Behaviour of Normal Concrete Us ing Superplasticizer under Different Curing Regimes
The performance of concrete primarily depends upon the type and ratio of its constituents, compaction, curing conditions and admixtures used during curing process. Part of this research emphasis to calculate the consequences on strength of concrete when water-cement ratio is constant and the increase in slump occurs with the increase in amount of superplasticizer by percentage. The rest of the investigation is carried out to study the effects of superplasticizer with different dosages under different curing regimes at an ambient field temperature ranges between 45°C-50°C. For this purpose, a concrete mix at 20MPa with all parameters constant was prepared by using an ASTM C494 type A, and F, anionic melamine polycondensate non-toxic superplasticizer with no chlorides. Different dosages of superplasticizer were used in different batches of all 95 specimens, and cured under different curing conditions and then tested for compressive and tensile strengths following ASTM standards. In all cases, th e water curing up to 28 days testing showed maximum strength. The highest and lowest values of compressive strength were obtained with the addition of 0.5% and 1% superplasticizer respectively. It was found that without increasing the W/C ratio, the addition of superplasticizer exhibits increase in strength.
COST-EFFECTIVE USE OF SUPERPLASTICIZERS
The article describes how innovative construction techniques are being used by contractors through the use of second- and third-generation superplasticizers. These materials can be used cost-effectively for such applicaitons as hot weather concreting, wall placements, crane and bucket placements, slabs on grade, and pumped concrete. Each of these areas are discussed in some detail.
Facies and microfacies of slope deposits
Abstract This paper reviews the facies and microfacies of the main types of slope deposits. Lamination and sorting, when preserved, are good evidence for overland flow. Features due to deformation (folds, boudins, coatings and tails due to the rotation of clasts) are associated with the early stages of deformation in earth slides. Other mass-movements such as debris flows, rock avalanches, earth flows, and to a certain extent, dry grain flows may be characterised by similar microscopic facies, typically a poorly sorted, porphyric material. Porosity gives evidence for both liquefaction (debris flows) and frost-induced mass-movement (solifluction). However, this criterion is thought to be irrelevant for fossil deposits owing to the rapidity and scale of post-depositional changes (wetting and drying, freezing and thawing, bioturbation). At present, only a detailed analysis of both the macro- and micromorphological characteristics of the deposits allows an accurate identification of past slope dynamics.