The increasing cost and scarcity of portland cement has impacted negatively on the delivery of affordable housing and infrastructural development in many parts in Sudan, especially in Darfur. This paper focused on the evaluation of the pozzolanic characteristics of the volcanic ash obtained from Jebel Marra (mountains) west of Sudan as potential Supplementary Cementitious Materials for use in blended cement and concrete. The study investigated the chemical, physical, and mineralogical characteristics of the volcanic ash and its reactivity toward lime and cement, in addition , the compressive strengths of blended mortar containing volcanic ash in percentage addition were tested at 7, 28, and 90 days. X-Ray Fluorescence and X-ray diffraction techniques were used for chemical and mineralogical analysis respectively. The results of the chemical analysis showed that the sum oxides of Silica, Alumina and Iron were 83.75%. The strength reactivity with lime was 4.2Mpa, while the 28-days compressive strengths for the replacement level with cement 10%, 20%, 30%, 40%, and 50% were 38.9, 35, 29.33, 28.64, and 25 Mpa respectively, against 41.33Mpa., for the control mix. These results indicated that the Jebel Marra Volcanic Ash possesses pozzolanic characteristics and is thus potential cementitious material for use in blended cement.

This paper aims to assess the pozzolanic characteristics of the volcanic ash obtained from Jebal Tagabo (Tagabo Mountains) in western Sudan (North Darfur State) as potential Supplementary Cementitious Materials for use in blended cement and concrete. Four natural Pozzolanic materials samples have been obtained; the first is volcanic ash from the Garma region (TG1VA), the second from the Mabo region (TG2VA), the third from the Mawo region (TG3VA) and the last from the Daim Sanosi region (TG4VA). This study has investigated the chemical and physical characteristics of the samples and their pozzolanic activities with Ordinary Portland cement (OPC) at different substitution levels of cement by weights, which are 10, 20, 30, 40, and 50%. And the results of chemical analysis show that all samples can be classified as Class N according to the American standard ASTM C618. The strength activity indices of the four samples at 20% level were found to be 75, 84, 89, and 83% respectively. These results indicate that the Jebal Tagabo Pozzolans are potential supplementary cementitious materials for use in blended cement.

Concrete hollow blocks (CHB) have an important place in modern building industry, and although the CHB is considered a better alternative to fired bricks from the ecological and economical points of view, however, its prices are still high, since the main cost-factor is the ordinary Portland cement (OPC). This study is mainly focusing on the utilization of volcanic ash (VA) from Jebel Marra as a low cost material for CHB. In this study a VA sample from Jebel Marra (Al-malam area) was investigated for its physical and chemical properties, different substitution levels of 10, 20, 30, 40, and 50% of the OPC with pozzolanas were tested. Combined aggregates of locally available sand and stone aggregates were also tested for their economical value of fineness modulus. Then the potential use of these materials was implemented in (CHB) with different blends and mix ratios. The results of the chemical and physical analysis of the VA showed their compliance to the international specifications. The strength activity index of the mix containing 20%VA of the OPC weight at 28 days was 87%. If consider 3.5 MPa as the minimum compressive strength of load bearing CHB required by the Indian standard, it can be concluded that the VA can be used successfully as low cost material in the CHB with the substitution level up to 40%, 30%, and 20%, for binder aggregates ratio by volume 1:6, 1:7, and 1:8, respectively, with subsequent reduction in binder cost by 34, 26, and 17%, In addition, increasing the compressive strength of blocks can be achieved by using high pressure blocks making machine.