No abstract

This research investigated the latent heat and energy storage of lightweight concrete containing high contents of phase change material (PCM) (up to about 7.8% by weight of concrete). PCM -Polyethylene Glycol (PEG) with a fusion temperature of approximately 42-46˚C was impregnated into porous lightweight aggregates up to 24% by weight. The PCM aggregates were then used to replace normal lightweight aggregate at a rate of 0, 25, 50, 75 and 100% by volume. The samples were subjected to series of experiments such as compressive strength (EN12390-3 2002), flexural strength (ASTM C78), thermal conductivity 1

A B S T R A C T R i~ S U M i ~This paper reports on the effect of an enhanced test method for the recently drafted CEN method for measuring the depth of carbonation of hardened concrete which was aimed at reducing the known variability of the test. Variations in environmental factors that may have led to a poor precision have been identified, for example the assumption that natural ventilation will provide the required level of carbon dioxide and relative humidity has been shown to be incorrect. This lead to the development of an environmental control system that actively controls the storage atmosphere. In addition to this, a two stage normalisation process of test data is proposed comprising the use of two additional mixes along with the mix being tested. Results from the assessment of the repeatability of a limited series of 10 mixes carried out by one operator of a 37 N/mm 2 PC/30% PFA concrete mix indicated that a significant improvement could be achieved following this type of control and normalisation. Cet article rend compte de l'effet d'une m~thode d'essai am(liore'e pour un projet re'cent du CEN, re&bode qui vise h mesurer la profondeur de carbonatation du b(ton durci, avec pour objet la rMuction de la variabilit( reconnue de l'essai. Ont {t~ ainsi identifi&s les variations dans les facteurs de l' environnement susceptibles d'dtre responsables du manque de pr&ision. A titre d' exemple, il a (t( d(montr( que l'hypoth&e selon laquelle la ventilation naturelle foumirait le niveau de dioxyde de carbone et un taux d'humidit~ relative n&essaires est incorrecte. Ceci a abouti au d&eloppement d'un systfme de contrale de l' environnement qui contr31e activement l' atmo-sph&e de stockage. JEst (galement propos( un proc(d( de normalisation en deux ~tapes des donn&s, comprenant l' utilisation de deux m~langes additionnels qui s'ajoutent au m~lange analys(. Les r&ultats de l'&aluation de la r(p&abilit( d'une s&ie limit& de dix m~langes de b(ton h 37 N/mm 2 ciment Portland / 30% cendres volantes entrepris par un op&ateur ont montr~ qu'une amelioration significative pouvait &re obtenue en suivant ce type de contr31e et de normalisation.

No abstract

In this study, the thermal storage properties of lightweight concrete incorporating two types of phase change materials (PCM) with two different fusion points were investigated. Two types of PCM, polyethylene glycol (PEG) and paraffin (PRF), were impregnated into porous aggregates using high temperatures. The PCM aggregates were mixed with concrete at different proportions of PEG/PRF aggregates from 0/100 to 100/0 with 25% intervals. The experimental series consisted of thermal property tests (such as thermal conductivity, specific heat, and latent heat), and some basic properties (such as compressive strength, density, water absorption, and abrasion resistance). The results showed that incorporating PCM aggregates into lightweight concrete helped increase the workability, lower the moisture absorption, and increase the mechanical properties. For thermal properties, both thermal conductivity (k) and specific heat were found to depend strongly on the state of PCM. The latent heat of lightweight concrete with PCM aggregates in hybrid form were found to be higher than that of single type PCM aggregates.