Influence of High Temperatures on the Workability of Fresh Ready-Mixed Concrete

Abstract

Abstract. Properties of fresh concrete made in tropical countries, which is mixed, transported (with agitation), placed and initially cured in places where the temperature ranges from about 20 o C to 40 o C and relative humidity above 60%, are not completely understood. Applicable requirements also differ from country to country and government agencies and private enterprises have their own specifications. Assuming such temperature and relative humidity conditions, the present study is an attempt at evaluating the properties of hot weather concrete in fresh state with using a method of ready-mixed concrete. The fresh concrete was mixed and agitated at varying concrete and ambient temperatures. Three groups of the component materials, each material having such temperature as to bring resulting temperature of the fresh concrete to about 20 o C, 30 o C, 35 o C, were chosen. The temperature of cement was conditioned to about20 o , 40 o C and 60 o C for each of groups respectively. The aggregate was made warm enough to simulate the condition of outdoor pile in ready-mixed concrete plant. The temperature of tap water was always 20 o C as it was easily controlled and unlikely affected by outdoor temperature. With the fresh concrete prevented from evaporation, slump loss is caused solely by increased temperature of concrete. During agitation, the slump loss increases rapidly during the first 30 minutes but moderately during the remaining period. Concrete-placing temperature (upon arrival at the work site) could be estimated by a proposed formula derived from this study. Besides the freshly mixed concrete temperature, this formula also takes into consideration the ambient temperature, agitating time in transit and hydration heat. The achievement as described in this study may be useful to control concrete quality in terms of strength, shrinkage and other properties of concrete to be placed in hot-humid environment.

A Comparison of Organic Cement Made from Recycled Waste Material and Portland Cement

“…The additional mineral is reactive and contributes to the hydration process. The use of saturated fly ash is one way to reduce high exposure in the process of hydration to the density of cement in concrete [12,13]. The use of alternative sources for the manufacture of cement developed in Japan produced ecocement made from municipal waste ash through incineration as a substitute for some of the main raw materials containing 50% of cement raw materials such as mud waste [14].…”

Analisis Kuat Tekan, Kuat Tarik Dan Sifat Fisis Semen Organik Terbuat Dari Bahan Limbah Daur Ulang

“…Nilai kuat tarik lentur terbesar pada beton umur 14 hari dengan penambahan abu ampas tebu sebanyak 5% maka beton akan memiliki kuat tarik lentur sebesar 6.221 MPa atau mengalami kenaikan kekuatan 2.45% dari beton tanpa menggunakan tambahan abu ampas tebu (Gerry Phillip Rompas dkk, 2013). Penggunaan fly ash jenuh merupakan salah satu cara untuk mengurangi penguapan tinggi dalam proses hidrasi terhadap kepadatan semen dalam beton (Victor Sampebulu, 2012). Tanah mediteran adalah tanah yang sifatnya tidak subur dan yang terbentuk dari pelapukan batu kapur yang memiliki kandungan kalsium dan magnesium, jenis tanah mediteran tidak banyak memberi keuntungan untuk pertanian namun jenis tanah ini sangat baik digunakan untuk bahan bangunan.…”

Analisis Sifat Fisik Semen Organik Terbuat dari Bahan Limbah Daur Ulang

“…Komponen mineral yang ditambahkan disebut mineral tambahan yang reaktif dan berkontribusi pada proses hidrasi. Penggunaan fly ash jenuh adalah salah satu cara untuk mengurangi proses hidrasi semen dalam beton [10].…”