rice husk ash using glass fiber for reinforcement not only satisfied all the requirements in the industrial standards (JIS A9510) but also gave 1.4 to 2 times higher bending strength than commercial products prepared from conventional siliceous materials, such as finely ground quartz sand, silica fume, and diatomaceous earth. A variety of rice husk ashes with different crystallinity are usable for manufacture of calcium silicate products, but the hydrothermal reaction condition should be optimized according to the crystallinity or amorphousness of the ash.

DOI:

10.14359/2123


Document: 

SP114-69

Date: 

May 1, 1989

Author(s):

TH. A. Bier J. Kropp, and H. K. Hilsdorf

Publication:

Symposium Papers

Volume:

114

Abstract:

During hydration of portland cement clinker and granulated slag in portland blast furnace slag cement, finely dispersed calcium silicate hydrates are formed as the major constituent of hydrated cement paste. With increasing slag content of cement, more C-S-H phases are formed, contributing to the well-known dense pore structure of pastes made of PBFS cements. Upon carbonation of the hydrated cement paste, all alkaline compounds are decomposed to form carbonates. Furthermore, the decomposition of CSH results in the formation of a porous silica gel. In an experimental investigation, different types of hydrated cement paste, mortars, and concretes manufactured with portland cement and portland blast furnace slag cements with different slag contents were subjected to carbonation and the resulting changes in the pore structure monitored. These tests demonstrated that the silica gel formed during carbonation shows pores in the range of approximately 300 nm pore radius. Where large quantities of silica gel are formed, carbonation leads to a coarser pore structure compared to the original structure. Permeability of these systems then increases significantly. The porous silica gel, however, proved to be reactive. Upon access of alkalies, new C-S-H phases may be rebuilt with a very fine port size distribution with pore radii ó 10 nm.

DOI:

10.14359/1817


Document: 

SP114-76

Date: 

May 1, 1989

Author(s):

Jan Bijen and Hennie Waltje

Publication:

Symposium Papers

Volume:

114

Abstract:

Cements consisting of 60 percent ground granulated blast furnace slag and 40 percent fly ash activated by 7 percent sodium hydroxide have been investigated. Various slags were used, including some laboratory-made synthetic slags. The influence of additives like superplasticizers and defoaming agents has been examined. The most favorable composition with respect to strength development has been subjected to a durability testing program. A negative aspect appeared to be the carbonation resistance, which is low in comparison with portland cement. Carbonation leads to a decrease in strength. Other properties were favorable.

DOI:

10.14359/1900


Document: 

SP114-40

Date: 

May 1, 1989

Author(s):

M. Berra, G. Ferrara, and S. Tavano

Publication:

Symposium Papers

Volume:

114

Abstract:

The effectiveness of silica fume to improve the erosion resistance of cement mortars used to repair hydraulic structures was investigated. The mortars were fiber-reinforced and contained a superplasticizer. Other factors investigated were erosion resistance, mechanical properties, shrinkage, atmospheric, under vacuum absorption, freeze-thaw resistance, and adhesion of mortars to concrete substrates.

DOI:

10.14359/2414


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