Creep and Shrinkage Behaviour of Disintegrated and Non-Disintegrated Cement Mortar

One way to prevent cement from ending up in landfills after its shelf life is to regain its activity and reuse it as a binder. As has been discovered, milling by planetary ball mill is not effective. Grinding by collision is considered a more efficient way to refine brittle material and, in the case of cement, to regain its activity. There has been considerable research regarding the partial replacement of cement using disintegrated cement in mortar or concrete in the past few decades. This article determines and compares the creep and shrinkage properties of cement mortar specimens made from old disintegrated, old non-disintegrated, and new non-disintegrated Portland cement. The tests show that the creep strains for old disintegrated and old non-disintegrated cement mortars are close, within a 2% margin of each other. However, the creep strains for new non-disintegrated cement mortar are 30% lower. Shrinkage for old disintegrated and non-disintegrated cement mortar is 20% lower than for new non-disintegrated cement mortar. The research shows that disintegration is a viable procedure to make old cement suitable for structural application from a long-term property standpoint. Additionally, it increases cement mortar compressive strength by 49% if the cement is disintegrated together with sand.

Multi criteria assessing approach of the slow-moving urban landslide hazard, the case of Moulay Yacoub town (Morocco)

Since many decades, the town of Moulay Yacoub (MY) has undergone an intensification of its urbanization to meet the demands of rental housing for the visitors of the hydrothermal springs, which is considered as the only attraction of the town. Unfortunately, the majority of the buildings, both private and public, suffer from varying levels of damages where the lithological and geomorphic field features are to blame, without omitting the anthropogenic effects. In fact, the town is built on a marly hill conducive to slope movements, ranging from shallow solifluctions to large landslides, besides the swelling/shrinkage behaviour of these marls. The paper presents a multi-source approach to investigate the activity and the interactions of slow urbanized landslides and expansive soils within the urban perimeter of Moulay Yacoub. Indeed, the desiccation cracks of marly soils reveal their expansive behaviour, also attested by the swelling values. The other geotechnical parameters obtained from laboratory tests show that the shallow marls samples are severely weathered compared to those of the compacted deep ones. The Borehole data and seismic noise survey allows the detection of several impedance contrasts corresponding to the shallow weathered-deep marls interfaces which in some cases represent the rupture surfaces of gravitational processes. The very slow but perennial activities of the later are attested by the inclinometers, the PS-InSAR monitoring and building damages. The case study provides a good opportunity to highlight the complementarity of the multi-source tasks which stand as a further contribution to fostering this kind of integrated approaches at the slope scale.

Shrinkage properties of natural and diesel oil-contaminated fine soils from central Poland

The objectives of this paper are to provide a regional description of the shrinkage parameters of Neogene clays and glacial tills from central Poland; and to present the effects of hydrocarbon contamination on the shrinkage behaviour of soils. Forty samples containing from 19 to 90% clay-size particles were tested. The comparison of the three methods applied has indicated that the shrinkage limit values obtained by the BS 1377-2 method provide a greater margin of safety when used in the classification of expansive soils and yield the best matching in the analysis of the variability of the shrinkage limit in relation to other soil index parameters. A good correlation was found between the shrinkability index and the consistency index, which leads to a new classification of soils. The shrinkage tests of clean and diesel oil-contaminated samples revealed that contamination has a significant and irregular effect on the values of shrinkage parameters. For low degree of contamination the shrinkage limit of both soils had the lowest values and the volumetric shrinkage was maximum, and then with increasing ON content the shrinkage limit values tend to increase, while the volumetric shrinkage decreased.

Mechanical Characterisation and Shrinkage of Thermoactivated Recycled Cement Concrete

This paper investigates the mechanical and shrinkage behaviour of concrete with recycled cement (RC) thermoactivated from waste cement paste and waste concrete. Overall, compared to ordinary Portland cement (OPC), for the same water/binder ratio, the mechanical strength and ultrasonic pulse velocity were not significantly influenced by the incorporation of RC. The elasticity modulus decreased with the addition of RC and the shrinkage tended to increase at high RC content. The incorporation of up to 15% RC allowed the production of workable concrete with identical shrinkage and similar to higher mechanical strength than concrete with only OPC. RC proved to be a very promising more eco-efficient supplementary cementitious material.