تأثير استخدام مادة النشأ على بعض خواص الخرسانة

Abstract EN

In this study,an experimental investigation was carried out to find the validity of using starch as a concrete retarding and water–reducing admixture.Aconcrete mix of proportions(1:1.5:2.2 ) was prepared.The design was based on the basic of medium slump (90±5) mm with a required compressive strength of (30Mpa) at age of (28)days.

The influence of using(1%,2%,3%,4%,5%)by cement weight of the admixture on water reduction of concrete mixes with a given slump (90±5) mm was investigated.Also the time of setting of concrete mixes was measured by means of penetration resistance measurements on mortor sieved from the concrete mixture.

The work also included the performing of some hardened concrete tests like compressive strength at ages(3,7,28,90)days and initial surface absorption at ages(1,3,7,28)days.Reasults indicated that the admixture had a little effect on the water reduction,but it had a clear influence in increasing the initial and final setting time of concrete mixes with different does of starch compared with refrence mix.

Also results showed that using a little dose of the admixture not exceed than(3%) would increase the initial setting time of concrete mix more than one hour at hot weather(38 – 40)0C without causing any significant effect on the properties of hardened concrete.