International Concrete Abstracts Portal

The sulphate resistance of mortar lng a superplasticizer and made with blends Type 10 cement, fly ash and granulated blast slag are compared with similar mortars conta ventional water reducing admixture. Compari made with mortars made with C.S.A. Type 50 c Changes in porosity, weight, length, dynamictain- elasticity and compressive strength of the exposed to alternate soaking and ium sulphate solutions for 300 days are desc lus of specified-Interrelationship of w/c ratio, alkalinity of the medium and porosity as primary factors in sulphate attack on the cement paste were investigated. The results indicate that mixes containing a 30% replacement of normal Portland cement by fly ash or slag and a superplasticizer are comparable to mixes made from sulphate resisting cement in their capacity to resist sulphate attack. The degree of attack noted in the superplasticized mixes was significantly reduced in com-parison with mortars where a conventional water reducing admixture was used.

Use of a naphtalene-based superplasticizer at high dosages in concretes made with fly ash (100-150 kg/m3) and a moderate content of portland cement (250-300 kg/m3) results in great water reductions and high strengths (75-80 MPa after 28 days) for concretes with normal workability (slump 5-10 cm). Laboratory investigations concerning mixture proportions and pro-perties of the fresh and hardened concretes with a discussion of physical and chemical influences of the use of the superplasticizer are presented. Increasing problems with the supply of good, in-expensive, natural coarse aggregates may be solved through combined additions of superplasticizers and fly ash to the concrete. This paper further presents experimental evidence of mixture proportions and phy-sical data for socalled "sand-concrete", i.e. concrete without coarse aggregates but with "normal" contents of portland cement and water obtained by the addition of rather large amounts of fly ash and superplasticizers.

The purpose of this study was to examine the effect of adding various dosages of a melamine-based superplasticizer in the manufacture of extra-high strength block. Seven batches of block were cast as follows: a) reference mixtures in which no admixture was added; b) reference mixtures using a conventional block plasticizer; c) four mixtures using various dosages of su-perplasticizer: 1% by weight cement, 2%, 3%, and 2% with additional water. Halfway through each batch, the feed finish times were increased. The block were steam-cured at low pressure. The testing program consisted of a) impact-resistance and compressive strength at 24 hours; b) absorption and unit weight; and c) compressive strengths at 7, 14, and 28 days. All block exceeded the 5000 psi (34.5 MPa) net compressive strength requirement of extra-high strength block. The effect of the superplasticizer increased as the dosage increased. The superplasticizer also allowed for shorter feed times to achieve the same finish times. The encouraging results of this preliminary study indicate more work needs to be done to investigate the possibility of leaner cement mixes, lower temperature curing conditions, and possibly shorter feed finish times to achieve the economic advantages inherent with the use of superplasticizers.

The studies reported were concerned with the application of high-strength concrete to structural members as related to some aspects of their design, construction and behavior. With regard to construction, tests were performed on the consistencies and strengths of concretes of low water-cement ratios using superplasticizers. The superplasticizers used were the 5 brands being marketed in Japan. The influence on consistency of fineness of cement was also studied. In examinations made by design calculations, monorail piers were used as case studies. The relation between concrete strength and cross-sectional dimensions, and quality of reinforcing bars required when applying high-strength concrete to structural members were investigated. In structural tests, the stresses, bending strengths and ductilities of model piers using high-strength concrete were studied.

This paper reviews the application of a sulphonated melamine formaldehyde condensate superplasticizer (Melment L10) as a water-reducer-under laboratory conditions and in practice. Emphasis is on basic data on the compressive strength and stabi of green concrete, especially as it affects the production of concrete blocks, pipes and extruded concrete products. The results indicate that whenever high performance concrete is required, the use of the superplasticizer permits placing and proper compaction at almost any water-cement ratio, thus ensuring high quality concrete.