Thibaut Lecompte

Effect of compaction on mechanical and thermal properties of hemp concrete

ABSTRACT Some preliminary studies, dealing with the process optimisation of pre-cast building elements made of Lime and Hemp Concrete (LHC), have shown that compression during casting lead to significant improvements: better mechanical characteristics and facing. However, this compaction leads to an increase of the weight to volume ratio and to a decrease in porous volume. Thus, the amount of entrapped air inside material, which contributes to decrease the thermal conductivity, is lower. Our data actually show a slight increase in thermal conductivity when compactness increases. The goal of this study is to compare the effect of compaction during casting on both mechanical and thermal characteristics of hardened specimens in order to evaluate the relevance of such a process.

A novel settling and structural build-up measurement method

A new device, consisting of a rough plate immersed in the fluid sample, was developed to enable a simpler measurement of the sedimentation and yield stress increase of non-Newtonian suspensions. Due to the deformation of the material at rest or due to changes in the solid volume concentration by sedimentation along the vertical axis, the plate apparent mass varies with time. The apparent yield stress value of a fluid and the sedimentation rate could be calculated from this measurement.

Tensile Characteristics of Coconut Fibers Reinforced Mortar Composites

Natural fibers such as coconut fibers are numerous in Indonesia. The tensile strength of coconut fibers produced in this country is among the highest of natural fibers ones. This paper is to determine the tensile strength of coconut fibers with or without special treatment (water washing dry) and assessment the ability of coconut fiber for reinforcement in mortar composites. Experimental observations on coconut fibers and mortars carried out. There were tensile tests and scanning electron microscopy (SEM) providing microstructural properties of coconut fibers. The results showed that the coconut fibers treatment increases tensile strength and provides higher failure strain values. It showed that coconut fibers largely improved tensile strength behavior of mortar composites. To a conclusion, the coconut fibers are able to be used as reinforcement for ductile mortar composites.

Effect of Fibers Content on the Tensile Properties of Coconut Fibers Reinforced Cement Mortar Composites

The coconut fiber presents higher ductile properties than other natural fibers. In previous studies, it demonstrated than Indonesian coconut fibers presents an improved tensile strength and failure strain after washed with water and dried. The coconut fibers have the potential to reinforce material for construction, especially in earthquake areas such as tropical countries. The purpose of this research is to assess the benefit brought by coconut fibers content on the tensile behavior of mortar composite. Splitting tensile strengths were measured and microstructure observed using scanning electron microscopy (SEM). The influence of fiber content (expressed by a mass ratio fiber/cement) is investigated. The results show that a fiber content of 5% allows a 10 times higher deflection and presents a 1.5 times higher tensile strength than mortar without fiber. Further studies will focus on the bond strength between the fiber and the cement mortar matrix.

Steel fibres effects on the flexural cracking behaviour of reinforced high strength concrete beams with particular reference to the major design codes crack width models

Abstract In the present experimental work, 28 reinforced concrete beams were manufactured and tested in bending under 2 concentrated loads. The beams, which were made in high strength concrete and in ordinary concrete for comparison purposes, had different quantities of fibres, with two aspect ratios. During the testing, a special attention was given to the monitoring of flexural cracking in terms of width, spacing and length, using a digital camera and Gom-Aramis software for the analysis of the recorded images. The measured crack widths were compared with theoretical values predicted by three major universal design codes for reinforced concrete, namely the American ACI 318, the British Standard 8110, the Eurocode 2, and by the technical document of Rilem TC 162-TDF. In the present experimental work, an amendment of the Rilem model, taking into consideration the three important parameters, namely the quantity of fibres, their orientation factor and their aspect ratio, is proposed. The predicted values of the crack width obtained by the modified Rilem model were compared with the test values and assessed against other experimental data on fibre-reinforced concrete beams taken from the literature. The results show that the modified Rilem model is fairly reliable in predicting the crack width of fibre-reinforced concrete.

Shear Behavior of High Performance Concrete Beams Using Digital Image Correlation Technique

Four-points bending tests were carried out on high performances concrete beams without stirrups and with stirrups, designed to consider shear behavior, and using digital image correlation technique (DIC). In the experimental device, the shear zone between the support and the loading point was digitized by high resolution camera. The numerical analysis of the recorded images is performed by Gom-Aramis software to obtain the deformation of concrete and to monitor the crack evolution in terms of width, spacing and length. The different models to determine the capacity of shear strength of reinforced concrete beams, used by the principal universal design codes such as the American ACI 318, the British Standard 8110, the European Eurocode 2 and the New Zealand NZS 3101, were extrapolated to high performance concrete to evaluate the applicability of these regulations originally developed for the ordinary concrete to the high performance concrete. The experimental results show that all the code models underestimate the shear contribution of high performance concrete and at the same time greatly overestimate the transverse reinforcement contribution. Among the four models, Eurocode 2 yields the best predictions of the ultimate shear strength of high performance concrete.

Effect of Coconut Fibers Addition to early Age Unfired Soil Lime Bricks Strength

Low rise buildings and rural houses in Indonesia are often constructed with non-standard bricks. In some provinces, like West Java, fired clay and unfired soil lime bricks co-exist as non standard bricks. These bricks are traditionally produced in home run plants with little adherance to appropriate mix designs. These unfired soil lime bricks enter the market within 2 weeks of production, which inflicts potential loss to the buyers due to their low performance quality. The paper discusses strength improvements of these early age unfired bricks by adding natural fibers. Untreated coconut fibers with three different lengths (1 cm, 2.5 cm and 4 cm) were prepared for bricks reinforcements. The effects of 2%, 4% and 6% fiber addition to the strength of bricks were investigated. The bricks reinforced with 4% fiber content resulted in better strengths compared to those reinforced with other percentage of fibers. The effect of fiber length uniformity to the bricks strength was also evaluated. A 4% non-uniform fiber addition, which constitutes 1/3 part each of 1 cm, 2.5 cm and 4 cm average fiber length, was investigated. The results show that unfired bricks added with uniform fiber resulted in better performances compared to those added with non-uniform fibers. Higher compressive and bending strengths, compared to those strengths of unfired plain soil lime bricks and traditional soil lime bricks, could be achieved through fiber addition.